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Altimeter / Encoder Check

Date: October 22, 2002

This morning, I woke at the crack of 1.5 hours before dawn, and headed out to the airport. I was supposed to deliver "Precious Time" to Aviation Electronics at Hanscom Field (BED) for an IFR Cert. of the altimeter and the altitude encoder (I already knew the altimeter was about 300 ft. off), as well as a check of the attitude indicator. I got off the ground at about 7:10 AM, and on the way in to BED, had the tower tell me that they weren't getting diddly squat from my transponder. Hmmmm - it had worked before......

Anyway, I land at BED, and the female controller was so busy watching the plane through her binoculars and asking me how it performed, that she forgot to tell me to contact ground on 121.7 -). I'm sure she turned a bit red when I asked her what I should do, and she admitted she was too busy looking at the cool plane -).

After finding Aviation Electronics, we dragged the plane inside, took off the canard and fuselage cover, and got to work. We removed the altimeter, encoder, and transponder. They calibrated the altimeter and encoder no problem, checked the static system for leaks (also no problem), and checked the transponder (no problem).

The transponder problem was in the antenna RF connector, which I had wired poorly (I hadn't soldered the center connector to the center tap of the tray connector). They made up a nice, new cable for me with an inline BNC connector tap for troubleshooting, and after reinstalling that, everything was copasetic.

They replaced the vacuum system air filter, saying that it was very possible that the attitude indicator problems I was seeing were caused by low airflow, even though the vacuum gauge was reading 5 psi. After reinstalling everything (instruments, fuselage cover, canard, etc.), we dragged the plane outside and fired it up to see if the attitude indicator would erect quickly and stabilize (maybe that controller should have been watching THAT). Anyway, it did, so I figured maybe that was the whole problem - they had copied down all the info on the attitude indicator in case I needed a trade-in, and I said I'd keep an eye on it. I shut down to wait for the gas truck, added 10 gallons, and then thanked the guys for everything - they had been extremely nice, had let me "help", and were very complimentary regarding the aircraft.

That's when the fun started. I got in the plane, went through my checklist, and turned the key to "start". Crunch!!!!! Weird sounds from the back.... Try again - same wierd crunching sounds. Dang. Get out, go around back, and look -unbelievable - the cast aluminum housing of the starter motor (that I had just borrowed from Wayne Wright!!) had cracked in half - there was nothing supporting the front of the starter pinion. Not bad, eh? I've managed to kill two starters in less than a week. So, the guys at AE let me tie down at one of their spots, and my wife comes to pick me up. I was pretty pissed off, but I really didn't know what's causing the problems.

While waiting for my wife to get there, I called Bart Lalonde at Aerosport Power (where I purchased my engine and starter) to ask what the heck was going on - 45 hours is not a lot of time to be killing starters. He asked a lot of questions regarding the failure modes of each, and then asked me a few questions about my ignition/starter switch. I told him I was using an Aircraft Spruce Aircraft Mag/starter key switch. He asked what I had for ignition, and I told him dual Mags. He asked if I had installed the jumper on the switch to ground the mag with the advanced timing, and that's when the lightning bolt hit.

He said that the ONLY time he'd ever seen a SkyTec starter fail is when the engine is firing on BOTH mags upon startup, so that the starter sees some intense kickbacks from the advanced mag. While there is a cryptic instruction on the switch about the jumper, I had no idea what it was talking about, so I brilliantly ignored it and did NOT install the jumper. Sigh. This jumper grounds one mag so that only the retard mag fires when the starter is engaged.

Well. I suppose it's good to know what the cause of the problem is, besides my innate ability to find every possible failure mode of everything I touch. My wife drove me out to FIT, I got my car and tools, drove back to BED, and installed the jumper. I also removed the 2nd starter (Wayne's). Mr. Lalonde recommended that I try to cobble the two starters together into one just to keep me going, and then send the other one back to him for repair. We'll see if I can do that over the next couple of days, so that I can get the plane back to FIT over the weekend.

So. What's the lesson here? I now understand how this aircraft ignition stuff works, anachronistic though it may be. INSTALL THOSE JUMPERS, YOU WHO USE THESE SWITCHES!!! I now also understand why I see some homebuilts with three switches - individual ones for the two mags, and a momentary one for the starter. Turn on the retard mag, start the engine, and then turn on the second mag. Pretty trivial wiring, and the only thing that's missing is a key that (from a theft reduction standpoint) could be mimicked with a hair pin.

Geez, I hope SOMEONE is learning something from my blowing things up - I sure don't seem to be -).


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