What happened
On 1 July 2012, a pilot was conducting a re-familiarisation flight in a De Havill and DH53 Humming Bird, registration G-EBHX, at Old Warden Aerodrome. The flight was intended to prepare for an air display scheduled for later that afternoon. The aircraft took off and initially performed level turns at an altitude between 600 and 800 feet without incident.
As the aircraft progressed, it flew downwind toward a copse of tall trees. During a turn near these trees, the aircraft's left wing dropped sharply, followed by a second drop that resulted in a steep roll. The aircraft then entered a severe, nose-down descent. Witnesses observed the aircraft enter a steep left turn that lasted approximately two to three seconds before it struck the ground near the intersection of Runway 25 and Runway 30. The pilot sustained fatal injuries.
The investigation
The investigation examined the aircraft's mechanical condition, the meteorological environment, and the pilot's handling of the aircraft. Investigators found no evidence of pre-impact mechanical failure in the engine or flight controls. While the magneto showed some oxidation on a tungsten contact breaker point, testing confirmed it was functioning correctly after cleaning. The aircraft's airframe and controls were found to be structurally intact prior to the impact.
Meteorological data indicated that the wind was gusty, with speeds reaching 22 to 25 knots. The investigation also noted that the aircraft's airspeed indicator had a very compressed scale at low speeds, making accurate readings difficult in turbulent air. The aircraft was also known to be prone to 'aileron tramping'—a phenomenon where the ailerons move erratically near the stall speed.
Findings
- The aircraft was operating in gusty wind conditions that were significantly impacting the margin between the flying speed and the stall speed.
- The flight path took the aircraft near a treeline, which likely created turbulent airflow.
- The loss of control was caused by a combination of the aircraft's challenging handling characteristics, the turbulent air from the trees, and the gusty wind conditions.
- The aircraft's instrumentation made it difficult for the pilot to maintain precise airspeed readings during the encounter with turbulence.