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

[sLYFa]

58 minutes ago, Callsign JoNay said:

Weird, I didn't get any of those empty fuel tank weight discrepancies int my tests last night.

FWIW I'm referencing the in cockpit IAS gauge, not the status bar. That might cause the discrepancy. I'll do more test tomorrow.

[Victory205]

1 hour ago, Katj said:

It has occurred to me that the extension of DLC (also in its "neutral" position) kills lift and thus increases approach speed. This should lower theoretical max trap weight accordingly.

Now, this may have been deemed necessary with the tf30 engines, but didn't it unnecessarily limit the max trap weight on the F110 equipped jets?

 

DLC was an answer to the float caused by relatively straight wings interacting with the aerodynamics behind the ship. Would have likely been needed no matter what engine was mated to the airframe. S3's had it, A6 pilots on occasion would do a quick set of lateral stick inputs to pop the spoilers and kill lift over the ramp. You can do that, or at least be aware of the loss of lift in the F14 when making lineup corrections.

11 hours ago, Baz000 said:

Reminds me of the "you can lead a horse to water but can't make it drink" idea.

Not in DCS. Try to lead a horse to water and ten people will complain that the horse is the wrong color, and is "broken, nerfed, borked or tanked" because it won't run as fast or as far as they read on Wikipedia. They'll demand that it be changed immediately to make it easier to ride, and to enhance "immersion".

[Callsign JoNay]

@Victory205

Same missile loadouts without the XTs:

 

 

Fuel quantity the same as before. I didn't adjust it since the tanks are only around 250 lb each, so the overall gross weight should still be between 53-54k. Speeds were all as expected, between 137-138 kts. Still not seeing any weird behavior with XTs on my end, maybe it's only an A-model thing. 

[Katj]

My point is that with the F110 engines there seems to be little reason for the spoilers to deploy halfway when you activate the DLC. Even if they would have stayed in you could still have extended them with the thumbwheel to kill lift. You'd lose the ability to increase lift, though.

Though I'm sure they considered this and decided not to do it for some reason.

Of course it was still possible to retract the spoilers manually, but I'm guessing that sort of hack didn't do you any good in terms of max trap weight.

[Baz000]

4 hours ago, Victory205 said:

Very good, did you try removing the tanks only, leaving only the original missile load out, and noting if there is a speed difference at 15 units AOA?

Same process, but add fuel to put the gross at 54K again. Any change in speed?

I had an idea come to mind, maybe the behavior in DCS of the external tanks starting empty by loading the plane with the empty external tanks vs having the tanks started full and burning or dumping the fuel from the external tanks is possibly exhibiting different behavior in DCS? i'll give it a test and see for myself if possibly that may be it.

 

Edited November 11, 2021 by Baz000

[captain_dalan]

9 hours ago, lunaticfringe said:

 

Diagram of Penny Benjamin:

1. Load up a copy of 'Career Opportunities'.

2. Fast forward to 1:08:35.

3. Go along with whatever she does. 

4. Involuntarily dig for quarters. 

Teaser! 

[Gunslinger22]

6 hours ago, Victory205 said:

DLC was an answer to the float caused by relatively straight wings interacting with the aerodynamics behind the ship. Would have likely been needed no matter what engine was mated to the airframe. S3's had it, A6 pilots on occasion would do a quick set of lateral stick inputs to pop the spoilers and kill lift over the ramp. You can do that, or at least be aware of the loss of lift in the F14 when making lineup corrections.

Not in DCS. Try to lead a horse to water and ten people will complain that the horse is the wrong color, and is "broken, nerfed, borked or tanked" because it won't run as fast or as far as they read on Wikipedia. They'll demand that it be changed immediately to make it easier to ride, and to enhance "immersion".

I thank-you for your input and what you’ve done for the module. Though I’m just curious mate, do you get time to play DCS for fun? Do you get enjoyment from flying around, or does the constant testing and whatnot burn you out? 

[Baz000]

Various IAS for on-speed AOA for me with max trap of 54,000 lbs (within 200 lbs margin) in the A model with following A-A loadouts, I used the mission editor with unlimited fuel so weight stayed constant (no fuel burn) to set the internal fuel weights for loadouts:

All tests with full gun ammo 200mm HEI, AN/ALE-39 set to 60 flares 0 chaff, fill LAU-138 with chaff selected. Chaff and Flare in the payload editor set to 140 chaff and 60 flare and greyed out so you can't change it.

