History of the Flight
The pilot conducted a standard approach and landing onto Runway 08 at Popham Airfield. During the flare, the pilot continued to apply back pressure on the control column to allow the nosewheel to lower gently onto the grass. When the nose landing gear touched down, the aircraft pitched down and came to rest on the propeller. The sole occupant exited the aircraft without injury.
Aircraft Information
G-BUDI was built in 1994 and had accumulated 114.55 hours. The current owner had flown it since construction and operated it from the grass airfield at Popham. Previously, it had been operated from paved runways and taxiways at Blackbushe.
The nose landing gear strut on this type of aircraft consists of a thick-walled square tube with a castoring nose wheel assembly attached to the lower end. Near the top of the strut, a drag brace is attached, running forward to the central longitudinal member of the engine mount assembly. This longitudinal member is welded to lateral bracing tubes. Some aircraft, including G-BUDI, have a damper incorporated with the drag brace.
Metallurgical Examination
The longitudinal engine mount tube failed at the location of the weld attaching it to the rear lateral bracing tube. The engine mount and drag brace were sent to the AAIB for examination. Magnetic tests indicated the tubing was manufactured from ferro-magnetic steel. The failure developed from multiple fatigue initiations across most of the tube face. The face was mechanically damaged during and after separation, but evidence of multiple, relatively low-cycle fatigue initiations was visible along the top edge where the weld was located. It was concluded that the separation resulted from fatigue damage induced by cyclic bending due to normal operating loads on the landing gear.
Safety Action
The PFA Type Acceptance Data Sheet (TADS) 202 was re-issued on 02/02/07, including a reference to Pulsar noseleg failures. The data sheet notes that noseleg failures have occurred due to failure of early 5/8" diameter noseleg castor pivot pins, leading to introduction of improved 3/4" diameter pins. Additionally, failures have occurred due to fatigue of the square steel tube support stub for the front noseleg suspension strut where welded to the forward engine mounting cross-beam. The PFA planned to issue a bulletin to Pulsar owners calling for reinforcement of the nose leg support stub, mandatory for issue or renewal of a Permit-to-Fly.