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

[Hummingbird]

This is one thing, the other is that the maneuver slats/flaps schedule should also be based on AoA, i.e. they need to gradually extend with gradual increases in AoA until the AoA of full extension is reached, that is as long as it's within the speed limit of the devices:

Spoiler

 

 

To explain with four different scenarios:

 

1) The F-14 flies at M 0.3 @ SL, thus full extension of maneuver slats/flaps is possible (Fig 2-51). Starting at 7.7+ units AoA the maneuver slats/flaps begin to gradually extend until at 10.5 units AoA where they are now fully extended (Fig 2-52) 

 

2) The F-14 flies at M 0.5 @ SL, thus full extension of maneuver slats/flaps is possible (Fig 2-51). Starting at 7.7+ units AoA the maneuver slats/flaps begin to gradually extend until at 10.5 units AoA where they are now fully extended (Fig 2-52)  [Same as scenario 1]

 

3) The F-14 flies at M 0.55 @ SL, thus only ~50% max slat/flap extension is now possible (Fig 2-51). Starting at 7.7+ units AoA the maneuver slats/flaps begin to gradually extend until at 10.5 units AoA where they are now commanded fully extended (Fig 2-52), however in this case it's limited to 50% of max by the speed limit schedule (Fig 2-51) 

 

4) The F-14 flies at M 0.6 @ SL, thus no slat/flap extension is allowed by the speed limit schedule (Fig 2-51). The maneuver slats/flaps extension command is halted by the speed limit schedule, no extension happens irrespective of AoA. 

 

 

Now upon testing this in DCS, it appears that atm the slat/flaps instead seem to only either fully extend or fully retract on either side of 7.7 & 10.5 units AoA in the schedule on Fig 2-52, with no gradual extension in between when within the max extension speed limit ( Mach 0.52), which I believe is a mistake as it means the slats/flaps aren't operating gradually according to AoA, which leads to weird occurences where full extension & retraction can happen in the same 7.7-10.5 AoA interval below M 0.52 depending on wether you're coming off or putting on the AoA. 

 

Example:  Speed M 0.37 (245 KTAS), alt 195 ft, 9.9 units AoA, yet zero maneuver slat/flap extension:

 

 

It is my understanding based on the charts & descriptions in the manual that the slats/flaps should instead be partially extended between 7.7 and 10.5 units AoA, with the speed limit schedule (Fig 2-51) then governing the max extension actually available. Thus in the case above (9.9 units AoA, M 0.37) the maneuver slats/flaps should've been about 80% extended, and 100% had the AoA been 10.5 units due to being within the max extension speed limit of M <0.52. 

 

 

Hope this makes sense, and I'd love some input incase you have anything to add.

 

PS: To anyone not in the know, do not confuse units AoA with degrees AoA.

Edited October 7, 2021 by Hummingbird

[captain_dalan]

On 10/3/2021 at 6:29 PM, maxsin72 said:

Thanks really a lot, both for the interesting info (i've seen your tacview file) and for your time you gift me/us to share all the details

I'm trying to understand if there is a way tou use wings swept back to bleed speed and turn very tight when chasing another plane who can use airbrakes over mach 0.7 (i've seen airbraks want not work for F14 over mach 0.7) and is able to decelarate very quickly when the pilot wants to be overtaked (f18 or M2000 for example).

I also wish you a beautiful WE.

 

 

Hey mate, sorry for the late reply. I took a week off from DCS, both the forums and the sim. I just did some tests though, as i was curious myself as to how this would work out. I had never overridden the wingsweep in DCS before. I remember experimenting with it in another sim, long time ago, and my reaction back then was, wings back and me just don't mix well

 

