Incident Overview
On 11 June 1999, a Cessna 182A (registration D-EEPY) was on a private flight from Galway to Londonderry, Northern Ireland. The pilot, aged 54 with 1,064 total flying hours (12 on type), reported that during the approach at 1150 UTC, the aircraft was slowed to 120 knots and the hydraulically powered landing gear was selected down. The green indicator light for the nosewheel down-and-locked failed to illuminate.
Pilot Actions
The pilot informed the tower and attempted to retract and lower the gear again, but the nosewheel light remained off. He then performed the manual gear extension procedure using the emergency hand pump. The main gear extended immediately, but the operating handle became stiff, as normally occurs at the end of manual extension. Despite approximately 20 additional pump strokes, the nosewheel light did not illuminate. Concerned about breaking the hand pump lever, the pilot stopped.
After exchanging the nosewheel bulb with a known serviceable bulb, the light still failed. The pilot conducted two slow fly-pasts for tower personnel to visually inspect the nose gear, but its status remained uncertain. An army helicopter flew alongside the aircraft, and its crew reported that the nose leg appeared correctly extended.
Landing and Evacuation
Emergency personnel were positioned, and the pilot landed carefully on the main wheels at the lowest possible speed. Despite maximum aft pressure on the control column, the nose descended to a steep angle as the aircraft slowed. Deceleration was not excessive, and both occupants evacuated via the normal doors immediately after coming to a halt.
Post-Flight Examination
Recovery of the aircraft revealed that the piston rod of the nose-leg operating jack had been prevented from achieving full travel in the gear-down sense. The inner ends of two lock pins, which engage the down-lock hooks when the gear is locked down, had migrated inboard within their mounting lugs on the bearing end. This caused the nut on the forward end of the piston rod to foul the protruding ends of the lock pins. Further examination showed that both lock pins had fractured approximately in the plane of their circumferential groove.
Normally, the groove permits locating pins (passing through vertical drillings in the lugs) to secure the lock pins. The fracture allowed the inner ends to migrate a short distance out of the lugs, preventing full piston rod movement. The repair agency noted that the replacement bearing end, lock pins, and locating pins used during the repair were of a different design. The new design featured lock pins of constant diameter without grooves, with locating holes drilled through their centers at right angles to their axes. Corresponding holes in the lugs allowed the locating pins to pass vertically through both the lugs and the lock pins, securing them. This redesign largely eliminated the stress concentrations created by the grooves in the original down-lock pins.