Beech 76, VH-JKE, Archerfield, Queensland, on 27 April 1989

Circumstances:

The aircraft had been involved in asymmetric training, and the landing gear had been cycled two or three times during the flight. On the final down selection, a green light was obtained for the mainwheels but not for the nosewheel. The landing gear was recycled with the same result. Emergency landing gear extension was carried out, again with the same result. The aircraft was landed with the nosewheel in the retracted position. Inspection of the nose landing gear system revealed that the forward pivot arms of the door operating mechanism had moved through the over-centre position. This condition, about which there is a warning in the Beech 76 Maintenance Manual, will cause the nose landing gear not to extend. Damage inside the nosewheel well indicated that, during the last retraction cycle, the landing gear drag brace pin became positioned outside the slot in the door actuating fork, forcing the forward pivot arms into the over-centre position. No fault was found with the rigging of the of the nose gear/door mechanism and extension/retraction of the landing gear was normal, apart from some stiffness in the nose gear door hinges. The fault could be duplicated during ground tests by applying side loads, such as might have occurred during unbalanced flight, to the nose landing gear doors. The stiffness in the door hinges might also have been of significance. In 1983 Beechcraft issued Service Instruction 1209 to reduce the possibility of binding in the door hinges or the landing gear linkage which could prevent nose landing gear extension. The records of VH-JKE indicated that the instruction had not been carried out.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. Malfunction of the nose gear assembly may have been caused by aerodynamic side-loads on the nose landing gear doors, stiffness in the door hinges, or a combination of these influences.

2. The nose landing gear could not be extended.