hairball192(at)yahoo.com
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 Posted: Wed Oct 11, 2006 8:01 pm Post subject: Yak-50 Electrical System Troubleshooting |
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All:
The problem with my Yak-50's electrical system has been found and repaired, and the working fix will get prettied up by a pro this weekend. Advisory info for those with similar planes below.
A heartfelt thanks to all who offered suggestions on how to find/fix it and to those who provided schematics. I'd specifically like to thank Mark Bitterlich, Rob Rowe, and Jorgen. Experienced hands of some folks at Palo Alto airport located the problem. Dave Masters was relentless in his pursuit of understanding Russian circuit diagrams and troubleshooting the system until the problem was found and fixed, so a special thanks goes out to him.
Here's what to check on other planes:
The Yak-50's relay box is on the fuselage side of the firewall. There is a 45-pin connector with a thick wire bundle attached. Most of the wires originate at the instrument panel and join into the bundle running forward along the left side of the fuselage. The bundle takes a hard right at the firewall and is routed through and around other components until it reaches the relay box. Both the air bottles are mounted aft of the firewall. There are four air lines and one fuel line with fittings attached to the firewall and the wire bundle is routed close to the topmost air line fitting. I'm sure a Russian engineer thought of this very failure mode when they decided between the fuel line and the air line being on top. Although the wire bundle is clamped very securely, it was routed in contact with the uppermost fitting and the vibration chafed through first one wire (hence the left gear down light symptom) and then others. When it chafed through additional wires they shorted and arked, burning through or damaging about seven wires in the bundle. Mark is right, I was indeed very lucky.
So I recommend taking a close look at the main wire bundle to ensure it is not touching anything the next time you're in your hell-hole with a flashlight. You have to look pretty darn close to tell.
Thanks again to everyone who contributed their time, experience and brain cells to help a guy they've never met. That's what this community is all about.
Sincerely,
Harry
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