***x4 AIM-9M, x4 AIM-7M, empty external fuel tanks (internal fuel set to 51%)= 140 kts as indicated inside the cockpit

***without tanks and internal fuel set to 53%= 138 kts so 2 delta

 

x4 AIM-9M, x2 AIM-7M,(in the tunnel, sta 6 and 3) empty external fuel tanks (internal fuel set to 58%)= 138 kts

without tanks and internal fuel set to 59%= 138 kts so 0 delta

 

x4 AIM-9M, x2 AIM-7M (in the tunnel, sta 4 and 5) empty external fuel tanks (internal fuel set to 58%)= 138 kts

without tanks and internal fuel set to 59%= 138 kts so 0 delta

 

x2 AIM-9M, x2 AIM-7M (on wings, tunnel clean), empty external fuel tanks (internal fuel set to 59%) and stations 5 and 3 pairs of Phoenix pallets removed= 138ish kts the IAS needle is slightly less than 140 kts

without tanks and internal fuel set to 61%= 138 kts, so a 2 kts delta

 

x2 AIM-9M, x2 AIM-7M, x4 AIM-54A-Mk47, empty external fuel tanks (internal fuel set to 35%)= 138ish kts, definitely the needle is a tad below the 140 kts mark

without tanks and internal fuel set to 37%=138ish kts so a 0 delta

 

x2 AIM-9M, x3 AIM-7M (one in the tunnel), x2 AIM-54-Mk47, empty external fuel tanks (internal fuel set to 44%)= 140 kts

without tanks and internal fuel set to 46%= 140 kts so 0 delta

 

x6 AIM-54-Mk47, empty external fuel tanks (internal fuel set to 31%)= 140 kts

without tanks and internal fuel set to 33%= 138 kts so 2 kts delta

 

In all tests the aircraft was configured full dirty as if landing onto the boat (SP, gear, flaps full, DLC, hook all engaged)

 

***= I thought I had found a possible 10 kts disparity in this test with no XT = 10 kts slower IAS but I took steps to see if I could reproduce the result and I wasn't able to. I was only able to replicate this exact result when I had my DLC disabled... What probably happened was I thought I had engaged DLC when I most likely did not, now when I test I take a brief look at external view to see if the aircraft is properly configured as desired.

Conclusion is the numbers have very little change between external tanks empty vs not equipped and internal fuel added to bring the plane to 54k gross total weight. (using the mission editor numbers at least)

The numbers i'm getting are hardly showing any significance between same gross weight on-speed AOA between having empty external tanks vs not having any tanks. 

Edited November 12, 2021 by Baz000

[Baz000]

13 hours ago, sLYFa said:

Putting tanks on makes things interesting...

I did three setups: Clean airframe, no gun ammo and: Full tanks, empty tanks, no tanks. Fuel levels adjusted to have 54000lbs (in ME)

Full tanks onspeed: 132kts - You would expect this to be the highest IAS out of these 3 figures

Empty tanks onspeed: 132kts - This would be the 2nd highest IAS out of these figures

No tanks onspeed: 138kts -This would be the lowest IAS out of these 3 figures... The expectation is that as you bolt more junk to the plane your approach speed would increase not if you remove stuff.

It seems like adding tanks removes weight from the FM rather than adding it. Looking at the numbers, about 3000-4000lbs go "missing" when putting on tanks, full or empty.

 

Edited November 12, 2021 by Baz000

[RustBelt]

6 hours ago, Gunslinger22 said:

I thank-you for your input and what you’ve done for the module. Though I’m just curious mate, do you get time to play DCS for fun? Do you get enjoyment from flying around, or does the constant testing and whatnot burn you out? 

You say that like testing isn't fun. 

[Katj]

 The expectation is that as you bolt more junk to the plane your approach speed would increase not if you remove stuff.

Why is that? If the aircraft is the same weight (internal fuel was adjusted to achieve this) the wings will have to generate approximately the same amount of lift, i.e. on-speed will be the almost the same.

Why do I write almost and approximately? Because e.g. wing tanks will probably generate some lift themselves when flown at 15 units AOA.

Also, trim changes at different loadout might have an effect.

