Introduction
On 5 April 2010 at 1253 UTC, a Cirrus SR22, registration N404RW, was destroyed during a takeoff accident at White Waltham Airfield, Berkshire. The aircraft, powered by a single Continental Motors IO-550-N piston engine and manufactured in 2009, was operating under private flight rules. The sole pilot, aged 51 and holding a Private Pilot's Licence with 400 hours total flying experience (including 15 hours on type), was accompanied by the aircraft owner, who was also a pilot and occupied the right-hand seat. Both occupants evacuated without injury before the cabin was engulfed in fire; the aircraft sustained substantial damage.
History of the Flight
The pilot planned to fly to a nearby airport to practice instrument approaches. Before departure, the pilot and the aircraft owner discussed the flight and agreed that the owner would act as co-pilot, operating the radio—their normal arrangement. Both understood that the pilot was in command. They boarded, started the engine, and taxied for departure. The wind was approximately 220/15 kt, and grass Runway 21 was in use. Flaps were set to 50% for takeoff, and the trim was set slightly towards the aft end of the takeoff range. After a normal power check, the pilot lined up and applied full power, keeping the control column approximately neutral in pitch during the takeoff roll.
The pilot reported that the aircraft became airborne quite early and that he intended to let it accelerate in ground effect before climbing away. However, without warning, the left wing dropped and contacted the ground, and the aircraft cartwheeled. Eyewitnesses recalled that the accident sequence began approximately at the intersection of Runway 21 with Runway 25. The aircraft fuselage came to rest erect but substantially damaged, with parts separated during the cartwheel. Both occupants evacuated before fire engulfed the cabin. The aircraft owner, who was more experienced on the type, reported that he had not been paying sufficient attention to the takeoff to intervene.
Runway Conditions
AAIB investigators found the grass runway surface somewhat rough in places, with a notable undulation at its intersection with Runway 25. Civil Aviation Publication (CAP) 168, which provides guidance on aerodrome licensing, describes a simple method for assessing surface evenness by driving over it in a suitable vehicle; the surface should not show undue signs of the vehicle's passage and should not cause discomfort to occupants if even.
Takeoff Technique and Wreckage Examination
The aircraft's Flight Manual recommends a smooth rotation at 70 kt but adds that soft or rough field takeoffs should be performed with 50% flaps, lifting the airplane off the ground as soon as practical in a tail-low attitude, then levelling off immediately to accelerate to a higher climb speed. The pilot's technique involved a neutral control column during the roll, and he reported that the aircraft lifted off early.
Examination of the wreckage found no evidence of any malfunction or failure that would account for the accident. The trim settings were approximately mid-range. Neither the seatbelt-mounted air bags nor the ballistic parachute had deployed.
Recorded Data and Analysis
The aircraft's displays contained three SD data cards recording various parameters at one sample per second. These were retrieved and downloaded. The data showed that after a small pitch oscillation at about 52 kt, the aircraft's pitch attitude began increasing at 57 kt, reaching 11° nose-up before the aircraft rolled right and then rapidly left. The Recoverable Data Module (RDM), which records a wider range of parameters, was not downloaded as the additional data were considered unnecessary for the investigation.
Analysis concluded that there was no technical cause for the accident. It is probable that the undulating runway contributed to the aircraft becoming airborne at a low speed, and the pilot lacked training and experience on the aircraft type that might have assisted him in controlling the situation.