Investigation Summary
The accident occurred during the aircraft's very first flight, intended to secure its Series Certificate of Airworthiness. The test schedule included stalling maneuvers with the aircraft's center of gravity near its aft limit. After successfully testing the stick shaker and stall recovery systems (which operated at 102 knots and 93 knots respectively), the crew disabled these safety systems for a fourth run to explore the aircraft's natural handling characteristics beyond the automated protection limits. During this final run at approximately 11,600 feet, the airspeed was reduced at a rate exceeding 1 knot per second. The pilot failed to initiate recovery before the aircraft reached a critical angle of attack. The T-tail design of the Trident made it susceptible to a deep stall or superstall, where the turbulent wake from the stalled main wing blankets the horizontal stabilizer, rendering the elevators ineffective. The aircraft pitched up 30 to 40 degrees and turned to port; the starboard wing then dropped sharply and, following a short burst of engine power, the aircraft entered a flat spin to the starboard (right) side, descending at a rate of one rotation every 6 to 8 seconds. The aircraft was not equipped with an anti-spin parachute, which might have assisted in recovery.
Final Conclusions
The Accidents Investigation Branch (AIB) concluded that the probable cause was the delay of decisive recovery action during a stalling test, which allowed the aircraft to enter a superstall from which recovery was impossible. The investigation noted that the speed reduction during the final run was more rapid than specified in the test schedule and that recovery was not initiated until the speed had fallen beyond the set limits. No evidence of pre-crash mechanical failure was found.
Video Analysis
1966 Felthorpe Trident (G-ARPY) Crash Aftermath Footage — Archival footage and eyewitness accounts of the aftermath of the Hawker Siddeley Trident crash in Norfolk, including the recovery efforts and the description of the aircraft's flat spin.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Pilot Peter Barlow
Pilot
Pilot George Errington
Systems & Failure Modes
Stall Recovery System
An automated system (stick pusher) designed to push the nose down when a stall is imminent; it was intentionally disabled for the final test run.
T-tail Configuration
A design where the horizontal stabilizer is mounted on top of the vertical fin, which can lead to a deep stall if the stabilizer is blanketed by the wing's wake.
Interesting Facts
- 01This was the first loss of a Hawker Siddeley Trident aircraft.
- 02The aircraft was being operated with its center of gravity towards its aft limit, which increases stall sensitivity.
- 03The aircraft was not equipped with an anti-spin recovery parachute.
- 04The flat spin involved a rotation rate of one turn every 6 to 8 seconds.
- 05The aircraft had only 1 hour of total airframe time at the time of the crash.
Safety Actions & Advisories
Anti-Spin Parachute Requirement
Following the accident, it became a mandatory requirement for all future Trident stalling tests to be conducted with an anti-spin recovery parachute fitted to the aircraft to provide a recovery mechanism from a deep stall.