It would seem to me that, with sufficient altitude, if you got a real plane into a deep stall and it was mushing and losing altitude fast the solution might be to get the nose down to build up airspeed. Once you're significantly above stall speed, pull back slowly to level off.

With MSFS 2024, it's not so forgiving. (It seems to me) that the way stalls are modeled, I can be nose down, full power, elevator neutral, and well above the stall speed with no pitch control at all. Of course, this odd behavior doesn't seem to show up in small aircraft with light wing loading.

I'm still testing this so it would be premature to declare a "bug".

But I would like to know if anyone else is seeing this.

P.S. I'm seeing this in Asobo 2024 aircraft.

1 hour ago, kcmo said:

It would seem to me that, with sufficient altitude, if you got a real plane into a deep stall and it was mushing and losing altitude fast the solution might be to get the nose down to build up airspeed. Once you're significantly above stall speed, pull back slowly to level off.

Not necessarily. That's the trouble with deep stalls: The turbulent wake from the main wing is blanketing the horizontal stabilizer and can make the elevator ineffective to a point where it is impossible to recover from the stall:

https://en.m.wikipedia.org/wiki/Stall_(fluid_dynamics)#Deep_stall

What aircraft type(s) are you seeing this on? Can you post a video where you're in a deep stall?

Martin,

Thanks for taking an interest. I'll study this more to record the flight data.

I first noticed this playing around with the F-18. I would be nose down, in full afterburner, airspeed higher than 200, elevators neutral. Pulling back on the stick should allow me to start leveling out right?

I mean with the plane in the above condition, I wouldn't think the angle of attack would be that high.

What caused me to post this was that I had just seen the same behavior in the A400.

But as I say, I'll collect some data.

Do you know what is definition of "deep stall" ? It has to do with certain kind of airplanes that you are not suppose to stall on the first place. Here is good read about it https://www.rbogash.com/Safety/deep_stall.html

2 hours ago, kcmo said:

I first noticed this playing around with the F-18. I would be nose down, in full afterburner, airspeed higher than 200, elevators neutral. Pulling back on the stick should allow me to start leveling out right?

You're saying you're faster than 200 knots -- by how much? 200 knots isn't very fast at all for an F-18 flaps up. I assume you'd be stalled, or close to it, at that airspeed.

You say you're nose down and in full afterburner, but not able to pull the nose up? Is this a steady state (i.e. is nothing changing about your attitude and airspeed)? That would definitely sound strange -- I don't see how you wouldn't be accelerating in that case.

Just to make sure: Are you holding a constant heading? (I.e. you're not in a spin?)

33 minutes ago, sd_flyer said:

Do you know what is definition of "deep stall" ? It has to do with certain kind of airplanes that you are not suppose to stall on the first place. Here is good read about it https://www.rbogash.com/Safety/deep_stall.html

It's complicated. While some use "deep stall" specifically to mean an unrecoverable condition (most typically seen on T-tail airplanes where the wake can blanket the horizontal stabilitzer and make the elevator ineffective), others use the term simply to mean flight well beyond the critical angle of attack. In the figher community, this is also often known as "high AOA". (See also the discussion in the Wikipedia article I linked to earlier.)

For clarity, I'll use the term "unrecoverable deep stall" to refer to the former condition.

I wouldn't expect the F-18 to be susceptible to an unrecoverable deep stall as it doesn't have a T-tail.

The A400M does have a T-tail, so it's likely that it is susceptible to an unrecoverable deep stall -- though only if the FBW protections are degraded.

As I say, it would be useful to see video to be able to tell exactly what you're experiencing.

Edited December 24, 20241 yr by martinboehme

A better understanding of stalls would help here.  Some pilots think of a stall in terms of airspeed, but this isn't correct.  An airplane does not stall because it slows to any particular airspeed, nor does it recover because it accelerates beyond that airspeed.  Airspeed is just a related element, but not the direct cause of the stall.

An airplane stalls because the critical angle of attack of the wing is reached.  It recovers from the stall when you reduce AoA below that critical value. 

AoA is a function of speed AND load factor.  The reality is that an airplane can be stalled at any airspeed, in any attitude.  You can be stalled in a 172 pointed straight down at 100kts... If you're pulling hard enough.  Conversely, you can be pointed straight up at zero airspeed and not stalled - if you're in a bunt at zero g.

In your example, 200kts in a clean swept wing high perf jet is not a lot of airspeed buffer (though in a real hornet, the FCS will extend flaps and LEDs as necessary for some stall buffer at higher AoA.).  That said, I doubt it's modeled very well in 2024 and I know it isn't in 2020.  The -18 flight model in 2020 was pretty toy-like, so I wouldn't use that as much of an example.

 

Edited December 24, 20241 yr by Stearmandriver

Thank you all for your EXCELENT lessons in aerodynamics. I'll bounce all of it against what I see in my testing.

7 hours ago, Stearmandriver said:

A better understanding of stalls would help here.  Some pilots think of a stall in terms of airspeed, but this isn't correct.  An airplane does not stall because it slows to any particular airspeed, nor does it recover because it accelerates beyond that airspeed.  Airspeed is just a related element, but not the direct cause of the stall.

An airplane stalls because the critical angle of attack of the wing is reached.  It recovers from the stall when you reduce AoA below that critical value. 

