Beer

Liberec Technical University developed a special thermochromatic pigment for textiles which changes colors depending on the ambient temperature from yellowish desert pattern to dark green patterns. The color change is said to be repeatable infinitely and the pigment is stable on the sun or in the water. The temperatures in which the color change happens can be adjusted in production, currently it is said to be around 37-40°C. For the moment there is a certain disadvantage in rustling of the material but that is said to be solvable in the near future. Further development shall continue in cooperation with Czech army. 
 
You can see a video in this article (the interesting part is @ 0:21): https://www.idnes.cz/liberec/zpravy/univerzita-liberec-bunda-armada-vynalez-meni-barvy.A190821_144009_liberec-zpravy_tm

Liberec Technical University developed a special thermochromatic pigment for textiles which changes colors depending on the ambient temperature from yellowish desert pattern to dark green patterns. The color change is said to be repeatable infinitely and the pigment is stable on the sun or in the water. The temperatures in which the color change happens can be adjusted in production, currently it is said to be around 37-40°C. For the moment there is a certain disadvantage in rustling of the material but that is said to be solvable in the near future. Further development shall continue in cooperation with Czech army. 
 
You can see a video in this article (the interesting part is @ 0:21): https://www.idnes.cz/liberec/zpravy/univerzita-liberec-bunda-armada-vynalez-meni-barvy.A190821_144009_liberec-zpravy_tm

Something more from Anna news.
 
2S1 on ZIL-131 "cabrio"

 
2A20 (?) on Ural 4320

 
 

Anti-tank guns will be rather short. The 4,7 cm gun used in the fortifications was already introduced. Here are the field ones. 
 
3,7 cm KPÚV vz.34 was the first serial purpose-built anti-tank gun of the army. It was produced by Škoda as all other guns. Some two hundred pieces were fielded. The gun was 270-300 kg heavy (per traction variant). With muzzle velocity 675 m/s it could penetrate 30 mm armor at 1000 meters in 1934 testing (but only 30 mm at 550 meters in 1937 when tested against new cemented armor). It was capable to follow a target moving at 40 km/h and fire up to 23 rounds per minute (12 aimed). This gun is most well known as a tank weapon. It was used in LT vz.34 and LT vz.35 (Pz.35(t) ) tanks which were sucessfully used by Wehrmacht, Slovakia, Bulgaria and Romania in the early stages of the war. One gun is on display in Prague Žižkov muzeum (currently closed due to ongoing reconstruction). 

 
3,7 cm KPÚV vz.37 was a new gun developed as a result of testing against new types of armor. This gun became the primary anti-tank weapon of the army (some 700 pieces were fielded at the fall of 1938). The gun had higher muzzle velocity (750 m/s) and an extreme rate of fire up to 40 rounds per minute. It used the same ammo with bigger propelant charges (or same). It managed to penetrate 32 mm at 1000 meters. It was heavier (around 370 kg) also due to the use of rubber wheels for motorized traction. In its time it was very powerful AT gun somewhat more powerful than the German PaK 35/36. Wehrmacht let the production run and in September 1939 had nearly 900 of these guns fielded (several hundreds were used by other countries such as Slovakia). Also this gun had its tank variant but this time rather different (shorter recoil etc.) even though the ballistic performance was nearly same. This gun was used in LT vz.38 (Pz.38(t) ) and some TNH-series export tanks. 

 
4,7 cm KPÚV vz.38 was a new gun which was not yet fielded by the fall of 1938 but I place it here because this gun became pretty well known during the WW2 as a primary armament of the first tank destroyer ever the Panzerjäger I. This 580 kg heavy gun could penetrate some 55 mm at 500 meters and 32 mm at 1500 meters in 1936 testing (the muzzle velocity was 775 m/s). Later in the war it used even more powerful ammo. the rate of fire was 12 aimed shots per minute. Till 1940 it was the most powerful AT gun in Wehrmacht posession. Unfortunately the whole first batch for the army went directly to Wehrmacht when it was produced in the second half of 1939. Meanwhile Yugoslavia got some 300 pieces and used them in the war against Germany. Wehrmacht captured most of the guns and used them as well. Altogether Wehrmacht had around 600 pieces and they served until they were replaced with PaK 40. Also this gun had a tank variant. It was supposed to be used in the medium tank ST vz.39 but only one armed piece was built I think. Wehrmacht didn't order this tank despite it was much better armed than Pz.III of that time. One piece of this gun is on display in Lešany muzeum. 

 
 

Let's continue about the artillery. Now about the field guns of the pre-WW2 Czechoslovak army. 
 
7,5 cm light gun vz.1897. This legendary French gun was still in reserve by the fall of 1938 (38 pieces). They were bought in 1919 as a stop-gap during the war with Hungarian Soviet Republic. I think that this gun was on display in the military museum in Prague Vítkov but I'm not sure (the museum is closed now due to ongoing reconstruction). 

 
8 cm ligh gun vz.5/8. These Škoda guns fired the first salvos of the WW1. First series still had brass barrel, later production after 1916 was all steel already. Most of the guns in Czechoslovak army was of post war production, but not all. Even though the gun was old in 1938 it was very light and used in higly mobile cavalry units and on armoured trains. 86 pieces were in service in 1938 (part in reserve). You can see it in Lešany museum. There is one peculiar thing about this gun. Small number of them was converted into anti-aircraft guns and a battery of four guns was still in service in Prague in 1938.   

 
8 cm light gun vz.17. Another škoda gun which was used in the late months of the WW1 on the Italian front. The Czechoslovak guns were from post-war production running till 1937 (the first series was actually originally ordered by Austro-Hungarian army before the end of war). The army had nearly 300 of these guns and despite many discussions about replacing the 76,5 mm barrels by 83,5 mm it was never realized because the army decided that in the future it's wise to replace the light guns with howitzers. The interesting thing about this gun is it's transport. Originally it was towed by horses but later it was being carried on the truck (not behind because its chassis could not cope with speed higher than 10 km/h). 

 
8 cm light gun vz.30. This gun was a bit of cat-dog design. It had a light barrel but a heavy over-dimensioned support from the howitzer vz.30 which allowed high elevation (80°) for anti-aircraft fire (that was later found not very usable). Nevertheless it had a pretty good 13 km range for its time. Part of the 202 guns in the army was used in motorized units, part with horse traction. Wehrmacht completely missed this category of guns by 1938 and took around 120 pieces. The strange thing about that is that the guns were officially sold to Germany 4 days before the occupation on 11th March 1939 (Germany never paid of course). The government was trying to sell large parts of the military equipment after the Münich. The war preparations hit the economy hard because the army was absolutely enormous compared to the country's size (imagine that a country of 15 million managed to mobilize more than 1 million soldiers and give them equipment in September 1938) and after the Münich it was clear that no fight is possible on the rest of the country (for many reasons which may be discussed later). 

 
7,5 cm mountain light gun vz.15. This is maybe the most legendary weapon of Škoda production ever. Very widely used in the WW1 and after by many countries. The gun was very easy to transport disassembled to six pieces with weight of 150 kg. It was capable of fire to 7 km distance and its crews were even trained to fight tanks. This gun was used by Czechoslovakia in the short war with Poland in 1919 and Hungarian Soviet Republic in the same year. Overall Czechoslovakia had some 235 pieces and sometimes in very unusual installations (in armoured trains, on Danube boats or as provisional equipment of the artillery blockhouses of the border fortifications). Wehrmacht took them and some other from other states and used them through the whole was especially in Italy and Balcan. This gun is on display in Prague Vítkov muzeum. Muzeum in Lešany has a more modern variant for Yugoslavia from late 20'.   

 
10,5 cm heavy gun vz.13. This French gun was used after the creation of Czechoslovkia but none was in service in the fall of 1938. As other French weapons 13 pieces were bought during the war with Hungarian Soviet Republic in 1919. One piece is on display in Lešany. 

 
10,5 cm heavy gun vz.35. This Škoda piece was for sure the most modern gun in the army inventory and one of the most modern guns in the world of its time. It was capable to deliver 18 kg round to 18 km with its own weight just 4,2 tons. It was also designed to directly engage tanks if needed (that was of course a total overkill against Pz.I and II in 1938 but very useful in the future). The army managed to get 106 pieces before Münich. There was a lot of interest in the gun from abroad but due to the political situation most of the export orders were taken by Wehrmacht (Yugoslavia, Latvia, Netherlands). Even USSR decided to buy this weapon but the agreement was never signed due to the post-Münich situation. Wehrmacht used some 140 pieces, the rest was used by Slovakia. One of these guns is preserved in Lešany museum. 

 
Next time anti-tank guns. 
 
 

A bit about the God of War. With Czechoslovak artillery it was exactly opposite than with the airforce. The artillery was very strong and had many very potent weapons, nearly all of them were local design and production. The guns were also widely exported. The field army had some 80 artillery regiments with over 2200 pieces (not counting any fortification guns or auxilliary units). As with most of other weapons large part of them (plus huge ammo stocks - and actually also hundreds of thousands Sudeten Deutsche soldaten) sadly presented a massive gift for the Wehrmacht. A bitter aftermath of Münich. 
 
10 cm Light howitzer vz.14/19 (towed by horses). Very well known weapon used by nearly everyone in the central Europe and during WW2 by Wehrmacht and Italy. In 1938 Czechoslovakia had around 600 pieces. Wehrmacht got 400+, Slovakia 180+. Together with Polish and Austrian ones Wehrmacht later had around 1000 pieces. 

 
10 cm light howitzer vz.30 (for motorized units and so called fast divisions). Very modern weapon for its time based on export Yugoslav model but widely modified for domestic use (not always in the better way due to various compromises such as necessity to allow use of older ammo for vz.14/19). 160+ guns were available in 1938. It was later successfully used by Wehrmacht and Slovakia. The only preserved piece is in USA.  

 
10 cm light howitzer vz.38 (for mechanized units). This modern weapon was never fielded despite it was addopted but too late - the complete order (260 pieces) was canceled after Münich. As with the previous gun it was again based on successful export models F and H (Yugoslavia, Romania, Iran, Latvia, Afghanistan). Germany took 84 guns made for Latvia and sold 57 to Romania and 27 to Finland. Those 27 Finnish guns officially fired 75 thousand rounds during the war and served successfully till 1970'. The prototype of the Czechoslovak version (H3) is on display in Lešany museum near Prague together with one Finnish piece (a place sure worth visiting). 

 
15 cm heavy howitzer vz.15 (usually towed by heavy tractors). This gun was already rather obsolete by 1938 but 40+ pieces were still used. The guns were taken over by Wehrmacht and used on the western front and a half was later sold to Finland. It's on display in Lešany. 
 
 
15 cm heavy howitzer vz.14/16 (for horse traction). Well known weapon of the WW1. Czechoslovakia used some 180 pieces built after WW1 and they were used till Münich. Hundreds of these guns were used by Italy, others by Austria, Romania, Greece etc. Wehrmacht took around 100 pieces and used most of them in Austrian units which were used to the same weapon. The gun is preserved in Lešany. 

 
15 cm heavy howitzer vz.25 (for horse traction). Czechoslovak army had 340 pieces of this rather light and potent weapon (still pretty good by late 30'). Werhmacht and Slovakia successfully used them till the end of war. You can see this gun in Lešany as well. 

 
155 mm heavy howitzer vz.15/17. This well known French gun was a stop-gap solution in 1919 when the army badly needed whatever it could get to fight the so-called Hungarian Soviet Republic (which was defeated by Romanian and Czechoslovak forces and ceased to exist the same year). Czechoslovakia had 50 pieces but all of them were retired by 1937. Maybe Wehrmacht got them from some storage but there is no record about that. Anyway it used plenty of these guns from French and Polish stocks. 

