What happened
On August 22, 2013, a Piper PA28RT, registration N4353U, was performing a private flight from Montpellier-Candillargues aerodrome toward the Pyrenees. During the takeoff roll on runway 14, the pilot applied takeoff power and released the brakes once maximum RPM was reached.
As the aircraft accelerated, the airspeed indicator became active, but by the first third of the runway, it showed a constant speed of 39 knots. By the midpoint of the runway, the pilot noted that the airspeed reading had not increased. Simultaneously, the pilot perceived a loss of engine power accompanied by abnormal engine noise. Fearing a mechanical issue, the pilot decided to abort the takeoff and applied maximum braking.
As the aircraft approached the end of the runway, the pilot steered to the left to avoid an adjacent pond located in the runway's axis. This maneuver caused the aircraft to exit the runway longitudinally, skid, and result in the collapse of the right main landing gear. The aircraft sustained heavy damage.
The investigation
The investigation focused on the engine performance and the accuracy of the cockpit instrumentation. While the pilot had previously experienced power fluctuations and detonations during high-temperature operations, recent maintenance had addressed several engine components, including cylinders, valves, and pistons.
Technical examinations of the engine revealed that the magnetos were in a degraded state and the fuel injection pressure was set higher than the manufacturer's specifications. Additionally, testing of the airspeed indicator revealed that a diaphragm compensation screw had become loose, which could lead to inaccurate speed readings.
Findings
- The degraded state of the magnetos and incorrect fuel injection pressure likely caused engine RPM fluctuations during the takeoff roll.
- A loose compensation screw on the airspeed indicator likely provided erroneous airspeed information to the pilot.
- The combination of perceived engine instability and the static airspeed reading prompted the pilot to abort the takeoff.
- At the time of the aborted takeoff, the aircraft's actual speed was likely much higher than the indicated 39 knots, leaving insufficient runway distance to stop before the end of the pavement.