What happened
On 23 July 2014, a Luscombe 8E Silvaire Deluxe, registration G-AGMI, was performing a private flight from a grass airstrip near Albourne, West Sussex. The weather conditions were clear with good visibility and light, variable winds. During the takeoff roll, the pilot observed that the indicated airspeed was only approximately 40 mph when the aircraft was two-thirds of the way down the 440 m strip.
Upon deciding to abort the takeoff, the passenger noted that the hinged cover on the pitot probe had failed to open. As the pilot applied the wheel brakes, the braking effectiveness appeared to diminish. The aircraft failed to decelerate as anticipated and began drifting toward the left side of the runway. With approximately 8 and 80 m of the strip remaining, the left wing of the aircraft struck a hangar at roughly 10 mph. This impact caused the aircraft to yaw, resulting in the propeller striking the wire mesh hangar gates. There were no injuries to the pilot or the passenger, though the aircraft sustained damage to the propeller and left wing.
The investigation
The investigation focused on the failure of the pitot probe cover and the subsequent loss of braking effectiveness. Investigators examined the pitot probe's hinged flap arrangement, which is designed to deflect under aerodynamic loads to expose the orifice. No specific cause was identified for why the cover failed to operate during this flight.
Regarding the braking issues, the aircraft's brakes were subsequently tested and found to be in normal working order. The pilot suggested that the uneven surface of the recently cut grass may have caused the aircraft to momentarily lose weight on the wheels, potentially leading to brake fade or wheel lock-up.
Findings
- The primary cause of the aborted takeoff was the failure of the hinged pitot probe cover to open under air loads, resulting in inaccurate airspeed readings.
- The aircraft overran the end of the grass strip and struck a hangar due to reduced braking effectiveness, likely caused by the aircraft passing over uneven ground which reduced tire contact with the surface.