Warning: stop using those cheap IR thermometers for engine bay checks

Honestly I used to just wave my $20 IR gun over the cowling and call it good. Last month I pulled one off a King Air that read 40 degrees low on the right engine exhaust. Swapped to a thermocouple probe setup and found a 150 degree split that wouldve cooked the turbine. Ngl those IR guns are useless on reflective metal. Has anyone else caught a bad reading that almost got you in trouble?

3 comments

3 Comments

black.pat1mo agoProlific Poster

50 degrees is a HUGE swing on a turbine exhaust, that would've been a real bad day if you hadn't caught it. The problem is those IR guns pick up reflected heat from everything around the engine, not just the part you're aiming at. I started using a thermocouple probe setup after a similar scare on a PT6 and haven't looked back since.

the_tessa1mo ago

Alice had a good point about knowing your target, but polished turbine parts are a whole different beast. Saw a comparison online where a shiny exhaust flange read 80 degrees low with a cheap IR gun compared to a contact probe.

alicesingh1mo ago

eh I dont know man, I've been using a cheapo IR gun for years on my own little piston stuff and never had an issue. Those King Air exhausts are polished metal, yeah they're gonna reflect everything. But on a regular painted or dirty engine part the readings are close enough for a quick check. Gotta know what you're pointing at and how shiny it is.