 
15 cm heavy howitzer vz.37. This weapon was arguably the best of its class by late 30' but as with many other weapons of Czechoslovak production it was largely exported (series K) but not used by the Czechoslovak army itself. When the army decided to addopt this weapon used already by Turkey, Romania or Yugoslavia it was hesitating that long about its modifications (for example whether it prefers a variant for motorized or horse traction) that the first guns were delivered only after Münich. Wehrmacht took a whole batch of 110+ pieces and used them till the end of war. Some sources say that Germany originally signed an order for another production but a lobby from German companies led to its cancelation. The Czechoslovak variant of the gun is on display in Lešany museum.  

 
10 cm mountain howitzer vz.16/19. This weapon was successfully used during the WW1 and extensively modernized by Czechoslovakia in 1920'. It was being transported disassembled into three pieces and with the overall weight 1350 kg it could fire to nearly 10 km distance (the modernized version). It was widely used by Italy, Austria (later Wehrmacht) and in small numbers also by Slovakia and Greece. Czechoslovakia had 66 pieces of which 44 were modernized and dislocated mostly in the mountains of Slovakia. This gun is on display in Lešany. 

 
That's it for howitzers. I have omitted many prorotypes, some of which are on display in Lešany as well. Let's continue later with field guns. 

Possibly last post dedicated to the fortification but a very long one dedicated to the heavy fortifications. I hope that a lot of those peculiar details are new for you. Most of the info comes from very knowledgeable staff of heavy infantry casemate N-S-82. If you ever want to visit some object of Czechoslovak fortification system you must not miss this one because this is the only one fully equipped as it shall have been (in fact it's a bit better equipped than in September 1938 then it was not totally finished inside). All photos are from my phone (it's allowed to take photos inside). 
 
N-S-82 is a stand alone infantry casemate located in a line on a slope upon the border crossing Náchod-Běloves. It was built in 1938 in a resistance class II. Which means that it had 2,25 m thick frontal wall (with a stones and earth cover). The roof was 2 m thick and the side and rear facing walls were 1 m thick. The border crossing is down bellow while roughly 1,5 km away on the hill there is an artillery fortress Dobrošov. It was guaranteed to withstand 240 mm artillery shells and 250 kg bombs (according to many authors Luftwaffe had no 500 kg bombs fielded at September 1938 yet) however during weapon testing on a casemate Jordán (experimental one used for fortification and weapon development) which had same resistance class even 305 mm heavy mortar hit didn't penetrate the roof (there were volunteers inside during the test fire!). It is said that there was some damage to the equipment but I don't know more details. 
 
On the same picture you can see also a combined anti-tank/infantry obstacle made of steel U-shape profiles welded together and stuck in a concrete base. Behind them there is anti-infantry barbed wire and a line of steel hedgehogs. Anti-infantry barbed wire could have been placed also in front of those rods. At certain place with high danger of tank attacks concrete anti-tank moats wete built too (sometime they can still be found). 
 
 
In 1938 you could find also these older concrete hedgehogs in the area. Those were used only earlier because they had two importnat drawbacks. The first one was that they offered better cover for the attacking infantry and the second was that their large area made them easier to move by shockwaves from artilery. 

 
A historical image showing how such line looked like in the September 1938 (where it was finished). This picture shows a heavy object K-S-35. 

 
N-S-82 was armed with one 47 mm AT gun, 5 HMG and 5-6 LMG. AT gun with coaxial HMG and a twin HMG were pointing down the valey towards the border crossing. On the opposite side (uphill) there were two single HMGs. LMG were used only in observation cupolas and for close defence of the object (normally the priority was to defend the neighbouring object with primary weapons). 
  
 
Let's go inside. There are three door covered by 2 LMG fire posts and one fire post for personal weapons directly in the entrance which alone had S-shape to prevent any direct fire into the object and on the main door. The first cage door are 200 kg heavy and on the left side behind them there is a fresh-air intake. On the right side there is armored door 600 kg heavy. Behind another corner there is third presurrized door 450 kg heavy. Both heavy door had emergency hatches in them so that the crew could get out if the door were deformed and stuck. 

 
The casemate has two floor. The top floor is combat and the bottom one is technical and living one. Every single heavy object had its own water source which must have been able to deliver at least 1,5 litres per minute. In this particular case it was around 4 litres per minute.

 
This is the electric generator which was pretty noisy. It's in fully working state. It's cooling was used for heating the interior but even in summer the inner temperature didn't get upon 17°C and the soldiers often suffered from respiratory or rheumatic issues. 

 
This is the filtering and air venting room. On the left side there is the ventilator with back-up handles for manual operation (I tried it myself and it's quite tough). On the right side there are filters which were used only in case of gas attack. The whole object had an overpressure in it which was used also for extracting the fumes from gunnery rooms. 

 
This particular object had 32 men crew (only the commander was an officer). The soldiers had one bedroom (see bellow). The sub-officers had their own room with own bed for each one and the commander had also his own room but located on the combat floor. Only Czech or Slovak nationals were allowed to serve in the permanent boarder units manning the heavy fortifications (no German, Poles or Hungarians because low loyality was expected with them). 

 
This is part of the bathroom (it's difficult to take some photos inside because it's quite cramped and I don't want to post gazillion of photos, rather only millions). The lavatories had a water filtration station used to prevent pollution of the main water source and a ventilation preventing methane acumulation). 

 
Down bellow there was also a food storage, hand granade storage (275 pieces) and a telephone room (on the picture). The bunker had several external telephone lines leading to the neighbouring objects and to the sector command post. As a backup a ground telegraph was used with cable antenas dug underground. Depending on the particular soil composition it was capable of morse communication to the range of 5-10 km. Ground radio antenas for voice communication were not installed by September 1938 (the radio was developed and tested but not fielded). 

 
Here you can see some internal communication means in the gunnery room. A simple speaking tube and a telephone. 

 
There was another way how to communicate between the observation cupolas and the gunnery rooms and that was a color code (in case of big noise from bombardning for example). 

 
With that we got onto the combat floor. This is the LMG firing post for the defence of the rear side. You can see observation insert on the left side which was interchangeable with the LMG. The LMG is vz.26 which I don't need to introduce to you for sure. There were 120 ready-to-fire magazines for each LMG in the object! 

 
Here is similar firing post with the observation insert mounted and a removable periscope to the right side of it. That was used to observe the close surroundings and the moats at the weapons. Under the periscope there is a tube for hand grenades used for close defence. 

 
A view inside the observation cupola from bellow. The very peculiar thing here is that the floor worked similarly to the office chair and the soldier could very simply adjust the floor position to his height. The middle column was also used for evacuation of spent cartridges. The cupola is made of 200 mm thick cast steel and the inner diameter is 1,35 m. 

 
This is a periscoipe which could have been errected through the cupola roof for 360° observation.

 
A simple lift was used to transport LMG mags to the cupola.

 
Some more details before we get to the main weaponry. These are JIGs for MG loading. Top is belt-loading JIG for HMG vz.37 and bellow is a one for mag loading of LMG vz.26.

 
This is the kitchen, gentelmen. Yes, for 32 people! The bunker had food reserves for 14 days but I can hardly imagine to fight 2 weeks inside without getting crazy. 

 
This is one very peculiar detail. When the bunker was bombarded by heavy weapons the ceiling could elastically deform. To prevent internal much thinner walls from collapsing they had on top of them a cork layer which worked like a spring reducing the pressure on the walls.

 
Except for the grenades all ammo was stored in the combat department close to the weapons. The capacity of this object was 600 47 mm shells and 600 thousand 7,92x57 rounds. Now imagine that 263 heavy and nearly 10000 light objects were actually built before Münich. What an insane amount of ammo stored in the fortification system!  In reality around 3/4 of the ammo was delivered at 28th September but I would say that it's still huge achievement of the army logistics. On the picture you can see AP and HE-FRAG round of the AT gun (from later war production). A third anti-infantry round was being developed but wasn't fielded. I don't know how it's called in English when the round is filled with steel balls. Can you help me?  

 
This is the right gunnery room with two single HMG vz.37 and one LMG vz.26 for close defence. Notice that all frontal and side walls and also the ceiling had metalic anti-spall and anti-vibration layer.

 
All main weapons (AT gun and the HMGs) had sights with 2x zoom (upon the gun there is a drawing of the surroundings). Unfortunately not a single original support for the single HMG was preserved and the plans shall be dug somewhere in the German archives. Therefore these are just approximate replicas. The HMG vz.37 (ZB-53) alone is basically what the Brits know as BESA (rechambered to 0.303). Each single HMG had 2 men crew, the shooter and the loader. 

 
This is one of only three preserved heavy barrels for the HMG vz.37 in Czechia. This barrel would be used exclusively in fortifications. 

 
This is a view into the left gunnery room with an AT gun with coaxial HMG and a twin HMG. Both weapons and supports are original. 

 
Both the HMGs and the AT gun could have been quickly aimed by the body force alone without using elevation and traverse screws (that was also a possibility). The twin HMG vz.37 on the picture had a crew of three (one shooter and two loaders). 

 
I believe the most interesting thing is the AT gun Škoda vz.36. This particular gun was moved to Atlantic Wall in Norway and in 2002 returned back into N-S-82 and moreover with a spare barrel. There are only around ten of such guns preserved worldwide and very few spare barrels (only one or two in Czechia) and these two have matching serial numbers (173 + 2173; 2173 means second barrel for 173) and moreover they originally belonged to this particular bunker!
 
The gun was capable of very rapid fire. Normally 20-30 aimed shots per mimute (depending on the skill of the crew) or up to 40 rounds per minute in autofire mode. That meant that it fired automatically once it was loaded (this was possible max. for 3 minutes and after a water cooling up to 6 minutes long was needed). The shooter could fire both the AT gun and the HMG by the same hand and he could use his second hand and his body to aim like with a gigantic rifle in a ball joint without using traverse and elevation screws. The gun had three loaders - two for the AT gun and one for the HMG. The gun penetration values vary in sources I saw but it shall be around 50 mm of cemented steel at 500 meters and 30°, i.e. more than enough for 1938. Later in the war special ammo with claimed double penetration values was developed by Škoda but I don't know if ever used anywhere.  

 
 
Well, that was N-S-82. Now some more peculiar things from other objects. This is a 15 cm Röchling shell still being stuck in a frontal wall of N-S-91. This object was built in class III therefore the wall on the picture is 2,75 meters thick and if the object was fully completed it would be covered by stones and earth (those would have likely little effect against the Röchling anyway). The wall was not penetrated. Czech fortifications were used for Röchling development just like later also the Belgian ones. However there is an important difference. I believe there is no Röchling hit in the roof in any Czech object while in Belgium the Germans tried the indirect fire and they achieved some very spectacular penetrations. The direct fire used against Czech fortifications was much less effective in terms of penetration but with the indirect fire it was close to impossible to actually hit something. 

 
I believe that this is another Röchling hit in the wall of N-S-49. Maybe a larger calibre for 21 cm guns, honestly I can't recognize. This is an object of an unfinished artilery fortress Skutina and the wall is 3,5 meters thick. It was too high to actually see inside and the object is not accesible from inside for public but it looked like it's not a penetration. Fun fact about this unfinished fortress. The guys who take care of it plan to connect the underground corridor betwen the existing objects where 27 meters were missing by the time when it was abandoned. 

 
Last thing is a replica of .380 ACP SMG vz.38 which was never fielded (on display in the object N-S-84). The SMG was basically developed in one month! It had two magazines, straight for 24 and drum for 96 rounds. 3500 pieces were ordered by the fortification command to be used to protect the entry door or in some light objects which were close to each other in difficult terrain instead of the LMG. The SMG was roughly 4x cheaper than the LMG. Only 15 were made before the order was canceled after Münich. Strangely Czechoslovakia which was very successful in small arms development never fielded an SMG in the interwar period. When the army realised it would be good to actually have one it was too late and moreover it had no money for it (at least the cavalery and artilery wanted it). 
 
Under the SMG You can also see Czechoslovak handgrenades from 1930'. 

 
  
 
 
 
 
 

Few photos (from my phone so pardon for the quality). I will add some more later. 
 
