mike20papa Posted June 13, 2015 Report Posted June 13, 2015 Just about the last thing I've ever wanted to deal with is a magnetic field possessing some part of my aircraft.. when ever I read about these problems..I cringe. Well, sure enough, I just had my turn. I first noticed my whiskey compass acting up - very unreliable and indicating up to 40 degrees off heading, then somewhat normal again. In my hangar, cowling off, I took an extra compass and began scanning for anomalies. I got some very weird readings, compass spinning, etc. around the battery box and engine mount. I took the battery out, scanned it and while it does have a field to it, not enough to account for the problems I had been experiencing. So, back to scanning the engine compartment and strong deviations appeared around the upper engine mount. After reading some info on line, about using a DC welding machine to magnetize or demagnetize steel, I thought about the engine mount bolt that the neg. battery cable bolts thru - grounding the entire airframe & engine. Maybe after years of 12v DC passing thru it, it had become magnetized enough to cause problems. So, after removing it (and it's a large bolt!) and holding it near the compass - it was obvious I had found the culprit. Not only the bolt, but also the nut and 3 washers were highly magnetic! So..fired up my rivet gun and after working them over for a minute - all the magnetic field had been removed. The Lord mounts showed no magnetic field, and the engine compartment tested "clean". So! Nice to have a true mag compass back in my M20A! Joe Philips N8335E 3 Quote
aerohawk Posted June 13, 2015 Report Posted June 13, 2015 Congrats on finding the gremlin. Those kinds of issues can be the worst. Quote
Mooneymite Posted June 14, 2015 Report Posted June 14, 2015 I've never heard of using a rivet gun to demagnetize, but it makes sense. Thanks for the tip! :-) Quote
HRM Posted June 14, 2015 Report Posted June 14, 2015 Great post, thanks! Rivet gun, clever. Humongous pulsed-AC coil. Quote
rbridges Posted June 14, 2015 Report Posted June 14, 2015 Thanks for posting. Stuff like that is good to know. Quote
Andy95W Posted June 15, 2015 Report Posted June 15, 2015 Great post, thanks! Rivet gun, clever. Humongous pulsed-AC coil. So, you're saying my pneumatic rivet gun won't be as effective. Damn. Quote
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