[Mark Ashiku]

I fly a 1965 Skymaster 337 (normally aspirated, front engine mechanical hydraulic pump) and had a gear door issue that recently occurred.

Briefly, on run-up as per the POH (gear handle in the down position with green light) all systems were normal. Upon retarding the throttle the gear warning horn sounded, the green gear door indicator light was off, and the gear indicator circuit breaker had tripped. Once parked and inspected the following was noted:

• All gear doors were open.
• Landing gear down and locked.
• Full hydraulic fluid reservoir on power pack.
• No hydraulic leaks.
• Tripped gear indicator circuit breaker.
• Gear handle in the down position with green gear down light off.
• No obvious electrical or mechanical issues.

Emergency landing gear hand pump would not pump using the “closed circuit closed doors, open circuit open doors” POH method.

Normal operation of the emergency landing gear hand pump system was reestablished by pushing the gear door indicator breaker in. The green gear down light came on when the breaker was pushed in.

Run-up as per the POH was completed uneventfully and the engines were run for several minutes with no tripping of the circuit breaker or any detectable anomalies in the system.

The Cessna service manual suggests checking for a short circuit in the landing wiring but, has little to offer other than this.

A review of the visible electrical circuit was negative including all gear up and down lock as well as squat switches. A more thorough examination of the electrical system is planned.

We plan to jack the plane and swing the gear, first by hand pump and then cycle it by using a hydraulic slave and observe for anomalies.

About 75 flight hours before this issue the entire landing gear system was inspected, hydraulics overhauled including all hydraulic cylinders, front main and power pack. The power pack was rebuilt by a certified shop with service to current specifications.


Any insight regarding this issue that I can pass on to the mechanic?



Thanks for your help,


Mark