Artilery casemate R-S-79 of Hanička fortress (north-east Czechia). It shall have been armed with three 100 mm rapid firing howitzers which were never installed (plus several MGs and granade tubes). This type of objects was the largest in the whole fortification system. It is made of 5600 tons of reinforced concrete and the walls and roof are up to 3,5 meters thick (same for all object of artilery fortresses). By the late 1938 neiter Wehrmacht nor Luftwaffe had any weapon capable of guaranteed penetration. You can see damage caused by German tests. They achieved some penetrations only when firing salvos point blank from the rearward side. Hanička fortres was used for development of special Röchling bunker-penetrating shells and hand-held cumulative bombs. I am not able to recognize damage potentially caused by them. For sure one Röchling shell is displayed (badly corroded) in the fortress. 

 
Infantry casemate R-S-78 of fortress Hanička. It was one of the object used to defend the main artilery object. Its main armament was a cupola armed with heavy twin MG (plus several other MGs and grenade tubes). Unfortunately what You see is only an observation cupola (light MG could have been fired from it) not the heavy MG one. As You can see all weapons were installed behind a deep moat with grenade tubes and covered by a thick roof from the top. Generally the heavy Czechoslovak fortresses were similar to the French ones but as I don't know those very well I can't tell you how exactly they differed. In the war the object would have a camouflage coloring and net. 
 
 
Stand-alone infantry casemate R-S-87 covering a road over a mountain ridge. It's main armament is a 90 mm mortar installed in the moat. Also 47 mm anti-tank gun and two twin heavy MGs and several light MGs. Its walls are up to 1,75 meters thick and it's therefore one of the less resistant heavy objects however it is placed in difficult terrain. The bunker is private and the chimney is of course not original. 

 
Here would be the mortar.

 
Twin heavy MG and a light MG on the left side of it. The firing posts are not original as those were removed probably for Atlantic Wall. 

 
Famous hedgehog and behind it you can see the anti-tank gun in a spherical armoured post.  

 
47 mm AT gun.

 
Stand-alone heavy infantry casemate R-S-81 after German tests (with armored firing posts taken to Atlantic Wall I believe). This object was built in the same resistance class as the one upon. Since it is one of the lightests heavy objetcs the results of the artilery tests on the normally inaccessible walls are not very impressive. 

 
An exampe of anti-infantry obstacles with a light object vz.37 in the background (this time from the southern border with Austria). Where armor attack was expcected the obstacles were made of mixture of concrete moats and steel or older concrete hedgehogs. The firing lines were of course free of trees which was advantage and disadvantage in the same time. Large majority of Czech border areas is hills, mountains and forests. That made it much more difficult for attackers but on the other hand the free of trees firing lines were clearly visible from the air.  

 
This is how the pillbox looks from the side of the enemy. Even these light pillboxes had walls up to 80 cm (120 cm for less common but still widely used reinforced variant). Together with stones and earth on the front side they are claimed to be capable to withstand 88 mm Flak fire (per German tests) or 105 mm howitzer hits (150 mm for the reinforced variant). The crew of max. seven men (depending on the type) had light MGs, grenade tubes and personal weapons. 

 
Detail of the firing post for the vz.26 light MG (sometimes also old heavy MG vz.24 was used I think - the MG vz.24 was rechambered Schwarzlose for 8 mm Mauser ammo). You can see how the firing post is covered by the  shielding wall from the fire coming from the enemy. These pillboxes covered basically all enemy borders (except extremely difficult terrain where only field fortifications weere used) and usually in several lines. Nearly 10000 of them were finished. Unlike in France there was nowhere to pass around. At the end of the war there was a skirmish between Wehrmacht and US army where German soldiers tried to use these pillboxes. They could however use them basically only as a shelter because at that time the fans were removed and when someone fired from inside the pillbox was immediately full of exhaust gasses. 

 
Pillbox vz.37 from the rear (friendly) side. The biggest problem of these bunkers was absence of any anti-tank weapons but by the time of Münich no fielded German tank had more than 14,5 armour and even the MGs could be dangerous for them since the gaps between the bunkers were usually short. Of course AT guns could and would be used in field positions to support the lines of bunkers. Another issue was with the ammo. It was simply not possible to store much ammo inside therefore the bunkers needed ammo supplies (unlike large fortresses with underground warehouses and even own water wells). 

 
Part of the pillboxes on the iron curtain were in use by the army till 1990' and are therefore in good condition. They have however often different firing posts (for UK vz.59) and often more stone and earth cover (officially to prevent overturning them by nuclear explosion). Normally the pillbox has some 2 meters of concrete undeground. 

 
 
 
 
 
 

Hello guys,
I think that possibly some of you might be interested in our interwar Czechoslovak stuff. For starter I've decided to share with you a wonderful online document about our fortification system. At the very beginning I'd like to say that I have nothing common with its creators. It's just an incredible gem that deserves to be shared with you. If you know it, sorry for that, nevertheless I think most of you don't. Since I am new here I will not waste your time debating what if scenarios. Don't worry.  
 
Well, enough of talking. What I want to share with you is a massive interactive map of our fortification system containing nearly 11 thousand objects with information about every single one of them. You can switch on even such crazy details like cable networks or construction facilities used for building of the fortifications. The map is directly linked with an online database of the fortification buildings where more than 2000 objects are listed with detailed description (plans, 3D models, photos, weapons, crew, important dates, recent state etc.). Unfortunately this database is only in Czech language but it can be a great source of information for you anyway (especially when linked with the map). The good thing is that the map alone supports other languages and you can easily switch them.  
 
This is the base view where I have already switched on all objects. You can change background map type, information etc. on the left side and visualise everything what You want to see on the right side. 
 
Let's zoom in a little bit. Here You can see one of the strongest fortified places - a valey at Králíky in north-east Czechia. As you can see the object marks have different shapes, colours etc. The shape is matching the menu on the right side. Triangles are concrete pillboxes vz. (mark) 36. Small circles are pillboxes vz. 37. The letter inside means type of the object (with one firing post, two on each side, angled one etc.). The color can be decoded from the information table in the bottom right corner. Basically it shows whether the object was actually built, if it was later destroyed or the works were only started or even not so. The heavy objects are the large circles. The numbers have also a meaning. It's a resistance class (1 -> 2 -> I -> IV from the lowest to the most resistant). 

 
You can switch on also the ground plans of the artilery groups (fortresses with underground network between the casemates). You can see it here (fortress Hůrka). 

 
You can also switch on the firing lines. Here You can see heavy artilery coverage of the most fortified section of the line (the sad thing is that no heavy artilery pieces were installed by the time of Münich crisis - but lets leave such details aside for now). 

 
You can switch on the firing lines even for the pillboxes as you can see here on the example from the souther border. Nearly all Czechoslovak objects were built for side fire having superheavy resistance frontal walls with stone and earth covers. 

 
If You zoom even more and switch for satelite map you get something like this. In this case the red color shows anti tank 47 mm guns and the blue color is 7,92 mm (sometimes double) heavy machine guns of a heavy separated casemate (possible use of light machine guns in observation cupolas is not marked). The grey color shows vz.26 light machine guns of the neighbouring pillbox. 

 
You can click on every single object and you get available details. The first icon shows detailed lines of fire including realistic range. Bellow the L: L1 M ZN 3-4 means: Left side: L1 = 47 mm anti tank gun with 7,92 mm coaxial heavy MG; M = twin 7,92 heavy MG; ZN is I think type of the cupola but I'm not actually sure about it. The codes for the weapons are shown at the table in the lower right corner (you need to keep the cursor on the question mark). 

 
The Second icon leads to a database of objects which is unfortunately only in our weird language. Anyway you can dig a lot of information from it as well (drawings, recent state, photos, exact location etc.).

 
 
The best thing is that most of the objects still exist till today (all of those heavy ones). The Germans managed to destroy roughly 2000 light objects (and gain some 11000 tons of steels from them). They managed to damage also many heavy ones when they were testing weapons and tactics for the future use duirng the WW2. They even moved some cupolas (and of course the famous hedgehogs) to other fortifications along the Atlantic wall or elsewhere. Many of them are made into better or worse museums today (large quantity is private now). Huge number of them is just left alone and freely accessible for anyone. If you are more interested I can give you tips which ones to visit. On the Czech map portal You can use a mode panorama which is basically the same thing as Google street view but it's much more up to date and it's nearly everywhere where they got at least with a motorbike. Since the fortifications are also visible there, you check where they are for easier access. 
 


 
If you are interested I can continue the fortification topic with some other information (I'm no historian but I have visited quite many of the objects myself and read some books about them). 
 
OK, so this was my first post on the forum. I hope you find it interesting and maybe for some of you it can be a reason for a trip, who knows :-) 
 
 
 
 

Some of his models details are also result of quess work, kek.

 
 

Hi-Res CAD of prototype 5-pair road wheels Puma:





http://btvt.narod.ru/4/puma2.htm

He can only climb in and out if the turret is in 11:30 position! That is also the position to drive with open hatch on road.

Intro
 

The MiG-3. All flying aircraft today have been re-engined with the V1710, and look slightly different.
 
The MiG-3 was one of the first fighters developed by the famous Mikoyan-Gurevich design bureau. An improvement on the troubled MiG-1, the MiG-3 was designed for combat at high altitude. Introduced in 1941, it gained less fame than its contemporaries like the Yakovlev and Lavochkin fighters. Germany's virtually nonexistent strategic bomber force, and the low-altitude nature of combat on the Eastern Front meant the MiG-3 was forced out of its element, and its performance suffered. Combined with the MiG's difficult flight characteristics and the horrible strategic situation for the Soviets in 1941, this meant the MiG-3 achieved little success.
 
While the MiG-3 did not spawn a successful series of fighters (like the Yak-1, Yak-9, and Yak-3, for instance), numerous variants were considered, and many of them were built in at least prototype form. However, for many reasons, such as lack of need or nTheonavailability of suitable engines, none of these variants entered large scale production.
 
 
 
 
I-230/MiG-3U
 

The resemblance to the baseline MiG-3 is easily seen. via aviastar
 
The I-230 was one of the more straightforward developments of the MiG-3. Development on the I-230 (also known as the MiG-3U) began in late 1941, with the objective to correct numerous flaws identified in the MiG-3. First was the armament; the MiG-3 had only two 7.62mm ShKAS machine guns and a single 12.7 Berezen (BS) machine gun, firing through the propeller. On the I-230, these were replaced with two 20mm ShVAK cannons (again synchronized to fire through the propeller).
 
Outwardly, the I-230 looked very similar to the production MiG-3, although the new aircraft was made mostly of wood instead of steel tubing and duralumin. The wing area and wingspan were increased (to 18 m^2 and 11 meters, versus 17.4 m^2 and 10.2 meters for the production MiG-3), and the fuselage was lengthened by .37 meters.
 
Soviet engineers originally intended to fit the I-230 with the AM-39 engine. However, by the time the I-230 airframe was completed in early 1942, the AM-39 was not yet available. As a result, the first I-230 was forced to use an engine built from both AM-38 and AM-35 parts (designated AM-35A). This engine was roughly 40 kilograms heavier than the intended engine, but produced a respectable 1350 horsepower. Even with such an odd engine, the I-230 flew by the end of 1942, achieving a top speed of over 650 km/hr at altitude. (Some sources say the I-230 first flew in May 1943, this is likely for the machines with AM-35A engines). Four more prototypes were built with AM-35A engines. These aircraft would serve in defense of the Moscow region while undergoing flight testing. While the design showed promise, by this point the AM-35 was obsolete and out of production. Additionally, some other deficiencies were identified. The I-230 was found to be difficult to land (a flaw shared with the MiG-3), and the engine tended to leak oil into the rest of the aircraft at high altitudes. As a result, the I-230 was not built.
 
I-231
 
The I-231 was a further evolution of the I-230, using the AM-39 engine that had originally been intended for use in the I-230. One of the I-230 aircraft had its engine replaced with the more powerful AM-39. This required modification of the cooling system; the radiator was enlarged, with another secondary radiator installed. There were also a few other modifications, such as moving the horizontal tail surfaces downward slightly, the fuselage fuel tank was enlarged and some modifications to the radios. Armament was the same as the I-230; two 20mm ShVAK cannons.
 
