Cessna 421 flight crew reported a nose gear collapse during a maintenance preflight check. Reportedly; the collapse resulted from maintenance test protocols not being followed resulted.
Synopsis
Cessna 421 flight crew reported a nose gear collapse during a maintenance preflight check. Reportedly; the collapse resulted from maintenance test protocols not being followed resulted.
Narrative
We intended to perform an operational maintenance test flight on Aircraft X after maintenance on the landing gear. The previous flight had two landings and taxi back for takeoff. After the second taxi back and take off; the landing gear would not retract. We left the gear down and flew back to ZZZ for maintenance.The airplane was jacked; and maintenance performed tests and found that relay was preventing gear retraction. They said the relay released and the gear was operated up and down several times while on jacks.On this maintenance test flight; we performed normal checklist outside and inside. When the left engine was started; the nose gear began to retract. At that time; I shut down everything. Then noticed the landing gear handle was in the up position. Maintenance must have left the gear handle in the up position after troubleshooting.There were no warning lights or gear horns when battery power was applied.It is my belief that the squat (Weight on Wheels) switch failed preventing warning indications but allowed the gear to retract.
Second reporter narrative
I was the safety pilot/observer sitting in the right seat. We had trouble adjusting the copilot seat; as it had been removed for maintenance work on the landing gear problem from a flight 2 weeks ago. I was occupied with fixing the copilot seat while the PIC (pilot in command) was conducting the preflight checks. As I was connecting my headset the PIC started the left engine. I did not check any of the switch positions prior to the engine start. The next thing I knew the nose dropped to the ground and the engine stopped. When checked the gear switch was in the up positions. There were no warning lights or horns; as would be normal with application of power and the gear switch not it the correct position.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.