AAIB Bulletin: 3/2012

Full document text

24 © Crown copyright 2012 AAIB Bulletin: 3/2012 G-BYTI EW/C2011/07/08 ACCIDENT Aircraft Type and Registration: Piper PA-24-250 Comanche, G-ByTI No & Type of Engines: 1 Lycoming o-540-A1d5 piston engine Year of Manufacture: 1963 Date & Time (UTC): 17 July 2011 at 1230 hrs Location: Field near Gamston Airport, Nottinghamshire Type of Flight: Private Persons on Board: Crew - 2 Passengers - None Injuries: Crew - None Passengers - N/A Nature of Damage: Propeller, fuselage, flaps, right wing spar Commander’s Licence: Private Pilot’s Licence Commander’s Age: 55 years Commander’s Flying Experience: 394 hours Last 90 days - 14 hours Last 28 days - 7 hours Information Source: Aircraft Accident Report Form submitted by the pilot and subsequent AAIB enquiries Synopsis Following takeoff from grass Runway 24 at Sherburn-in-Elmet Airfield, the landing gear failed to retract fully. The pilot was unable to lower the landing gear either by normal means or by using the emergency extension system. The pilot carried out a wheels-up landing in a crop field adjacent to Runway 21 at Gamston Airport. The propeller and lower fuselage skin were damaged during the landing, but the pilot and passenger were uninjured and vacated the aircraft without assistance. It was determined that deflation of the right landing gear oleo had prevented full retraction of the landing gear. during subsequent attempts to lower the landing gear, a clevis pin in the landing gear operating mechanism had fouled against the edge of an access hole in a structural beam and jammed, preventing the landing gear from operating. History of the flight The aircraft was being flown by two qualified pilots who intended to conduct some circuits and local flying from Gamston Airport. After completing two circuits with full stop landings at Gamston, Pilot A flew the aircraft to Sherburn-in-Elmet Airfield. The approach and landing on grass Runway 24 and the taxi to the tarmac parking area at Sherburn were uneventful. After a short break at Sherburn, Pilot B (hereafter referred 25 © Crown copyright 2012 AAIB Bulletin: 3/2012 G-BYTI EW/C2011/07/08 to as ‘the pilot’) elected to fly the aircraft back to Gamston. He reported that the aircraft walkround and pre-takeoff checks were completed normally. The pilot subsequently described the takeoff run on Runway 24 as somewhat bumpy, but no more so than he considered reasonable for a departure from a grass surface. When the pilot selected the landing gear selector switch to uP at 500 ft, he observed that the amber indication light above the gear selector switch did not illuminate to indicate that the landing gear was up and locked. He also noted that the landing gear emergency handle was in approximately the 45º position. The pilot continued the climb to 2,000 ft and turned towards Gamston. He recycled the landing gear selector switch a number of times, but the landing gear did not move. on arrival at Gamston he declared a PAN and carried out two fly-pasts. ATC confirmed that the landing gear appeared to be partially retracted. Further attempts by the pilot to lower the landing gear were unsuccessful and he then operated the emergency landing gear extension system, also without success. He performed another fly-past and ATC reported that the landing gear was still in the same position. The pilot then departed the circuit to the south of the airfield in order to use up some fuel prior to landing. on returning to Gamston, he elected to land in a field of rapeseed crop to the right of asphalt Runway 21. The aircraft landed in the field, coming to rest after a ground run of 27 m; the propeller struck the ground causing the aircraft to turn through approximately 300º. Both pilots were uninjured and were able to vacate the aircraft through the normal exit without assistance. Maintenance information Some weeks prior to the accident the pilot had noticed during a pre-flight walkround that the right landing gear oleo was slightly deflated. It was subsequently re-inflated to the correct extension by a maintenance engineer and no further problems were reported. The aircraft underwent a 6 month/50 hour check on the day prior to the accident and there were no findings related to the landing gear. After the accident the right landing gear oleo was observed to be fully compressed. Landing gear system description The PA-24 Comanche has a fully retractable, electrically operated tricycle landing gear. The air-oil oleo struts of the main landing gear legs must extend in order to provide sufficient clearance to allow the wheels to enter the wheel well during the retraction cycle; the Pilots’ operating Handbook advises that it is important that the aircraft is not operated with flat or deflated oleos. The retraction mechanism consists of an electric motor, transmission assembly and torque tube assembly, which actuate push-pull cables and rods to each of the landing gear legs. The motor is activated by a selector switch on the instrument panel. An anti-retraction switch on the left main gear prevents the electric circuit to the landing gear motor from being completed until the gear oleo is fully extended. If the electric motor fails, an emergency extension system can be operated. This requires the pilot to move the landing gear electrical selector switch to the oFF position so that the motor does not oppose the movement of the gear mechanism when the gear is manually lowered. The pilot must then position the electrical release arm fully forward to disconnect 26 © Crown copyright 2012 AAIB Bulletin: 3/2012 G-BYTI EW/C2011/07/08 the electric motor from the gear operating mechanism before opening the emergency extension handle. This moves backwards and forwards in normal operation as the gear is raised and lowered and therefore provides a coarse indication of gear position; the telescopic handle is extended to lower the landing gear manually. Aircraft examination