First flight of the I-231 was in October 1943. However, in early November, the prototype was forced to make an emergency landing after the supercharger failed at high altitude. Two weeks later, flight testing of the repaired I-231 resumed. The prototype, with the more powerful AM-39 (1800 horsepower), reached a top speed of 707 km/hr at an altitude of about 7000 meters. It also climbed to 5000 meters in under 5 minutes. Flight testing continued in early 1944, and in March, the I-231 was damaged after overrunning the runway during landing. The program suffered another setback when the repaired I-231 suffered an engine failure, damaging the precious AM-39 engine. Following this last mishap, work on the I-231 was discontinued.
 
 

The similarities between the radial and inline engined models are still visible. via airvectors
 
I-210/MiG-9 M-82
 

I-210 with radial engine. via airpages.ru
 
The I-210 was a more substantial modification of the MiG-3 which began in the summer of 1941. Production of the Shvestsov M-82 radial engine had recently begun, and many design bureaus, including MiG, were instructed to find ways to incorporate the engine into their designs. In the case of the MiG-3, this was especially important, as the Soviet government sought to discontinue the AM-35 to free up production space for the AM-38 used by the all-important Il-2.
 
In theory, the M-82, with 1700 horsepower, would provide a significant performance increase over the AM-35. Soviet engineers projected that the M-82 equipped MiG-3 (now known as the I-210) would reach nearly 650 km/hr at altitude. It was also projected that performance would be massively improved at low altitude, important for combat on the Eastern Front. The new aircraft was received the designation “MiG-9 M-82”, denoting that it was a substantially new type (this designation would later be reused for a twin-jet fighter in the late 1940s).
 
In addition to fitting of the M-82, there were several other differences between the MiG-3 and the I-210. Armament was increased to three 12.7mm UBS machine guns (two 7.62mm ShKAS were fitted initially, but soon removed). Several systems related to the engine, including the oil coolers and fuel system were also updated. The fuselage was widened slightly to accommodate the new engine.
 
The I-210 first flew in July 1941. However, it became quickly apparent that it was not meeting its performance targets. The top speed at an altitude of 5000 meters was a mere 540 km/hr, far inferior to to projects (as well as the production MiG-3!). Part of this was due to having a different model of propeller installed than what was intended. However, wind tunnel testing and inspection showed that the engine cowling was poorly designed and sealed to the rest of the airframe, causing significant drag.
 
Several months were required to correct the various defects, and it was not until June 1942 that three I-210s were ready for trails. During testing, the three aircraft were assigned to the PVO for use on the front. State trials began in September, and the I-210 fared poorly. Maximum speed was still only 565 km/hr, far inferior to existing types. Overall, the I-210 was judged to be unsatisfactory and inferior to the La-5 and Yak-7. The aircraft did not enter production, although the three completed prototypes would serve in Karelia until 1944.
 
I-211/MiG-9E
 
The failure of the I-210 was not the end of efforts to install a radial engine into the MiG-3 airframe. In late 1942, work on the I-211 began. A new Ash-82 engine, an improved variant of the M-82 installed on the I-210, was fitted. With the help of the Shvetsov bureau, the aerodynamics of the engine and its cowling were substantially improved. Further modifications reduced the empty weight of the “MiG-9E” by 170 kg. The three 12.7mm machine guns were replaced by two 20mm ShVAK cannons.
 
Testing of the I-211 began in August 1942 (other sources variously say that testing did not begin until early 1943, my interpretation is that this is when state trials officially happened). Performance was markedly superior to the I-210; the I-211 reached a top speed of 670 km/hr, and was able to climb to altitudes in excess of 11000 meters. However, the La-5, which was already in production using the M-82 engine, had similar performance. Moreover, the La-7 was in development, and was felt to have better potential. In all, only ten I-211s were built.
 
Interestingly, at least one source claims that a variant of the I-211 equipped with a Lend-Lease R-2800 engine was considered. There is no evidence that such an aircraft was actually built.
 
 
I-220/MiG-11
 
The I-220 (and the rest of its series up to the I-225) were substantially different from the production MiG-3, sharing little aside from the basic design and concept. These aircraft took the original mission of the MiG-3, interception of targets at high altitude, to the ultimate extreme.
 
The initial request that led to development of the I-220 was issued in July 1941, in response to high-altitude overflights by Ju-86P reconnaissance aircraft. These aircraft, capable of operating at over 13000 meters, were outside the reach of almost any Soviet fighter. A few Ju-86Ps at slightly lower altitude were intercepted by MiG-3s before the start of the war, so the MiG-3 was a natural starting point for a high-altitude interceptor.
 
Work on the I-220 prototype began in late 1942. Originally, it had been planned to install the AM-39 engine, but it was not ready at the time construction began on the prototype. Instead, one source (OKB MiG, Page 48) states anAM-38F engine was installed, which still provided more power (1700 hp) than the AM-35 on the MiG-3. However, it had the drawback of losing power at high-altitudes; the AM-38F would be an interim installation at best. A different source reports that an AM-37 was the first engine installed.
 
In addition to the new engine, the wingspan was lengthened by .80 meters, with a slight sweep added to the outer portion of the leading edge. The radiator was relocated from the belly of the aircraft to inside the wing center section, with new air intakes added at the wing roots. Armament was increased to four ShVAKs, making the I-220 one of the heaviest armed Soviet fighters.
 
The I-220 first flew in January 1943. Testing of the aircraft proceeded, as the AM-39 was still not yet ready. Despite being handicapped by the AM-38F engine, the I-220 prototype was still able to reach 650 km/hr during testing in January 1944. It was agreed that the aircraft had potential, but would need the AM-39 to reach its maximum performance. The second I-220 prototype was eventually fitted with the AM-39, but by that point it had been decided to substantially redesign the aircraft.
 
 
 

I-220 vs. I-221
 
I-221/MiG-7
 
While the I-220 had done well, it had not been able to reach the altitudes its designers had hoped for. Numerous changes would be required to get the best possible performance out of the airframe.
 
The most obvious area for improvement was the engine. Rather than the AM-38F, an AM-39A with a turbocharger was installed. Not only was the AM-39 more powerful than the AM-38, but the twin turbocharger would allow the engine to continue developing power at altitude. Additionally, the wingspan was increased further, to 13 meters. Armament was reduced to two ShVAK cannons, to save weight. Significantly, the I-221 was fitted with a pressurized cockpit, to allow the pilot to survive at extreme altitude.
 
By the time the I-221 made its first flight in December 1943, the Ju-86 threat had disappeared. One of the high-altitude intruders had been intercepted by a Yak-9PD (a high-altitude version of the Yak-9 designed and built in three weeks), though it had not been destroyed, overflights ceased. Nevertheless, the Yak-9PD was very much an interim solution, armed with only one ShVAK and requiring 25 minutes to climb to 12000 meters. So, development of the I-221 continued.
 
The test program of the I-221 was cut very short. On the eighth flight of the aircraft, in February 1944, the pilot bailed out at altitude, after seeing flames coming from the turbocharger and smoke in the cockpit. The pilot survived unharmed, but obviously the I-221 was completely destroyed.
 
I-222/MiG-7
 
 

Side view of I-222. via ruslet.webnode.cz
 
The I-222 was a continued development of the I-221. Not only did it have several additional performance improvements, but it was the closest of MiG's high altitude fighters to a “production ready” aircraft. The AM-39A engine was replaced with a more powerful AM-39B, with twin turbo-superchargers, plus a new four-bladed propeller. An improved intercooler was also installed (clearly visible under the central fuselage). To improve the I-222's potential utility as a combat aircraft, 64mm of armored glass was installed in the windscreen, and the cockpit pressure bulkheads were reinforced with armor plate. The fuselage contours were also modified to give the pilot better rearward visibility. Armament was two B-20 cannons, replacing the ShVAKs.
 
The I-222 made its first flight in May 1944. Relatively little testing was done before the aircraft went to the TSAGI wind tunnel for further refinement. It emerged in September and underwent further testing. Test flights proved that the I-222 had truly exceptional performance. A speed of 691 km/hr was reached, quite respectable for a piston-powered aircraft. The truly astonishing performance figure was the ceiling of 14500 meters, well in excess of any German aircraft (save for the rare and latecoming Ta-152H).
 
Though the I-222 could likely have been put into production, Soviet authorities assessed (correctly) that by late 1944 there was little threat from high-altitude German aircraft. Nuisance flights by Ju-86s were of little consequence, and German bomber programs such as the He-274 universally failed to bear fruit. Testing of the I-222 continued through late 1945, when the program was cancelled.
 
 
I-224/Mig-7
 

As can be seen the I-224 is similar to the I-222. From OKB MiG by Butowski and Miller
 
The I-224 was a development of the I-222 with an improved AM-39FB engine. Several other minor improvements, such as an improved propeller and modified cooling system. The new aircraft first flew in September 1944. After five flights, it was heavily damaged in an emergency landing. Difficulties continued after the aircraft was repaired in December; the engine had to be replaced in February due to the presence of metal particles in the oil.
 
Like the I-222, the I-224 demonstrated very good performance at altitude, also climbing to over 14000 meters and recording speeds over 690 km/hr. But by now, it was October 1945, and the war was over. It was decided to fit the I-224 with a fuel-injected AM-44 engine. This was not completed until July of 1946, and by then the time of the piston-engine fighter had passed. Both the I-222 and I-224 programs were shut down in November.
 
I-225/MiG-11
 

From OKB MiG by Butowski & Miller
 
The I-225 was born from the second I-220 prototype. Although the I-225 was still designed for operation at high-altitude, it was decided not to optimize the aircraft for such extreme heights as the I-222 and I-224. It was hoped that this would allow for a higher top speed and heavier armament, among other improvements.
 
A turbocharged variant of the AM-42 engine (similar to that used on the Il-10 ground attack aircraft) was fitted, providing 2200 horsepower at takeoff. The pressurized cabin was deleted to save weight, and allow the cockpit to be optimized for better visibility. Armament was the same as the I-220; four ShVAK cannons. Armor was added to the windscreen, as well as the pilot's headrest. Improved instrumentation and a new radio system was also added.
 
As predicted, the I-225 had exceptional performance. The aircraft was capable of speeds in excess of 720 km/hr, and demonstrated good handling characteristics. Unfortunately, the first I-225 prototype was lost after only 15 flights, due to an engine fire.
 
A second prototype was completed with an AM-42FB engine, and first flew in March 1945. This second prototype was fitted with four B-20 cannons instead of ShVAKs, This prototype was also reported to be capable of over 720 km/hr, as well as able to climb to 5000 meters in under 4 minutes. However, due to continued vibrations, the AM-42 was replaced with an AM-44 in January 1946. This did not solve the issues though, and the I-225, like its predecessors, was not selected for production. All work on the I-225 was shut down in March 1947.
 
 
 
Remarks
 
While none of the advanced MiG-3 variants entered production, they did provide the Mikoyan-Gurevich bureau with valuable engineering and design experience. In a different world, one might imagine that some of their designs could have found a niche. The I-210/1 and I-230/1 would have little reason to be built in a world where Yakovlev and Lavochkin fighters exist in the way they did. However, if Germany or another enemy had a developed strategic bombing arm, then the I-220 series fighters could have found a use. Either way, by 1945, it was clear that jet aircraft were the future. Even the Soviets, who had a relatively late start on jet engines, quickly developed aircraft like the MiG-9 and Yak-15 whose performance exceeded any of the MiG-3 variants.
 