The tacview is bellow the short text of my impressions. All the breaks are executed with wings back at 68 degrees manual setting, except for the last one, which is executed with the wings in auto for comparison. 
1. Wings back limits the g's you have available at a given mach-airspeed; So if you want a 10g pull, you'll need to enter the break at higher airspeed then you would with the wings in auto. This is essentially by the book, that is, it fits well with the math;
2. The effective bleed rate isn't really higher. Or better said, it's higher in the first 5-6 seconds of the break (if you enter it at very high speed, i.e. over 450 knots), but because of the lower lift available, after reaching certain airspeed you just stop bleeding and sort of hang in there. For me in this configuration it was about 200-250 knots, with the former being very hard to achieve as as soon as the plane reaches 200ish knots, it doesn't want to fly anymore and you just drop from the sky;
3. As a result of the above, you end up with a slower turn and a wider turn radius. When comparing the breaks with the last one (the one with the wings on auto), you can see, both the turn rate and the turn radius are much better with the wings on auto. I could tighten the radius to less then 1000ft for short transient periods of time as opposed to no less 1220ft with the wings back;
4. Because of the unfavorable L/D, after dumping energy with the wings back and the higher stall speed you end up with, you can do about 180 degrees of such a turn before turning into a leaf on the wind. Maybe a dozen degrees more, if you enter real fast. Like 470-490 knots fast. Contrast this with the at least 270 degrees that you get, even with 400-420knots when breaking with the wings on auto, before you lose all turning ability. 
5. And this is not in the charts and on the track is the actual stability. Now this may a deciding factor on whether you find tactical application for turning with your wings back. The plane IS MUCH MORE stable with the wings back. Only MINIMAL rudder input was required to keep the desired bank angle and over flutter behavior was much more docile.

Would i recommend doing it. If your goal is to get from 500-250 knots in a very short period of time, with the minimum of leg-work, then probably. Is it absolutely needed? IMO, no. You can achieve the same goal with better AoA management as long you are proficient with rudder use. My major gripe    with using this in a dogfight is that i feel like i'm gimping myself for very little (if any) gain. With wings back at 250 knots i'm stuck in a situation i can't get out of quickly enough. It will take several seconds before the wings come forward when i select AUTO or Forward. My flaps won't be able to deploy until the wings are about half-way there. And my nose is essentially stuck until either of these comes to past. Several seconds are a microscopic time in BFM and luxury i wouldn't allow for myself. But then again, i don't have problems staying at the edge of lift with wings forward, even at 100 knots. In fact, it was last week i discovered a new Jester quote that went something like "100 knots.....falling in style", while practicing BFM against a Viper. No spin, no flameout, but it did lose that fight as you can imagine. Can you somehow combine the benefits or the early break with wings forward by say breaking to 350-300 and then switching to auto? Like we do when we break on CASE I? Possibly? Will it be worth it? Can't say. Maybe if practiced to perfection...... but i still have so much to do regarding AoA management and desent control during my first break into a merge, i'm a long way from exploiting any such advantages even if they are noticeable enough.

But the plane was always under control. But enough of me indulging in essay writing, here's the track!  
Tacview-20211009-170148-DCS-F-14 low level EVAL.zip.acmi

[maxsin72]

On 10/9/2021 at 6:35 PM, captain_dalan said:

Hey mate, sorry for the late reply. I took a week off from DCS, both the forums and the sim. I just did some tests though, as i was curious myself as to how this would work out. I had never overridden the wingsweep in DCS before. I remember experimenting with it in another sim, long time ago, and my reaction back then was, wings back and me just don't mix well

 

The tacview is bellow the short text of my impressions. All the breaks are executed with wings back at 68 degrees manual setting, except for the last one, which is executed with the wings in auto for comparison. 
1. Wings back limits the g's you have available at a given mach-airspeed; So if you want a 10g pull, you'll need to enter the break at higher airspeed then you would with the wings in auto. This is essentially by the book, that is, it fits well with the math;
2. The effective bleed rate isn't really higher. Or better said, it's higher in the first 5-6 seconds of the break (if you enter it at very high speed, i.e. over 450 knots), but because of the lower lift available, after reaching certain airspeed you just stop bleeding and sort of hang in there. For me in this configuration it was about 200-250 knots, with the former being very hard to achieve as as soon as the plane reaches 200ish knots, it doesn't want to fly anymore and you just drop from the sky;
3. As a result of the above, you end up with a slower turn and a wider turn radius. When comparing the breaks with the last one (the one with the wings on auto), you can see, both the turn rate and the turn radius are much better with the wings on auto. I could tighten the radius to less then 1000ft for short transient periods of time as opposed to no less 1220ft with the wings back;
4. Because of the unfavorable L/D, after dumping energy with the wings back and the higher stall speed you end up with, you can do about 180 degrees of such a turn before turning into a leaf on the wind. Maybe a dozen degrees more, if you enter real fast. Like 470-490 knots fast. Contrast this with the at least 270 degrees that you get, even with 400-420knots when breaking with the wings on auto, before you lose all turning ability. 
5. And this is not in the charts and on the track is the actual stability. Now this may a deciding factor on whether you find tactical application for turning with your wings back. The plane IS MUCH MORE stable with the wings back. Only MINIMAL rudder input was required to keep the desired bank angle and over flutter behavior was much more docile.