AoA is a function of speed AND load factor.  The reality is that an airplane can be stalled at any airspeed, in any attitude.  You can be stalled in a 172 pointed straight down at 100kts... If you're pulling hard enough.  Conversely, you can be pointed straight up at zero airspeed and not stalled - if you're in a bunt at zero g.

In your example, 200kts in a clean swept wing high perf jet is not a lot of airspeed buffer (though in a real hornet, the FCS will extend flaps and LEDs as necessary for some stall buffer at higher AoA.).  That said, I doubt it's modeled very well in 2024 and I know it isn't in 2020.  The -18 flight model in 2020 was pretty toy-like, so I wouldn't use that as much of an example.

 

When I was studying for my PPL, may years ago, I got a book called Stick and Rudder by Langewiesche which I read cover to cover several times. I always remember that he stated that  you could put a piece of tape on the yoke post just prior to the aircraft stalling , and if you never went past that tape when pulling on the yoke, you would never stall the aircraft no matter what your airspeed was. I used to think about that everytime I would slow fly. 

3 hours ago, Bobsk8 said:

When I was studying for my PPL, may years ago, I got a book called Stick and Rudder by Langewiesche which I read cover to cover several times. I always remember that he stated that  you could put a piece of tape on the yoke post just prior to the aircraft stalling , and if you never went past that tape when pulling on the yoke, you would never stall the aircraft no matter what your airspeed was. I used to think about that everytime I would slow fly. 

You sure that's from Stick and Rudder?  It's been years since I read it but it doesn't seem likely Langewiesche would say something like that.  Seems like it wouldn't really work; it would depend on aircraft loading, trim state, airspeed etc.  It would only ever work if you only flew the airplane solo (or always with the same loading anyway), were perfectly in trim, and at 1g.  At that point, you might as well just use airspeed as a stall reference. 

What's really needed (and is starting to be added) is an AoA indicator.  I've conducted UPRT in a super decathlon with an AoA indexer and it's a huge visual aid for folks learning how airspeed and load factor (and coordination or lack thereof) go together to affect AoA.

 

1 hour ago, Stearmandriver said:

You sure that's from Stick and Rudder?  It's been years since I read it but it doesn't seem likely Langewiesche would say something like that.  Seems like it wouldn't really work; it would depend on aircraft loading, trim state, airspeed etc.  It would only ever work if you only flew the airplane solo (or always with the same loading anyway), were perfectly in trim, and at 1g.  At that point, you might as well just use airspeed as a stall reference.

I'm pretty sure it's not dependent on airspeed or load factor. That's the beauty of it. Fore-aft stick position really has a much more direct correspondence with angle of attack than airspeed. It is dependent on CG (pretty obviously), but unless you have a trimmable horizontal stabilizer, it shouldn't be dependent on trim position. If you think about it, for aircraft that use a trim tab, if you keep the stick in the same position, the only thing that trim really does is change the stick load -- but a given stick position always corresponds to the same position of the elevator.

Edited December 24, 20241 yr by martinboehme

1 hour ago, Stearmandriver said:

You sure that's from Stick and Rudder?  It's been years since I read it but it doesn't seem likely Langewiesche would say something like that.  Seems like it wouldn't really work; it would depend on aircraft loading, trim state, airspeed etc.  It would only ever work if you only flew the airplane solo (or always with the same loading anyway), were perfectly in trim, and at 1g.  At that point, you might as well just use airspeed as a stall reference. 

What's really needed (and is starting to be added) is an AoA indicator.  I've conducted UPRT in a super decathlon with an AoA indexer and it's a huge visual aid for folks learning how airspeed and load factor (and coordination or lack thereof) go together to affect AoA.

 

Read it 45 years ago, might be mis rembering it.

1 hour ago, martinboehme said:

I'm pretty sure it's not dependent on airspeed or load factor.

We call it an accelerated stall when we view the load factor. You may be at a higher speed and make an abrupt input and get into the tickle. This would happen a lot when doing steep turns in a DC10. You already have the tickle during the steep turn and some would make it worse by adding sharp inputs to keep the nose up. It's a good way to get into a secondary too. Also, nothing like having the urge to get your nose on another aircraft and input aggressively and have the jet roll off🤣. Patience and rudder is key🤣.

Edited December 25, 20241 yr by G550flyer
edit

Two things - I'd listen to Stearman - He's a real pilot (as opposed to those who claim that title after staying at a Holiday Inn) and he's forgotten more about flying than most of us will ever know - PPL or not. 2nd, you're expecting a lot from an Asobo default aircraft. That's like expecting your dog to pass a test to be a Rhodes Scholar. 

Thanks for all your help, guys!

I put on my test pilot hat this morning and ran the test again on the f-18. Twice I couldn't get it to recover.

Then I decided to change my primary "recovery indicator" from the airspeed indicator to the AOA indicator. 

I am humbled to see that, when trying to recover, you can reach a flyable airspeed and yet STILL be flying at too high an AOA.

I thought I was reaching a reasonable attitude to start pulling in back pressure, but I had been ignoring the fact I could be at full power with nose down, and STILL have to wait until the relative wind returns to a laminar flow over the wings.

Thanks again for walking me through this...

On 12/25/2024 at 3:09 AM, Mike T said:

He's a real pilot (as opposed to those who claim that title after staying at a Holiday Inn)

I did stay at a Holiday Inn and I did get my pilot license, a few years later. obviously it did work.

Edited December 27, 20241 yr by turbomax