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CV-22 Crash Caused by Pilot Error, Engine "Power Loss" May Have Contributed

Air Force officials are pointing to pilot error and possible engine problems as the cause of the first ever combat loss of a CV-22 Osprey, according to a press release summarizing the investigation report released last night.

While the service's accident investigation board couldn't determine the cause of the crash "by the standard of 'clear and convincing evidence,' in part because the flight incident recorder, the Vibration Structural Life and Engine Diagnostics control unit, and the right engine were destroyed," it did find that 10 factors likely contributed to the fatal accident.

Those factors that combined to doom the flight, which was the crew's first combat mission, were:

Inadequate weather planning, a poorly executed low visibility approach, a tailwind, a challenging visual environment, the mishap crew's task saturation, the mishap copilot's distraction, the mishap copilot's negative transfer of a behavior learned in a previous aircraft, the mishap crew's pressing to accomplish their first combat mission of the deployment, an unanticipated high rate of descent and engine power loss.
Engine power loss. That's going to give Osprey critics plenty of fodder to throw at the program.

Here's an excerpt from the accident investigator's actual report. It further damns the engines:

Close analysis of video indicates that there is an unidentified contrail type emission from the MA during the last 17 seconds of flight.  (Tab Z-27, Tab HH-26, Tab II-59)  The greater weight of credible evidence indicates that the abnormal and intermittent emission could be heat or fuel mist from an attempted engine auto-relight, or smoke.

I considered engine percent performance, which was last measured on 6 April 2010 (99.5% for the left engine and 95.3% for the right engine).  The MA performed four austere landings, including one with a left engine air particle separator failure, after that 6 April 2010 measurement.  (Tab D-4, Tab U-5 thru U-6, Tab V-59.3, Tab BB-64, Tab II-3, II-52)  Degraded engines could have led to engine failure, surge/stall or insufficient power when a high power demand was required.  I determined, by the greater weight of credible evidence, that one or both of the MA’s engines was degraded below acceptable standards.

The report later states say that a likely engine malfunction forced the pilot to execute a "remarkable" rolling landing rather than a helicopter-style landing, which is standard for the V-22. Apparently the tiltrotor hit a two foot ditch after the pilot executed a near perfect "roll on landing" and flipped, killing four, including the pilot, and injuring another 16.

But here's where it gets a little strange. The press release states that investigators could not conclude with 100 percent confidence that engine power loss "substantially" contributed to the crash.

The convening authority approved the board president's report, with comments. While legally sufficient, he assessed the evidence in the AIB report did not support a determination of engine power loss as one of the 10 substantially contributing factors. The convening authority made this decision based upon the evidence in the AIB report and additional analysis of the evidence in the report. The convening authority concluded the preponderance of credible evidence did not indicate engine power loss as a substantially contributing factor of the mishap.
The press release goes on to say that Air Force Chief Gen. Norton Schwartz actually requested a second investigation into the crash after the first was completed. That investigation looked at data from the Navy's air systems command -- who runs the V-22 program for the DoD -- and video footage of the crash. Still, the only thing the second investigation found different from the first was the estimated airspeed of the tiltrotor at the time of the crash; 80 knots compared to 75.

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