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:
- A Bellanca 7ECA experienced an in-flight burning smell due to an alternator wire shorting against the firewall, necessitating replacement of multiple electrical components.
- A Cessna 340A developed pinhole leaks in its crossfeed fuel lines, caused by corrosion from a heater duct in contact with the lines after extended idle time.
- Multiple carburetor reports (Facet and Precision Airmotive) detailed failures where hollow plastic or polymer floats took on fuel and lost buoyancy, leading to erratic engine performance and recommendations for improved manufacturing, recalls, or Airworthiness Directives.
- A Lamar PM2401 starter failed due to a commutator segment separating, which subsequently destroyed the internal brushes.
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