Would i recommend doing it. If your goal is to get from 500-250 knots in a very short period of time, with the minimum of leg-work, then probably. Is it absolutely needed? IMO, no. You can achieve the same goal with better AoA management as long you are proficient with rudder use. My major gripe    with using this in a dogfight is that i feel like i'm gimping myself for very little (if any) gain. With wings back at 250 knots i'm stuck in a situation i can't get out of quickly enough. It will take several seconds before the wings come forward when i select AUTO or Forward. My flaps won't be able to deploy until the wings are about half-way there. And my nose is essentially stuck until either of these comes to past. Several seconds are a microscopic time in BFM and luxury i wouldn't allow for myself. But then again, i don't have problems staying at the edge of lift with wings forward, even at 100 knots. In fact, it was last week i discovered a new Jester quote that went something like "100 knots.....falling in style", while practicing BFM against a Viper. No spin, no flameout, but it did lose that fight as you can imagine. Can you somehow combine the benefits or the early break with wings forward by say breaking to 350-300 and then switching to auto? Like we do when we break on CASE I? Possibly? Will it be worth it? Can't say. Maybe if practiced to perfection...... but i still have so much to do regarding AoA management and desent control during my first break into a merge, i'm a long way from exploiting any such advantages even if they are noticeable enough.

But the plane was always under control. But enough of me indulging in essay writing, here's the track!  
Tacview-20211009-170148-DCS-F-14 low level EVAL.zip.acmi

Very interesting and detailed, thank you one more time . To benefit of manual wings swept i think a dedicated axis is absolutely necessary but  we must also keep in mind that flight model is goings to change very soon , maybe in the next few day, the 14 october and, probably, the cat will have finally his own sustained turn rate, expecially between 320-380 knots. I'm very curious to test new FM

Edited October 10, 2021 by maxsin72

[r4y30n]

To benefit of manual wings swept i think a dedicated axis is absolutely necessary…

Even if you mapped (emergency) sweep to an axis, the actuators will lag behind your lever movements. You’d always have to be thinking ahead of the wings, like F1 drivers dealing with turbo lag in the ‘80s. Even if there was a benefit to manual control, a human will make more mistakes than the CADC.

[maxsin72]

2 minutes ago, r4y30n said:

Even if you mapped (emergency) sweep to an axis, the actuators will lag behind your lever movements. You’d always have to be thinking ahead of the wings, like F1 drivers dealing with turbo lag in the ‘80s. Even if there was a benefit to manual control, a human will make more mistakes than the CADC.

You are right, i know, but with the mouse it is even worse.

[Snappy]

On 10/5/2021 at 8:46 PM, Hummingbird said:

Did some testing today to see if the maneuver flaps/slat schedule was on point, but alas:

 

 

That's M 0.52, 18 units AoA, but zero extension of maneuver flaps/slats. According to the manual, at SL the maneuver slat/flaps should start to extend at M 0.58, be about half way extended by 0.55, and by 0.52 they should be fully extended: 

  Reveal hidden contents

 

 

Based on further testing it appears the extension schedule is incorrectly set to initiate right below M 0.52, instead of at the correct M 0.58.

 

Now forgive me if I'm mistaken, but wasn't this listed as addressed?

 

@Hummingbird could you kindly make an official bug report on this? I also thought this was adressed as fixed a few patches ago, but it wouldnt be first time , something slipped through on the actual update that gets released.

It doesnt seem to get a lot of attention in this thread.

 

Thanks,

 

Regards,

Snappy

Edited October 11, 2021 by Snappy

[captain_dalan]

9 hours ago, Snappy said:

@Hummingbird could you kindly make an official bug report on this? I also thought this was adressed as fixed a few patches ago, but it wouldnt be first time , something slipped through on the actual update that gets released.

