During the approach, and while below the maximum limit speed of 270 Kts, the flight crew of the Boeing 767 aircraft lowered the landing gear to assist in speed reduction. After a normal landing at Darwin, the crew was informed by a maintenance engineer that the right main landing gear (MLG) strut door had separated from the aircraft. Although an extensive search was conducted by the operator's maintenance staff, the separated door and some attachment fittings were not recovered.
A subsequent examination of the remaining MLG shock strut door attachment fittings revealed that they all showed fractures characteristic of rapid overloading, and were damaged as a result of the door separation but had not contributed to the initial failure sequence.
The aircraft manufacturer issued a Fleet Team Digest (767-FTD-52-01005, revised 21 Nov 2001), referring to Service Bulletin (SB) 767-32A0051, revision 3, dated 27 Mar 1997. The Digest indicated that the manufacturer had received reports of loose or fractured MLG shock strut door attach bolts and that they had "identified details in the MLG door attach joint assembly that can lead to bolt preload loss." The Digest also indicated that operators may wish to inspect the applicable MLG shock strut door attachment joints for looseness. Looseness or premature failure of MLG shock strut door attach bolts could have lead to the loss of the door from the aircraft.
A similar event occurred to an Australian registered B767 aircraft, VH-NOA, on 26 August 2000, during approach to Amsterdam airport in the Netherlands. The Dutch Transport Safety Board is investigating this occurrence.
As a result of this occurrence, the operator raised an Engineering Instruction (EI), EI-767-032-0102 Rev 0, to immediately inspect all B767 MLG shock strut doors and check the torque values of the door attaching hardware. All of the operator's B767 aircraft were subsequently checked between 23 November 2001 and 8 December 2001. The inspection revealed that a number of MLG shock strut door mounting bolts were found to be below the required Aircraft Maintenance Manual (AMM) torque value and were retorqued to the correct value. As a result of the EI inspection, the operator subsequently issued a revised EI (EI-767-032-0102 Rev 1) requiring that the inspection be conducted on a regular basis; every 3 months.
As a result of reports of loose or fractured MLG shock strut door attach bolts, the aircraft manufacturer developed an engineering change to prevent the MLG shock strut door attach bolts from loosening and indicated that a Service Bulletin to incorporate those changes would be released in the second quarter of 2002.
As there have been two similar events on Australian registered aircraft, The Australian Transport Safety Bureau will continue to monitor actions relating to B767 MLG shock strut door separation occurrences pending the release of the Service Bulletin.
|Date:||20 November 2001||Investigation status:||Completed|
|Time:||1600 hours CST|
|Location:||2 km ESE Howard Springs, Locator|
|Release date:||05 March 2002||Occurrence category:||Incident|
|Report status:||Final||Highest injury level:||None|
|Aircraft manufacturer||The Boeing Company|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Minor|
|Departure point||Cairns, QLD|
|Departure time||1400 hours CST|