Investigation Summary
The flight, VH-AET, was operating significantly behind schedule; it was originally slated to depart at 4:50pm but did not take off until 8:50pm local time. The cockpit was unusually occupied by three pilots: the Captain, a First Officer, and a supernumerary pilot undergoing his first airline orientation. Witnesses at Seven-Mile Beach observed the aircraft climb normally to just over 400 feet before it performed a slight left turn and plunged into the sea. The impact was so severe that the aircraft disintegrated, with the rear fuselage being one of the few large sections recovered after it floated to the surface. The subsequent investigation, led by John Watkins and later a formal inquiry by Justice Simpson, focused on the layout of the DC-3 cockpit. In the dark, the lever for the Sperry autopilot was located in close proximity to the fuel cross-feed lever. If the autopilot was engaged while the aircraft was in a climbing attitude without being properly trimmed for level flight, the system would have immediately applied a strong nose-down force to maintain the set altitude. Calculations suggested the aircraft descended at a rate of 4,000 feet per minute, reaching 160 mph before impact. The inquiry also revealed that Captain Thomas Spence had hidden a diagnosis of diabetes from civil aviation authorities, having previously been discharged from the RAAF for the condition. It was theorized that he may have been suffering from the effects of insulin at the time of the error.
Final Conclusions
The inquiry concluded that the crash resulted from the aircraft being inadvertently flown into the sea following a sudden nose-down pitch. The most probable trigger was the accidental engagement of the autopilot in place of the fuel cross-feed. The Captain's medical condition (diabetes) and the lack of runway lighting at Cambridge Aerodrome were noted as significant factors. Justice Simpson's report led to major changes in Australian aviation, including the requirement for government-appointed doctors to conduct pilot medicals and the standardization of cockpit lever shapes to prevent tactile confusion.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Thomas Spence, aged 30. Had been a DC-3 captain for one year.
First Officer
David Collum, aged 21.
Supernumerary Pilot
Austin Gibson, aged 37. Experienced RAAF instructor but had no prior DC-3 experience.
Systems & Failure Modes
Sperry Autopilot
A hydraulic system that, if engaged while the aircraft was climbing, would immediately attempt to level the plane, causing a violent nose-down pitch.
Fuel Cross-feed Lever
A cockpit control used to manage fuel flow between tanks; its proximity and similar feel to the autopilot lever led to the suspected pilot error.
Interesting Facts
- 01The aircraft was approximately 900 pounds below its maximum authorized takeoff weight.
- 02The elevator trim tab was found set for a shallow climb, indicating no mechanical failure of the primary flight controls.
- 03The Captain had 3,500 hours of experience but had concealed a diabetes diagnosis to maintain his commercial license.
- 04The investigation used a de Havilland Dragonfly to perform reenactment flights for witnesses to estimate the crash altitude.
Safety Actions & Advisories
Medical Examination Reform
Recommended that medical examinations for pilot licenses be conducted by doctors chosen and paid for by the Department of Civil Aviation to prevent pilots from withholding medical history.
Cockpit Ergonomics
Recommended that levers for the autopilot and fuel cross-feed be modified to have distinct shapes and appearances to prevent tactile confusion.
Night Operations Lighting
Proposed regulations to prohibit night takeoffs without a flare path or runway lighting system that must remain lit until the aircraft is safely clear.
Supernumerary Pilot Review
Source ↗Recommended a review of the practice of allowing pilots under instruction to gain experience in the cockpit of aircraft carrying passengers.
Maintenance Record Keeping
Source ↗Recommended that ground engineers completing daily inspections must keep copies of their inspection records.
Known Controversies & Unanswered Questions
Concealment of Medical Condition
Reference ↗The investigation revealed that Captain Thomas Spence had been discharged from the RAAF in 1941 for diabetes but successfully concealed this from civil aviation authorities for years. This sparked a significant debate regarding the efficacy of pilot medical examinations and the ability of pilots to withhold critical health information from the Department of Civil Aviation.