Are those maneuvers doable in the F1 in DCS ?

[cmbaviator]

Starting from 41:10
 

 

[E69_DaniV]

Well, translating what the video tells, I asume that those are stall tests, in different altitude and speed patterns.

They're mainly induced manouvers to cause/start various stall situations and video reporting the different ways that pilot uses to recover to stable flight, (recorded from different cameras on cockpit hud, rear seat, and other aircrafts).

These reactions would have to be tested in the configurations and altitudes/speeds indicated in the video if you want to simulate perfectly the evolutions of the aircraft during the stall in the Sim... (never tried, would do, that´s something to test!)  I don't think they can be of any use in combat or any other situation (?) unless stall recovery practice.

I think it is useful to see how it recovers the stalls.

Nice & interesting vid, by the way!

[Morskoul]

Correct, this is part of flight tests done to caracterize aircraft stability and recovery capability.

I am not qualified to say if the FM is realistic or not,but such behavior appears with the Aerges F1. Usually you will enter it at high altitude and pulling hard the stick in a turn (dynamic stall).

You can see that one test is done at 45'000ft (when you can see the backseat stick moving on its own). It looks easier to recover in the video that the feeling I have in DCS (in fact it may depends if you quickly release the stick when it happens). And it is said "In some case the engine can stall and flameout". Right now, the stall almost always happen for me.

That being said, the module is early access and the flight model changes with every release. I found the first  F1 release very tolerant (you was able to pull whatever you want on the stick, the wings were stalling without entering any spin). The last time I tried was before 2.8 release.

[sedenion]

I would say this kind of lose of control is even too much easy to produce in the DCS Module... You practically can't apply both pitch up and bank without generating aircraft destabilisation and spin departure...

[Thinder]

On 11/13/2022 at 12:46 PM, cmbaviator said:

Starting from 41:10
 

 

At 3:00, those spins are test flights, not everyone can do them and go away with it...

[Dragon1-1]

On 11/19/2022 at 2:30 PM, sedenion said:

I would say this kind of lose of control is even too much easy to produce in the DCS Module... You practically can't apply both pitch up and bank without generating aircraft destabilisation and spin departure...

This is correct, even in the F-16, if you do it at the wrong moment, you'll end up in trouble. Roll inputs when pulling up are a bad idea.

[Thinder]

On 1/12/2023 at 9:34 PM, Dragon1-1 said:

This is correct, even in the F-16, if you do it at the wrong moment, you'll end up in trouble. Roll inputs when pulling up are a bad idea.

Sure thing but not for the same reason... On some aircraft like the F-16 and some Sukois, in the transonic regime with an assymetric load, you just can't pull Gs because the aircraft will depart, so there is a zone where they are g-limited in those conditions.

With the F1 it's another story, the spoilers always generate some amount of induced yaw but it seems that with this module the effect is way overdone, plus it doesn't carry more than a Sidewinder or Matra Magic on the wing tips with negligible drag, while the USAF did find funny to fit an AIM-120 there for the pilots to sweat it when caught unaware.

The aerodynamics and drag of external load in those conditions are different.

As for the use of rudder at high AoA, the problem only really occurs at lower speed when you are close to a stall, then  you need to use the rudder or one wing will drag more than the other, one will have less lift, stall earlier and you risk an asymmetrical departure, we actually learn that even before landing on trainers because you'll have to flare them so the problem might occur.

Dynamic stall at high speed, I wouldn't use the rudder, it is speed limited, better keep the controls at neutral minus the pitch that you'll need to apply down to reduce AoA.

So both modules are not really close to the real thing just yet...

 

Edited January 21, 2023 by Thinder

[Dragon1-1]

I was actually talking about the violent departure you get when rolling and pulling up at the same time at insufficient speed, not when transsonic. Large pitch and roll inputs at the same time are bad regardless of which plane you're in.

[Thinder]

1 hour ago, Dragon1-1 said:

I was actually talking about the violent departure you get when rolling and pulling up at the same time at insufficient speed, not when transsonic.

That's precisely the same thing, except that the F16 module has this out of the area of its flight envelop where it is prone to depart, its FBW system is programmed to prevent departures of this kind and it would normally work out of this particular area.

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Large pitch and roll inputs at the same time are bad regardless of which plane you're in.

That's not accurate. It depends largely on the aerodynamic features of each aircraft, they are all different although some aerodynamic features provide with more resistance to departure than other, by memory, the F-16 is limited to 29° AoA because of risks of deep stall but its FBW will prevent you to get there, Roll will not be such an issue for the same reasons.