[Baz000]

You aren't considering additional drag from adding stores. Weight Isn't the only impact

If you have XT tanks installed you have more drag (honestly forget if induced or parasitic but I wanna say induced) vs if don't have them installed.

More drag = higher IAS approach speed

Simple test: take a completely clean plane and add internal fuel only to gross weight of 54k lbs, fly on-speed fully dirty and note the IAS.

Do the same but put 6 Phoenix and adjust internal fuel (33%) to get gross weight of 54k lbs, fly on-speed fully dirty and note the IAS.

What do you predict will happen? IAS will be the same for both? Or will one be faster IAS than the other at on-speed AOA of 15 cockpit units?

Remember, your total lifting power is coming from the engines, wings and "pancake" it isn't just a vector pointing straight up perpendicular to the wings that generates your overall lift vs an opposite vector representing gravity/weight.

You have thrust and drag to take into account too when trying to determine total overall lifting force, not just only the force of the wings.

Do the wings generate much lift if you fly at 80 kts? Not really, the wings need air moving over them to generate more lift. So, conversely if you fly at 300 kts your wings are generating way more lift. It is the same wings, nothing changed except the thrust that was added, drag works against thrust. Means you need more thrust to overcome drag.

I found these cool NASA pictures to help explain, picture your F-14 at on-speed AOA fully dirty and in level flight... It is going to look something like the image "forces in a climb" with your nose pitched up like that, except you aren't climbing because all of the forces on the plane are balancing like in image "balanced forces" the F-14 is still moving in a straight line. Except the nose is hiked up and if you add power in this regime you will climb and speed up depending on how much power you add. Pitch for power and throttle for altitude comes into play here for smaller magnitude corrections. If you give a large power correction without a corresponding stick correction it will effect both your speed (AOA) and altitude. (rate of climb or descent)

Edited November 12, 2021 by Baz000

[Katj]

You aren't considering additional drag from adding stores. Weight Isn't the only impact
If you have XT tanks installed you have more drag (honestly forget if induced or parasitic but I wanna say induced) vs if don't have them installed.
More drag = higher IAS approach speed
Simple test: take a completely clean plane and add internal fuel only to gross weight of 54k lbs, fly on-speed fully dirty and note the IAS.
Do the same but put 6 Phoenix and adjust internal fuel (33%) to get gross weight of 54k lbs, fly on-speed fully dirty and note the IAS.
What do you predict will happen? IAS will be the same for both? Or will one be faster IAS than the other at on-speed AOA of 15 cockpit units?
Remember, your total lifting power is coming from the engines, wings and "pancake" it isn't just a vector pointing straight up perpendicular to the wings that generates your overall lift vs an opposite vector representing gravity/weight.
You have thrust and drag to take into account too when trying to determine total overall lifting force, not just only the force of the wings.
Do the wings generate much lift if you fly at 80 kts? Not really, the wings need air moving over them to generate more lift. So, conversely if you fly at 300 kts your wings are generating way more lift. It is the same wings, nothing changed except the thrust that was added, drag works against thrust. Means you need more thrust to overcome drag.



I found these cool NASA pictures to help explain, picture your F-14 at on-speed AOA fully dirty and in level flight... It is going to look something like the image "forces in a climb" with your nose pitched up like that, except you aren't climbing because all of the forces on the plane are balancing like in image "balanced forces" the F-14 is still moving in a straight line. Except the nose is hiked up and if you add power in this regime you will climb and speed up depending on how much power you add. Pitch for power and throttle for altitude comes into play here for smaller magnitude corrections. If you give a large power correction without a corresponding stick correction it will effect both your speed (AOA) and altitude. (rate of climb or descent)

Lets stick to horizontal flight for now. In this case drag is in the opposite direction of the aircraft velocity, i.e. also horizontal. Whatever that horizontal component of the lift vector is in your picture, you can just move it from the lift to the drag vector and we have a nice vertical lift vector.

Now, this just leaves thrust, which has to be large enough to counter the drag. But at 15 units of AOA it also has a significant vertical component, i.e. the more you increase drag the more lift you will get from thrust. Exactly the opposite of what you're saying.

[sLYFa]

I was indeed unable to reproduce some of my findings but ONE thing I was able to reproduce:

Start with a clean AC (no tanks), set fuel to approx 10000lbs (GW54000) -> onspeed 138

Change loadout in ME to clean AC with FULL tanks, set internal fuel to 6000lbs (same 54000 GW) -> onspeed 132

Change loadout to clean AC with EMPTY tanks, set internal fuel to 9800lbs (again 54000GW) -> onspeed 138.

