Incident Overview
On 31 January 2002, at approximately 1056 hours, a Piper PA-24-260 Comanche (registration G-BRXW) experienced an inadvertent landing gear retraction during the landing roll at Coventry Airport. The aircraft, manufactured in 1964 and powered by a single Lycoming O-540-E4A5 piston engine, was on a private flight with two pilots on board. No passengers were carried. Both crew members were uninjured, and the aircraft sustained damage to the propeller and underside of the fuselage.
Flight and Landing Details
The aircraft was returning to the circuit at Coventry Airport after a local flight. The pilots intended to carry out a touch-and-go landing on Runway 23, followed by a further circuit. The approach and landing, using the first stage of flap, were normal. The wind was from 200° at 13 to 15 knots. During the landing roll, the pilot-in-command (PIC), who was the non-handling pilot in the right seat, observed that the handling pilot selected the landing gear up.
Mistaken Selection
Their normal procedure was to confirm identification of the flap control switch before making any selection. On this occasion, the handling pilot mistakenly placed his hand on the landing gear selector switch and selected it up before the PIC could intervene. Consequently, the landing gear retracted, and the aircraft, with a groundspeed of approximately 30 knots, settled onto its fuselage and slid to a halt on the runway. The handling pilot shut down the aircraft, and both crew members disembarked normally. The airfield fire and rescue services attended without delay, but there was no fire.
Maintenance and Oleo Extension
The aircraft had undergone an annual maintenance inspection two weeks before the accident. Before that, the owners had reported to the maintenance organisation that the oleo extensions appeared low. During the maintenance, these were checked and the oleos were inflated. Because the aircraft did not have the full fuel load as specified in the maintenance procedure, the oleos were inflated "slightly more" than prescribed, with the intention that, with a full fuel load, the oleos would settle to their correct extension. According to the aircraft Service Manual, the recommended main landing gear oleo extension was 2.75 inches. Following the accident, the oleo extensions were found to be significantly greater than the recommended amount, but they were still within the range in which the anti-retraction switch, located on the left main landing gear, could provide retraction protection in the event of an inadvertent 'UP' selection with the aircraft's weight on its wheels. The handling pilot commented that the excessive oleo extension was noted during the pre-flight inspection, but it was decided to operate the aircraft with the oleos in that condition.
Likely Mechanism
It is therefore likely that, during the landing roll, the combination of the aircraft's ground speed and the wind velocity resulted in an airspeed of approximately 40 to 45 knots. This, combined with the flap setting and the additional static oleo extension, would have been sufficient to extend the oleo out of the anti-retraction switch protection range. The lack of scuff marks on the mainwheel tyres or damage to the landing gear doors is further evidence that the aircraft was at least 'light on its wheels' when the landing gear retraction process occurred.
Pilot Comments
The pilot's report candidly explained that the wrong selection was made during the landing roll. The handling pilot also commented that he wished to highlight the importance of ensuring that the correct oleo extension exists prior to flight so that the design landing gear retraction protection facility is not compromised.