PSA: F-14 Performance/FM Development Status + Guided Discussion

[maxsin72]

1 hour ago, fat creason said:

Based on the timing I want to say tomorrow or Friday but not totally sure...

 

I have tested climb rate because i've seen F14B having some problems chasing opponents in bfm on the vertical and i've found that climb rate seems tanked.

Starting from about 100 ft, 760 KIAS, 20°C, unlimited fuel 4000lbs, full afterburner pulling gently at 88° pitch and misuring time to climb untill the stall:

With new FM

F14A 41.000 feet in 1min and 11 sec

F14B 41.000 feet in 1min and 11 sec (same performance as F14A)

Old FM

F14B 45.200 feet in 1min and 13 sec

 

So with the new FM F14A and F14B seems to have the same performance and this is strange because GE F110 has much more thrust at high altitude under mach 0,8 than TF30, i think

 

[Airhunter]

4 minutes ago, maxsin72 said:

 

 

So with the new FM F14A and F14B seems to have the same performance and this is strange because GE F110 has much more thrust at high altitude under mach 0,8 than TF30, i think

 

No. The TF30 performed better at the top end as the AICS (ramps) weren't adjusted for the F110, thus the A was faster.  Acceleration should probably still be better on the B at lower alts by a good bit but up high the A should be slightly faster based on available data and some SME statements. 

[maxsin72]

6 minutes ago, Airhunter said:

No. The TF30 performed better at the top end as the AICS (ramps) weren't adjusted for the F110, thus the A was faster.  Acceleration should probably still be better on the B at lower alts by a good bit but up high the A should be slightly faster based on available data and some SME statements. 

No, TF30 performed better at high mach number and F110 improved climb rate very much. At subsonic speed F110 is much better and when you climb almost 90° you'll be subsonic very early.

[Airhunter]

5 minutes ago, maxsin72 said:

No, TF30 performed better at high mach number and F110 improved climb rate very much. At subsonic speed F110 is much better and when you climb almost 90° you'll be subsonic very early.

Ok I get what you are saying now. Yeah that should generally be the case. Just the FM and thrust being WIP I guess.

[maxsin72]

 Here are tacview files of my tests. Both F14 A and B are at about mach 0,8 at about 24.000 ft and climb almost the same.

F14B.zip.acmiF14A.zip.acmi

 

Edited October 27, 2021 by maxsin72

[Baz000]

I was flying that new Lantirn training mission at 30k ft MSL (no, I didn't change altimeter to 29.92 passing transition altitude at 18k)

Was getting a lot of compressor stalls on mostly my right engine, but sometimes both would have it... Was trying to fly at 10 units AOA for max conserve most of the flight. Maybe flew around 8 (within the range of that triangle symbol bug on AOA scale) just so I didn't have to wrestle around with the maneuver flaps.

Straight and level I had about 2,000 pph each English, in a half standard rate turn I'd push them up to 3,000 pph each engine. I had altitude autopilot engaged holding 30k ft

Maybe the autopilot inputs would exacerbate things, I did notice it liked to get my AOA up where the maneuvering flaps deploy (which I logically suppose you wouldn't want that extra drag for max conserve)

The compressor stalls were more of a problem flying RTB back to the boat holding 30k ft and because the net was lighter because of burning fuel and dropping bombs (I had only the forward starboard side bomb remaining under the nose) I was holding around near idle power for max conserve... About 1,000 pph per engine.

I had way more than only 1 compressor stall too, sometimes on only the right engine, sometimes both engines and sometimes back to back successively on the right engine (to me the right engine had it happening in a greater frequency)

Sure made trying to fly back to the boat very sporty!

[lunaticfringe]

5 hours ago, maxsin72 said:

I have tested climb rate because i've seen F14B having some problems chasing opponents in bfm on the vertical and i've found that climb rate seems tanked.

