Tuesday, November 6, 2012
Fundamental failures by pilots still figure in some accidents
A Raytheon G36 (Beechcraft Bonanza) struck a building and crashed into a parking lot near Hawthorne Municipal Airport, Hawthorne, Calif. An ATP-rated pilot, who also was an instructor, was conducting a demonstration flight for the private pilot on board and a passenger. This was the third time the private pilot had received a demonstration flight in the airplane. The first two times were with representatives of the manufacturer. The instructor had a total time of 3,500 hours, while the private pilot had a bit over 200 hours. All three occupants were killed in the accident. Visual meteorological conditions prevailed.
The airplane had taken off, executed a full-stop landing and taxied back for another takeoff. During the second takeoff roll, the instructor radioed the local tower controller that the airplane had an open door and they were aborting. After tending to the door, a successful takeoff was executed. The aircraft remained in the pattern and was lined up on final for another landing when the pilot radioed the controller that they were going around, but didn't say why.
Witnesses reported that, as the airplane was climbing upwind during the go-around, it made a left turn followed by a hard right turn. A witness observed the airplane trailing black smoke and reported the wings were rocking.
The airplane struck the building's rooftop and a wall approximately 45 feet high, then descended to a parking lot.
The airframe, engine and turbocharging system were examined with no mechanical anomalies identified that would have precluded operation. However, examination of the spark plugs and cylinders indicated that the engine was running with an overly rich fuel/air mixture, which would be consistent with the witness statements of black exhaust coming from the airplane. The electric fuel boost pump switch is located next to the landing gear selector handle. The G36 Pilot Operating Handbook cautions that use of the electric boost pump during normal operations can cause an overly rich mixture, possibly flooding the engine. It says the boost pump is designed for use during starting and emergency operations only.
The NTSB suggested that if either pilot inadvertently activated the fuel boost pump while attempting to retract the landing gear during the go-around, it could have resulted in a temporarily rich mixture, reducing the available engine power and distracting the pilots.
The NTSB determined that the probable cause of this accident was the pilot's failure to maintain an adequate airspeed during a go-around, which resulted in a loss of airplane control. Contributing to the accident was the inadvertent activation of the fuel boost pump during the attempted go-around.
Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, N.Y. 10602-0831.
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