Finally got a stubborn LRU to pass after swapping the test adapter

This 737's flight management computer kept failing the BITE check for three days straight. Swapped out the standard test adapter for a calibrated one from the shop, and it passed instantly. Anyone else run into test gear giving you a false fail?

3 comments

3 Comments

samflores1d ago

Ugh, been there.

nguyen.morgan1d ago

Yeah, swapping the test adapter for a calibrated one is a classic fix. I read a service bulletin a while back about certain older adapters having worn pins that cause intermittent connection issues, especially on those FMC LRU tests. It's one of those things you don't think to check until you've swapped everything else. Ever have to log the bad adapter for calibration after?

michaelgrant1d ago

Reminds me of a time we chased a ghost in a nav system for two days. Kept failing the same test, swapped every LRU in the rack. Turns out someone had put a regular pin in a spot that needed a spring-loaded one. The manual had a tiny footnote about it. Felt like a real idiot after that one.