What happened
On 27 June 2015, an Auster J1N Alpha, registration G-AHSS, was conducting a private flight at Great Massingham Airfield in Norfolk. Following a standard approach, the pilot landed into the wind on Runway 28. After touchdown, the aircraft began to drift toward the left side of the runway. The pilot was unable to maintain the aircraft on the paved surface, and it transitioned into the long grass bordering the runway.
As the aircraft moved off the pavement, the left landing gear struck several large stones that had been obscured from the pilot's view. This impact caused the aircraft to tip forward suddenly, resulting in the propeller striking the ground. When the aircraft settled back onto its landing gear, the movement caused additional damage to the tail section and the fuselage. The engine ceased operation during the event, and the pilot was able to safely secure the aircraft and exit without injury.
The investigation
The investigation examined the sequence of events following the landing and the physical damage sustained by the aircraft. The investigation established that the aircraft suffered damage to the propeller, cowlings, exhaust, tail, and the spring connecting the wheel mount. The pilot noted that the initial drift was likely triggered by a wind gust and admitted that his response was delayed once the aircraft had stabilized after landing. The pilot also identified that the presence of large, invisible stones was a critical factor in the sudden forward pitch of the aircraft.