Hi Rod:
I have been reading your articles on the AOPA web site and enjoy them very much. We had a little incident last week that turned out all right but could have been bad. I would like to tell you about it and maybe you can relate it to your readers and it may save somebody down the road.
They said the run-up was normal and the engine was running all right. They made a normal take-off from South Lake Tahoe Airport on runway 36. I had told them that any take-off from an airport with an elevation of 6200' with tree's and 10,000' peaks around them should be a maximum performance take-off, get as much altitude as possible as soon as possible. Before meandering down runway 36 they noted that the ammeter was still showing a strong charge.
They climbed to 1,000' AGL before raising the flaps. They noted that there was a little lack of power during climb out and the amp meter was still "way up there." Something just wasn't right with this flight so they called the tower, mentioned that they might have a problem and suggested they would like to stay in the pattern until they got things sorted out. The tower cleared them for a right downwind to runway 36.
They made a right turn to enter a right downwind for runway 36. Just as they made the right turn they had an electrical failure and lost the panel (the electrical equipment stopped working). This was followed by the smell of smoke. They turned the master off. Since they were still south of runway 18, they slipped the airplane to lose altitude and landed on runway 18. It was a safe landing, everyone, plane included, was fine.
As soon as they cleared the runway they shut down and exited the airplane. There was no fire and they tried to figure out what had happened. With the fire truck standing by they turned the master switch on to see what would happen. As soon as the master was activated the engine turned over. Wouldn't you know it? The starter was stuck in the on mode.
We now have at least two members who are reading the POH (Pilot's Operating Handbook) from cover to cover. This was a good lesson in that we now have members that realize that if everything is not right you don't go. Also the POH, in small print, tells you that if the amp meter peaks out you have a stuck starter. So this goes to show how important it is to read the small print as well as the large print.
Keep up the good work,
Darrell Bowling
Thanks Darrell.
That's a wonderful description of what can happen when the starter contactor is stuck in the "on" position. The starter contactor is a solenoid-type device which allows a lot of current to flow to the starter motor. Twisting (or pushing) the starter switch in the cockpit engages the starter contactor which engages the starter. Sometimes the starter contactor stays stuck in the "on" position even when the starter switch is turned off. The starter continues turning, drawing enormous amperage from the battery. This energy must be replaced; therefore, the alternator begins charging at a high rate. A stuck starter is identified by a large needle swing in the positive charging direction on a charge-discharge ammeter (Figure 1).
On airplanes equipped with a loadmeter, you'll see a high amperage reading with a stuck starter. Loadmeters show the load (amperage) placed on the alternator (thus the reason for the name loadmeter). A high loadmeter reading suggests that the alternator is having to replace the energy consumed by the starter.
Reading a loadmeter requires you to know the normal amperage supplied by the alternator upon engine startup. This is anywhere from 10 to 20 amps (depending on what type and how much electrical equipment is in operation). After startup, when power is increased, loadmeter indications of 40 to 60 amps (or full-scale right deflections), indicate that something's wrong. A stuck starter is the likely problem. Shut the engine off and let your mechanic take a look at the problem. In case you're wondering why these folks didn't hear the engaged starter, they couldn't hear it. Airplanes are too noisy. You can't hear a starter once the engine's running.
For more information on this subject, see "Aircraft Electrical Systems, Part 3" and "Aircraft Electrical Systems, Part 2."