Starting from about 100 ft, 760 KIAS, 20°C, unlimited fuel 4000lbs, full afterburner pulling gently at 88° pitch and misuring time to climb untill the stall:

With new FM

F14A 41.000 feet in 1min and 11 sec

F14B 41.000 feet in 1min and 11 sec (same performance as F14A)

Old FM

F14B 45.200 feet in 1min and 13 sec

 

So with the new FM F14A and F14B seems to have the same performance and this is strange because GE F110 has much more thrust at high altitude under mach 0,8 than TF30, i think

 

This is not how Rate of Climb or comparative climb performance is tested.  Two aircraft beginning at the same airspeed are going to have the same immediate rate of climb, and the one with the higher Ps (in this instance, being the A) is going to start walking.  At that point, it's a shape drag comparison; the F-14A and F-14B are within fractions of a percent with respect to comparable induced drag. 

[maxsin72]

6 hours ago, lunaticfringe said:

This is not how Rate of Climb or comparative climb performance is tested.  Two aircraft beginning at the same airspeed are going to have the same immediate rate of climb, and the one with the higher Ps (in this instance, being the A) is going to start walking.  At that point, it's a shape drag comparison; the F-14A and F-14B are within fractions of a percent with respect to comparable induced drag. 

Sorry but i don't agree with you. It's true both A and B start at the same speed but at about 24.000 feet they are both at mach 0.8, they are both slowing down and, at this point, it's expected that F110 will give a much better performance slowing down less than TF30 and finishing the climb at higher altitude.

Edited October 28, 2021 by maxsin72

[Noctrach]

There's another key difference between the TF30 and F110 that you might be missing. While the installed thrust of the F110 is much higher than the TF30s, the actual thrust in full AB might be lower in certain scenarios.

The TF30 fuel feed will just basically give the engine as much mass as it asks for, while the F110 will schedule fuel flow in a way to greatly reduce risk of flameout due to oxygen starvation. This does mean that in certain speed conditions, the F110 will have equal or even less thrust than the TF30. You can notice this best in very slow turn fights and acceleration at supersonic speeds.

I wouldn't be entirely surprised if something like this is also affecting your climb test. As you near low-end speeds of your climb profile, the TF30 will continue to push massive amounts of fuel into the AB, while the F110 will have been throttling down fuel flow to prevent engine stall.

Repeat this test by just maintaining a certain airspeed and I think the F110 will have the advantage.

Edited October 28, 2021 by Noctrach

[maxsin72]

22 minutes ago, Noctrach said:

There's another key difference between the TF30 and F110 that you might be missing. While the installed thrust of the F110 is much higher than the TF30s, the actual thrust in full AB might be lower in certain scenarios.

The TF30 fuel feed will just basically give the engine as much mass as it asks for, while the F110 will schedule fuel flow in a way to greatly reduce risk of flameout due to oxygen starvation. This does mean that in certain speed conditions, the F110 will have equal or even less thrust than the TF30. You can notice this best in very slow turn fights and acceleration at supersonic speeds.

I wouldn't be entirely surprised if something like this is also affecting your climb test. As you near low-end speeds of your climb profile, the TF30 will continue to push massive amounts of fuel into the AB, while the F110 will have been throttling down fuel flow to prevent engine stall.

Repeat this test by just maintaining a certain airspeed and I think the F110 will have the advantage.

 

TF30 perform better than F110 only at high mach number, in any other case, expecially low speed, subsonic speed or any other condition with a low air flux to the engines, i know F110 is much better than TF30. F110 let the F14 take off from the carrier without afterburners while with TF30 there is the need of full afterburners.

[maxsin72]

[lunaticfringe]

4 hours ago, maxsin72 said:

Sorry but i don't agree with you. It's true both A and B start at the same speed but at about 24.000 feet they are both at mach 0.8, they are both slowing down and, at this point, it's expected that F110 will give a much better performance slowing down less than TF30 and finishing the climb at higher altitude.

 

That's the thing- the actual EM performance charts (rather than uninstalled comparative tables) don't agree with your assessment.  

You want to see the subsonic difference in climb performance, you run the climb tables.  They're clear as day if you look; but you don't get to put the airplane with superior supersonic performance in a supersonic run, then call BS when the aircraft with lower supersonic performance had to play catch up.

[Golo]

3 hours ago, maxsin72 said:

F110 let the F14 take off from the carrier without afterburners while with TF30 there is the need of full afterburners.

No, F-14s with TF30 could take off without burners just fine.