It doesnt seem to get a lot of attention in this thread.

 

Thanks,

 

Regards,

Snappy

 

I think he had at one point. It might be buried under tons of other reports though  

On 10/10/2021 at 8:35 PM, maxsin72 said:

I'm very curious to test new FM

 

Looking forward to that as well, but looks like it's gonna take a while. 

[maxsin72]

8 minutes ago, captain_dalan said:

I think he had at one point. It might be buried under tons of other reports though  

Looking forward to that as well, but looks like it's gonna take a while. 

Fat Creason last month wrote about new FM in the october patch so i hope it will arrive

 

[Spurts]

But not for for the TF30 rework, and IIRC @captain_dalan prefers the A model.  As I understand it the TF30 will have the same tune as the F110 after this patch, so it will be a weaker B throughout the envelope.  I look forward to the TF30 rework and doing some interception tests.  Tried a test last week and even with 2 tunnel Sparrows and 2 winders I barely reached 1.6M at 40,000 and it dropped to 1.5M by 45,000.  

[Golo]

@HummingbirdI find nothing wrong with slats deployment, I tested it moment ago and slats were deploying fine for me. They just started opening at M .58 (actually looked like .6, but that is probably my reading error) when I pulled for just above 10AOA at about 1500ft. When I let go of the stick and accelerated little they closed around same M (I go by the airspeed indicator in cockpit only). Tested with F-14A in MP, latest OB.

 

Note: No idea about main flaps deployment, cant see them from cockpit.

Edited October 11, 2021 by Golo

[captain_dalan]

1 hour ago, Spurts said:

But not for for the TF30 rework, and IIRC @captain_dalan prefers the A model.  As I understand it the TF30 will have the same tune as the F110 after this patch, so it will be a weaker B throughout the envelope.  I look forward to the TF30 rework and doing some interception tests.  Tried a test last week and even with 2 tunnel Sparrows and 2 winders I barely reached 1.6M at 40,000 and it dropped to 1.5M by 45,000.  

Yep! 

[Hummingbird]

21 hours ago, Snappy said:

@Hummingbird could you kindly make an official bug report on this? I also thought this was adressed as fixed a few patches ago, but it wouldnt be first time , something slipped through on the actual update that gets released.

It doesnt seem to get a lot of attention in this thread.

 

Thanks,

 

Regards,

Snappy

 

 

I'll make a new one

[Hummingbird]

20 hours ago, Golo said:

@HummingbirdI find nothing wrong with slats deployment, I tested it moment ago and slats were deploying fine for me. They just started opening at M .58 (actually looked like .6, but that is probably my reading error) when I pulled for just above 10AOA at about 1500ft. When I let go of the stick and accelerated little they closed around same M (I go by the airspeed indicator in cockpit only). Tested with F-14A in MP, latest OB.

 

Note: No idea about main flaps deployment, cant see them from cockpit.

 

 

I only tested the F-14B, and as you can see from the pictures, it didn't function as described in the manual. 

 

The maneuver flaps & slats (they are two seperate devices) should both start to gradually/incrementally deploy at 7.7 units AoA and be at max allowed extension (which also varies with speed) by 10.5 units AoA - unless you're going faster than the M 0.58 speed limit at SL, after which point no extension is permitted. 

 

In short the speed limit schedule governs max available extension (e.g. at M 0.55 only ~50% max extension is allowed) , whilst AoA governs level of extension within the above limit. 

 

 

 

Edited October 12, 2021 by Hummingbird

[Golo]

2 hours ago, Hummingbird said:

I only tested the F-14B, and as you can see from the pictures, it didn't function as described in the manual. 

 

The maneuver flaps & slats (they are two seperate devices) should both start to gradually/incrementally deploy at 7.7 units AoA and be at max allowed extension (which also varies with speed) by 10.5 units AoA - unless you're going faster than the M 0.58 speed limit at SL, after which point no extension is permitted. 

 

In short the speed limit schedule governs max available extension (e.g. at M 0.55 only ~50% max extension is allowed) , whilst AoA governs level of extension within the above limit.

Tested it again today. They are off schedule you are right, not mach schedule they are off in AOA schedule. 

 

They open fine for me at M .58, to the correct amount by as far as I can tell by just looking at them, big BUT, they only deploy after 10.5 AOA, which is incorrect as you say they should start deploying at around 7.7 AOA.

