Statuts:	Enquête Officielle
Date:	29 MAI 1947
Heure:	19:05
Type/Sous-type:	Douglas DC-4
Compagnie:	United Air Lines
Immatriculation:	NC30046
Numéro de série:	18324
Année de Fabrication:	1944
Heures de vol:	5950
Equipage:	victimes: 2 / à bord: 4
Passagers:	victimes: 41 / à bord: 44
Total:	victimes: 43 / à bord: 48
Dégats de l'appareil:	Perte Totale
Conséquences:	Written off (damaged beyond repair)
Lieu de l'accident:	New York-La Guardia Airport, NY (LGA) (Etats-Unis d'Amérique)
Phase de vol:	Au décollage (TOF)
Nature:	Transport de Passagers Nat.
Aéroport de départ:	New York-La Guardia Airport, NY (LGA/KLGA), Etats-Unis d'Amérique
Aéroport de destination:	Cleveland Municipal Airport, OH (CLE/KCLE), Etats-Unis d'Amérique
Numéro de vol:	521

Détails:
At 19:04, United's DC-4 "Mainliner Lake Tahoe" was ready to depart, and the pilot advised: "Ready for take-off." The tower operator asked whether the flight wished to wait out a storm on the ground. The captain answered. "I'll take off." The tower then advised the flight: "Cleared for immediate takeoff, or hold; traffic on final approach north of Riker's Island." Flight 521 rolled onto runway 18, and accelerated for takeoff immediately. The captain applied back pressure to the control column but the controls felt heavy and the aircraft did not respond. The captain decided to discontinue take-off. About 1,000 feet from the south end of the runway he applied brakes, ordering the co-pilot at the same time to cut the engines. A ground-loop was attempted by heavy application of left brake. The aircraft, however, proceeded to roll straight ahead. Then, with both brakes locked it continued over the remainder of the runway, crashed through the fence at the airport boundary, and half-bounced, half-flew across the Grand Central Parkway. The aircraft finally came to rest immediately east of the Casey Jones School of Aeronautics, a distance of 800 feet from the end of runway 18 and 1,700 feet from the point at which brakes were first applied. It was almost immediate enveloped in flames.
Investigation revealed that the guts locks on the plane had been altered, permitting it to remain locked even after removal of the gust lock warning tape.

PROBABLE CAUSE: "The Board determines that the probable cause of this accident was either the failure of the pilot to release the gust lock before take-off, or his decision to discontinue the take-off because of apprehension resulting from rapid use of a short runway under a possible calm wind condition."

Sources:
» CAB Accident Investigation Report
Sample newspaper article from Newspaperarchive.com