What happened
On October 4, 2005, a Piper PA-28-181, registration HB-PHB, departed Marrakech, Morocco, for a VFR flight to Ouarzazate. The aircraft was occupied by a pilot, a flight instructor, and two additional passengers. The flight path followed a route similar to a previous successful flight conducted two days earlier.
As the aircraft progressed southeast, it entered a narrow, eastward-curving valley south of Azgour. At approximately 07:08 UTC, the aircraft was flying at an altitude of roughly 8,500 ft AMSL. The valley's lowest ridge point was approximately 8,600 ft AMS/L. The aircraft subsequently collided with a descending mountain flank, resulting in four fatalities and the total destruction of the aircraft.
The investigation
Swiss investigators examined the wreckage and conducted reconstruction flights to determine the circumstances of the impact. The investigation reviewed onboard photographs taken by passengers, which provided critical evidence regarding the flight path and terrain. Technical inspections of the engine and instruments revealed no pre-existing mechanical failures, and the engine was still producing power at the moment of impact. The investigation also noted that while visibility was good, the low position of the sun and the lack of prominent landmarks made terrain assessment difficult.
Findings
- The primary cause of the accident was a collision with terrain because the crew selected a flight altitude in a narrow valley that provided neither enough room for a turnaround nor sufficient clearance to safely cross the lowest ridge under the prevailing conditions.
- The crew lacked familiarity with the specific geographical characteristics of the High Atlas mountains.
- The aircraft's performance capabilities were significantly reduced due to high mass and high density altitude.
- The low angle of the sun made it difficult to accurately judge the flight path relative to the terrain.
- Potential turbulence and downdrafts, common in this area when winds originate from the south, may have further complicated the flight.