They also seem to not close gradually, but all at once if you get below 7.7 AOA. If you stay between 7.7 and 10.5 they just stay deployed to their M schedule amount (or they will extend if you slow down if you are above 10.5 AOA)

 

I think their M scheduling is OK its the AOA schedule that is off.

Tested in A only.

Edited October 12, 2021 by Golo

[Hummingbird]

They're off in both Mach and AoA schedule in the B, where they won't open until M 0.52. 

Edited October 12, 2021 by Hummingbird

[Golo]

Im actually looking at the AOA schedule diagram and it does not say it should extend at 7.7. It shows retract at 7.7 and extend at 10.5.

So if Im reading that correctly they would only deploy if you go past 10.5 AOA (below M .58 on deck) and retract if you go below 7.7 AOA.

If that is the case they are actually operating correctly as is.

 

For A, have not tested B.

Edited October 12, 2021 by Golo

[Hummingbird]

1 hour ago, Golo said:

Im actually looking at the AOA schedule diagram and it does not say it should extend at 7.7. It shows retract at 7.7 and extend at 10.5.

So if Im reading that correctly they would only deploy if you go past 10.5 AOA (below M .58 on deck) and retract if you go below 7.7 AOA.

If that is the case they are actually operating correctly as is.

 

For A, have not tested B.

 

 

I accept it's open for interpretation, however IMHO it wouldn't make much sense, as such devices are meant to operate incrementally, otherwise you'd experience sudden noticable changes in pitch trim & moment.

 

Hence if you look at the maneuver device schedule on other 4th gen fighters, like for example the F/A-18 or F-16 (LEF & TEFs), the devices are incrementally deployed/retracted as a function of AoA & speed. Because if they deployed/retracted fully at a certain AoA, and not incrementally as AoA increased/decreased, you'd experience a very sudden & annoying disturbance in pitch.

 

 

Edited October 12, 2021 by Hummingbird

[Victory205]

The maneuver flaps are operating correctly. They extend fully at 10.5, retract at 7.7 units if the wings are at less than 50 degrees sweep.
 

Think about it, if the system extended incrementally between the two AOA values, then the flaps would be moving constantly as pilot inputs rapidly changed the AOA while between those parameters. Changing flap movement directions, stresses the actuators and causes constant pitch changes and tracking bobbles. Remember, it’s not a FBW aircraft, and the separation between the extend/retract AOA values is meant to avoid rapid or constant change in direction of the flaps for the reasons stated. 
 

The maneuver flaps would lockout in a partially extended position if an asymmetry or disagreement was detected while they were actuating, which was addressed by holding the man flap thumbwheel full forward and pressing the Master Reset switch.  This reset the logic and hopefully resulted in recovering the use of all flaps. 

[Hummingbird]

23 minutes ago, Victory205 said:

The maneuver flaps are operating correctly. They extend fully at 10.5, retract at 7.7 units if the wings are at less than 50 degrees sweep.
 

Think about it, if the system extended incrementally between the two AOA values, then the flaps would be moving constantly as pilot inputs rapidly changed the AOA while between those parameters. Changing flap movement directions, stresses the actuators and causes constant pitch changes and tracking bobbles. Remember, it’s not a FBW aircraft, and the separation between the extend/retract AOA values is meant to avoid rapid or constant change in direction of the flaps for the reasons stated. 
 

The maneuver flaps would lockout in a partially extended position if an asymmetry or disagreement was detected while they were actuating, which was addressed by holding the man flap thumbwheel full forward and pressing the Master Reset switch.  This reset the logic and hopefully resulted in recovering the use of all flaps. 

 

Ok, thank you for the clarification Victory205, it just appears strange when compared to likes of the F-16 & F/A-18 where the LEFs & TEFs move incrementally with AoA to a) maximize L/D for the given AoA and b) avoid sudden upsets in pitch moment & trim. However if that's not the way it worked in the F-14, then plz ignore that part of the bug report.

 

That said, the main issue remains, i.e. incorrect deployment vs speed, because as you can see in my pictures the devices are not fully deployed at M 0.52 & 18 units AOA as they should be according to Fig 2-51 in the manual, infact at 2% they're basically not deployed at all:

 

 

Note: Full 100% maneuver slat/flap extension is defined as "FLP 28%" in DCS, which again according to Fig 2-51 should be available at M 0.52.

