Field Technical Supervisor at Southwest Airlines
Solves Ground Circuit Problem
I received an email from Matt Couture the Field Technical Supervisor at Southwest Airlines.
While conducting an evaluation of the Bartol Mag-Probe to be used at Southwest Airlines Matt Couture developed an effective procedure isolating a ground circuit problem using the Mag-Probe The procedure is written below.
Good Morning Bob,
That Mag-Probe came in very handy last night!! Here is a copy of the turnover I wrote… Thanks again!! I will keep up the testing…
This plane just came out of check from MCI. The CDS had a current fault 31-68861. The GPWS had inflight faults for the #1 terrain relay for 10 legs. We accessed the R745 in the FWD R/H NWW. I turned on the TERR with the captains EFIS panel and used my mag-probe to see if the relay was powered, it was not. Pulled R745 and checked for power, there was 28vdc. Since I knew the relay was not powered I went after the ground circuit; that is when I hit pay dirt. The ground circuit was open from the GPWS to the R745 pin 6. I broke down the circuit and found pins 30 and 31 swapped at D40698. That connector also had two other pins pushed. It had a fresh label sticker on it, so my guess is that those guys were in it at MCI. I swapped the pins to the correct location and everything worked.
Ground circuit problems do exist. In the event you suspect a ground circuit problem we recommend using a Bartol Mag-Probe. Here is another post where another ground circuit problem existed. Aircraft Technician Saemi walks you through the test in a video recording. This was the final test before the plane was to be grounded by the FAA permanently.