What happened
On 20 April 2012, a Squirrel HT1, registration ZJ276, operated by the Defence Helicopter Flying School (DHFS), was conducting a solo-student sortie as part of the Single Engine Rotary Wing syllabus. The mission involved flying from RAF Shawbury to Chetw and performing a series of Quick Stop (QS) manoeuvres.
At approximately 1546 hrs, while performing a downwind flare and turn manoeuvre, the aircraft experienced an unexpected increase in the rate of descent. This resulted in the first impact with the ground within Chetwynd field. Following this initial incident, the pilot elected to continue the sortie and attempted an into-wind Quick Stop manoeuvre.
During the final stages of this second manoeuvre, the pilot noted a developing rate of descent and suspected the aircraft was experiencing vortex ring state. Despite attempts to gain forward airspeed by adjusting the cyclic and collective, the height decreased rapidly. The pilot made a conscious decision to adopt a landing attitude in anticipation of an inevitable impact. At 1551 hrs, the aircraft struck the ground at another location within Chetwynd field.
The pilot remained uninjured following the second impact and was able to shut down the engine and egress the aircraft once the rotors had slowed. The aircraft sustained significant damage, including a failed tail pylon, fractured vertical stabiliser, and damaged undercarriage.
The investigation
The investigation examined the sequence of events leading to both impacts, the pilot's actions during the vortex ring state suspicion, and the physical condition of ZJ276 following the second crash. Investigators reviewed the student pilot's training records, noting they had completed approximately 32 hours of total flying time prior to the accident.