Gulfstream G650 Crash - Roswell - 4 Dead

[hawk37]

A minor mishap transpired during G-IV "unstick" testing. The jet partially stalled and banged a wingtip

Thanks GVFlyer.

Would fly by wire prevent this high an angle of attack on a G650?

Or maybe envelope protection is normally diabled this close to the ground?

[barit1]

NTSB preliminary, apologies if already posted.

[GVFlyer]

Would fly by wire prevent this high an angle of attack on a G650?

Or maybe envelope protection is normally diabled this close to the ground?

In that you're comparing dramatically different wings, it's really comparing apples to orangutans unless you're only conceptionally speaking. In that case it would be determined by the FCS control laws and whether it was a hard stop or soft stop system.

[Volume]

Or maybe envelope protection is normally diabled this close to the ground?

Envelope protection is probably disabled during flight testing to determine the borders of the envelope. Thats what testing is for.

[specialbrew]

Very sad indeed.....

NTSB Issues Preliminary Report on G650 Crash
The flight-test Gulfstream G650 that crashed in Roswell, N.M., on Saturday “was performing a takeoff with a simulated engine failure to determine takeoff distance requirements at minimum flap setting” at the time of the accident, according to an NTSB preliminary report released this morning. The two test pilots and two technical specialists aboard were killed in the crash, and the twinjet was destroyed. The report said the aircraft slid approximately 3,800 feet from where the first wing scrapes were seen on Runway 21 at Roswell International Air Center Airport, and struck several obstructions before it came to rest on fire, but upright about 200 feet from the airport’s control tower. In a statement issued this morning, Gulfstream pledged its cooperation with the NTSB. “We are participating fully in the aircraft investigation, and will resume flying the G650 only when we and the [FAA] are satisfied it is safe to do so,” said Pres Henne, Gulfstream’s senior vice president for programs, engineering and test. The airframer noted that all other certification and production work on the program would continue. Earlier this week, Jay Johnson, chairman and CEO of parent company General Dynamics expressed his sympathy for the families of the crew, along with his confidence in the 650 program. The accident G650, S/N 6002, had accumulated more than 425 flight hours since it first flew in February last year.

[787FOCAL]

One of the pilots was named Dave Mccollum in case anyone knew him.

[GVFlyer]

David McCollum was a flight-test engineer.

[Graybeard]

That name Dave McCollum is spookily similar to Dave McGollum (sp?), who was copilot of the flight test Canadair that was lost over Edwards in about 1980. The FTE bailed ok; Dave bailed almost too late, and was in hospital six months recovering from broken legs, etc. The Capt didn't get out. I met Dave in about 1983, when he was FAA pilot DER.

GB

[theficklefinger]

Maybe someone can elaborate on 'unstick testing'.

Would that be similar to holding the yoke back on departure and trying to find the lowest airspeed the plane comes off into ground effect? Or is that more of a dynamic yank back type of maneuver to get the plane into ground effect?

Also, 'envelope protection'...that set up in a flight computer somewhere in fly by wire aircraft?

[FCeng84]

Vmu - Minimum Unstick Velocity

I have no connection to Gulfstream and thus my comments are not specific to this event.

Vmu is the minimum unstick speed. It is the minimum speed at which the airplane can generate enough lift with its tail on the ground to takeoff. This speed ends up being the basis for some of the takeoff operational speeds and associated field length requirements.

The testing to demonstrate / determine Vmu involves rotating early and having the tail in contact with the ground at the time that liftoff occurs. The trick is to get the tail down at just the right moment so that it does not drag too much and yet the demonstrated Vmu is as low as possible. Tail skids (a suitable block of wood) are often used during this testing.

I am aware of control law provisions on non-Gulfstream fly-by-wire airplanes that reduce the likelihood of an inadvertent tailstrike during takoff, but I don't know of any that completely prevent hitting the tail. To do so would be to reduce the available performance of the airplane and thus in my opinion would not be wise.

[GVFlyer]

That name Dave McCollum is spookily similar to Dave McGollum (sp?), who was copilot of the flight test Canadair that was lost over Edwards in about 1980. The FTE bailed ok; Dave bailed almost too late, and was in hospital six months recovering from broken legs, etc. The Capt didn't get out. I met Dave in about 1983, when he was FAA pilot DER.

GB

Dave Gollings, who since his retirement from the FAA has been a consultant DER, was the co-pilot on this CL-600 certification flight.

The jet was Challenger serial number 1001. During stall testing the jet pitched-up and could not be returned to controlled flight without deploying the stall chute.

The least desirable stall characteristic any jet can have is to pitch-up when it stalls, the reason being that the wing can blank out the horizontal stabilizer causing a loss of pitch control and the ability to get the nose down to fly out of the stall. A stall chute, when deployed, gets the nose down to reestablish airflow over the tail and subsequent pitch control. It is then cut away.

The crew could not get rid of the stall chute after getting the nose down. Subsequently, there was insufficient thrust available for sustained flight and controllability was suspect. The three crew members bailed out. Pilot Eric Norman Ronaasen died when his chute did not deploy. Dave who was functioning as the scribe received minor injuries. Flight-test engineer Bill Scott was not injured.

This stall characteristic seems to be emblematic of the breed. During Global Express development while demonstrating recovery from unaccelerated aerodynamic stalls with a FAA test pilot at the controls, the Global also pitched-up and could not be returned to controlled flight without deploying the stall chute.

[rak64]

The least desirable stall characteristic any jet can have is to pitch-up when it stalls, the reason being that the wing can blank out the horizontal stabilizer causing a loss of pitch control and the ability to get the nose down to fly out of the stall.

That is a common explanation. But there is a better one.
Flaps settings are not only alter chambers it alter as well average incidence angle.
Assume the fuselage itself acts as a wing.
That can lead to situations in which the wing produce less lift than the wing.
the scenario is at low IAS and at low flap settings the fuselage can produce more lift than the elevator can counteract.Supercritical wings are knows (esp. the earliest) for poor lift creation, what increase the effects. That lead into a not controllable but stable situation, in that the wing itself isn't stalled, called superstall. During landing the flaps are set, running the wing at notable higher angle of attack than the fuselage, so that the fuselage can't produce lift.
I used x-plane for investigation the flying wing and lather on together with a fuselage formed from wing shape. I discovered severe problems with liftoff and also in diving, when the fuselage produce lift (in that case-negative lift).
That isn't a suspect into the case, just a comment into the general relation. If more discussion about this, admins split into a own tread.

[atakacs]

Apparently flight tests resumed a few days ago with airframe 6001.

Any news about the Roswell crash ?