History of the Flight
The pilot of Piper PA-22-150 G-ARDS departed from Sherburn in Elmet to Beverley Airfield under good weather conditions. Runway 12 was active with a left-hand circuit and a crosswind from 180° at 10 kt. After an overhead join, the pilot flew a normal circuit and reported a stable final approach aligned with the runway's extended centreline.
As the aircraft descended through 150 ft agl, the pilot encountered strong turbulence requiring immediate correction to keep the wings level. He continued the approach using the wing-low crosswind method. During the flare, a sudden violent gust lifted the right wing. The pilot applied right aileron and added power for a go-around, but the aircraft continued to move left, missing a ditch north of the runway but striking the ground in a field beyond, causing substantial damage.
Airfield Information
Beverley Airfield is an unlicensed airfield 4 nm north-northeast of Beverley with a 710 m grass runway oriented 12/30. The aeronautical plate identifies a wind turbine installation 1 nm south of the airfield comprising twelve 82 m diameter turbines. The most northerly turbine is approximately 1.4 km south of Runway 12 threshold and 1.2 km south southwest of Runway 30 threshold.
Pilot Comments
The pilot reported that the turbulence during final approach and loss of control during the flare may have been associated with wake turbulence downstream of the wind turbine installation. He also noted that the aircraft still had its rudder/aileron interlink installed, which may have affected the aircraft's response when coordinating rudder and aileron inputs during the gust.
AAIB Comment
The AAIB noted that available literature suggests the possibility of encountering wake turbulence from the windfarm at this airfield is remote, but could not be entirely ruled out. The accident aircraft flew an approach that crossed downwind of the turbines, but the distance from the closest turbine to the upset location exceeded 16 rotor diameters—the furthest distance identified in CAP 764 for noticeable turbulence—and was well outside the more recent estimate of eight rotor diameters for windfarms. The AAIB commented that analysis has been based on limits for commercial aircraft and may not fully account for effects on general aviation operations, encouraging pilots to submit Mandatory Occurrence Reports if they suspect wind turbine wake turbulence.