Investigation Summary
On a cold, snowy evening, the aircraft was prepared for a scheduled service to Glasgow on behalf of Scottish Airways. The aircraft, manufactured in 1944 (MSN 12455), had a significant military history as a former USAAF C-47A (42-92633) and RAF KG420 before being registered to Railway Air Services in March 1946. Although the Dakota had been de-iced, a heavy snowstorm caused significant outbound delays. The aircraft waited for over an hour for takeoff clearance, during which time the temperature dropped and fresh snow froze onto the wing surfaces. Upon receiving clearance, Captain W.J. Johnson applied 45.5 inches of manifold pressure, but as the aircraft lifted off, it failed to climb. Realizing it was too late to abort, the pilot attempted to maintain flight, but the left wing struck a rooftop on Angus Drive. The aircraft slewed 90 degrees and came to rest perched on the roofs of numbers 44 and 46 Angus Drive. In a remarkable escape, the crew and the single passenger exited the aircraft through emergency windows, entered the loft of the house, and walked down the stairs to exit through the front door.
Final Conclusions
The investigation determined that the primary cause was the accumulation of snow and ice on the wings during the one-hour delay, which severely degraded the aircraft's aerodynamic lift. A contributing factor was the pilot's error in judgment for attempting a takeoff when the aircraft was almost entirely covered with snow. The radio officer survived because he was standing between the pilot seats at the moment of impact; a propeller blade pierced his empty seat, which likely would have killed him had he been strapped in.
Video Analysis
Douglas C47 Dakota - Landed On A House — On the 19th December 1946, a Railway Air Services Douglas Dakota crashed on a house in Ruislip. Miraculously no-one was hurt.
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Airframe & Maintenance
Systems & Failure Modes
Wing Aerodynamics
The accumulation of frozen snow on the upper wing surfaces disrupted the laminar flow of air, significantly reducing lift and increasing drag.
Pratt & Whitney R-1830-92 Engines
The two Twin Wasp engines were operated at 45.5 inches of manifold pressure during the takeoff attempt.
Interesting Facts
- 01The aircraft came to rest on the roof of a house where a four-month-old baby was sleeping; the child did not wake up during the crash.
- 02The house at 46 Angus Drive was subsequently nicknamed 'Dakota's Rest'.
- 03Captain Johnson earned the nickname 'Rooftop Johnson' following the incident.
- 04The radio officer avoided death because he was standing up to look through the windshield instead of being strapped into his seat.
- 05Oil stains from the wreckage continued to reappear on the ceilings of the repaired houses for ten years after the accident.
- 06While most sources record the date as December 19, 1946, some accounts cite December 14.
Safety Actions & Advisories
De-icing Procedure Reinforcement
The investigation highlighted the critical need for flight crews to ensure aerodynamic surfaces remain clear of snow and ice following long ground delays, even if initial de-icing has been performed.
Pilot Judgment and Surface Inspection
The accident underscored the pilot's ultimate responsibility to verify the aircraft's airworthiness and surface cleanliness before attempting takeoff in freezing conditions, leading to stricter adherence to pre-flight inspection protocols in inclement weather.