Bellanca 7ECA Shorting Ammeter Wire “While in flight,” states a technician, “the pilot reported he could smell something burning-he landed as soon as was practical. Investigation revealed the wire from the alternator to the ammeter (p/n 112) had shorted against the firewall….” “Wires 112, 114, the master relay, starter relay, voltage regulator and alternator were all replaced.” 288
Leaks and Shorts
After sitting idle on a ramp for at least 10 months, the airplane underwent maintenance. A strong fuel odor was observed in the cabin; an exterior inspection failed to detect anomalies. The odor subsided. Once the engines were started and the fuel selector placed in crossfeed, the odor returned. After removing the floorboards, a heater duct running perpendicular to the crossfeed lines was observed to be in contact, causing corrosion. Pinhole leaks had developed in both lines, p/n 5300108-53 and -54.
Key Takeaways:
- An alternator-to-ammeter wire in a Bellanca 7ECA shorted against the firewall, causing a burning smell and requiring multiple component replacements.
- A Cessna 340A developed pinhole leaks in its crossfeed fuel lines due to contact and corrosion from an adjacent heater duct, leading to a strong fuel odor.
- Two separate carburetor incidents reported floats failing by taking on fuel and losing buoyancy, causing erratic engine performance and fuel leaks; one recommended a recall for polymer floats due to premature wear.
- A Lamar PM2401 starter on a Cessna 172 experienced a commutator segment separation, which destroyed the internal brushes.
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