 
 
Sources:
 
OKB MiG, a History of the Design Bureau and its Aircraft, by Piotr Butowski and Jay Miller
 
http://www.airvectors.net/avmig3.html
 
http://www.aviastar.org/air/russia/a_mikoyan-gurevich.php
 
https://ruslet.webnode.cz/technika/ruska-technika/letecka-technika/a-i-mikojan-a-m-i-gurjevic/ 
(I-230, I-210, I-211, I-220, I-221, I-222, I-224, and I-225 pages)
 
http://www.airwar.ru/fighterww2.html
(I-230, I-231, I-210, I-211, I-220, I-221, I-222, I-224, and I-225 pages)
 
http://soviethammer.blogspot.com/2015/02/mig-fighter-aircraft-development-wwii.html

There is a website which holds records about known aircraft crash sites in Czechia since 1918. Unfortunately it's all in Czech but with a decent translator you can dig a lot out of it (base data even without). It contains information about known circumstances of each crash site, its location and if possible also an information about artifacts found on the crash site. It can be particularly interesting for everyone interested in WW2 air war or for someone whose relatives were airmen who died somewhere over Czechoslovakia. 
 
This is the link to the website.
 
Particularly interesting sections are these:
WW2 per type
WW2 per date
 
Unfortunately there is only one-way link between the map and the database and that is from the map to the database. 
 
Of course not everything is in and with the time it's getting more and more difficult to search for what happened so long time a go... 
 
One example of what you can find is this. Capt. Robert B. Holmes from 82th Fighter Squadron 78. Fighter Group 8. AF was shot down by FlaK on 16th April 1945 during an attack on Prague Ruzyně (Václav Havel Airport today) airport. He died in the cockpit of the plane and was burried in a near Ruzyně cemetery. His body was later moved by the US officials to a French US military cemetery and later back to USA per wish of the family. The fragments of his Mustang were found in a forest and neighbouring fields in the period of 2007 to 2012 including some rather large parts such as a piece of the wing with the US star still well visible on it. The people behind this website were later contacted by a man whose father was one of the first responders on the crash site (he was working on the field nearby). This family built a small memorial dedicated to Capt. Holmes on the crash site and they keep taking care of it. 
 
There are some interesting records even after the WW2. For example this one. Two F-84F of the Luftwaffe crashed into a forest behind Czechoslovak frontier in 1959 due to navigation error in bad weather (both pilots managed to eject after first impact with the treetops). Long article (in Czech only) about this particularly interesting incident can be found here.  
 
 
Is there something similar for other countries? 

But if you try sometimes...

Fighter aircraft became much better during the Second World War.  But, apart from the development of engines, it was not a straightforward matter of monotonous improvement.  Aircraft are a series of compromises.  Improving one aspect of performance almost always compromises others.  So, for aircraft designers in World War Two, the question was not so much "what will we do to make this aircraft better?" but "what are we willing to sacrifice?"


 
To explain why, let's look at the forces acting on an aircraft:

Lift
 
Lift is the force that keeps the aircraft from becoming one with the Earth.  It is generally considered a good thing. 
 
The lift equation is L=0.5CLRV2A where L is lift, CL is lift coefficient (which is a measure of the effectiveness of the wing based on its shape and other factors), R is air density, V is airspeed and A is the area of the wing.

Airspeed is very important to an aircraft's ability to make lift, since the force of lift grows with the square of airspeed and in linear relation to all other factors.  This means that aircraft will have trouble producing adequate lift during takeoff and landing, since that's when they slow down the most.
 
Altitude is also a significant factor to an aircraft's ability to make lift.  The density of air decreases at an approximately linear rate with altitude above sea level:



Finally, wings work better the bigger they are.  Wing area directly relates to lift production, provided that wing shape is kept constant.

While coefficient of lift CL contains many complex factors, one important and relatively simple factor is the angle of attack, also called AOA or alpha.  The more tilted an airfoil is relative to the airflow, the more lift it will generate.  The lift coefficient (and thus lift force, all other factors remaining equal) increases more or less linearly until the airfoil stalls:





Essentially what's going on is that the greater the AOA, the more the wing "bends" the air around the wing.  But the airflow can only become so bent before it detaches.  Once the wing is stalled it doesn't stop producing lift entirely, but it does create substantially less lift than it was just before it stalled.  

Drag
 
Drag is the force acting against the movement of any object travelling through a fluid.  Since it slows aircraft down and makes them waste fuel in overcoming it, drag is a total buzzkill and is generally considered a bad thing.

The drag equation is D=0.5CDRV2A where D is drag, CD is drag coefficient (which is a measure of how "draggy" a given aircraft is), R is air density, V is airspeed and A is the frontal area of the aircraft.

This equation is obviously very similar to the lift equation, and this is where designers hit the first big snag.  Lift is good, but drag is bad, but because the factors that cause these forces are so similar, most measures that will increase lift will also increase drag.  Most measures that reduce drag will also reduce lift.

Generally speaking, wing loading (the amount of wing area relative to the plane's weight) increased with newer aircraft models.  The stall speed (the slowest possible speed at which an aircraft can fly without stalling) also increased.  The massive increases in engine power alone were not sufficient to provide the increases in speed that designers wanted.  They had to deliberately sacrifice lift production in order to minimize drag.
 
World War Two saw the introduction of laminar-flow wings.  These were wings that had a cross-section (or airfoil) that generated less turbulent airflow than previous airfoil designs.  However, they also generated much less lift.  Watch a B-17 (which does not have a laminar-flow wing) and a B-24 (which does) take off.  The B-24 eats up a lot more runway before its nose pulls up.


 
There are many causes of aerodynamic drag, but lift on a WWII fighter aircraft can be broken down into two major categories.  There is induced drag, which is caused by wingtip vortices and is a byproduct of lift production, and parasitic drag which is everything else.  Induced drag is interesting in that it actually decreases with airspeed.  So for takeoff and landing it is a major consideration, but for cruising flight it is less important.


However, induced drag is also significant during combat maneuvering.  Wing with a higher aspect ratio, that is, the ratio of the wingspan to the wing chord (which is the distance from the leading edge to the trailing edge of the wing) produce less induced drag.
 


So, for the purposes of producing good cruise efficiency, reducing induced drag was not a major consideration.  For producing the best maneuvering fighter, reducing induced drag was significant.

Weight
 
Weight is the force counteracting lift.  The more weight an aircraft has, the more lift it needs to produce.  The more lift it needs to produce, the larger the wings need to be and the more drag they create.  The more weight an aircraft has, the less it can carry.  The more weight an aircraft has, the more sluggishly it accelerates.  In general, weight is a bad thing for aircraft.  But for fighters in WWII, weight wasn't entirely a bad thing.  The more weight an aircraft has relative to its drag, the faster it can dive.  Diving away to escape enemies if a fight was not going well was a useful tactic.  The P-47, which was extremely heavy, but comparatively well streamlined, could easily out-dive the FW-190A and Bf-109G/K.

In general though, designers tried every possible trick to reduce aircraft weight.  Early in the war, stressed-skin monocoque designs began to take over from the fabric-covered, built-up tube designs.


The old-style construction of the Hawker Hurricane.  It's a shit plane.
 

Stressed-skin construction of the Spitfire, with a much better strength to weight ratio.
 
But as the war dragged on, designers tried even more creative ways to reduce weight.  This went so far as reducing the weight of the rivets holding the aircraft together, stripping the aircraft of any unnecessary paint, and even removing or downgrading some of the guns.


An RAF Brewster Buffalo in the Pacific theater.  The British downgraded the .50 caliber machine guns to .303 weapons in order to reduce weight.
 
In some cases, however, older construction techniques were used at the war's end due to materials shortages or for cost reasons.  The German TA-152, for instance, used a large amount of wooden construction with steel reinforcement in the rear fuselage and tail in order to conserve aluminum.  This was not as light or as strong as aluminum, but beggars can't be choosers.


Extensive use of (now rotten) wood in the rear fuselage of the TA-152
 
Generally speaking, aircraft get heavier with each variant.  The Bf-109C of the late 1930s weighed 1,600 kg, but the Bf-109G of the second half of WWII had ballooned to over 2,200 kg.  One notable exception was the Soviet YAK-3:


 
The YAK-3, which was originally designated YAK-1M, was a demonstration of what designers could accomplish if they had the discipline to keep aircraft weight as low as possible.  Originally, it had been intended that The YAK-1 (which had somewhat mediocre performance vs. German fighters) would be improved by installing a new engine with more power.  But all of the new and more powerful engines proved to be troublesome and unreliable.  Without any immediate prospect of more engine power, the Yakovlev engineers instead improved performance by reducing weight.  The YAK-3 ended up weighing nearly 300 kg less than the YAK-1, and the difference in performance was startling.  At low altitude the YAK-3 had a tighter turn radius than anything the Luftwaffe had.  
 
Thrust
 
Thrust is the force propelling the aircraft forwards.  It is generally considered a good thing.  Thrust was one area where engineers could and did make improvements with very few other compromises.  The art of high-output piston engine design was refined during WWII to a precise science, only to be immediately rendered obsolete by the development of jet engines.
 
Piston engined aircraft convert engine horsepower into thrust airflow via a propeller.  Thrust was increased during WWII primarily by making the engines more powerful, although there were also some improvements in propeller design and efficiency.  A tertiary source of thrust was the addition of jet thrust from the exhaust of the piston engines and from Merideth Effect radiators.
 
The power output of WWII fighter engines was improved in two ways; first by making the engines larger, and second by making the engines more powerful relative to their weight.  Neither process was particularly straightforward or easy, but nonetheless drastic improvements were made from the war's beginning to the war's end.

The Pratt and Whitney Twin Wasp R-1830-1 of the late 1930s could manage about 750-800 horsepower.  By mid-war, the R-1830-43 was putting out 1200 horsepower out of the same displacement.  Careful engineering, gradual improvements, and the use of fuel with a higher and more consistent octane level allowed for this kind of improvement.


The R-1830 Twin Wasp

However, there's no replacement for displacement.  By the beginning of 1943, Japanese aircraft were being massacred with mechanical regularity by a new US Navy fighter, the F6F Hellcat, which was powered by a brand new Pratt and Whitney engine, the R-2800 Double Wasp.


The one true piston engine

As you can see from the cross-section above, the R-2800 has two banks of cylinders.  This is significant to fighter performance because even though it had 53% more engine displacement than the Twin Wasp (For US engines, the numerical designation indicated engine displacement in square inches), the Double Wasp had only about 21% more frontal area.  This meant that a fighter with the R-2800 was enjoying an increase in power that was not proportionate with the increase in drag.  Early R-2800-1 models could produce 1800 horsepower, but by war's end the best models could make 2100 horsepower.  That meant a 45% increase in horsepower relative to the frontal area of the engine.  Power to weight ratios for the latest model R-1830 and R-2800 were similar, while power to displacement improved by about 14%.
 
By war's end Pratt and Whitney had the monstrous R-4360 in production:



This gigantic engine had four rows of radially-arranged pistons.  Compared to the R-2800 it produced about 50% more power for less than 10% more frontal area.  Again, power to weight and power to displacement showed more modest improvements.  The greatest gains were from increasing thrust with very little increase in drag.  All of this was very hard for the engineers, who had to figure out how to make crankshafts and reduction gear that could handle that much power without breaking, and also how to get enough cooling air through a giant stack of cylinders.

Attempts at boosting the thrust of fighters with auxiliary power sources like rockets and ramjets were tried, but were not successful.


Yes, that is a biplane with retractable landing gear and auxiliary ramjets under the wings.  Cocaine is a hell of a drug.

A secondary source of improvement in thrust came from the development of better propellers.  Most of the improvement came just before WWII broke out, and by the time the war broke out, most aircraft had constant-speed propellers.



For optimal performance, the angle of attack of the propeller blades must be matched to the ratio of the forward speed of the aircraft to the circular velocity of the propeller tips.  To cope with the changing requirements, constant speed or variable pitch propellers were invented that could adjust the angle of attack of the propeller blades relative to the hub.