 

Likewise I can't get them to partially deploy in between M 0.58 and M 0.52 (say at 0.55) either, even when pulling well over 10.5 units AoA, where again the documentation says they should be about half way out.

 

Edited October 12, 2021 by Hummingbird

[captain_dalan]

Is this purely a cosmetic issue? As in, is flap deployment on the physical model related to actual changes in the L/D ratio, that is effecting the flight characteristics, or well....not? 

[Hummingbird]

On 10/13/2021 at 3:20 AM, captain_dalan said:

Is this purely a cosmetic issue? As in, is flap deployment on the physical model related to actual changes in the L/D ratio, that is effecting the flight characteristics, or well....not? 

 

It appears to affect the FM as far as I can tell, as there's a noticable change in pitch trim when they're deployed vs retracted. I've experienced this many times at low speeds and heavily laden where the AoA requirements are higher, but never actually stopped and given it a thought until now.

Easing up in a  turn I'd wonder why the aircraft basically wanted to keep turning by itself for a bit, and then I realized it was because of the slats/flaps being deployed,,and as soon as AoA decreased below a certain point (7.7 units) all of a sudden pitch trim markedly changed and I didn't have to push the stick forward anymore to counteract the extra nose up trim generated by the slats/flaps. It's also noticable on take offs where you're not using the aux flaps, and just take off with everything in auto,, as you rotate the maneuver slats/flaps deploy and the aircraft again gains positive trim in pitch, and once airborne you need to force the nose down a bit and decrease AoA to get the devices to retract, after which point you again feel the change in pitch trim, this time it goes negative.

Hence why I'm struggling to understand why these devices didn't deploy/retract incrementally according to what Victory205 is saying, as the reason they do this on the F-16 & F/A-18 is exactly to avoid a sudden large change in pitch trim & moment, and provide the optimum L/D for the given AoA. But these are FBW aircraft, whilst the F-14 is not, so that might be part of the explanation.

But I digress, the main and very real issue that needs addressing is the incorrect speed limit schedule, as the maneuver slats/flaps clearly aren't beginning to function below M 0.58 as they should, and instead don't begin to extend until around M 0.52 where they should infact already be fully extended. 

Edited October 14, 2021 by Hummingbird

[Hummingbird]

Hopefully this won't delay the FM update too much...

[r4y30n]

 
Hence why I'm struggling to understand why these devices didn't deploy/retract incrementally according to what Victory205 is saying, as the reason they do this on the F-16 & F/A-18 is exactly to avoid a sudden large change in pitch trim & moment, and provide the optimum L/D for the given AoA. But these are FBW aircraft, whilst the F-14 is not, so that might be part of the explanation.

I assumed it was because the actuators on an FBW plane are much faster and don’t mind sudden reversals. No torque tubes to break. Doesn’t the Hornet use LEFs and TEFs to augment the ailerons?

[Hummingbird]

6 hours ago, r4y30n said:

I assumed it was because the actuators on an FBW plane are much faster and don’t mind sudden reversals. No torque tubes to break. Doesn’t the Hornet use LEFs and TEFs to augment the ailerons?

 

Maybe, I am not ajour with the limits of the actuators. But the F-16's LEF & TEF's use rotary actuators with torque tubes.

Edited October 15, 2021 by Hummingbird

[Hummingbird]

First quick results after FM change, at SL & 400 KTAS:

 

DCS F-14B STR, 55,620 lbs, 4x AIM7 + 4x AIM9, SL, 15 deg C std. day:

400 KTAS (M 0.6) = 6.3 G 

Based on the performance charts, I calculated a 6.55-6.65 G's sustained turn rate here, a ~1 G improvement from 5 kft [5.6 G], which is a similar improvement seen  for example for the F-15 & F-16.

So the initial verdict is that at 400 KTAS (M 0.6) at SL the DCS F-14B appears a bit lacking, however at 5 kft I actually managed to sustain 5.6 G @ M 0.6 (389 KTAS), as on the charts, so here it appears spot on. So I'm not sure why it's not performing as expected at SL ?  

 

 

 

 

Edited October 21, 2021 by Hummingbird