Edited October 28, 2021 by Golo

[maxsin72]

59 minutes ago, Golo said:

No, F-14s with TF30 could take off without burners just fine.

 

Sorry but you are wrong, please read this link http://www.anft.net/f-14/f14-detail-engine.htm

And like this link there are many others that state the same

1 hour ago, lunaticfringe said:

That's the thing- the actual EM performance charts (rather than uninstalled comparative tables) don't agree with your assessment.  

You want to see the subsonic difference in climb performance, you run the climb tables.  They're clear as day if you look; but you don't get to put the airplane with superior supersonic performance in a supersonic run, then call BS when the aircraft with lower supersonic performance had to play catch up.

Sorry but i don't agree with you, please look better at my tacview files and you will se both A and B having the same performance (along all the climb) both supersonic and subsonic speed even if they have completely different engines

Edited October 28, 2021 by maxsin72

[draconus]

Patch is up. All tests are no longer valid

[lunaticfringe]

17 minutes ago, maxsin72 said:

Sorry but you are wrong, please read this link http://www.anft.net/f-14/f14-detail-engine.htm

And like this link there are many others that state the same

Sorry but i don't agree with you, please look better at my tacview files and you will se both A and B having the same performance (along all the climb) both supersonic and subsonic speed even if they have completely different engines

 

 

F14AAA-1.1 and F14AAP-1.1 don't concern themselves with whether or not your improperly conceived testing arrangement agrees with them. 

[Golo]

15 minutes ago, maxsin72 said:

Sorry but you are wrong

Oh wow, its written on the internet, therefore it must be indisputable truth. I stand corrected.

[maxsin72]

11 minutes ago, Golo said:

Oh wow, its written on the internet, therefore it must be indisputable truth. I stand corrected.

At least "it's written on the internet" while what you said is written nowhere.

Here is Flight International 30 March 1985 but, if you want, you can go on doing bla bla bla

[Victory205]

Theoretical Question-

Two identical aircraft are flying in formation at the same steady state speed and altitude, only difference is one is 20% heavier than the other.
 

Both simultaneously pull into a vertical climb at same angle, no changes to thrust. 
 

Which aircraft climbs quicker and attains the greater height?

[maxsin72]

2 minutes ago, Victory205 said:

Theoretical Question-

Two identical aircraft are flying in formation at the same steady state speed and altitude, only difference is one is 20% heavier than the other.
 

Both simultaneously pull into a vertical climb at same angle, no changes to thrust. 
 

Which aircraft climbs quicker and attains the greater height?

The lighter one, but I suppose there is an ulterior motive to your question

[captain_dalan]

20 hours ago, fat creason said:

Based on the timing I want to say tomorrow or Friday but not totally sure...

 

Copy that. Best to wait for the update then

[maxsin72]

55 minutes ago, draconus said:

Patch is up. All tests are no longer valid

I've seen, thx but the theoretical discussion is always valid

 

[fat creason]

There's no reason to be testing stuff right now, wait til we let you know the FM is done or close enough in certain regimes to test... Better yet, I'll test things and post results here when I have the time.

Just about the only thing I'd test right now is level flight acceleration and top speed, which is an indicator of excess power (Ps), but even that is being refined to be closer. After that, more tuning will be done to get sustained turns closer. Then we'll check climbs and all kinds of other stuff... 

Edited October 28, 2021 by fat creason

[Hummingbird]

12 minutes ago, fat creason said:

There's no reason to be testing stuff right now, wait til we let you know the FM done or close enough in certain regimes to test... Better yet, I'll test things and post results here when I have the time.

Just about the only thing I'd test right now is level flight acceleration and top speed, which is an indicator of excess power (Ps), but even that is being refined to be closer. After that, more tuning will be done to get sustained turns closer. Then we'll check climbs and all kinds of other stuff... 

 

[Golo]

51 minutes ago, maxsin72 said:

At least "it's written on the internet" while what you said is written nowhere.

F-14A NATOPS manual.

51 minutes ago, maxsin72 said:

Here is Flight International 30 March 1985 but, if you want, you can go on doing bla bla bla

If you read it carefully tho, not just selectively, there is a "launched at maximum weight" part. F-14A can definitely launch at mil. AB usage? It depends.

Edited October 28, 2021 by Golo