There was also improvement in using exhaust from the engine and the waste heat from the engine to increase thrust.  Fairly early on, designers learned that the enormous amount of exhaust produced by the engine could be directed backwards to generate thrust.  Exhaust stacks were designed to work as nozzles to harvest this small source of additional thrust:


The exhaust stacks of the Merlin engine in a Spitfire act like jet nozzles

A few aircraft also used the waste heat being rejected by the radiator to produce a small amount of additional thrust.  The Meredith Effect radiator on the P-51 is the best-known example:



Excess heat from the engine was radiated into the moving airstream that flowed through the radiator.  The heat would expand the air, and the radiator was designed to use this expansion and turn it into acceleration.  In essence, the radiator of the P-51 worked like a very weak ramjet.  By the most optimistic projections the additional thrust from the radiator would cancel out the drag of the radiator at maximum velocity.  So, it may not have provided net thrust, but it did still provide thrust, and every bit of thrust mattered.
 
 
For the most part, achieving specific design objectives in WWII fighters was a function of minimizing weight, maximizing lift, minimizing drag and maximizing thrust.  But doing this in a satisfactory way usually meant emphasizing certain performance goals at the expense of others.
 
Top Speed, Dive Speed and Acceleration
 
During the 1920s and 1930s, the lack of any serious air to air combat allowed a number of crank theories on fighter design to develop and flourish.  These included the turreted fighter:



The heavy fighter:



And fighters that placed far too much emphasis on turn rate at the expense of everything else:



But it quickly became clear, from combat in the Spanish Civil War, China, and early WWII, that going fast was where it was at.  In a fight between an aircraft that was fast and an aircraft that was maneuverable, the maneuverable aircraft could twist and pirouette in order to force the situation to their advantage, while the fast aircraft could just GTFO the second that the situation started to sour.  In fact, this situation would prevail until the early jet age when the massive increase in drag from supersonic flight made going faster difficult, and the development of heat-seeking missiles made it dangerous to run from a fight with jet nozzles pointed towards the enemy.
 
The top speed of an aircraft is the speed at which drag and thrust balance each other out, and the aircraft stops accelerating.  Maximizing top speed means minimizing drag and maximizing thrust.  The heavy fighters had a major, inherent disadvantage in terms of top speed.  This is because twin engined prop fighters have three big lumps contributing to frontal area; two engines and the fuselage.  A single engine fighter only has the engine, with the rest of the fuselage tucked neatly behind it.  The turret fighter isn't as bad; the turret contributes some additional drag, but not as much as the twin-engine design does.  It does, however, add quite a bit of weight, which cripples acceleration even if it has a smaller effect on top speed.  Early-war Japanese and Italian fighters were designed with dogfight  performance above all other considerations, which meant that they had large wings to generate large turning forces, and often had open cockpits for the best possible visibility.  Both of these features added drag, and left these aircraft too slow to compete against aircraft that sacrificed some maneuverability for pure speed.

Drag force rises roughly as a square function of airspeed (throw this formula out the window when you reach speeds near the speed of sound).  Power is equal to force times distance over time, or force times velocity.  So, power consumed by drag will be equal to drag coefficient times frontal area times airspeed squared times airspeed.  So, the power required for a given maximum airspeed will be a roughly cubic function.  And that is assuming that the efficiency of the propeller remains constant!
 
Acceleration is (thrust-drag)/weight.  It is possible to have an aircraft that has a high maximum speed, but quite poor acceleration and vice versa.  Indeed, the A6M5 zero had a somewhat better power to weight ratio than the F6F5 Hellcat, but a considerably lower top speed.  In a drag race the A6M5 would initially pull ahead, but it would be gradually overtaken by the Hellcat, which would eventually get to speeds that the zero simply could not match.

Maximum dive speed is also a function of drag and thrust, but it's a bit different because the weight of the aircraft times the sine of the dive angle also counts towards thrust.  In general this meant that large fighters dove better.  Drag scales with the frontal area, which is a square function of size.  Weight scales with volume (assuming constant density), which is a cubic function of size.  Big American fighters like the P-47 and F4U dove much faster than their Axis opponents, and could pick up speed that their opponents could not hope to match in a dive.

A number of US fighters dove so quickly that they had problems with localized supersonic airflow.  Supersonic airflow was very poorly understood at the time, and many pilots died before somewhat improvisational solutions like dive brakes were added.


Ranking US ace Richard Bong takes a look at the dive brakes of a P-38

Acceleration, top speed and dive speed are all improved by reducing drag, so every conceivable trick for reducing parasitic drag was tried.


The Lockheed P-38 used flush rivets on most surfaces as well as extensive butt welds to produce the smoothest possible flight surfaces.  This did reduce drag, but it also contributed to the great cost of the P-38.


The Bf 109 was experimentally flown with a V-tail to reduce drag.  V-tails have lower interference drag than conventional tails, but the modification was found to compromise handling during takeoff and landing too much and was not deemed worth the small amount of additional speed.


The YAK-3 was coated with a layer of hard wax to smooth out the wooden surface and reduce drag.  This simple improvement actually increased top speed by a small, but measurable amount!  In addition, the largely wooden structure of the aircraft had few rivets, which meant even less drag.


The Donier DO-335 was a novel approach to solving the problem of drag in twin-engine fighters.  The two engines were placed at the front and rear of the aircraft, driving a pusher and a tractor propeller.  This unconventional configuration led to some interesting problems, and the war ended before these could be solved.


The J2M Raiden had a long engine cowling that extended several feet forward in front of the engine.  This tapered engine cowling housed an engine-driven fan for cooling air as well as a long extension shaft of the engine to drive the propeller.  This did reduce drag, but at the expense of lengthening the nose and so reducing pilot visibility, and also moving the center of gravity rearward relative to the center of lift.
 
Designers were already stuffing the most powerful engines coming out of factories into aircraft, provided that they were reasonably reliable (and sometimes not even then).  After that, the most expedient solution to improve speed was to sacrifice lift to reduce drag and make the wings smaller.  The reduction in agility at low speeds was generally worth it, and at higher speeds relatively small wings could produce satisfactory maneuverability since lift is a square function of velocity.  Alternatively, so-called laminar flow airfoils (they weren't actually laminar flow) were substituted, which produced less drag but also less lift.  
 

The Bell P-63 had very similar aerodynamics to the P-39 and nearly the same engine, but was some 80 KPH faster thanks to the new laminar flow airfoils.  However, the landing speed also increased by about 40 KPH, largely sacrificing the benevolent landing characteristics that P-39 pilots loved.

The biggest problem with reducing the lift of the wings to increase speed was that it made takeoff and landing difficult.  Aircraft with less lift need to get to higher speeds to generate enough lift to take off, and need to land at higher speeds as well.  As the war progressed, fighter aircraft generally became trickier to fly, and the butcher's bill of pilots lost in accidents and training was enormous.
 
Turn Rate
 
Sometimes things didn't go as planned.  A fighter might be ambushed, or an ambush could go wrong, and the fighter would need to turn, turn, turn.  It might need to turn to get into a position to attack, or it might need to turn to evade an attack.



Aircraft in combat turn with their wings, not their rudders.  This is because the wings are way, way bigger, and therefore much more effective at turning the aircraft.  The rudder is just there to make the nose do what the pilot wants it to.  The pilot rolls the aircraft until it's oriented correctly, and then begins the turn by pulling the nose up.  Pulling the nose up increases the angle of attack, which increases the lift produced by the wings.  This produces centripetal force which pulls the plane into the turn.  Since WWII aircraft don't have the benefit of computer-run fly-by-wire flight control systems, the pilot would also make small corrections with rudder and ailerons during the turn.

But, as we saw above, making more lift means making more drag.  Therefore, when aircraft turn they tend to slow down unless the pilot guns the throttle.  Long after WWII, Col. John Boyd (PBUH) codified the relationship between drag, thrust, lift and weight as it relates to aircraft turning performance into an elegant mathematical model called energy-maneuverability theory, which also allowed for charts that depict these relationships.

Normally, I would gush about how wonderful E-M theory is, but as it turns out there's an actual aerospace engineer named John Golan who has already written a much better explanation than I would likely manage, so I'll just link that.  And steal his diagram:


E-M charts are often called "doghouse plots" because of the shape they trace out.  An E-M chart specifies the turning maneuverability of a given aircraft with a given amount of fuel and weapons at a particular altitude.  Turn rate is on the Y axis and airspeed is on the X axis.  The aircraft is capable of flying in any condition within the dotted line, although not necessarily continuously.  The aircraft is capable of flying continuously anywhere within the dotted line and under the solid line until it runs out of fuel.

The aircraft cannot fly to the left of the doghouse because it cannot produce enough lift at such a slow speed to stay in the air.  Eventually it will run out of sky and hit the ground.  The curved, right-side "roof" of the doghouse is actually a continuous quadratic curve that represents centrifugal force.  The aircraft cannot fly outside of this curve or it or the pilot will break from G forces.  Finally, the rightmost, vertical side of the doghouse is the maximum speed that the aircraft can fly at; either it doesn't have the thrust to fly faster, or something breaks if the pilot should try.  The peak of the "roof" of the doghouse represents the aircraft's ideal airspeed for maximum turn rate.  This is usually called the "corner velocity" of the aircraft.

So, let's look at some actual (ish) EM charts:


 
 


Now, these are taken from a flight simulator, but they're accurate enough to illustrate the point.  They're also a little busier than the example above, but still easy enough to understand.  The gray plot overlaid on the chart consists of G-force (the curves) and turn radius (the straight lines radiating from the graph origin).  The green doghouse shows the aircraft's performance with flaps.  The red curve shows the maximum sustained turn rate.  You may notice that the red line terminates on the X axis at a surprisingly low top speed; that's because these charts were made for a very low altitude confrontation, and their maximum level top could only be achieved at higher altitudes.  These aircraft could fly faster than the limits of the red line show, but only if they picked up extra speed from a dive.  These charts could also be overlaid on each other for comparison, but in this case that would be like a graphic designer vomiting all over the screen, or a Studio Killers music video.

From these charts, we can conclude that at low altitude the P-51D enjoys many advantages over the Bf 109G-6.  It has a higher top speed at this altitude, 350-something vs 320-something MPH.  However, the P-51 has a lower corner speed.  In general, the P-51's flight envelope at this altitude is just bigger.  But that doesn't mean that the Bf 109 doesn't have a few tricks.  As you can see, it enjoys a better sustained turn rate from about 175 to 325 MPH.  Between those speed bands, the 109 will be able to hold on to its energy better than the pony provided it uses only moderate turns.

During turning flight, our old problem induced drag comes back to haunt fighter designers.  The induced drag equation is Cdi = (Cl^2) / (pi * AR * e).  Where Cdi is the induced drag coefficient, Cl is the lift coefficient, pi is the irrational constant pi, AR is aspect ratio, or wingspan squared divided by wing area, and e is not the irrational constant e but an efficiency factor.

There are a few things of interest here.  For starters, induced drag increases with the square of the lift coefficient.  Lift coefficient increases more or less linearly (see above) with angle of attack.  There are various tricks for increasing wing lift nonlinearly, as well as various tricks for generating lift with surfaces other than the wings, but in WWII, designers really didn't use these much.  So, for all intents and purposes, the induced drag coefficient will increase with the square of angle of attack, and for a given airspeed, induced drag will increase with the square of the number of Gs the aircraft is pulling.  Since this is a square function, it can outrun other, linear functions easily, so minimizing the effect of induced drag is a major consideration in improving the sustained turn performance of a fighter.

To maximize turn rate in a fighter, designers needed to make the fighter as light as possible, make the engine as powerful as possible, make the wings have as much area as possible, make the wings as long and skinny as possible, and to use the most efficient possible wing shape.

You probably noticed that two of these requirements, make the plane as light as possible and make the wings as large as possible, directly contradict the requirements of good dive performance.  There is simply no way to reconcile them; the designers either needed to choose one, the other, or come to an intermediate compromise.  There was no way to have both great turning performance and great diving performance.

Since the designers could generally be assumed to have reduced weight to the maximum possible extent and put the most powerful engine available into the aircraft, that left the design of the wings.

