Investigation Summary
The investigation revealed a systemic disregard for safety regulations by Strato-Freight. The aircraft was configured with only 65 seats but carried 75 passengers, forcing many to share seats or sit on laps. The weight manifest was falsified to show 44,500 lbs, while the actual weight was 48,709 lbs. Maintenance performed just days before the crash involved the installation of AC-LS-87 spark plugs, which were explicitly prohibited for use in the Pratt and Whitney engines of the C-46. During the accident flight, the right engine began backfiring at an altitude of only 250 feet. Post-crash inspection found the right magneto switch set to 'Left', meaning only the rear row of spark plugs was firing. These plugs, already unapproved, suffered extreme heat damage and fused, leading to total power loss. The crew did not attempt to feather the propeller. Furthermore, the right cowl flaps were fully open and the landing lights were extended, creating significant parasitic and interference drag. The overloaded airframe, burdened by this additional drag, could not maintain flight, resulting in a ditching 200 yards offshore.
Final Conclusions
The Civil Aeronautics Board determined the probable cause was the loss of power in the right engine before reaching optimum single-engine climb speed, exacerbated by the aircraft's overloaded condition. Contributory factors included the use of unapproved spark plugs, improper magneto switch positioning, and the operator's general indifference toward civil air regulations.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Pilot
Acting as pilot during the accident flight; Chief Pilot and Vice-President of Strato-Freight.
Copilot
Acting as copilot during the accident flight.
Captain
Designated Captain in command of the flight; was riding in the passenger cabin at takeoff and entered the cockpit when the engine backfired.
Copilot
Part of the crew complement for the flight.
Systems & Failure Modes
Pratt & Whitney R-2800 Engines
The powerplants required specific approved spark plugs; the use of unapproved AC-LS-87 plugs led to overheating and failure.
Magneto Ignition System
The ignition switch was improperly set to the 'Left' position, isolating the front row of spark plugs and overloading the rear row.
Weight and Balance Manifest
The manifest was inaccurately prepared, underreporting the aircraft's weight by over 4,000 pounds.
Interesting Facts
- 01The aircraft was 3,709 pounds over its maximum certified takeoff weight of 45,000 pounds.
- 0230 of the 36 spark plugs in the right engine were AC-LS-87 models, which were not approved for the C-46.
- 03The cabin contained only 65 seats for 75 passengers, leading to seat-sharing.
- 04The right engine magneto switch was found in the 'Left' position, firing only the rear spark plugs.
- 05At the time, this was the deadliest accident in the history of commercial aviation.
- 06None of the passengers had received instructions on the location or use of emergency equipment prior to the ditching.
- 07On the inbound leg to San Juan, the flaps extended fully when only 1/4 was selected due to a frayed follow-up cable.
- 08There was a discrepancy in emergency equipment: the operator claimed 13 life rafts were on board, but a CAA inspection two months prior recorded only seven.
Safety Actions & Advisories
Revocation of Operating Certificate
Strato-Freight's operating license was suspended immediately after the crash and permanently revoked effective November 8, 1949, due to a pattern of safety violations and indifference to regulations.
Location
ACCIDENT SITE · Coordinates taken from the wikidata coordinate.