Harrier entering flat spins/ loss of control at 350Kts?

[jeffyd123]

Since a major patch a couple of months ago (cant remember which one), Ive been experiencing loss of control at hard maneuvering (approx 6 - 7G). the plane will just lose control and spiral in. I can typically feel it coming and ease up on the stick but about 25% of these departures I cant recover from. The plane is lightly loaded and fuel is usually above 5,000 lbs.

 

Is anyone else experiencing this? Is this a bug that a patch caused?

 

 

 

thanks

[mvsgas]

Are you symmetrically loaded?

[jeffyd123]

yes... im carrying gunpod and sidearms with 5000 lbs. I was testing it some more and if I slightly let the stick off it seems to correct itself, then i can pull harder again. Just seems like it shouldn't be behaving this way at 350 kts.

[mvsgas]

What was your AOA?

[Vannipo]

...

Is anyone else experiencing this?

...

 

Yes. When pullinh hard on stick on low speed, it rolls.

[NeMoGas]

I noticed this a patch or two ago, but if you pull pitch and roll at the same time until you start to shake and then quickly recenter the stick the airplane will go into a violent spin. I have not tested it in a while so it may be fixed.

 

Okay I just retested this and it still happens. Here is a video I just made, is this the issue you have?

 

Edited October 9, 2018 by NeMoGas

[NeMoGas]

This stall behavior seems quite unrealistic to me. I wonder if this is intended by RAZBAM or just another bug?

 

I would imagine that with the amount of forward speed an instantaneous spin like that would be quite hard to get into. It's like the vertical stab provides zero stability in this situation.

 

If the harrier could enter a spin like this you would think the airplane would break apart at such a high speed. If I stay below 450KIAS it tends to survive most of the time.

[Revs]

Please make a video dodging sams using this maneuver. That would be awsome to watch

[jeffyd123]

NeMoGas - It looks like you are inducing a large negative G on the airframe when you release the stick. I think it may be breaking one of the airlerons or elevators.

 

MVGas - My AoA isnt relevant I think... Im cornering with my wings perpendicular to the ground, Entering the turn at about 500kts, pulling 6 -7Gs. As the speed drops to about 350, the plane will typically want to roll inverted and starting spiraling down.

 

I can usually tell when the plane is starting to do this and If I reduce the G load, the plane will not enter the spin and I can start to pull hard again when the speed comes up. Im wondering if the wings having negative dihedral (anhedral?) has anything to do with it. Or maybe its just a bug. thanks Jeff

Edited October 10, 2018 by jeffyd123

[mvsgas]

 

MVGas - My AoA isnt relevant I think... Im cornering with my wings perpendicular to the ground, Entering the turn at about 500kts, pulling 6 -7Gs. As the speed drops to about 350, the plane will typically want to roll inverted and starting spiraling down.

 

AOA is always relevant. Your wing position in reference to the ground has nothing to do with AOA.

11.4.1.2 AOA Limited Aircraft

At tactical speeds below 400 KCAS below 15,000 feet or above 15,000 at less than tactical KCAS, the aircraft becomes more “traditionally”AOA limited. Pilots should befamiliar with this type offlight regime from their earliest days of flight training. There are two factors that can cause the AV--8B pilot maneuvering and stability problems in this regime.

11.4.1.2.1 AOA Lag

During high AOA and/or g onset rates the HUD AOA has been seen to lag by up to 5 units. Therefore, as a pilot is maneuvering in this regime if an attempt is made to pull instantaneously to a specific AOA the True AOA of the aircraft will exceed the HUD displayed AOA. If the True AOA overshoots the lift limit the aircraft will enter stall or a departure.

Loaded Rolls

Loaded rolls create stability problems in several ways. First, if the AOA is just beneath the lift limit,rolling the aircraft increases the camber of the up--rolling wing which may cause either laminar or shock--induced flow separation, resulting in a loss of lift and an increase in drag away from the initial roll direction. At lower IMNs this will result in wing rock; at higher IMNs it can accelerate immediately into a departure. Next, rolling the aircraft with AOA

present increases the AOA on the down rolling wing, which can be thought of as “roll friction” because it is opposite the initial roll direction. Also, loaded rolls will induce the detrimental effect of kinematic coupling that turns AOA into sideslip. The result of these effects is that a loaded roll that creates sideslip and rolling moments beyond the ability of DEPRES to compensate will lead to a departure.

1.4.4.3 Angle of Attack Sensitivity

As airspeed decreases, AOA increases. It is important to recognize the aircraft’s sensitivity to AOA. At slow airspeeds, small amounts of back--stick pressure and in some cases the release of small amounts of forward--stick pressure may create a high AOA excursion. This may in turn lead to wing rock, directional instability, which the pilot will recognize as a wandering sideslip vane, and a possible departure from controlled flight. The target AOA during any slow speed flight should be 10 to 15 units AOA, although 15 to 20 units may be acceptable under certain

circumstances. AOA will always increase with roll when any sideslip is present and can rapidly increase as afunction of sink rate without significant pilot aggravation. During slow speed flight when the flight controls provide reduced effectiveness, AOA management becomes critical.

At low AOA, the Harrier exhibits dynamic directional stability -- that is, if the nose becomes pointed out of the relative wind, it will tend to correct itself. The vertical tail is the big contributor here; when it gets kicked out of the relative wind, it is simply a wing on its side. It produces a net lift in the direction that puts the nose back into the relative wind.

At high AOA, however, the fuselage essentially blocks the vertical tail from much of the relative airflow, so the tail becomes largely ineffective. The tail’s lack of effectiveness at high AOA causes a loss of directional stability.

 

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Edited October 10, 2018 by mvsgas

[al531246]

It's absolutely a bug in the FM. You'd have a hard time getting any aircraft to depart as violent as that.

[jeffyd123]

Ahh OK.... Thanks mvgas.... I mistakenly assumed the AoA was more relevant to lower airspeeds.

 

Ill keep my speed above 400 when Im cornering.

 

 

thanks for the help

 

 

Jeff

[jeffyd123]

It's absolutely a bug in the FM. You'd have a hard time getting any aircraft to depart as violent as that.

 

 

 

 

thats what I was thinking too. But, I have to admit the FM is indicating the onset of a stall and the harrier has those tiny little wings. Many of the spins ive had I could recover from too.

 

On the other hand, Some of the FM behaviors do seem unrealistic and need more tuning IMO.