Accident
On 14 May 2022 at 1515 UTC, a DH82A Tiger Moth (registration G-AXAN) was landing on a private farm strip near Duxford, Cambridgeshire. The pilot, a 49-year-old Commercial Pilot with 3,687 hours total (533 on type), was conducting a private flight with one passenger. During the landing on grass Runway 22, the pilot reported an unusual touchdown and the aircraft bounced. It then landed in a three-point attitude and came to a sudden stop, nosing over and becoming inverted. Both occupants were uninjured and exited the aircraft without assistance.
Inspection revealed that the left wheel had touched down in soft ground, causing the landing gear to fail at the lower fork end fitting on the compression leg. The pilot had walked the runway before the flight and noted soft ground at the sides but considered the conditions adequate.
Aircraft and Modifications
The aircraft, manufactured in 1942, was a DH82A Tiger Moth powered by a De Havilland Gipsy Major 1F piston engine. The original design used an aluminium alloy lower fork end fitting, but service experience indicated failures after repeated hard landings. A steel lower fork end fitting was later introduced, and De Havilland Support Ltd Technical News Sheet (TNS) 22 recommends its installation on all standard Tiger Moths. G-AXAN was fitted with the steel fitting and also equipped with wheel brakes, a modification described in TNS 22 but not endorsed by the design holder because the landing gear was not designed for braking loads. Cases of fractures have occurred with brakes installed.
Examination
The design approval holder considered that the ground conditions combined with a hard landing or bounce might not have been sufficient to cause the failure, and considered whether braking loads contributed. A representative examined the aircraft: the fuselage tubular structure above the compression leg attachment was undamaged, suggesting no extreme hard landing. However, the left compression leg top attachment bolt showed shear failure, indicating a very hard landing either on the accident flight or previously. The compression leg to axle joint had separated, and the pin failed with no discernible fracture features. The lower fork fitting sustained substantial damage when striking the ground, obscuring most of the fracture face, but some evidence of shear failure was noted on the forward lug. The stub axle was bent slightly upwards, indicative of a hard landing.
Comment
The damage was consistent with a hard landing having occurred at some time. It was not possible to determine whether any pre-existing defect or failure, such as related to braking loads, contributed to the failure. The design approval holder highlighted the warning in TNS 22 regarding the fitment of wheel brakes.