Gripen pulling -3g to +9g Video

[A.P. Richelieu]

 

[vostok]

Swedish engineers can be proud - this is probably the best single-engine fighter of our days. And one of the best at all.

 

[AmirPatriot]

Tough pilot. -3G and +9G is no joke. Most people would black out at those levels.

 

[Hassan Guy]

i could probably pull 9gs

 

[egodoc222]

Tough pilot. -3G and +9G is no joke. Most people would black out at those levels.

Yeah red out too!

 

[TOPGUN]

Tough pilot , great aircraft no doubt was always a fan.

 

[Thorough Pro]

Awesome video. Beautiful city down there.
Shot by Sony Action Cam, excellent resolution, and clarity.

 

[Gomig-21]

Interesting breathing he's doing throughout the whole flight, Rich, not just during the higher Gs. Does this seem a bit excessive to you, all the breathing he's doing? At one point he sounds like he's in pain @0:49. He's only doing 2-3 Gs and he sounds like he's hurting. You usually hear them breathing and grunting once they're in the higher G's. I know US pilots do the "hick" breathing when they sustain higher Gs while holding their breath and clinching their abdomen to keep the blood from leaving their brain. Maybe it's a different thing going on here or some type of breathing exercise. He is doing a lot of maneuvers one after the other.

Couple of interesting things is he pulls a light negative G @0:20 during that barrel roll right after he pulls the gear up. And before that at lift off, it's amazing how it doesn't take much of that stick moving back to lift the front nose. Looks like he barely pulls it back 1 or maybe 2 centimeters and the response is instantaneous and drastic.

There's a tutorial for flying a MIG-15 (yes I know, it's very old lol) but the pilot's explaining the same principle that at takeoff, if you pull the stick too far back beyond that tiny little bit that's needed, the aircraft will actually do a back flip. That's how responsive the airframe is to those movable surfaces, especially the horizontal stabs. Even with limiters in the FBW software in these new jets and the sensitivity to responses to the pilot's command, there seems to be an inherent danger to too much movement of the stick.

 

[A.P. Richelieu]

Awesome video. Beautiful city down there.
Shot by Sony Action Cam, excellent resolution, and clarity.

I believe it is Linköping, 200 km south of Stockholm, where they design and build the plane

Interesting breathing he's doing throughout the whole flight, Rich, not just during the higher Gs. Does this seem a bit excessive to you, all the breathing he's doing? At one point he sounds like he's in pain @0:49. He's only doing 2-3 Gs and he sounds like he's hurting. You usually hear them breathing and grunting once they're in the higher G's. I know US pilots do the "hick" breathing when they sustain higher Gs while holding their breath and clinching their abdomen to keep the blood from leaving their brain. Maybe it's a different thing going on here or some type of breathing exercise. He is doing a lot of maneuvers one after the other.

Couple of interesting things is he pulls a light negative G @0:20 during that barrel roll right after he pulls the gear up. And before that at lift off, it's amazing how it doesn't take much of that stick moving back to lift the front nose. Looks like he barely pulls it back 1 or maybe 2 centimeters and the response is instantaneous and drastic.

There's a tutorial for flying a MIG-15 (yes I know, it's very old lol) but the pilot's explaining the same principle that at takeoff, if you pull the stick too far back beyond that tiny little bit that's needed, the aircraft will actually do a back flip. That's how responsive the airframe is to those movable surfaces, especially the horizontal stabs. Even with limiters in the FBW software in these new jets and the sensitivity to responses to the pilot's command, there seems to be an inherent danger to too much movement of the stick.

The first two crashes were due to pilot induced oscillation, but then they fixed the flight control system.
They figured out that when the aircraft made a sharp turn and flew into its own turbulence over Stockholm, the pilot was moving the stick in a pattern similar to whipping cream to correct the problem. This overloaded the CPU so the low level control loop did not get any CPU cycles.

 

[Windjammer]

Excellent piece of demo and footage captured simultaneously from air and ground, however i am dismayed as why was the pilot breathing so heavily even at 1G.

 

[Gomig-21]

This overloaded the CPU so the low level control loop did not get any CPU cycles.

I remember reading about that 1989 landing crash. The way it clipped its wings to the ground and went into that violent rollover was brutal. The way the engine flames out from debris entering the intakes is tremendous.

BTW, the same exact thing happened with the YF-22 in 1992, as far as the cause, but that test pilot was lucky that the aircraft just belly landed as a result of the PIO.