With close-coupled canards, the Gripen and Rafale are naturally spin resistant even with asymmetrical loads to which adverse effects they are a lot less sensitive than conventional tailed configuration or long moment arm canard configuration such as X-31 or Eurofighter Typhoon.

During test flight on the Gripen prototype, they relaxed the FCS limits, took it to the vertical down to 250Kt, pulled like donkeys on the stick so as to reach 90° AoA, then locked the stick full deflection in ROLL, which triggered an induced yaw moment with an amplitude of 90°/sec, the rotation was stopped by applying opposite roll deflection.

Rafale too managed post-stall maneuvers during high AoA testing, reaching 100° AoA and -40Kt and it still can roll at speeds below 80Kt with its actual limiter, as demonstrated during an ATC vs a F-22, there is no speed limiter on Rafale and during mock combat vs Mirage 2000 they flew it as low as 18kt (flew it mean under full control authority).

The aerodynamic are very different, there are no vortex breakdown around the ailerons at extreme AoA because the canard tip vortexes energize the boundary layer, so they can retain full control authority at very high AoA.

The reason why their are artificlally limited by their FCS is to avoid your average squadron jockey to loose it due to spacial disorientation, but also because the Air Force stick to old-boy-Boyd high energy management for which those aircrafts are particularly well suited, they don't suscribe to post-stall maneuvers for combat.

The canard triggers vortex lift on the delta much lower on the AoA scale so they experience  much less induced drag for an equivalent amount of lift and alternatively recover energy much faster than conventional deltas or long moment arm.

The F-22 has this vortex breakdown issue and DRYDEN recommended a redesign of the ailerons from YF-22 to minimize vortex bashing due to them breaking down over the ailerons, it needs TVC to roll the same way at high AoA and if you look carefully both F-22 and Rafale have the same wing plan with 70°  LEX and 48° wingsweep.

So reality is not fully represented in both Mirage F1 and F-16 modules in this case, you should able able to handle them both a lot more firmly than the actual module flight envelop allows for, but the issue of departure in transonic regime of the F-16 remains, it is the result of an aerodynamic solution, it is prone to depart in this flight regime "if mishandled".

 

 

Edited January 21, 2023 by Thinder

[Dragon1-1]

55 minutes ago, Thinder said:

That's precisely the same thing, except that the F16 module has this out of the area of its flight envelop where it is prone to depart, its FBW system is programmed to prevent departures of this kind and it would normally work out of this particular area.

No it's not. 250kts at medium altitude is nowhere near transsonic. Try doing a pirouette (pull up vertically, roll 90 degrees and pull down) with insufficient airspeed and hamfisted control inputs. The FBW on the Viper can't ensure stability if more than one limiter is hit at the same time. AoA and roll limiters work well on their own, but when you hit the AoA limiter and roll at maximum rate, you'll end up in a seriously nasty condition known as a deep stall. This has nothing to do with transsonic regime, and everything to do with the FLCS for the Viper being developed in the 70s, when this was a very new thing. It's a simple, but clever set of limiters and control curves, not some magic computer thingy that prevents every input that'd get you in trouble.

The point is: nasty behavior when doing pitch and roll at the same time, particularly large inputs in both, is expected and realistic. Don't do it and you'll have one less way to end up in a flat spin or worse.

Edited January 21, 2023 by Dragon1-1

[Thinder]

It is, it's departure like it or not.

You could try all you want, on the real aircraft, its FCS will prevent you to do it, as simple as that...

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limiter and roll at maximum rate, you'll end up in a seriously nasty condition known as a deep stall.

You visibly have no clue what you're talking about, the F-16 FCS even developed in the 70 was precisely designed to prevent the pilot to put the aircraft in the attitude you mention, so in this module it simply shouldn't happen.

Deep stall means that you'll lose the pitch control authority because the elevators are shielded from the airflow by the wing at a given AoA and it doesn't imply any roll input, it happens to other aircraft in particular those with high mounted elevators without any other axis than pitch being involved.

i'm done arguing with a guy who doesn't know his A from A to Z in the subject, I have flown aircraft from 1975 and before it leaned enough theoretical to know those things only to have access to a grant in order to pay for my flight hours, perhaps you should start by learning instead of arguing in forums...

 

 

Edited January 21, 2023 by Thinder