reported F-16 Excessive AoA in level flight

[Exorcet]

With the new flight model changes the F-16 seems to have become more responsive, but the AoA required for level flight has increased. It's especially obvious with two external tanks.

Pre patch single tank loadouts at altitude would sit around 3-4 degrees AoA, now even an AA loadout can exceed 5 degrees. Two tank loads can approach 7 and are far too draggy for the F-16 to maintain speed.

Is this expected behavior, or is the FM in need of more tuning?

F-162tank24k.trk

[Crptalk]

It can't be accurate. If it was then these loadouts wouldn't exist;

[BIGNEWY]

Hi, 

this is correct as is, if you have any unclassified information suggesting it is not please let us know. 

thank you

[cofcorpse]

For better test results change temperature to +15C. Default is +20C and hence the need for recalculations.

[Carbon715]

I posted some test results from earlier in another thread, may do good here. All using wing tanks and little over half load of fuel. Threw on burner to get to around .88 to .9 mach then into mil power and left it. Alt Hold at 25k or 30k ft depending on the test and just fast forwarded the mission until speed steadied. Read left to right...Altitude, mach speed ag ordinance T2 (Wing tanks) (all pods except for A2A config with wing tanks test) aa ordinance 2 aim 120c's and 2 9x's and fuel flow in pounds per hour 

[TobiasA]

Please supply unclassified data proving otherwise.

There is a manual out there, but it supports the current flight model. 

[Carbon715]

1 hour ago, TobiasA said:

Please supply unclassified data proving otherwise.

There is a manual out there, but it supports the current flight model. 

Supports the high alpha mil power cruise loaded with wingtanks?

[Spartan111sqn]

It cannot be correct as is today, a viper can accelerate better than hornet with same loadout and climb higher...

And for sure keep M.9ish with 2 tanks and air to air config above FL300, which is not the case today.

I guess once they adjust the FM we will have the CRUS page...

Edited March 22, 2022 by Spartan111sqn

[Crptalk]

I find it difficult to believe nations would fly their F-16's with CFT's, centerline tanks and 600 gallon wing tanks if the F-16's AOA and drag were as bad as it is in DCS with heavy loadouts.

[Dragon1-1]

If you load the Viper like a bomb truck, it won't cruise well. 4 JSOWs aren't very common for a good reason, and that reason is, they really weigh the poor Viper down. It's a small, lightweight fighter, and in a fighter configuration, it can cruise at 30kft no sweat. Strap a B-17 level bombload to it, and it'll fly like a B-17... one with a wing way too small for its weight. If you need to carry that sort of load, fly lower. This matches both the manual and the other sim. Just give it more throttle, why do you think the Viper has the reputation for being thirsty?

CFTs aren't as bad for the drag as air to ground loads, not to mention you don't need 600 gal bags when you have CFTs. This, however, is the reason why US doesn't use CFTs. AAR doesn't weigh down the poor Viper nearly as much as extra fuel does.

[Glide]

Good chat about fuel loadouts:

 

[wilbur81]

4 hours ago, Spartan111sqn said:

It cannot be correct as is today, a viper can accelerate better than hornet with same loadout and climb higher...

 

Hey, Spartan. I just did a quick little test with both jets loaded with 80% internal fuel, 2 wingtip 9X's, three drop tanks, and no other pylons or pods. At 16K msl, both jets starting at 400kts and going full burner immediately at mission start, the Viper beat the Hornet to Mach 1.0 by about 4 seconds (it took the Hornet 34 sec and the Viper 30). Air temp was whatever the default one is on the Caucasus map.

Happy to attach the mission if you'd like or you can run some more extensive ones yourself. 

Edited March 23, 2022 by wilbur81

[Crptalk]

23 minutes ago, Dragon1-1 said:

If you load the Viper like a bomb truck, it won't cruise well. 4 JSOWs aren't very common for a good reason, and that reason is, they really weigh the poor Viper down. It's a small, lightweight fighter, and in a fighter configuration, it can cruise at 30kft no sweat. Strap a B-17 level bombload to it, and it'll fly like a B-17... one with a wing way too small for its weight. If you need to carry that sort of load, fly lower. This matches both the manual and the other sim. Just give it more throttle, why do you think the Viper has the reputation for being thirsty?

CFTs aren't as bad for the drag as air to ground loads, not to mention you don't need 600 gal bags when you have CFTs. This, however, is the reason why US doesn't use CFTs. AAR doesn't weigh down the poor Viper nearly as much as extra fuel does.

Israel sure seems to like using 600 gallon bags with CFT's. Regardless, a normal sead load of 2x harm, 2x 370gal, and a jammer even has a hard time cruising at anything above 20k feet. Is that a bomb truck as well?

[Dragon1-1]

It's not, you just have to go reasonably fast, about 300kts should be fine. The Viper doesn't like being too high, try cruising at about 25k. Remember that in warm air AoA will be higher, so it'll also depend on the weather. Most of all, handle it gently, don't expect behavior that you get in a dogfight at 400kts or so. Hornet is easier to handle in high altitude cruise because it has a big, straight wing. It pays the price in other areas, though.