The larger the wings, the more lift they generate at a given angle of attack.  The lower the angle of attack, the less induced drag.  The bigger wings would add more drag in level flight and reduce top speed, but they would actually reduce drag during maneuvering flight and improve sustained turn rate.  A rough estimate of the turning performance of the aircraft can be made by dividing the weight of the aircraft over its wing area.  This is called wing loading, and people who ought to know better put far too much emphasis on it.  If you have E-M charts, you don't need wing loading.  However, E-M charts require quite a bit of aerodynamic data to calculate, while wing loading is much simpler.
 
Giving the wings a higher aspect ratio would also improve turn performance, but the designers hands were somewhat tied in this respect.  The wings usually stored the landing gear and often the armament of the fighter.  In addition the wings generated the lift, and making the wings too long and skinny would make them too structurally flimsy to support the aircraft in maneuvering flight.  That is, unless they were extensively reinforced, which would add weight and completely defeat the purpose.  So, designers were practically limited in how much they could vary the aspect ratio of fighter wings.

The wing planform has significant effect on the efficiency factor e.  The ideal shape to reduce induced drag is the "elliptical" (actually two half ellipses) wing shape used on the Supermarine spitfire.



This wing shape was, however, difficult to manufacture.  By the end of the war, engineers had come up with several wing planforms that were nearly as efficient as the elliptical wing, but were much easier to manufacture.

Another way to reduce induced drag is to slightly twist the wings of the aircraft so that the wing tips point down.



This is called washout.  The main purpose of washout was to improve the responsiveness of the ailerons during hard maneuvering, but it could give small efficiency improvements as well.  Washout obviously complicates the manufacture of the wing, and thus it wasn't that common in WWII, although the TA-152 notably did have three degrees of tip washout.

The Bf 109 had leading edge slats that would deploy automatically at high angles of attack.  Again, the main intent of these devices was to improve the control of the aircraft during takeoff and landing and hard maneuvering, but they did slightly improve the maximum angle of attack the wing could be flown at, and therefore the maximum instantaneous turn rate of the aircraft.  The downside of the slats was that they weakened the wing structure and precluded the placement of guns inside the wing.


leading edge slats of a Bf 109 in the extended position

One way to attempt to reconcile the conflicting requirements of high speed and good turning capability was the "butterfly" flaps seen on Japanese Nakajima fighters.


This model of a Ki-43 shows the location of the butterfly flaps; on the underside of the wings, near the roots

These flaps would extend during combat, in the case of later Nakajima fighters, automatically, to increase wing area and lift.  During level and high speed flight they would retract to reduce drag.  Again, this would mainly improve handling on the left hand side of the doghouse, and would improve instantaneous turn rate but do very little for sustained turn rate.
 
In general, turn performance was sacrificed in WWII for more speed, as the two were difficult to reconcile.  There were a small number of tricks known to engineers at the time that could improve instantaneous turn rate on fast aircraft with high wing loading, but these tricks were inadequate to the task of designing an aircraft that was very fast and also very maneuverable.  Designers tended to settle for as fast as possible while still possessing decent turning performance.
 
Climb Rate
 
Climb rate was most important for interceptor aircraft tasked with quickly getting to the level of intruding enemy aircraft.  When an aircraft climbs it gains potential energy, which means it needs spare available power.  The specific excess power of an aircraft is equal to V/W(T-D) where V is airspeed, W is weight, T is thrust and D is drag.  Note that lift isn't anywhere in this equation!  Provided that the plane has adequate lift to stay in the air and its wings are reasonably efficient at generating lift so that the D term doesn't get too high, a plane with stubby wings can be quite the climber!

The Mitsubishi J2M Raiden is an excellent example of what a fighter optimized for climb rate looked like.


A captured J2M in the US during testing

The J2M had a very aerodynamically clean design, somewhat at the expense of pilot visibility and decidedly at the expense of turn rate.  The airframe was comparatively light, somewhat at the expense of firepower and at great expense to fuel capacity.  Surprisingly for a Japanese aircraft, there was some pilot armor.  The engine was, naturally, the most powerful available at the time.  The wings, in addition to being somewhat small by Japanese standards, had laminar-flow airfoils that sacrificed maximum lift for lower drag.

The end result was an aircraft that was the polar opposite of the comparatively slow, long-ranged and agile A6M zero-sen fighters that IJN pilots were used to!  But it certainly worked.  The J2M was one of the fastest-climbing piston engine aircraft of the war, comparable to the F8F Bearcat.

The design requirements for climb rate were practically the same as the design requirements for acceleration, and could generally be reconciled with the design requirements for dive performance and top speed.  The design requirements for turn rate were very difficult to reconcile with the design requirements for climb rate.
 
Roll Rate
 
In maneuvering combat aircraft roll to the desired orientation and then pitch.  The ability to roll quickly allows the fighter to transition between turns faster, giving it an edge in maneuvering combat.

Aircraft roll with their ailerons by making one wing generate more lift while the other wing generates less lift.



The physics from there are the same for any other rotating object.  Rolling acceleration is a function of the amount of torque that the ailerons can provide divided by the moment of inertia of the aircraft about the roll axis.  So, to improve roll rate, a fighter needs the lowest possible moment of inertia and the highest possible torque from its ailerons.

The FW-190A was the fighter best optimized for roll rate.  Kurt Tank's design team did everything right when it came to maximizing roll rate.


The FW-190 could out-roll nearly every other piston fighter
 

 
The FW-190 has the majority of its mass near the center of the aircraft.  The fuel is all stored in the fuselage and the guns are located either above the engine or in the roots of the wings.  Later versions added more guns, but these were placed just outside of the propeller arc.

Twin engined fighters suffered badly in roll rate in part because the engines had to be placed far from the centerline of the aircraft.  Fighters with armament far out in the wings also suffered.



The ailerons were very large relative to the size of the wing.  This meant that they could generate a lot of torque.  Normally, large ailerons were a problem for pilots to deflect.  Most World War Two fighters did not have any hydraulic assistance; controls needed to be deflected with muscle power alone, and large controls could encounter too much wind resistance for the pilots to muscle through at high speed.

The FW-190 overcame this in two ways.  The first was that, compared to the Bf 109, the cockpit was decently roomy.  Not as roomy as a P-47, of course, but still a vast improvement.  Cockpit space in World War Two fighters wasn't just a matter of comfort.  The pilots needed elbow room in the cockpit in order to wrestle with the control stick.  The FW-190 also used controls that were actuated by solid rods rather than by cables.  This meant that there was less give in the system, since cables aren't completely rigid.

Additionally, the FW-190 used Frise ailerons, which have a protruding tip that bites into the wind and reduces the necessary control forces:


 
Several US Navy fighters, like later models of F6F and F4U used spring-loaded aileron tabs, which accomplished something similar by different means:



In these designs a spring would assist in pulling the aileron one way, and a small tab on the aileron the opposite way in order to aerodynamically move the aileron.  This helped reduce the force necessary to move the ailerons at high speeds.

Another, somewhat less obvious requirement for good roll rate in fighters was that the wings be as rigid as possible.  At high speeds, the force of the ailerons deflecting would tend to twist the wings of the aircraft in the opposite direction.  Essentially, the ailerons began to act like servo tabs.  This meant that the roll rate would begin to suffer at high speeds, and at very high speeds the aircraft might actually roll in the opposite direction of the pilot's input.



The FW-190s wings were extremely rigid.  Wing rigidity is a function of aspect ratio and construction.
 


The FW-190 had wings that had a fairly low aspect ratio, and were somewhat overbuilt.  Additionally, the wings were built as a single piece, which was a very strong and robust approach.  This had the downside that damaged wings had to be replaced as a unit, however.
 
Some spitfires were modified by changing the wings from the original elliptical shape to a "clipped" planform that ended abruptly at a somewhat shorter span.  This sacrificed some turning performance, but it made the wings much stiffer and therefore improved roll rate.



Finally, most aircraft at the beginning of the war had fabric-skinned ailerons, including many that had metal-skinned wings.  Fabric-skinned ailerons were cheaper and less prone to vibration problems than metal ones, but at high speed the shellacked surface of the fabric just wasn't air-tight enough, and a significant amount of airflow would begin going into and through the aileron.  This degraded their effectiveness greatly, and the substitution of metal surfaces helped greatly.
 
Stability and Safety
 
World War Two fighters were a handful.  The pressures of war meant that planes were often rushed into service without thorough testing, and there were often nasty surprises lurking in unexplored corners of the flight envelope.
 

 
This is the P-51H.  Even though the P-51D had been in mass production for years, it still had some lingering stability issues.  The P-51H solved these by enlarging the tail.  Performance was improved by a comprehensive program of drag reduction and weight reduction through the use of thinner aluminum skin.



The Bf 109 had a poor safety record in large part because of the narrow landing gear.  This design kept the mass well centralized, but it made landing far too difficult for inexpert pilots.



The ammunition for the massive 37mm cannon in the P-39 and P-63 was located in the nose, and located far forward enough that depleting the ammunition significantly affected the aircraft's stability.  Once the ammunition was expended, it was much more likely that the aircraft could enter dangerous spins.
 


The cockpit of the FW-190, while roomier than the Bf 109, had terrible forward visibility.  The pilot could see to the sides and rear well enough, but a combination of a relatively wide radial engine and a hump on top of the engine cowling to house the synchronized machine guns meant that the pilot could see very little.  This could be dangerous while taxiing on the ground.


 

Anti-tank guns will be rather short. The 4,7 cm gun used in the fortifications was already introduced. Here are the field ones. 
 
3,7 cm KPÚV vz.34 was the first serial purpose-built anti-tank gun of the army. It was produced by Škoda as all other guns. Some two hundred pieces were fielded. The gun was 270-300 kg heavy (per traction variant). With muzzle velocity 675 m/s it could penetrate 30 mm armor at 1000 meters in 1934 testing (but only 30 mm at 550 meters in 1937 when tested against new cemented armor). It was capable to follow a target moving at 40 km/h and fire up to 23 rounds per minute (12 aimed). This gun is most well known as a tank weapon. It was used in LT vz.34 and LT vz.35 (Pz.35(t) ) tanks which were sucessfully used by Wehrmacht, Slovakia, Bulgaria and Romania in the early stages of the war. One gun is on display in Prague Žižkov muzeum (currently closed due to ongoing reconstruction). 

 
3,7 cm KPÚV vz.37 was a new gun developed as a result of testing against new types of armor. This gun became the primary anti-tank weapon of the army (some 700 pieces were fielded at the fall of 1938). The gun had higher muzzle velocity (750 m/s) and an extreme rate of fire up to 40 rounds per minute. It used the same ammo with bigger propelant charges (or same). It managed to penetrate 32 mm at 1000 meters. It was heavier (around 370 kg) also due to the use of rubber wheels for motorized traction. In its time it was very powerful AT gun somewhat more powerful than the German PaK 35/36. Wehrmacht let the production run and in September 1939 had nearly 900 of these guns fielded (several hundreds were used by other countries such as Slovakia). Also this gun had its tank variant but this time rather different (shorter recoil etc.) even though the ballistic performance was nearly same. This gun was used in LT vz.38 (Pz.38(t) ) and some TNH-series export tanks. 

 
4,7 cm KPÚV vz.38 was a new gun which was not yet fielded by the fall of 1938 but I place it here because this gun became pretty well known during the WW2 as a primary armament of the first tank destroyer ever the Panzerjäger I. This 580 kg heavy gun could penetrate some 55 mm at 500 meters and 32 mm at 1500 meters in 1936 testing (the muzzle velocity was 775 m/s). Later in the war it used even more powerful ammo. the rate of fire was 12 aimed shots per minute. Till 1940 it was the most powerful AT gun in Wehrmacht posession. Unfortunately the whole first batch for the army went directly to Wehrmacht when it was produced in the second half of 1939. Meanwhile Yugoslavia got some 300 pieces and used them in the war against Germany. Wehrmacht captured most of the guns and used them as well. Altogether Wehrmacht had around 600 pieces and they served until they were replaced with PaK 40. Also this gun had a tank variant. It was supposed to be used in the medium tank ST vz.39 but only one armed piece was built I think. Wehrmacht didn't order this tank despite it was much better armed than Pz.III of that time. One piece of this gun is on display in Lešany muzeum. 

