Aux Power Cable Short

[patrolpilot]

About a week and a half ago, I experienced a total loss of electrical power just as I leveled off at 2000'. There was a powerful electrical smell in the cabin; I saw a puff of smoke go through the vent window (it was open because the temp and humidity were unbearable). As I reached for the master switch, never quite touching it, the airplane experienced a total electrical failure. I turned around, ran the "Electrical Fire In Flight" checklist, and then got busy pumping the gear down. While pumping the gear down, I called my mechanic via my phone (bluetoothed to my headset) to come out and give me a visual check on the landing gear and to see if I was trailing any smoke. I had added mirrors for both situations, but it's great to hear a "you're good."

I still had an active short smoking the battery after shutdown. The mechanic got it disconnected. The battery was "rocket" hot, and it couldn't be touched for about 30 minutes. We thought the new battery had shorted, but not so. Something else failed.

When my mechanic got to looking at what happened, he discovered that the aux power plug cable (which runs from the plug to the voltage regulator) had been rubbing against the front cowling flap actuator rod. This is very tough to see, down low on the firewall against the nose wheel well.

The short happened at the moment that I actuated the cowl flaps closed. The cable, once rubbed, immediately delivered the battery's capacity into the cowl flap actuator rod. The aux power cable has no breaker or fuse protection.

The cowl flap motor took the brunt of the charge, but there was some arching that cut the fresh air control cable. The "Electrical Fire In Flight" Checklist calls for the "Vents/Cabin Air/Heat" controls to be closed. The electrical burning smell was not dissipating in the cabin because the panel control actuation had done nothing.

It is a bit weird, to both my mechanic (an experienced 337 guy) and I that this OEM cable (Cessna PN on cable) is black. Usually, these large cables are white so that wear or heat indications can be viewed.

Bob Bena of RLB Accessory Service is rebuilding the motor. He said it is fried crispy, but he can handle it. I think if I sent it somewhere else, they would not have accepted as a core (yet, would probably rebuild it if I didn't pay to ship it back to me).