I know this theme chewed many times, but I tried to make a little bit deeper insight tot he Leopard 2A4 protection level…
I hope my analyses will be interesting/useful
According to the very-well known swedish presentation, the distribution of the protection level are the following:
500mm < 6%
400-500mm ~14% (cumulative: 20%)
350-400mm ~25% (cumulative: 45%)
300-350mm ~17% (cumulative: 62%)
300mm> 38%
https://i.imgur.com/0zK5TH9.jpg
It is important to note, that there are measuring points on the graph in the swedish document. these are the abovementioned levels. But the measuring points are simply connected with a linear line. It means, to read the protection level scale between the measuring points are missleading. I mean, to say for example the 13% protected area at 450mm is not correct.
I used militarysta’ measures for the LOS thicknesses published on the btvt.narod
So, the results:
500mm < area is the turret roof section (modelled: 6%, swedish presentation: 6%)
400-500mm: we can assume the best protected area is the turret’ NERA armor blocks (orange blocks on the drawings). These are 14% of the total area, according to my calculation (vs. 14% in the swedish document)
350-400mm: we can assume that the NERA blocks in the hull front (20%+2,5%) and behind the EMES (2,5%) are in this range. these are 25% of the total area (vs. 25% in the swedish document)
300-350mm: upper glacis (where it is 40mm thick) is certainly in this band; it is 4,9% of the total area. Other possible candidate is the gun mantlet (13%). Total modelled: 17,9% (vs. 17% of swedish document).
300mm> the driver’ hatch area, the gun barell and the lower part of the hull.
The remeaning question is that, how much can be the „exact” protection level.
First, we use logic. The swedish document gives us 2 important additional infomation: The protected area between 400-500mm from angle 20 and 30 deg.
The upper side of the drawing shows the area protected (and unprotected) between 400-500mm from attack angle 20, and the lower side showed this from angle 30. If we keep in mind that the heavy skirt covered only 40% of the hull’ height, we can get the result the area protected between 400-500mm is 23% and 31% from attack angle 20 and 30, respectively. These figures are almost identical what we can see in the swedish document.
This statement implies that the hull front NERA block gives protection between 400-500mm from attack angle 30 but do not from 20. And also implies that turret NERA block gives protection between 400-500mm from attack angle 30, which is almost diagonal impact.
We should note, that in the case of longrod apfsds higher the attack angle higher the LOS perforation. In the case of 20, 30 and 60 degree the LOS perforation thickness is higher by 1.5%, 4% and 17% than against flat target. It means we should adjust with these figures the Sin/Cos values to get the „effective” LOS thickness of the armor (against longrod apfsds). For example, in the case of the turret’ NERA block (which angled at 35 degree) we should use the multiplier 1.17 (1.22/1.045) instead of 1.22.
So, the hull NERA block protection can be between 360 and 380mm (360*(1.16/1.04)>400 and 382*(1.06/1.016)<400)
The turret NERA block protection can be between 401 and 427mm (427*1.17<500, 401*1>400)
We have some additional informations. We know the germans designed the Leopard2 to whitstand the KE38 apfsds from 1500m. According to the RH105mm gun test, the KE38 perforated 305mm armor angled at 85 deg (almost flat) at 1390m/s speed limit. Fired from 120mm gun the DM13 speed at 1500m is around 1530 m/s (assume 75m/s/km speed loss) which means around (1530/1390)^2-1~22% higher kinetic energy. It suggests the DM13 perforation capacity at 1500m is around 1,22*305~370mm against flat armor. (it is definitely in the abovementioned range)
If we assume that the turret’ NERA and hull’ NERA blocks have similar efficiency then the ratio of the LOS thicknesses can be a good proxy for the turret’ NERA protection. LOS thicknesses (in both cases assume diagonal impact) are 640mm (hull) and 700mm (turret). So, turret’ NERA block protection level can be 700/640*370~405mm. against frontal attack: 405*1,17=475mm. With similar calculation we can get the armor block’ protection behind the EMES is around 380mm (660/640*370mm)
Further considerations: the yellow line which shows the protection level of the C-type armor, we can see 45% of the area protected at (least) 450mm level. As we calculated before in the case of B-tech armor the area which protected at least 400mm actually has a protection level 475mm. It is 20% of the area. So, with the C-tech armor additional 25% area becomes at least 450mm protected (45%-20%). It equals of the total surface area of the behind EMES armor, the front part of the hull and the UFP’ part which covered by the NERA block. And the turret front’ protection from 0 degree can be 700/640*450*1,17~575mm. It is higher by 21% than the B-tech armor’ protection (475mm), which totally in line with the british document’ (about the „Chieftain replacement program”) statement.
