Statuts:	Enquête Officielle
Date:	05 SEP 1954
Heure:	02:39
Type/Sous-type:	Lockheed L-1049C-55-81 Super Constellation
Compagnie:	KLM Royal Dutch Airlines
Immatriculation:	PH-LKY
Numéro de série:	4509
Année de Fabrication:	1953
Heures de vol:	2498
Moteurs:	4 Wright R-3350-972-TC-18-DA-1
Equipage:	victimes: 3 / à bord: 10
Passagers:	victimes: 25 / à bord: 46
Total:	victimes: 28 / à bord: 56
Dégats de l'appareil:	Perte Totale
Conséquences:	Written off (damaged beyond repair)
Lieu de l'accident:	2,5 km (1.6 milles) SE de Shannon Airport (SNN) (Irlande)
Phase de vol:	En montée initiale (ICL)
Nature:	Transport de Passagers Intern.
Aéroport de départ:	Shannon Airport (SNN/EINN), Irlande
Aéroport de destination:	New York-Idlewild International Airport, NY (IDL), Etats-Unis d'Amérique
Numéro de vol:	633

Détails:
The KLM Super Constellation, named "Triton", operated on the Amsterdam-New York route. A scheduled refueling stop was made at Shannon. The flight left Shannon Terminal Building at 02:30 hours at night and taxied to runway 14 (5643 feet long). The before take-off run-up was completed in take-off position.
Take-off was made at 02:38. V1 speed was reached at 3500 feet and lift-off at 125 knots was made just over the V2 speed at approximately 4000 feet from threshold. The flight then passed over the remaining 1600 feet of runway in a shallow climb, retracting its landing gear. The Constellation entered a shallow descent over the River Shannon. The duration of the flight was about 31 seconds from the time it passed over the end of the runway until the aircraft first contacted the water in a tail-down slightly right-wing low attitude. It came to rest on the Middle Ground, a shallow mudbank 8170 feet from the end of the runway., after losing engines nr. 3 and 4.

PROBABLE CAUSE: "1) Failure of the captain to correlate and interpret his instrument indications properly during flap retraction, resulting in necessary action not being taken in sufficient time. This failure was partially accounted for by the effect on instrument indications of inadvertent and unexpected gear re-extension. 2) Loss of aircraft performance due to inadvertent landing gear re-extension. 3) The captain failed to maintain sufficient climb to give him an opportunity of meeting unexpected occurrences."

Sources:
» ICAO Accident Digest Circular 50-AN/45 (20-33)
» Nederlandse Constallations / H.Dekker