21 April 2017

Namibia: Low-Level Stall Probable Cause of Plane Crash

NO INDICATIONS that a mechanical defect or malfunction was the cause of the plane crash in which three pilots were killed at Hosea Kutako International Airport early last year could be found during the official investigation of the accident.

The probable cause of the crash, in which pilots Uwe Herbert (62), Fritz Alpers (41), and Ole Friede (43) lost their lives on 29 January 2016, was that the Cessna 425 aircraft in which they were flying stalled at low altitude before it crashed into the ground, aircraft accident investigator Hafeni Mweshixwa concluded in his report on the investigation of the accident.

The report, which is the result of the investigation that the works ministry's Directorate of Aircraft Accident Investigations carried out after the crash, has now been released.

Herbert, Friede and Alpers died when the Cessna 425 in which they were doing a flight to test Herbert and Friede's skills for the renewal of their commercial pilot licences crashed about 300 metres north of the runway at Hosea Kutako International Airport.

Mweshixwa recorded in his report that the pilots - Herbert was not seated in the front two seats of the aeroplane at the time of the crash - had been doing a landing approach when the airport's air traffic controller was asked for permission to make a right turn out of the approach in order to circle back and do another landing approach.

The air traffic controller reported that he last saw the twin-engined aircraft on final approach, looked away for a moment, and then heard a bang before he saw a ball of flames north of the runway.

The aircraft first made ground contact with its nose section, it is stated in the accident report.

As a result of the ensuing fire that engulfed the plane, it was difficult to verify the positions the different flight controls had been in at the time of the crash, it is also stated in the report.

No evidence to indicate that a mechanical defect or malfunction could have contributed to the accident could be found with an examination of the engine and mechanical components of the aircraft.

Although there was also no evidence that the pilots had been doing a training manoeuvre in which the loss of power of one of the plane's engines during a landing approach was simulated, Mweshixwa recorded that the investigation revealed such a manoeuvre was a common practice that was performed.

The accident report states that performing such a manoeuvre was a highly risky operation, and that most flight operations prohibit it, unless it is done in a flight simulator or at high altitude to ensure enough altitude to recover should the aircraft stall or a pilot lose control.

It is further stated in the report that an "asymmetrical thrust scenario" - a situation in which one engine was producing more thrust than the other, causing the aircraft to veer to one direction and to flip to the underpowered side - could also not be ruled out.

The Namibia Civil Aviation Authority should review the practice in which the loss of an aircraft's engine power during a landing approach is simulated to test pilots' skills, and this should possibly be restricted to tests in a flight simulator or at high altitude to assure enough height should a stall occur, the directorate recommended at the end of the investigation report.


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