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Statuts:Enquête Officielle
Date:vendredi 22 août 2003
Heure:08:10
Type/Sous-type:Silhouette image of generic F406 model; specific model in this crash may look slightly different
Reims Cessna F406 Caravan II
Compagnie:Vincent Aviation
Immatriculation: ZK-VAF
Numéro de série: F406-0057
Année de Fabrication: 1990
Equipage:victimes: 0 / à bord:
Passagers:victimes: 0 / à bord:
Total:victimes: 0 / à bord:
Dégats de l'appareil: Substantiels
Conséquences: Repaired
Lieu de l'accident:Darwin Airport, NT (DRW) (   Australie)
Phase de vol: Au décollage (TOF)
Nature:Charter National
Aéroport de départ:Darwin Airport, NT (DRW/YPDN), Australie
Aéroport de destination:Katherine-Tindal Airport, NT (KTR/YPTN), Australie
Détails:
A Reims Cessna F406 Caravan II aircraft, registered ZK-VAF, was being operated on a passenger charter flight from Darwin to Tindal, Australia. At approximately 85-90 kts during the take-off roll, the nose landing gear (NLG) collapsed. The aircraft slid to a stop, the pilot shutdown the engines and all occupants evacuated the aircraft uninjured. Prior to this occurrence, on 2 and 19 June 2003, pilots reported difficulties obtaining a 'down and locked' indication for the NLG. Maintenance actions rectified the problems at that time.
An examination of the aircraft following the NLG collapse revealed that no damage was evident to any NLG components, or the NLG attachment structure. The NLG rigging was checked and reported to be within tolerances. Damage to the aircraft included abrasion damage to the lower forward fuselage and NLG doors. Both propellers were substantially damaged from ground contact.

The NLG hydraulic actuator was removed from the aircraft for further examination by the ATSB and was taken to a specialist hydraulic facility for functional testing prior to disassembly. The actuator passed all required functional tests, however, it was noted that the integral microswitch had been incorrectly adjusted to the point that it did not obtain switchover during operation of the hydraulic actuator. The microswitch was effectively always providing a signal indicating that the actuator was 'down and locked'. However, as the actuator microswitch was wired in series with the NLG overcentre microswitch on the aircraft, the landing gear indications would have appeared normal. The aircraft landing gear hydraulic system was powered during landing gear extension, however hydraulic power was removed once all three landing gear downlock microswitches were activated.

Probable Cause:

Advice from the aircraft manufacturer confirmed that the installation of the incorrect NLG actuator rod-end locking device, combined with a incorrectly adjusted NLG actuator microswitch, could lead to a NLG collapse if the dynamic loads experienced during take-off overcame the overcentre mechanism of the NLG drag brace assembly.

Alternatively, the hydraulic landing gear system power is removed once all three landing gear downlock microswitches are activated. It is also possible that, with the nose landing gear actuator microswitch incorrectly adjusted to the `down and locked' position, hydraulic power was removed from the landing gear system after activation of the two main landing gear down lock microswitches. If this occurred prior to the NLG actuator internal locking devices engaging, the NLG may have been held in the down position by the overcentre mechanism of the drag brace assembly. Had this occurred, then external dynamic loads would be able to collapse the NLG.

Sources:
» ATSB


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Plan
Ce plan montre l'aéroport de départ ainsi que la supposée destination du vol. La ligne fixe reliant les deux aéroports n'est pas le plan de vol exact.
La distance entre Darwin Airport, NT et Katherine-Tindal Airport, NT est de 284 km (177 miles).
Accident location: Approximate; accuracy within a few kilometers.

Les informations ci-dessus ne représentent pas l'opinion de la 'Flight Safety Foundation' ou de 'Aviation Safety Network' sur les causes de l'accident. Ces informations prélimimaires sont basées sur les faits tel qu'ils sont connus à ce jour.
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