Introduction
On 7 March 2011, at 1022 UTC, a Piper PA-34-200T Seneca II (registration G-BTGV) experienced an uncommanded nose landing gear (NLG) retraction during landing at Gloucestershire Airport, Cheltenham. The aircraft was engaged in a training flight for a Commercial Pilot's Licence skills test, with two crew members and no passengers on board. Neither occupant was injured.
Circumstances
The aircraft had departed from Oxford and, after an uneventful navigation exercise, was routed to Gloucestershire Airport to conduct circuits. The student was instructed to descend on the dead side and join the circuit downwind for Runway 09. After a normal circuit, the aircraft was cleared for a touch-and-go on final approach. The approach was stable, and in calm conditions the commander assessed the touchdown point as deeper into the runway than normal but still safe. He described the touchdown as "slightly flat and firm," though not heavy. Immediately after touchdown, the nose landing gear retracted, causing the nose to drop and the propellers to contact the runway surface. The aircraft came to a halt further down the runway, and both occupants evacuated without difficulty.
Examination
After the aircraft was raised and the nose gear pulled into the locked-down position, examination revealed that the upper eye end of the downlock link was severely distorted, with additional damage to the front bulkhead. The damage was likely caused by the drag brace folding during the collapse, transferring loads from the nose leg into the actuator and its attachment to the bulkhead.
History and Contributory Factors
The Piper PA-34 series has a long history of NLG collapses, with no single cause identified. The manufacturer issued Service Bulletin (SB) 1123 (later revisions A and B) to address the issue, mandating maintenance actions and inspections at 50-hour intervals. SB 1123B had been applied to G-BTGV on 28 February 2011, approximately 28 flight hours before the accident. Maintenance personnel noted that misrigging, possibly from rotating the threaded eye end of the downlock spring link by 180 degrees, could lead to an out-of-rig condition. They also considered that heavy landings since the last SB compliance might have caused damage affecting rigging.
Discussion
The accident was the latest in a series of similar NLG retraction events. While the specific cause could not be determined, potential contributory factors included an out-of-rig condition or damage from an earlier heavy landing. The relative lack of recent similar events suggested that SB 1123B had been effective in reducing such occurrences. The operator's internal investigation recommended formal use of the Technical Log to report engineering concerns, including suspected heavy landings, rather than informal discussions with the Operations department.