Thursday, November 15, 2012

Return to Service (Part III)

Date Aircraft Route of Flight Time (hrs) Total (hrs)
15 Nov 2012 N21481 5G0 (LeRoy, NY) - GVQ (Batavia, NY) - FZY (Fulton, NY) - 5G0 2.4 1102.8

On Sunday, a gorgeous November day peaking at 74°F, I pulled Warrior 481 out of the hangar in hopes of flying.  After a careful preflight, I boarded and ran through the engine start procedure.  All was going well until I reached the checklist item: "Starter...Engage".

Absolutely nothing happened; no movement, no sound.

This was a reasonable indication that my eight year old Gill G35 battery had finally shuffled off its mortal coil. Perhaps all that cranking at the time of the fire on top of old age was what did it in.  Considering that the shop in Columbia County had to charge the battery to start the airplane after the repairs, I am grateful that it clung to enough charge for one last start.  The final act of that heroic battery was to turn a cold Lycoming O-320 over at a remote airport so that the Warrior could finally come home.

With flying thwarted for the day, I removed the top portion of the vertical fin to inspect the VOR antenna in hopes of finding a logical reason for the Warrior's aberrant VOR reception.  I found the ground for the antenna to be completely detached.  That looked like a smoking gun to me.

Additionally, the carburetor heat control had become very stiff; collateral damage to the cable sheath from the fire.

And, still I wondered: why would the airplane not start while warm at Columbia County, the incident that snowballed into the eventual fire?

With all of these discrepancies adding up, it was time to call Jim for more help.

By Monday night, I had a new Concorde sealed battery installed.  That night, I gave the Warrior a much needed bath in the hangar as a storm raged outside.

On Thursday morning, we flew to the shop in Batavia.  The new battery spun the prop just fine, but the engine still seemed reluctant to catch.  By midday, the VOR antenna wiring was fixed, the carburetor heat cable lubricated, and the left magneto (the one with the induction coupling responsible for starting the engine) had a new coil.  The old coil was weak and, though resistance through it was within specification at room temperature, application of heat caused it to immediately climb beyond specification limits.

"And that's why your airplane wouldn't start when warm," Jim commented.

Warrior 481 now starts within a single blade, more crisply than I can recall her starting in a long time.  Clearly, coil performance had degraded slowly over time and I simply did not notice it was happening.

Although the landing light worked when I departed Le Roy that morning, I discovered on preflight that it had burned out sometime that morning.  That nasty little maintenance gremlin just had to get the last word in for the day.

After departure, we intercepted and tracked good ol' Victor 252 directly to the Geneseo VOR and the CDI indicated accurately the entire time.  I suspect that instrument training might be facilitated by accurately-reading navigation radios!


Satisfied that I finally had my airplane back, that training and pleasure flying could finally resume, I made a relaxing flight east to Oswego County for fuel and returned along the Lake Ontario shoreline.


It felt pretty darn good to have the airplane properly returned to service!

I am tremendously grateful to Jim and Brian at Boshart Enterprises for getting me into the shop on short notice to get 481 all fixed up.  These guys take great care of me and the events of the last three weeks have made me even more keenly aware of it.

3 comments:

  1. Chris - Excellent troubleshooting all around. I had been curious what caused the backfire on a warm engine. Induction coil makes perfect sense. We find a lot of intermittent electronic failures with heat guns and/or freeze spray! Glad to hear 481 is fully operational again.

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    1. I would love to know what caused the backfire. Unfortunately, most of the guys who know a lot about these things are a little perplexed, too. Carb fires are pretty well known to occur when using the throttle accelerator pump to prime the engine. But I don't do that. So why would I have gotten an induction system fire using the primer to spray fuel directly into the cylinders? The best hypothesis offered to me came from one of the other Le Roy pilots: with my engine entering mid-time, perhaps I had an intake valve that did not seal well such that the combustion in the cylinder was able to back up into the induction system. That seems to fit the data well, though I don't have any evidence that my compressions are poor. Given the way the valves rotate as they operate, maybe I was just unlucky at the worst possible moment. I did dump the data out of my engine analyzer into a computer to look for EGT spikes indicative of, at least, poor exhaust valve closure. But the traces were pretty boring. At the next annual the engine will be about 50% of the way to TBO - I think I'll ask for a borescope inspection to examine the valves and seats.

      What's really awesome is that Jim predicted that the induction coil was the problem before we did any troubleshooting. "Doesn't want to start when it's warm, huh?"

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  2. I'll be extremely brief...

    Yay! :)

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