11-19-2002 Ask Mike! Archive
When I tried to retract the gear the breaker kept popping

I recently purchased a 1955 F-35 Bonanza.  I only have a 35 amp generator and the other day I was flying with both landing lights on (total of 6.6 amps for special GE Halogen bulbs) but when I tried to retract the gear the breaker kept popping.  I turned off the lights and the gear seemed to come up okay. The gear draws 35 amps!!  From your experience (since I have such a low-amp generator), should I simply turn off all lights before operating the gear? I suppose a 50 amp generator or alternator (expensive) would solve this problem?

Your input is much appreciated!
John

John,

You didn't indicate which breaker popped. I will answer this both ways. If you mean the gear motor breaker, that is considerable draw; I would check for drag in the system (lack of lubrication, possible bearing drag in the gear actuator, a very sticky step cable when gear is extended) or a motor that is not up to spec.

If you are referring to the generator breaker, then the problem gets more interesting.

In theory, the generator is current limited by the regulator, so the potential for the 35 amp breaker to throw is very small. (As opposed to an alternator, which will put out what is asked.) Once the generator has reached it's limit and demand is still present for more power, the voltage will drop and you will supplement generator output with stored energy (aircraft battery). Normally, continuous electrical load should not exceed 80% of generator output. Continuous load is defined as lights, radios, etc., but doesn't count gear and flaps (intermittent load). I would look for the following: correct regulator, proper wiring size for generator output to bus (if aircraft had been converted from 20 amp and wiring not upsized), terminal connections corroded, loose, or wire strands breaking, and the proper grounding of engine - airframe - battery.

In either case, a 50 amp generator or alternator conversion will only alleviate a brown-out, where your continuous load will drop below the 80% figure. If you fly IFR, or much night work, I would certainly recommend the 50 amp alternator conversion; the alternator will give you more available wattage at lower engine speeds. Depending on what other options are bolted to your accessory case, it can be tight, but it will fit. (Tee drive for Hartzell prop, Sunrise oil filter.)

If you choose to upgrade to a 50 amp generator, be certain the regulator and wiring sizes are upgraded appropriately.

Good choice on buying the STC'd landing light modification; that will help you considerably.

Gear Green,
Mike