 
 

Anti-tank guns will be rather short. The 4,7 cm gun used in the fortifications was already introduced. Here are the field ones. 
 
3,7 cm KPÚV vz.34 was the first serial purpose-built anti-tank gun of the army. It was produced by Škoda as all other guns. Some two hundred pieces were fielded. The gun was 270-300 kg heavy (per traction variant). With muzzle velocity 675 m/s it could penetrate 30 mm armor at 1000 meters in 1934 testing (but only 30 mm at 550 meters in 1937 when tested against new cemented armor). It was capable to follow a target moving at 40 km/h and fire up to 23 rounds per minute (12 aimed). This gun is most well known as a tank weapon. It was used in LT vz.34 and LT vz.35 (Pz.35(t) ) tanks which were sucessfully used by Wehrmacht, Slovakia, Bulgaria and Romania in the early stages of the war. One gun is on display in Prague Žižkov muzeum (currently closed due to ongoing reconstruction). 

 
3,7 cm KPÚV vz.37 was a new gun developed as a result of testing against new types of armor. This gun became the primary anti-tank weapon of the army (some 700 pieces were fielded at the fall of 1938). The gun had higher muzzle velocity (750 m/s) and an extreme rate of fire up to 40 rounds per minute. It used the same ammo with bigger propelant charges (or same). It managed to penetrate 32 mm at 1000 meters. It was heavier (around 370 kg) also due to the use of rubber wheels for motorized traction. In its time it was very powerful AT gun somewhat more powerful than the German PaK 35/36. Wehrmacht let the production run and in September 1939 had nearly 900 of these guns fielded (several hundreds were used by other countries such as Slovakia). Also this gun had its tank variant but this time rather different (shorter recoil etc.) even though the ballistic performance was nearly same. This gun was used in LT vz.38 (Pz.38(t) ) and some TNH-series export tanks. 

 
4,7 cm KPÚV vz.38 was a new gun which was not yet fielded by the fall of 1938 but I place it here because this gun became pretty well known during the WW2 as a primary armament of the first tank destroyer ever the Panzerjäger I. This 580 kg heavy gun could penetrate some 55 mm at 500 meters and 32 mm at 1500 meters in 1936 testing (the muzzle velocity was 775 m/s). Later in the war it used even more powerful ammo. the rate of fire was 12 aimed shots per minute. Till 1940 it was the most powerful AT gun in Wehrmacht posession. Unfortunately the whole first batch for the army went directly to Wehrmacht when it was produced in the second half of 1939. Meanwhile Yugoslavia got some 300 pieces and used them in the war against Germany. Wehrmacht captured most of the guns and used them as well. Altogether Wehrmacht had around 600 pieces and they served until they were replaced with PaK 40. Also this gun had a tank variant. It was supposed to be used in the medium tank ST vz.39 but only one armed piece was built I think. Wehrmacht didn't order this tank despite it was much better armed than Pz.III of that time. One piece of this gun is on display in Lešany muzeum. 

 
 

Idlibostanians losses during SAA Northen Hama operation so far:
 
 

m735 m774 m833 m829 m829a1 m829a2

Okhotnik UAV first flight
 

bold - not 3BM29? DOI1985?

Left to right:
125 mm 3BM-15, 120 mm DM 13, 125 mm 3BM-22, 120 mm DM 23, 125 mm 3BM-32, 125 mm 3BM-42, 120 mm DM 33, 120 mm DM 53, 125 mm 3BM-59.

Let's continue about the artillery. Now about the field guns of the pre-WW2 Czechoslovak army. 
 
7,5 cm light gun vz.1897. This legendary French gun was still in reserve by the fall of 1938 (38 pieces). They were bought in 1919 as a stop-gap during the war with Hungarian Soviet Republic. I think that this gun was on display in the military museum in Prague Vítkov but I'm not sure (the museum is closed now due to ongoing reconstruction). 

 
8 cm ligh gun vz.5/8. These Škoda guns fired the first salvos of the WW1. First series still had brass barrel, later production after 1916 was all steel already. Most of the guns in Czechoslovak army was of post war production, but not all. Even though the gun was old in 1938 it was very light and used in higly mobile cavalry units and on armoured trains. 86 pieces were in service in 1938 (part in reserve). You can see it in Lešany museum. There is one peculiar thing about this gun. Small number of them was converted into anti-aircraft guns and a battery of four guns was still in service in Prague in 1938.   

 
8 cm light gun vz.17. Another škoda gun which was used in the late months of the WW1 on the Italian front. The Czechoslovak guns were from post-war production running till 1937 (the first series was actually originally ordered by Austro-Hungarian army before the end of war). The army had nearly 300 of these guns and despite many discussions about replacing the 76,5 mm barrels by 83,5 mm it was never realized because the army decided that in the future it's wise to replace the light guns with howitzers. The interesting thing about this gun is it's transport. Originally it was towed by horses but later it was being carried on the truck (not behind because its chassis could not cope with speed higher than 10 km/h). 

 
8 cm light gun vz.30. This gun was a bit of cat-dog design. It had a light barrel but a heavy over-dimensioned support from the howitzer vz.30 which allowed high elevation (80°) for anti-aircraft fire (that was later found not very usable). Nevertheless it had a pretty good 13 km range for its time. Part of the 202 guns in the army was used in motorized units, part with horse traction. Wehrmacht completely missed this category of guns by 1938 and took around 120 pieces. The strange thing about that is that the guns were officially sold to Germany 4 days before the occupation on 11th March 1939 (Germany never paid of course). The government was trying to sell large parts of the military equipment after the Münich. The war preparations hit the economy hard because the army was absolutely enormous compared to the country's size (imagine that a country of 15 million managed to mobilize more than 1 million soldiers and give them equipment in September 1938) and after the Münich it was clear that no fight is possible on the rest of the country (for many reasons which may be discussed later). 

 
7,5 cm mountain light gun vz.15. This is maybe the most legendary weapon of Škoda production ever. Very widely used in the WW1 and after by many countries. The gun was very easy to transport disassembled to six pieces with weight of 150 kg. It was capable of fire to 7 km distance and its crews were even trained to fight tanks. This gun was used by Czechoslovakia in the short war with Poland in 1919 and Hungarian Soviet Republic in the same year. Overall Czechoslovakia had some 235 pieces and sometimes in very unusual installations (in armoured trains, on Danube boats or as provisional equipment of the artillery blockhouses of the border fortifications). Wehrmacht took them and some other from other states and used them through the whole was especially in Italy and Balcan. This gun is on display in Prague Vítkov muzeum. Muzeum in Lešany has a more modern variant for Yugoslavia from late 20'.   

 
10,5 cm heavy gun vz.13. This French gun was used after the creation of Czechoslovkia but none was in service in the fall of 1938. As other French weapons 13 pieces were bought during the war with Hungarian Soviet Republic in 1919. One piece is on display in Lešany. 

 
10,5 cm heavy gun vz.35. This Škoda piece was for sure the most modern gun in the army inventory and one of the most modern guns in the world of its time. It was capable to deliver 18 kg round to 18 km with its own weight just 4,2 tons. It was also designed to directly engage tanks if needed (that was of course a total overkill against Pz.I and II in 1938 but very useful in the future). The army managed to get 106 pieces before Münich. There was a lot of interest in the gun from abroad but due to the political situation most of the export orders were taken by Wehrmacht (Yugoslavia, Latvia, Netherlands). Even USSR decided to buy this weapon but the agreement was never signed due to the post-Münich situation. Wehrmacht used some 140 pieces, the rest was used by Slovakia. One of these guns is preserved in Lešany museum. 

 
Next time anti-tank guns. 
 
 

Let's continue about the artillery. Now about the field guns of the pre-WW2 Czechoslovak army. 
 
7,5 cm light gun vz.1897. This legendary French gun was still in reserve by the fall of 1938 (38 pieces). They were bought in 1919 as a stop-gap during the war with Hungarian Soviet Republic. I think that this gun was on display in the military museum in Prague Vítkov but I'm not sure (the museum is closed now due to ongoing reconstruction). 

 
8 cm ligh gun vz.5/8. These Škoda guns fired the first salvos of the WW1. First series still had brass barrel, later production after 1916 was all steel already. Most of the guns in Czechoslovak army was of post war production, but not all. Even though the gun was old in 1938 it was very light and used in higly mobile cavalry units and on armoured trains. 86 pieces were in service in 1938 (part in reserve). You can see it in Lešany museum. There is one peculiar thing about this gun. Small number of them was converted into anti-aircraft guns and a battery of four guns was still in service in Prague in 1938.   

 
8 cm light gun vz.17. Another škoda gun which was used in the late months of the WW1 on the Italian front. The Czechoslovak guns were from post-war production running till 1937 (the first series was actually originally ordered by Austro-Hungarian army before the end of war). The army had nearly 300 of these guns and despite many discussions about replacing the 76,5 mm barrels by 83,5 mm it was never realized because the army decided that in the future it's wise to replace the light guns with howitzers. The interesting thing about this gun is it's transport. Originally it was towed by horses but later it was being carried on the truck (not behind because its chassis could not cope with speed higher than 10 km/h). 

 
8 cm light gun vz.30. This gun was a bit of cat-dog design. It had a light barrel but a heavy over-dimensioned support from the howitzer vz.30 which allowed high elevation (80°) for anti-aircraft fire (that was later found not very usable). Nevertheless it had a pretty good 13 km range for its time. Part of the 202 guns in the army was used in motorized units, part with horse traction. Wehrmacht completely missed this category of guns by 1938 and took around 120 pieces. The strange thing about that is that the guns were officially sold to Germany 4 days before the occupation on 11th March 1939 (Germany never paid of course). The government was trying to sell large parts of the military equipment after the Münich. The war preparations hit the economy hard because the army was absolutely enormous compared to the country's size (imagine that a country of 15 million managed to mobilize more than 1 million soldiers and give them equipment in September 1938) and after the Münich it was clear that no fight is possible on the rest of the country (for many reasons which may be discussed later). 

 
7,5 cm mountain light gun vz.15. This is maybe the most legendary weapon of Škoda production ever. Very widely used in the WW1 and after by many countries. The gun was very easy to transport disassembled to six pieces with weight of 150 kg. It was capable of fire to 7 km distance and its crews were even trained to fight tanks. This gun was used by Czechoslovakia in the short war with Poland in 1919 and Hungarian Soviet Republic in the same year. Overall Czechoslovakia had some 235 pieces and sometimes in very unusual installations (in armoured trains, on Danube boats or as provisional equipment of the artillery blockhouses of the border fortifications). Wehrmacht took them and some other from other states and used them through the whole was especially in Italy and Balcan. This gun is on display in Prague Vítkov muzeum. Muzeum in Lešany has a more modern variant for Yugoslavia from late 20'.   

 
10,5 cm heavy gun vz.13. This French gun was used after the creation of Czechoslovkia but none was in service in the fall of 1938. As other French weapons 13 pieces were bought during the war with Hungarian Soviet Republic in 1919. One piece is on display in Lešany. 

 
10,5 cm heavy gun vz.35. This Škoda piece was for sure the most modern gun in the army inventory and one of the most modern guns in the world of its time. It was capable to deliver 18 kg round to 18 km with its own weight just 4,2 tons. It was also designed to directly engage tanks if needed (that was of course a total overkill against Pz.I and II in 1938 but very useful in the future). The army managed to get 106 pieces before Münich. There was a lot of interest in the gun from abroad but due to the political situation most of the export orders were taken by Wehrmacht (Yugoslavia, Latvia, Netherlands). Even USSR decided to buy this weapon but the agreement was never signed due to the post-Münich situation. Wehrmacht used some 140 pieces, the rest was used by Slovakia. One of these guns is preserved in Lešany museum. 

 
Next time anti-tank guns.