Pilot induced oscillation can actually still happen even with all the advanced flight control systems in today's aircraft if the pilot doesn't overreact to any of the aircraft's slight lags at low speed. It's different at high speeds because the flight controls surfaces react much faster at those air speeds. At lower speeds, there's a lag time in the reaction of the aircraft to the movement of the flight control surfaces and the pilot needs to be patient with that lagging. It's almost like his reaction time has to change in conjunction to the aircraft's speed.

The other Gripen crash is a bit bizarre. Flying into his own turbulence causing the aircraft not to react to the pilot's stick commands is amazingly strange. You can see it suddenly go into a full pitch up prior to him ejecting.

This is also quite the testament to what the Russians do with their Sukhois. When Pugachev first attempted the Cobra, he said he had to turn off the AoA limiter to allow him to pull the stick back far enough to get the nose to pitch up like it does. The trick was, he had to maintain adequate airspeed and altitude to pull that off. Below a certain speed and at a lower altitude and he would've stalled the AC and plummeted to the ground.

 

[A.P. Richelieu]

I remember reading about that 1989 landing crash. The way it clipped its wings to the ground and went into that violent rollover was brutal. The way the engine flames out from debris entering the intakes is tremendous.

BTW, the same exact thing happened with the YF-22 in 1992, as far as the cause, but that test pilot was lucky that the aircraft just belly landed as a result of the PIO.

Pilot induced oscillation can actually still happen even with all the advanced flight control systems in today's aircraft if the pilot doesn't overreact to any of the aircraft's slight lags at low speed. It's different at high speeds because the flight controls surfaces react much faster at those air speeds. At lower speeds, there's a lag time in the reaction of the aircraft to the movement of the flight control surfaces and the pilot needs to be patient with that lagging. It's almost like his reaction time has to change in conjunction to the aircraft's speed.

The other Gripen crash is a bit bizarre. Flying into his own turbulence causing the aircraft not to react to the pilot's stick commands is amazingly strange. You can see it suddenly go into a full pitch up prior to him ejecting.

This is also quite the testament to what the Russians do with their Sukhois. When Pugachev first attempted the Cobra, he said he had to turn off the AoA limiter to allow him to pull the stick back far enough to get the nose to pitch up like it does. The trick was, he had to maintain adequate airspeed and altitude to pull that off. Below a certain speed and at a lower altitude and he would've stalled the AC and plummeted to the ground.

The problem with the second crash was not that it did not react to the pilot stick.
The high level control loop decodes the stick movement and generates commands to the low level control loop to change or maintain the position.
The low level control loop primary job is to maintain stability and accept commands from the high level control loop to change the direction of the aircraft.
It has to do with priorities and scheduling of the two loops in the Real Time Operating System.
It was known by the designers that if the pilot would do *a lot of* stick movements in a short time, the CPU would be overloaded, and due to the scheduling algorithm, the low level control loop would not run enough to maintain stability of the aircraft.
They could not envisage a situation where such stick movements would happen, so they did not tell the pilot about it.
If he had let go of the stick, the aircraft would have recovered.
In fact, if You check out longer videos of the second crash, you see the control surfaces working hard and at the point of the crash, the aircraft is in ”level flight”.

 

[Gomig-21]

The problem with the second crash was not that it did not react to the pilot stick.
The high level control loop decodes the stick movement and generates commands to the low level control loop to change or maintain the position.
The low level control loop primary job is to maintain stability and accept commands from the high level control loop to change the direction of the aircraft.
It has to do with priorities and scheduling of the two loops in the Real Time Operating System.

Interesting. So what was the original problem from the turbulence that caused the pilot to whip-cream the stick? There must've been something that instigated the need for him to over-correct the aircraft. Either the aircraft's sensors detected something with the turbulence that caused the computer to take control and stopped responding to the stick movement or something else.

If I'm not mistaken, it seems there were 2 problems.
1) The FBWS and control surfaces stopped responding to the pilot's stick input because of the turbulence and
2) the pilot's over-correcting and whip creaming of the stick overloading the CPU.

 

[A.P. Richelieu]

Interesting. So what was the original problem from the turbulence that caused the pilot to whip-cream the stick? There must've been something that instigated the need for him to over-correct the aircraft. Either the aircraft's sensors detected something with the turbulence that caused the computer to take control and stopped responding to the stick movement or something else.

If I'm not mistaken, it seems there were 2 problems.
1) The FBWS and control surfaces stopped responding to the pilot's stick input because of the turbulence and
2) the pilot's over-correcting and whip creaming of the stick overloading the CPU.

The turbulence made the aircraft deviate from the intended flight path,
so the pilot started correcting, but the deviation varied, so the nose started pointing all over the place, and the pilot did multiple corrections.
Due to overloading the CPU, the control surfaces did not get the commands needed
to correct the deviation, and the aircraft superstalled, and the pilot decided to call it a day.