History of the Flight
G-BGBN, a Piper PA-38-112 Tomahawk, departed Runway 03 at Cranfield Aerodrome at 1232 hrs on 5 June 2013 for a circuit training flight. The instructor occupied the right seat and the student the left. The aircraft completed a right-hand circuit and an approach for a touch-and-go landing, which observers described as uneventful. The aircraft touched down near the touchdown zone markers and lifted off near the intersection of the runway and Taxiway C.
Approximately two seconds after lift-off, the instructor transmitted "golf bravo november rough running engine turning around for runway 21." The aircraft entered a gentle right turn, then abruptly reversed to a left turn. As it passed the upwind end of the runway, the nose dropped. The aircraft descended and crashed 100 m north-west of the threshold of Runway 21, within the aerodrome boundary.
Witness Information
The air traffic controller, upon hearing the instructor's transmission, sounded the crash alarm as the aircraft appeared to be in distress. The controller estimated the aircraft climbed to a maximum of 50 to 75 ft agl during the right turn, then made a very sharp reversal with a high angle of bank. Another witness estimated the maximum altitude at approximately 200 ft.
Information from the Instructor
The instructor did not recall the circuit and touch-and-go; his recollection was that the accident occurred immediately after takeoff. He noted that normal practice was to select carburettor heat to hot when reducing power on base leg.
Approximately two hours before the accident, the instructor flew G-BGBN and experienced rough running on short final. After landing, he performed a magneto check that showed a drop of about 500 rpm on one magneto and rough running leading to engine stop on the other. He reported the issue to the flying school owner. Before the accident flight, the owner stated the magneto problem had been rectified and the aircraft was "all fine." The pre-takeoff checks, including the magneto check, were normal.
During the accident flight, the instructor reported that the engine ran rough soon after takeoff; he took control and considered turning to land on Runway 21. As the aircraft was unable to climb, he turned left away from a sports club towards a clear area within the aerodrome, believing there was sufficient space to land. During the turn, the engine stopped completely and the stall warning operated immediately.
Aircraft Information
The PA-38 Tomahawk is a single-engine, two-seat aircraft with a Lycoming O-235-L2C piston engine and two magnetos. The aircraft was equipped with flow strips on the wing leading edges per FAA Airworthiness Directive 83-14-08. The magneto switch was located beneath the left control yoke.
Accident Site
The aircraft impacted ground 100 m on a bearing of 320° from the Runway 21 threshold. The left wing struck first on a heading of 180°, with an estimated pitch of 50° nose-down. The aircraft came to rest on a heading of 090°. The left wing was destroyed; the nose section, cockpit, and engine were badly damaged. The right wing had compression damage to the leading edge. The fuel selector valve was found in the right tank position. The left fuel tank was empty; a small quantity of clean fuel was recovered from the right tank. The flying controls were intact and serviceable with no evidence of restriction. The flaps were set at 15° down. The key in the magneto switch was found in the left magneto position, undamaged; however, it could have been moved post-accident.
Detailed Examination
An examination at the AAIB facility found both fuel tanks clean with clear filters. No blockages were present in fuel lines, and the fuel selector valve was fully open. The electrical fuel pump operated normally. The carburettor heat flap was in the cold position. The engine turned freely, valves operated normally, and no seizure was evident. Both magnetos tested serviceable; spark plugs operated satisfactorily. The carburettor had no blockages, floats intact, and mixture control assessed as fully rich. The mechanical fuel pump and internal seals were serviceable. The left magneto was not producing a spark externally, but internal testing revealed no fault. The exact reason for the engine failure could not be determined.