I've attached the mission, can anyone try the above to confirm/refute my results?

 

f14_ext_tank_weight_test.miz

[Baz000]

15 hours ago, sLYFa said:

I was indeed unable to reproduce some of my findings but ONE thing I was able to reproduce:

Start with a clean AC (no tanks), set fuel to approx 10000lbs (GW54000) -> onspeed 138 - I got 138 kts too, no delta

Change loadout in ME to clean AC with FULL tanks, set internal fuel to 6000lbs (same 54000 GW) -> onspeed 132 - I got 125 kts configured exactly like you said but I'm not getting 54,000 lbs GW configured like this like you said, so 7 kts delta but i'm not at 54k lbs either

Change loadout to clean AC with EMPTY tanks, set internal fuel to 9800lbs (again 54000GW) -> onspeed 138. -I got 135 kts, so 3 kts delta 

I've attached the mission, can anyone try the above to confirm/refute my results?

 

 

f14_ext_tank_weight_test.miz 9.09 kB · 3 downloads

I tried the mission as downloaded (without any editing) and I got 130 kts as onspeed AOA with how you have the aircraft setup in the mission, which is not anything like the 3 you noted above, I have XT with fuel and as shown in this image, loading your mission.

Your second loadout I get if I follow exactly what you said is this: But I am not at max trap at 54,000 lbs I am short of that putting 6,000 lbs of fuel internal

I think part of our problem is "what is a clean aircraft?" when I load that mission I have 4 Phoenix pallets loaded in the tunnel (to me this isn't "clean" exactly)

How are you configuring the aircraft for landing in your tests? I'm doing my configuration as if I am trapping onto the boat.

Something interesting in DCS is how depending on what pylon you choose to remove it changes what Phoenix pallets are removed and I wonder if something funny is happening there depending on what station you remove.

Edited November 13, 2021 by Baz000

[Baz000]

17 hours ago, Katj said:

Lets stick to horizontal flight for now. In this case drag is in the opposite direction of the aircraft velocity, i.e. also horizontal. Whatever that horizontal component of the lift vector is in your picture, you can just move it from the lift to the drag vector and we have a nice vertical lift vector.

Now, this just leaves thrust, which has to be large enough to counter the drag. But at 15 units of AOA it also has a significant vertical component, i.e. the more you increase drag the more lift you will get from thrust. Exactly the opposite of what you're saying.

Let's experiment!

Clean (no pallets) F-14B using sLYFa's mission, 62% internal fuel at max trap of 54k gives me an on-speed AOA of 135 kts IAS

same exact plane but loaded with 6 AIM-54A-Mk47 missiles and 4 pallets in the tunnel and empty external fuel tanks and 23% internal fuel at max trap of 54k gives me an on-speed AOA of 138 kts IAS

Edited November 13, 2021 by Baz000

[Callsign JoNay]

15 hours ago, sLYFa said:

I was indeed unable to reproduce some of my findings but ONE thing I was able to reproduce:

Start with a clean AC (no tanks), set fuel to approx 10000lbs (GW54000) -> onspeed 138

Change loadout in ME to clean AC with FULL tanks, set internal fuel to 6000lbs (same 54000 GW) -> onspeed 132

Change loadout to clean AC with EMPTY tanks, set internal fuel to 9800lbs (again 54000GW) -> onspeed 138.

I've attached the mission, can anyone try the above to confirm/refute my results?

 

f14_ext_tank_weight_test.miz 9.09 kB · 3 downloads

Yeah, something hella-weird is happening with the weights. I'm not seeing the same thing you are, but I tested the following clean loadouts (no phoenix pylons or missiles).

Aircraft #1: 54000 lbs in ME with empty XTs = ~130 kts

Aircraft #2: 54000 lbs in ME with full XTs= ~130 kts

Aircraft #3: 54000 lbs in ME no XTs= ~133-135 kts

 

According to the chart the weights are actually more like:

Aircraft #1: 48000 lbs

Aircraft #2: 48000 lbs

Aircraft #3: 49000 lbs

 

 

 

I think HB needs to prioritize reviewing the weights of the stores, XTs, and pylons before doing too much more to the flight model. These results are all over the place. "Swerved into something" indeed.

