Sloppy work

[Rich]

Occasionally one encounters some sloppy upgrades/maintenance on various airplanes. Here's the latest one I came across:

A guy had our mutual mechanic perform an engine STC from 150 to 180 HP on his late-70's era 172. I happened into the hangar and helped them wrestle the lower cowling into place (new cooling baffling - aluminum and silicon). In the process the baffling rubbed slightly against the wires for the landing/taxi light, and one of the terminals promptly broke off. The terminal had been eroded to the merest state of existence over the years.

To shorten up the story, the landing light sealed beam was 250 watts. The wiring looked far to small to support the necessary 20 amps or so. Both terminals were severely scorched and paper-thin. The connector for this circuit (located behind and outside the baffling) was blackened. After replacing the terminals and getting the lower cowling in place, we determined that the landing light didn't work because of the damage to the scorched connector. Wiggling the connector would make the light flicker on and off.

Afterwards I got to thinking that 250 Watts was non-standard for this aircraft. I figure that somewhere along the line the original the (probably) 100 Watt lamp was swapped out for a 250 and probably the circuit breaker changed but the wiring was not upgraded. Connectors, terminals and such are typically the high-resistance points in any circuit, so often this is where the hotspots happen. We recommended that he swap the lamp out for a LED replacement, which will bring the amps way down and hopefully avoid an inflight fire. The owner lives and hangars his aircraft at an airpark right near me, so who knows what'll happen next. But it did seem he was up for this mod.

[Spinner]

The older 172's with single light are showing a 4522 lamp which is a 14 volt 250 watt bulb. The wiring diagram shows 12 gauge wire. The newer ones with dual lights on the cowl show the venerable 4509 (14 volt 100 watt) bulb and using the same gauge of wire.

Definitely the switch to LED's will help. I see on one website the expectancy of a 4509/4522 is 25 hours lol.

[Rich]

This did not look like 12 gauge wire. More like 16 or 18. Whatever it was, the wiring was not up to the task.