Tuesday, April 1, 2008
Analyzing some recently investigated accident statistics
Examination revealed that the left main lower landing-gear tube had fractured due to overstress. According to the NTSB, this was consistent with a hard landing. The airplane had been operated 25 hours at the time of the accident. The NTSB determined that the probable cause of the accident was an overloading of the aircraft during landing leading to the total failure of the left main gear strut, which resulted in loss of control and subsequent nose-over. A factor contributing to the accident was the chief pilot’s inability to maintain directional control of the airplane after the landing gear failed.
On April 2, 2006, a CZAW Parrot was taking off from runway 09, a 1,980-foot-long turf runway at Palm City, Fla. The weather was good with no ceiling, visibility 10 miles, and wind from 130 degrees at seven knots. During the takeoff roll, the engine was only able to develop 4,300 rpm. (Full power is 5,500 rpm.)The airplane lifted off and made it over the tops of some trees. However, the rate of climb decreased, and the pilot didn’t think the airplane would make it over additional obstructions ahead. So, he maneuvered back to the airstrip. During a hard landing, the right main landing gear broke off and the 5,000-hour commercial pilot received serious injuries. Examination of the engine revealed that the throttle cables were bent.
The NTSB determined that the probable cause of this accident was failure of the pilot to abort the takeoff after recognizing that the engine was not developing full power during the takeoff roll. A contributing factor was the bending of the throttle cables which prevented full movement of the throttle control.
On November 11, 2006, a private pilot was flying a CZAW Zenith Air in the area around Basye, Va., on November 11, 2006. It was a good VFR day, with no ceiling, visibility 10 miles, and the wind from 180 degrees at five knots. When the airplane was about one mile northeast of the airport, the engine surged and then quit. The airplane subsequently descended into trees in a residential area. The pilot, who was the only occupant, was killed.
Examination of the wreckage revealed only traces of fuel in the tanks and fuel system. There was no evidence that the propeller was rotating at impact. Investigators determined that the accident flight was the airplane’s seventh since it was last refueled. Total operating time since the refueling was about 6.3 hours. The airplane could carry 30 gallons, and the Rotax 912 ULS engine burned a high of 7.1 gph at takeoff performance and about 4 gph at maximum cruise power. The Airplane Flight Manual advises to “visually confirm fuel level” during preflight and to “check fuel quantity” before takeoff.
The NTSB determined that the probable cause of this accident was the pilot’s inadequate preflight inspection, which resulted in a total loss of engine power due to fuel exhaustion.
On August 7, 2005, an Allegro 2000 was being used for a dual instructional flight in the area around Oak Island, N.C. Visual meteorological conditions prevailed, with no ceiling, visibility of 10 miles and the wind from 100 degrees at six knots. When the airplane failed to return to the airport as scheduled, a search was initiated. The airplane was found to have crashed in an open field. Both the flight instructor and student had been killed.
Investigators noted that damage to the airframe was consistent with a low-energy impact after an uncontrolled descent, leading them to find that the airplane was in a stall as it descended. The flaps were found extended to 15 degrees. According to literature from the manufacturer, the airplane’s stall speed with 15 degrees of flaps and the engine at idle power is 48 mph. During a test run of the engine, no preimpact mechanical problems were identified. The engine ran at full power. The only discrepancy noted was that an FAA inspector had approved issuance of the airworthiness certificate for the aircraft to operate in the S-LSA (special LSA) category without ensuring that the Pilot Operating Handbook contained all required information. Missing from the documentation was information on fuel capacity, service ceiling, best angle and rate of climb, and a few other items. But, the Safety Board said this had nothing to do with the accident.
The NTSB determined that the probable cause of the accident was the instructor’s failure to maintain airspeed for unknown reasons, resulting in an aerodynamic stall and subsequent collision with the ground.
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, NY 10602-0831.
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Labels: Accident Statistics, Columns, Decision Making, Features, Flight Hazards, Flying Skills, Learning Center, LSAs, NTSB Reports, Pilot Skills, Safety