An improper stabilizer trim setting caused a Boeing B-52 to crash into the ocean off Guam in July, killing six crewmembers as they practiced a flyby for the next day's island parade.So why was the stab trim set to 4.5 - 5 degrees nose down?
The USAF's accident investigation board (AIB) has two theories. Either the pilot made a fatal error and forgot the unusual trim setting as he entered a shallow, descending turn, or the B-52 has a fatal mechanical problem.
The suspected mechanical problem is called runaway stabilizer trim, caused perhaps by a failure of the pilot's trim switch or the hydraulic actuator for the stab trim. It has happened once before to a B-52G on the ground. Another B-52D mishap was "most likely" caused by a stabilizer control system malfunction, the USAF's AIB says.
As part of the crash investigation, Boeing simulated the effect of a runaway stabilizer trim problem in the pilot's flight profile. It took the simulator crew 29 seconds to recognize the stabilizer trim problem. By then, it was too late to recover the aircraft "even if the pilots executed response actions perfectly."
(Photo credit)
Recent Comments