Edited November 13, 2021 by Callsign JoNay

[Katj]

Let's experiment!
Clean (no pallets) F-14B using sLYFa's mission, 62% internal fuel at max trap of 54k gives me an on-speed AOA of 135 kts IAS
same exact plane but loaded with 6 AIM-54A-Mk47 missiles and 4 pallets in the tunnel and empty external fuel tanks and 23% internal fuel at max trap of 54k gives me an on-speed AOA of 138 kts IAS

I wouldn't base my understanding of mechanics on the dcs F-14. Nevertheless, it is basically the same, with only a 3 knot difference.

The only way this could happen is if the stores have a negative effect on lift. Drag should have the opposite effect as mentioned earlier.

It isn't very far fetched to think that stores in the tunnel might have a detrimental effect on lift on the F-14, but I'm not convinced that this is modeled.

I think it's more that the weight showing in the ME doesn't match whatever weight the flight model uses.

Or maybe it's the trim I mentioned before, who knows at this point.

[captain_dalan]

2 hours ago, Katj said:

It isn't very far fetched to think that stores in the tunnel might have a detrimental effect on lift on the F-14, but I'm not convinced that this is modeled.

 

Doesn't DCS allow it?

[sLYFa]

6 hours ago, Baz000 said:

Your second loadout I get if I follow exactly what you said is this: But I am not at max trap at 54,000 lbs I am short of that putting 6,000 lbs of fuel internal

You need to explicitly set full tanks on ST 2 and 7 (in my mission its set to empty tanks IIRC). The 6000lbs of total fuel will of course not add up to 54000lbs GW

 

6 hours ago, Baz000 said:

think part of our problem is "what is a clean aircraft?"

As clean as it gets in DCS: No missiles/ordnance, no tanks (tank rails remain on though), no gun ammo, no PH rails, although the latter doesnt matter. This gives an empty weight of 44000lbs which is in line with RW docs.

[Baz000]

I did have full XT (not empty XT) and 6,000 lbs internal and it didn't add up to max trap of 54k.

We need to be uniform with our testing or of course we will all be getting different results. Minimize the testing variables between all of us by setting standard criteria. For example in all my tests before your mission I had gun ammo set to 100%.

Edited November 13, 2021 by Baz000

[sLYFa]

1 hour ago, Baz000 said:

I did have full XT (not empty XT) and 6,000 lbs internal and it didn't add up to max trap of 54k.

That cant be, 44k base weight +4k tank fuel +6k internal adds up to 54k

Btw the "internal fuel" value in the ME counts both tank and internal fuel, so make sure to set that to 10k. 

Gun ammo or not doesnt matter, as long as your gross weight adds up to 54k, or whatever weight you want to test at. 

[Baz000]

22 minutes ago, sLYFa said:

Btw the "internal fuel" value in the ME counts both tank and internal fuel, so make sure to set that to 10k. 

That may explain why I was 4k short on weight but why say to set internal fuel to 6k in the first place and not just 10k? To avoid DCS imposed confusion... I always thought if you put XT tanks in DCS they are always full normally and the fuel slider only changes the internal fuel load in the aircraft.

How do you think I'm editing these payloads? All in the mission editor and then reference to mission editor weight values.

Let's use the same values and methodology so our tests can be more of a uniform nature.

Edited November 13, 2021 by Baz000

[Callsign JoNay]

I hope by this point HB has realized there's some configuration/weight issues that need to be addressed, and maybe we can leave it in their hands to fix since they undoubtedly have tools at their disposal to squash bugs better than we can. My concern was that they were dumping time/effort into perfecting the FM before they had the foundational weights nailed down and bug free. If they weren't already aware of the inconsistent weight issues and missing phoenix pylon weight, hopefully they are by now and can rectify those things without having to take their FM progress back to square one.

[Katj]

Doesn't DCS allow it?

I have zero insight into the inner workings of the DCS flightmodels and the API so I really can't say.

I'm not the sort of person who is afraid to make a guess though:

Considering the amount of trouble 3rd party developers and ED are having with more simple aspects of external stores, like weight and drag, it wouldn't surprise me if the API is making these things difficult. It probably wasn't designed for this level of fidelity from the beginning. So at the end of the day I'm guessing that it's possible but inconvenient, perhaps prohibitively so.