Bagram Airfield Crash

[KBScobravert]

Wow. Glad we never flew on National's cargo planes. There charter passenger flights were bad enough. I watched one land with no front gear. No thanks.

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[CJ]

It gets worse:

Scenarios that considered the effect of the aft movement of up to five MRAP vehicles assumed that the rear M-ATV moved aft to the location of the stabilizer jackscrew and that each remaining MRAP vehicle moved aft to occupy the available space. For the scenarios in which all hydraulic systems were assumed fully functional, the study found that the simulated airplane remained pitch-controllable when up to five MRAP vehicles shifted aft, resulting in calculated CG shift from 31.7% (all MRAP vehicles in place) to at most 56% (all five MRAP vehicles shifted aft); for each CG configuration, the simulated airplane could be returned to a level pitch attitude in less than 5 seconds.

Basically, they calculated the rear MATV breaking loose, and it was easily remedied with control inputs. They calculated every MRAP/MATV breaking loose, and it was controllable.

One such source of nose-up pitch considered in the study was a loss of horizontal stabilizer functionality, such as what could result if the horizontal stabilizer’s jackscrew actuator and surrounding structure were struck and damaged by an impact from the rear M-ATV. Assuming such damage, two loss-of-functionality scenarios were considered: the horizontal stabilizer moves leading-edge down (from its set takeoff position) and becomes fixed in the new position, or the stabilizer floats and rotates freely to different positions (rather than remaining in its set takeoff position).

The study determined that a range of fixed leading-edge-down stabilizer positions could result in the inability of the available flight control surfaces to counter the airplane’s nose-up pitching moment. In one such scenario, when an aft movement of only the rear M-ATV and the failure of hydraulic systems Nos. 1 and 2 were assumed, the study determined that a shift of the horizontal stabilizer from the set takeoff position of 4 units to at least a position of 9 units (which produced a 5° leading-edge-down position of the stabilizer) resulted in an inability of the available flight control surfaces to counter the nose-up pitching moment. Study calculations determined that, for a 5° deflection of the horizontal stabilizer’s leading edge, the corresponding displacement at the stabilizer’s root correlated approximately with the displacement of the fractured stabilizer jackscrew and surrounding structure as found in the wreckage. For the freely floating stabilizer scenario, the study determined that the simulated airplane’s stabilizer would move to a leading-edge-down (airplane nose-up) condition under its own weight and air loads. However, when elevator deflection occurred (such as commanded by the flight crew), the floating stabilizer would react to the loads imposed by the elevator deflection and move in a direction opposite that of the elevators in response. Thus, the application of airplane-nose-down elevator control inputs (which would result in trailing-edge-down movement of the elevators) would contribute to the leading-edge-down movement of a freely floating stabilizer. That is, in an airplane with a freely floating stabilizer, any crew-commanded nose-down inputs on the control column would worsen the airplane’s pitch-up condition.

So that tells us one or all of them broke loose, and damaged the horizontal stabilizer, presumably the rear jackscrew was struck in the rear, and the horizontal stabilizer was essentially broken free of input. When the pilots pushed the nose down, it pulled back even further, bleeding more airspeed, and essentially prolonging the stall. I'm sure there is far more experienced people in here to interpret this information, but the summary is it wasnt a CG shift that took the plane down. It was cargo smashing into and disabling control surfaces.

[jw33]

[KBScobravert]

WOW! The strap counts didn't even sound to me the layman.

I flew on a cargo outfitted C17 from Dywer to Ramstein back in August. I rode a jump seat along the wall with the chains to cargo literally at my feet and under me. There was a massive trailer/generator/comms trailer in front of me and watching that thing bounce around and shift was scary as hell. This flight here is all I could think of. I even video'd the take off and shake.