Investigators have disclosed that the Learjet 35A which veered off the runway and fatally collided with a parked business aircraft at Scottsdale had touched down with a misaligned left-hand main landing-gear.
As the aircraft conducted the approach to runway 21 on 10 February, video images captured from a golf course reveal the jet’s left main-gear trailing rearwards from its normal position.
The video also shows a bright spot beneath the left wing flap, consistent with the landing-gear strut facing aft and the landing-gear light pointing the wrong way.
According to preliminary findings from the US National Transportation Safety board, the crew “did not make any radio calls” indicating they were aware of a landing-gear malfunction.
As the Learjet touched down at 112kt, its left wing immediately dipped and the aircraft veered off the left side of the runway.
It crossed rock-covered islands and the parallel taxiway B, struck the windsock, and entered an apron area where it collided with the aft right fuselage of a parked Gulfstream G200.
Of the Learjet’s four occupants, its captain was fatally injured, and the first officer and one passenger were seriously injured. An individual inside the G200 also received serious injuries.
The Learjet travelled about 2,700ft between touchdown and the impact.
Its engines, which continued to run after the collision, were not equipped with thrust-reversers and the jet’s drag chute was not deployed.
Investigators discovered the left main landing-gear assembly had separated from the aircraft. It was located on taxiway B10.
The landing-gear trunnion casting is normally attached the to the wing spar with an aft trunnion pin which, in turn, is fixed in place with a retaining bolt.
But the inquiry says that, while the retaining bolt was in place and secured, the aft trunnion pin was “not present” in the trunnion casting. The pin was still inserted in the wing spar.
The inquiry says that, during landing-gear installation, it is possible for the retaining bolt to miss its locating hole in the aft trunnion pin if the pin is not fully pushed into the trunnion casting.
While the inquiry is yet to reach conclusions, the aircraft had suffered a hard landing at McAlester, Oklahoma, in June last year, touching down just short of the runway and bouncing several times.
As a result, both main landing-gear assemblies had been removed to facilitate inspections, by a mechanic who had worked on the jet under its previous owner.
The mechanic told the inquiry that he followed the maintenance manual for all of the work he performed.
Investigators have not ascertained the Learjet’s hours and cycles since this maintenance was carried out.
A technician who serviced the landing-gear in December last year noticed nothing unusual but observed that the left-hand assembly required “excessive” grease. If the aft trunnion pin is not fully engaged, it can allow grease to escape, and investigators found large quantities of deposited grease beneath the pin in the jet’s wing spar.
Investigators are aware of three other events, at least, in which a Learjet’s landing-gear had disconnected from the airframe because the retaining bolt was not engaged through the aft trunnion pin.