[TobiasA]

vor 8 Stunden schrieb Carbon715:

Supports the high alpha mil power cruise loaded with wingtanks?

Support the turn rates, speeds, fuel flows and sustainable MIL power speeds which depends directly on AOA and lift. If there are numbers proving otherwise, I would be interested as well.

vor 6 Stunden schrieb Crptalk:

Israel sure seems to like using 600 gallon bags with CFT's. Regardless, a normal sead load of 2x harm, 2x 370gal, and a jammer even has a hard time cruising at anything above 20k feet. Is that a bomb truck as well?

I cruise with that loadout quite regularly, even with a TGP and HTS. You need to maintain a speed of about Mach 0.7 to Mach 0.8 to minimize the sum of induced drag and parasite drag. This is also the most fuel efficient area at altitude. 

If you get slower, the induced drag of the high AOA will be a large factor, slowing you down until you fall out of the sky.

[Spartan111sqn]

14 hours ago, wilbur81 said:

Hey, Spartan. I just did a quick little test with both jets loaded with 80% internal fuel, 2 wingtip 9X's, three drop tanks, and no other pylons or pods. At 16K msl, both jets starting at 400kts and going full burner immediately at mission start, the Viper beat the Hornet to Mach 1.0 by about 4 seconds (it took the Hornet 34 sec and the Viper 30). Air temp was whatever the default one is on the Caucasus map.

Happy to attach the mission if you'd like or you can run some more extensive ones yourself. 

 

cool @wilbur81, but I mean in MIL power, in full burner Viper is a beast, but MIL power is far from RL, as a comparison, MIL in buster should be like hornet in medium burner with same loadout.

[TobiasA]

Just tested it, the limit with 2 HARM, 2 bags 3 AIM-120, 1 9X plus ECM plus TGP plus HTS is 30k on Mach 0,7. In MIL.

[TheBigTatanka]

Tobias.... What's your assessment, is the jet where it's supposed to be in terms of achievable altitude, AOA, speed, and fuel flow with those loadouts.

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[TobiasA]

It looks pretty much like what one would assume looking at the chart.

[TheBigTatanka]

Yeah, that's what I'm gathering too.   I'm away at ground school learning a new jet, but i ran some of the cruise charts yesterday for a few loadouts i commonly use, and the numbers matched what i remember from the new flight model.  I'll do some flight tests when I get home, but I'm excited about how it's looking. 

[Spartan111sqn]

21 hours ago, TobiasA said:

Just tested it, the limit with 2 HARM, 2 bags 3 AIM-120, 1 9X plus ECM plus TGP plus HTS is 30k on Mach 0,7. In MIL.

Really matching the charts?  That speed is not operative, is even below optimum speed for cruise...

[TobiasA]

vor 2 Stunden schrieb Spartan111sqn:

Really matching the charts?  That speed is not operative, is even below optimum speed for cruise...

Optimum speed is the one with the slowest total drag in that case. A high drag index shifts the optimum speed to the slower. It might be possible with Mach 0.8 though. Just not with 0.95 or 0.5. Need to dig up the charts.

I can calculate it some time at the weekend, just now I am flying

Ah wait I don't have a drag index for the HTS and ALQ-131... Might add a drag index display to the wishlist 

[fapador]

On 3/18/2022 at 9:07 PM, Exorcet said:

With the new flight model changes the F-16 seems to have become more responsive, but the AoA required for level flight has increased. It's especially obvious with two external tanks.

Pre patch single tank loadouts at altitude would sit around 3-4 degrees AoA, now even an AA loadout can exceed 5 degrees. Two tank loads can approach 7 and are far too draggy for the F-16 to maintain speed.

Is this expected behavior, or is the FM in need of more tuning?

F-162tank24k.trk 28.61 kB · 4 downloads

I have flown the Lockheed Martin Viper Simulator setupe'd with 2 external fuel tanks . I don't remember 7 degrees AOA level flight in any speed range especially in the low range.  Personally, I think the whole  DCS FM  handling is very different in a weird way. BMS FM approach  is more preferable to me but still doesn't  quite hit the spot,  it's  stick feedback  is also rather  vague. On the other hand, these are  the best and only Viper  representations available to consumers we have. For this reason, I am gratefull and my criticism is aimed in a constructive manner.

[Exorcet]

After reviewing it looks like the flight model is not as far off in cruise as I thought it might be, however it might still be slightly underperforming. I will continue to look into it to make sure I'm not making any mistakes. The F-16 being such a light fighter means it will struggle with heavy payloads and it seems like the wing tanks really produce a large amount of drag (speaking of which it would help if DCS listed drag indexes).

[TheBigTatanka]

Right, we don't have drag indexes for ECM pod, litening pod, or HTS pod. We might be able to get that from the other sim, but who knows where they got it from.

Running the charts for optimum mach is the key, then figuring out where you want to cruise, and what kind of fuel flow you should expect at that altitude for that mach number. Can't wait to get home to test it.

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