What's a few typical combat radius scenarios?

[renhanxue]

You see this number quoted so much and yet it means so little without a lot more details. If you've got drop tanks, do you get rid of them when you're empty? Do you even drop your payload when you reach your halfway point? How much fuel do you reserve for maneuvering/as a safety margin? Does the scenario include loitering, and if so for how long? Does "high altitude" mean most economical cruise altitude?

In the flight manual for the Viggen I've got nice graphs for max range with a few different loadouts, but they all assume you're carrying everything all the way. I want to calculate some decently comparable numbers, so help a fellow nerd out?

[Collimatrix]

I'd have to do more research, but off the top of my head an air to ground combat radius is usually calculated with a high-low-high flight path and a nominal weapons load.  That is to say, the aircraft takes off, climbs to optimal cruise altitude (where the air is thinner and there's less drag), then descends to attack level (because radar can't pick it up as easily near the ground and it's easier to aim the weapons), and then returning at high altitude again.  I believe the return leg of the trip is calculated with weapons expended, but there are some exceptions especially if you're talking smart bombs because those are too expensive to just toss at the ground if the enemy doesn't oblige you by showing up.

 

For air to air there is usually some reserve time built in.

 

There should be a chart with reference drag numbers for the clean airframe and the various weapons added to the airframe.  From that you can roughly calculate ranges.

[Collimatrix]

Or, to put it more succinctly, I don't think there's an accepted standard.  It's whatever the manufacturer thought looked good in the sales brochures.

[LostCosmonaut]

Depending on what aircraft you're looking for, you might be able to find range in various configurations in spec sheets or the pilot's manual. For instance, this F-106 info sheet lists range for a couple missions with various loadouts, on both internal and external fuel.

[LostCosmonaut]

A better answer, courtesy of goon iyaayas01 in the SA Cold War thread (reposted for those who don't have $10);

 

 

Good assumptions for any flight manual combat radius number would be:

- Dropping external tanks when they're empty
- Getting rid of payload at the planned employment point (notionally halfway)
- Planning to arrive back at base at the published fuel minimums and not one pound more. For some data on this you can go to the USAF e-pubs site and search for "11-2." What you're looking for are the Vol 3's for various air frames..."11-2(MDS)V-3." This is the pub that contains basic procedures and limits for operating a particular airframe. For example, if you look at the F-16's, you'll see that normal recovery fuel for a Block 10 through 32 Viper is 1,000 lbs, while for a Block 40 and up it's 1,200 lbs. Any combat radius data would be built on arriving back at the airfield at the Vol 3 limits.

So really there's a couple likely scenarios I can think of for the timeframe we'd be talking about with the Viggen ('70s-'80s Cold War):

For air to air:
- High (best cruising) altitude at high subsonic (best fuel efficiency) speed, 30 minute period at high altitude at supersonic (use of burner) speeds while maneuvering, and then a high altitude high subsonic transit back to base.

For air to ground:
- Interdiction: High-Low-Low-High. Approach target at high (best cruising) altitude at high subsonic (best fuel efficiency) speed, drop to low altitude and supersonic (use of burner) speed when x miles out from the target (where x is contingent on the range of enemy air defenses), and then once clear of the enemy air defenses after egressing climb back up to high (best cruising) altitude and high subsonic (best fuel efficiency) speed for the transit back home. If you are talking about this profile when dealing with a not top tier air defense and with a robust ECM/SEAD capacity, then it's likely more of a high-med-high due to the better survivability out of the range of medium AAA and MANPADS once you've taken down the IADS.

- CAS/Maritime Strike: Approach and egress is same as above, but once at the target area plan in an x minute (20-30 minutes) loiter at low to medium altitude for target search/engagement/re-attack.

- In the Viggen's case I suppose you could also toss in a Maritime Search profile, which would have a lot more low to med altitude time built in to account for the time spent searching.

 

[renhanxue]

There should be a chart with reference drag numbers for the clean airframe and the various weapons added to the airframe.  From that you can roughly calculate ranges.

Yep, I have a shitton of graphs. I got drag coeffs for various loadouts, I got fuel expended per minute or per km in a whole bunch of different scenarios, I got range graphs, I got acceleration graphs, I got climb graphs, I got descent graphs, I'm basically drowning in graphs. Problem is figuring out what to use them for.