Incident
On 3 July 1998 at 2145 UTC, a Cessna 310L (registration G-AZUY) operated by a private pilot was completing its sixth flight of the day, arriving from Barton (Manchester) to its base at Liverpool Airport. During final approach to Runway 27, the pilot was distracted by a passenger concerned about the proximity of trees. After looking out to confirm the glidepath on VASIS, he continued the approach. His normal practice was to select 5° flap and ‘fly’ the aircraft at 10-20 feet along the runway, touching down near the midpoint with relatively high power. During this phase, he glanced at the landing gear indicators and noticed no green light for the nose gear; he did not recall hearing the configuration warning horn. He immediately initiated a go-around, applying power and selecting the landing gear up, but felt the right main wheel touch and the right propeller strike the ground. He then selected gear down, leaned off the mixture, switched off the magnetos, and landed. The aircraft slid on its belly, and the pilot evacuated the two passengers normally. Fire services attended but there was no fire.
Aircraft and Systems
The Cessna 310L is a twin-engine aircraft with two Continental IO-470-V piston engines, built in 1966. Landing gear extension and retraction are performed by a single electric motor and gearbox moving linkages to all three gears simultaneously. A manual extension handle is available. Indicator lights include three green (down and locked) and a red light for disagreement. A warning horn sounds when throttles are reduced below about 12"Hg manifold pressure with gear up or unsafe. The Gear Unsafe/In-transit light filament was found unserviceable, which was known to the pilot.
Examination
After the accident, the aircraft was examined. With the aircraft lifted, the main gears drooped from a fully retracted position, and the nose gear did not move. Manual retraction of the main gears was accomplished without difficulty using the emergency handle. However, manual extension of the main gears encountered strong resistance preventing full downlock. By disconnecting the nose gear actuating linkage, the main gears could be wound into downlock. Damage to the main gear doors suggested they had folded up while on the runway. The nose gear had no such damage. A fracture was found in the ‘adjusting bellcrank’ and ‘fork bolt’ of the nose gear actuating linkage, preventing transmission of motor movement. The failed parts were sent to AAIB, which found no pre-existing damage or cracking; they appeared to have failed in a single fast fracture.
Discussion
The pilot reported that previous takeoffs and landings that day at Barton and Haydock were noticeably ‘bouncy’ due to uneven grass strips. The type of failure found is typical when landing loads are applied to a nose gear not fully down and locked, causing the actuating linkage to react the loading. However, if the fork bolt and bellcrank had fractured during takeoff at Barton, the nose gear would have been unable to retract and the red gear unsafe light should have illuminated throughout the flight, unless the failures occurred after the nose gear went into uplock. The unserviceable filament would have prevented this warning. The landing gear configuration warning horn only sounded with throttles fully closed.