Friday, August 05, 2016

Beech F33A Bonanza, N6728X: Accident occurred August 01, 2016 in Blythe, Riverside County, California

Aviation Accident Final Report - National Transportation Safety Board: 

Docket And Docket Items - National Transportation Safety Board:

National Transportation Safety Board - Aviation Accident Factual Report:

NTSB Identification: GAA16CA411 
14 CFR Part 91: General Aviation
Accident occurred Monday, August 01, 2016 in Blythe, CA
Probable Cause Approval Date: 01/18/2017
Aircraft: BEECH F33, registration: N6728X
Injuries: 3 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The pilot was conducting a night, visual meteorological conditions flight from a rural desert airport, and reported that prior to the flight, she did a weight and balance, checked the temperature, and did performance calculations.

The pilot reported that after rotation, the airplane was not producing "sufficient power and not climbing as anticipated" and the stall warning horn was audible. She lowered the airplane's nose, and the stall warning horn silenced. The pilot further reported that she heard "scraping" [ground impact] against the airplane, but she could not see the terrain due to the night conditions. Subsequently, the airplane impacted the ground off of the airport, which resulted in substantial damage to the fuselage.

In a follow up email conversation with the pilot's attorney, the attorney said that the pilot reported that the engine was producing power at the time that the aerodynamic stall warning horn was audible and just before impact, but noted that the power was not sufficient. 

A photograph of the accident airplane provided by the FAA inspector that responded to the accident, showed all three blades exhibited tip curl, torsional twisting and S-bending, consistent with the engine producing power at the time of impact.

The airplane performance and weight and balance calculations that the pilot performed prior to the accident flight were requested by the National Transportation Safety Board investigator-in-charge (IIC), but were not provided. 

The pilot stated she was unaware of any preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.

It is likely that the pilot exceeded the critical angle of attack during takeoff at night resulting in an aerodynamic stall. 

The Federal Aviation Administration has published the Airplane Flying Handbook FAA-H-8083-3A (2004). This handbook discusses aerodynamic stalls and states in part:

The key to stall awareness is the pilot's ability to visualize the wing's angle of attack in any particular circumstance, and thereby be able to estimate his/her margin of safety above stall. This is a learned skill that must be acquired early in flight training and carried through the pilot's entire flying career. The pilot must understand and appreciate factors such as airspeed, pitch attitude, load factor, relative wind, power setting, and aircraft configuration in order to develop a reasonably accurate mental picture of the wing's angle of attack at any particular time. It is essential to flight safety that a pilot takes into consideration this visualization of the wing's angle of attack prior to entering any flight maneuver.

Stall accidents usually result from an inadvertent stall at a low altitude in which a recovery was not accomplished prior to contact with the surface.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's failure to attain adequate airspeed to climb and her exceedance of the airplane's critical angle-of-attack during takeoff initial climb at night, which resulted in an aerodynamic stall at low altitude.

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