Cessna 208B Caravan, G-BZAH, 4 November 2004
Cessna 208B Caravan, G-BZAH
Summary:
An instructor pilot was carrying out a training flight with another qualified club pilot to address The aircraft, MTOW 8,750 lbs, was being taxied from the dispersal in preparation to depart when the pilot hear two loud bangs from the area of the nose wheel and returned the aircraft to the dispersal. Examination found that the rear support of the nose landing gear spring had come away from its fuselage mounting point. Metallurgical examination of the nose landing gear spring rear support’s four attachment bolts showed that one had failed due to bending fatigue and the remaining three had pulled from their self locking anchor nuts causing the bolt threads to strip. The fatigue failure was initiated and propagated by the support casting being loose. There was good evidence of long term fretting between the attachment bolts and the rear support casting. Examination of elongated holes in the fuselage structure showed that the elongation had occurred in a forward direction, indicating that the nose gear spring had moved forward. Towing the aircraft by the nose wheel increases the forward load on this support. A sudden start, jerk or attempt to start towing with the parking brake on or wheel chocks in place could substantially increase the forward loads on the attachment bolts.
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