sierrakilo99
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- Apr 20, 2011
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Our Arrow experienced a serious fault in the main electrical feed from the alternator this weekend. 60A CB popped immediately after attempting to bring the alternator online after engine start. Student (with instructor) recycled the alternator switch off, reset the main breaker, then attempted to bring the alternator online, immediately resulted in 60A CB pop again.
Fortunately they shut down and called me. Several hours later this is what I found:
Turns out one of the (original) Adel clamps holding the alternator feed wire to the firewall had chaffed thru, causing the short. The second time it was reset, the short resulted in the alternator wire welding itself to the throttle cable outside sheath. Image if this had been done while in-flight at cruise power setting? The wire might have welded itself to the inside cable and the throttle would have been stuck in the cruise power setting.
Advise: don't reset the main breaker if it pops (especially not in-flight)
Next time you have your cowl off, please check your alternator feed wire where it passes thru any of the adel clamps and replace ANY worn out clamps, this one was difficult to see (and took considerable time to locate) because it was behind the engine vent tube.
sk
Fortunately they shut down and called me. Several hours later this is what I found:
Turns out one of the (original) Adel clamps holding the alternator feed wire to the firewall had chaffed thru, causing the short. The second time it was reset, the short resulted in the alternator wire welding itself to the throttle cable outside sheath. Image if this had been done while in-flight at cruise power setting? The wire might have welded itself to the inside cable and the throttle would have been stuck in the cruise power setting.
Advise: don't reset the main breaker if it pops (especially not in-flight)
Next time you have your cowl off, please check your alternator feed wire where it passes thru any of the adel clamps and replace ANY worn out clamps, this one was difficult to see (and took considerable time to locate) because it was behind the engine vent tube.
sk
