What happened
On August 30, 1964, a Cessna 170A, registration HB-CAZ, was performing a flight from Prangins to Lausanne. While approaching Lausanne-Blécherette, the pilot contacted the control tower to request landing instructions. The tower controller instructed the pilot to enter the circuit and report at the base and final approach positions for runway 01, specifically noting a crosswind of approximately 20 knots coming from the right.
Misinterpreting this communication, the pilot believed the wind was only a light side breeze. During the landing sequence, the aircraft touched down approximately 240 meters past the runway threshold. Following the touchdown, the aircraft experienced a series of bounces and was pushed increasingly to the left by the wind. After a final bounce, the pilot applied power; however, the left wing dipped, the tail lifted, and the aircraft pivoted 90 degrees to the left before ultimately flipping onto its back approximately 35 meters west of the marked runway.
The investigation
The investigation examined the meteorological conditions, the pilot's communication with the tower, and the mechanical state of the aircraft. At the time of the accident, the region was experiencing a bise wind following a cold front, with visibility at 15 km and winds from the North/Northeast reaching 20 to 25 knots, with gusts up to 30 knots. Ground turbulence was reported as moderate to strong.
Investigators reviewed the radio recordings from the control tower, which confirmed the controller had warned the pilot of the significant crosswind. The investigation also noted the pilot's previous flight history, including a prior forced landing in 1961.
Findings
- The pilot failed to realize the severity of the crosswind due to a misunderstanding of the tower's instructions.
- The pilot did not rely on the windsock for accurate wind direction and speed assessment.
- The aircraft sustained substantial damage, including a destroyed propeller, a heavily damaged engine and carburetor, and deformed wings, struts, and rudder, leading to a near-total loss of the airframe.