Don't talk to me about mechanical gremlins. In my driving lifetime I've owned a string of if-it-ain't-broke-it-ain't-mine vehicles, including several Volkswagen vans and one 1960s'-vintage Bug, a BMW 2002, a couple of old Volvo wagons, a few motorcycles, and the king of constant maintenance, an MG Midget. Every-other-week tune-ups and repair sessions were a fact of life. Our airplane isn't as maintenance-intensive as some of the groundbound vehicles I've owned, but it shares two of their characteristics: it, too, suffers the aches and pains of advancing age; and often those age-related problems are not easily diagnosed.
As far as I'm concerned, electrical problems belong at the top of the list of aging-aircraft gremlins. The common denominator of electrical problems is their inscrutability. The symptoms are often inconsistent and illogical, making the diagnosis extremely difficult.
Unfortunately, a short circuit was behind our most recent unscheduled maintenance event. The first symptom of a problem was anything but inscrutable. When I tried to retract the gear after takeoff, it would not. I moved the landing gear switch up to the Retract position, but nothing happened. The gear stayed down, and the green light stayed green. I cycled the gear switch a couple of times to make sure I was not stopping in the neutral position. I wasn't.
Next step in the troubleshooting plan: Scan the circuit-breaker panel. And there it was—the telltale white shank of a popped circuit breaker. The label identified it as the landing gear breaker.
Based on the sensible policy that you get one, and only one, free reset of a popped circuit breaker (if it pops again after resetting, it's likely there is a short somewhere in the electrical path, and repeatedly resetting the breaker could lead to an electrical fire), I pushed the black-tipped button in until it clicked into place—and stayed. The gear retracted, the green gear-down light went dark, and the amber gear-up light illuminated. The dark clouds presaging expensive maintenance receded. Whew! It must have been a transient voltage spike in the system (translation: electrical gremlin) that caused the breaker to pop, much like a light bulb checking out with a brilliant flash as you flip on the wall switch.
All was well—until the third takeoff after the initial problem. I selected gear up, but it did not go up. Sure enough, the breaker had popped again. So much for a transient electrical spike. This one was taking up permanent residence. True to form for electricity, the problem was inconsistent. The breaker didn't pop every time I tried to raise the gear.
The problem was not in retracting the gear. The breaker was popping on gear extension—just after the green gear-down light illuminated, in fact. My partner and I asked around, collecting various theories: a worn gear motor, a weak circuit breaker, limit switches on the individual gear mechanisms that were out of limits, or a defective solenoid that controls electrical power to the gear motor.
All we had to go on for the repair was a major symptom, and some suggestions as to the root of the problem. This was shaping up to be one of those maintenance events that resembles a TV cop show, where they eventually nab the perpetrator by investigating and eliminating suspects one by one. The difference was that the TV show lasts an hour, including commercials. It can take days of trial and error to sort out an aircraft electrical problem of unknown origin.
We arranged to borrow a friend's concrete-floor T-hangar so that we could work comfortably, and a couple of jacks so we could swing the gear. Then the three of us—my partner and I and our A&P/IA—went to work. We removed a panel on the floorboard to expose the motor and the mechanism that raises and lowers the landing gear, and began cycling the gear. We discovered that the motor continued to run after the gear was down and locked. Whatever is supposed to shut off electrical power to the motor when the gear has reached full extension was not doing its job.
Through the process of elimination we ruled out the gear motor, the solenoid that provides power to the motor, the circuit breaker, and even the limit switch on each gear that signals when the gear is down and locked. Each component worked without fail, yet the circuit breaker continued to pop when the gear was extended.
As a last resort, we tried yanking on the wire bundles snaking from the limit switches on each main gear, but to no effect. Then I tried tugging the nose gear wires, which were loosely tie-wrapped to the gear mechanism. When I pulled, the breaker popped. Finally! We traced the wires up into the gear well and discovered that 36 years of living in that harsh environment, and bending and straightening with each nose gear extension and retraction, had taken a toll. The insulation on a couple of wires had become brittle and had worn away, allowing the exposed, energized wires to touch. It took about 15 minutes to repair.
I have little patience for ailing amps, volts, and watts, thanks to my early struggles with the Lucas "Prince of Darkness" electrical system on my '63 Midget. Thankfully, my one-year-younger airplane is not vintage Lucas-equipped. One of the consequences of owning and operating an older aircraft is dealing with the occasional maddening maintenance issue, one not easily diagnosed and treated. And the really bad news: There's a pretty good chance it will involve electrons that no longer flow as they should.
