Peter

About Peter

plbarrett.com | Certified Flight Instructor (Single & Multi-Engine, Instrument, and Advanced Ground) | Commercial Helicopter

Flap calibration and brake bleeding

This entry was posted in Final Testing on by

First on the docket. The flaps still aren’t working as they should. They work perfectly in calibration mode but not in normal mode. According to the interwebs this means the flap switch and flap motor wires need to be swapped. Ok. So i did that. Still no joy. Now they work properly at least – except only for like 15 – 30 seconds. Then they don’t work at all.

I had to call Garmin for this one. Savannah asked me to send my configuration file as well as a screen shot. In the end – the problem was I only had a maximum airspeed set for full flap deployment. It also needed the partial flap speed set. Man. Too smart for its own good sometimes.

Next up. Bleeding the brakes. This went awesome. Until of course. It didn’t. I borrowed a pump from my buddy Woody across the way. Plan was to bleed from the bottom up. I set up an overflow pipe and container to catch the excess fluid.

First issue. A small leak at the master cylinder for one of the nylon compression fittings. Turns out I had a bad sleeve. Luckily this is a part that is available in the aviation aisle of Lowes. So a quick trip and that was fixed. Good thing that was my only issue.

Except it wasn’t! Inspecting the brake lines for torque – I forgot that unlike the fuel vents, the brake lines have a connection as they leave the fuselage for the gear legs. Guess what wasn’t fully torqued? You guessed it! Result. Brake fluid all over the place in the cockpit.

Great. Well that was a good stopping point for the night. Drain the brake fluid. Get some kitty litter. Attack again the next day. First step was a thorough cleanup of the spilled brake fluid. Next – torque the fittings. Now, start the brake bleed process again. This time 100% success!

Instrument Panel Finalization

This entry was posted in Avionics Electrical on by

There is a ton to report in this post. I won’t be able to cover it all. I’ve been working hard to finalize all the electrical wiring and avionics installations. I’ve finally gotten to the area behind the panel and the instrument panel itself. Things that were accomplished in this session: final install of pitot static boa lines, final wrapping and organizing of all wires and cables, removal of instrument panel, carbon fiber wrapping instrument panel, reinstalling all switches and avionics into the panel, labeling all switches, elt nut plate installation, and installation of a few wires remaining for functionality such as fuel pump switch to bus power and power for panel led lights.

CAN BUS ERROR!!! OH GAWD!

This entry was posted in Avionics Electrical on by

So a few days ago, I turned on the avionics to find that nothing was communicating. How could this be? It was all working perfectly, and then something happened? At first i thought perhaps I hadn’t trickly charged the batteries enough and a low voltage was causing some LRUs to drop offline. Nope. Speaking with Garmin they told me to disconnect LRUs and reconnect individually to try to identify a bad unit. That didn’t work either. The only other possible culprit – the CAN Bus. So i pulled the connector on the GDU 460 and buzzed it out. I got the appropriate 60 ohms across CAN HI and CAN LO. Which told me that the CAN Bus was contiguous and terminated properly. Perhaps a short to ground? Bingo. CAN LO was buzzing as shorted to ground. Great. Finding that isn’t going to be easy. The only real way to do so, is to divide the CAN BUS in two, and figure which is the bad half, and keep doing that until the offending segment / connector is isolated. So i did that, and found that the bad area was the GMC 507 to GEA24 to GTR20 segment. The GEA 24 is really hard to reach, and is where i had just been cinching wires together. I buzzed it out, and thought i determined taht was the bad connector. Reinstallation of the connector didn’t solve the problem. But i did it from inside the airplane. Which, given the GEA24 is down by the fuel pump… is difficult. I decided to pull both segments out of the plane so i could diagnose and correct on the bench. Long story short, I isolated the leg that was bad. Then tried to determine which connector was bad. Ultimately, even after cutting both ends off the cable, the cable still buzzed as shorted to ground. I completely tore the cable apart and examined everything with a magnifying glass. I was unable to find the offending section.

I built two new segments and reinstalled them in the plane. With all the troubleshooting this was a major time sink, and quite frustrating. But everything is back to 100% functionality. While human error cannot be ruled out, i was extremely meticulous in testing the cable on the bench. I really think there was a flaw in the cable somewhere that was exposed when i began cinching wires with zip ties.