Incident Description
Following departure, the nose gear unsafe light remained illuminated during gear retraction. Attempts to obtain a safe light indication with the nose gear in the extended position were unsuccessful. When the aircraft landed, it settled onto a partially retracted nose gear.
Inspection Findings
Inspection of the aircraft revealed that the nose gear strut had not fully extended. During retraction, the nose gear tires caught the nose gear doors, preventing them from opening. The gear retracted against the doors, causing failure of the retract jackscrew. A microswitch designed to cut the gear motor off under this condition was found out of adjustment and did not operate.
Maintenance Issues
It was further discovered that the mechanics who performed the last gear retract test on the aircraft used a maintenance manual for an earlier model aircraft that did not have this safety switch. Consequently, they failed to check the microswitch for adjustment.
No reason as to why the nose gear strut did not fully extend was found.