History of the Flight
After takeoff from Lydd Airport, the pilot retracted the landing gear normally. During the approach to the destination airfield, when the landing gear was selected down, a loud mechanical noise was heard and no green landing gear 'down and locked' lights illuminated. The pilot recycled the landing gear. The retraction phase appeared normal, but the extension phase produced illuminated nose and right landing gear 'down and locked' lights, but not the left. The pilot recycled the landing gear once more; again, only the nose and right lights illuminated, accompanied by a loud and unusual noise.
The pilot conducted a low flight past the control tower; the controller informed him that all three landing gears appeared extended and normal. Suspecting a landing gear problem, the pilot decided to return to Lydd Airport, where the wind was more favorable and he could burn off fuel. During the return flight with landing gear extended, he attempted manual extension but only managed half a turn of the emergency handle before encountering a mechanical limit. He checked the Airplane Flight Manual but found no procedure for this situation.
Upon contacting ATC at Lydd, the pilot requested alerting the rescue and firefighting service. After arrival, he performed another low pass; the RFFS confirmed all gears appeared down and locked. During landing, the pilot touched down gently on the right gear and used aileron to keep weight off the left gear as long as possible. As speed decreased and weight transferred, the left gear slowly collapsed. At about 10 kt, the left flap contacted the ground, and the aircraft slewed left off the runway. The pilot switched off electrical systems and exited via the right door.
Previous Landing Gear Problem
On the previous flight, about 10 weeks earlier, the same pilot heard a loud noise when lowering the gear, followed by only nose and right gear lights illuminating. After an uneventful landing, he taxied to the apron and reported the issue to maintenance. Examination found the left landing gear extension/retraction rod bent in two places and the downlock not engaged. The rod was replaced, and no further fault was found.
Engineering Examination
Examination after the accident revealed that the replacement left landing gear extension/retraction rod had bent in an almost identical manner to the previous rod. The landing gear lock mechanism was not free to move around its pivot due to corrosion and lack of lubrication, and the uplock roller was seized. Examination of the right landing gear showed restricted movement of the lock mechanism pivot and a very stiff uplock roller. Both uplock rollers were of the latest standard with grease nipples.
Maintenance
The aircraft was maintained in accordance with CAP 411, Light Aircraft Maintenance Schedule (LAMS) issue 2. A 50-hour check was carried out on 21 January 2008, and an Annual check on 19 June 2007. The accident occurred 7 and 45 hours after these checks, respectively. The manufacturer requires re-greasing of uplock rollers every 100 flight hours or 12 months, which was done during the June 2007 annual check. No specific inspection or maintenance requirements existed for the main landing gear lock mechanism pivot.
Similar Occurrence
In April 2008, a Beech B58 Baron aircraft, G-OSDI, experienced a right landing gear collapse after a similar failure to obtain a 'down and locked' indication. Examination revealed the right landing gear extension/retraction rod bent similarly to those on G-CDJV, and the right landing gear uplock roller was seized. The landing gear systems on both aircraft types are similar.
Other Information
The aircraft was parked in the open, mainly at coastal airfields. The manufacturer's Maintenance Manual notes that airplanes operated in extremely humid or cold, damp climates may need more frequent inspections for corrosion and lubrication. There is no similar statement in LAMS.
Safety Action
The aircraft manufacturer, Hawker Beechcraft, reviewed the accident and intends to include the uplock roller mechanism in the Pre-flight Inspection section of the A36 Airplane Flight Manual.