RDuplechin Posted March 22, 2021 Report Share Posted March 22, 2021 I recently had my compass swung and made my first flight this weekend since the work was done. It appears to be reading accurately on the ground with all radios, lights, electronics powered up. I flew from Grand Prairie to San Angelo (west southwesterly) and it appeared to be reasonably accurate in flight. On the return trip later the same day the compass indicated about 30-35 degrees all the way home. That should have been 74 degrees minus a few for the northerly winds...say 65 degrees for discussion. Any idea what's happening here? I’m assuming some sort of magnetized airframe maybe, but why would it not show up on the ground and not show up in flight for a few hours. My airplane has original panel configuration, KX-155s, Garmin 327 xpndr, Garmin 796...nothing new or unusual. IPad mini with a cooling deck plugged into cigar lighter. The only electrical work I have done in the last year is to put in a 406 ELT, put in a tail beacon ADS-B, put in LED nav/strobes, wire up the pitot heat, put in an electric step motor. Nav lights stay on all the time since it powers the ADS-B. Thanks for any insight. Quote Link to comment Share on other sites More sharing options...
Oscar Avalle Posted March 22, 2021 Report Share Posted March 22, 2021 On the ground was the engine running? The alternator was it charging.I had a similar issue and it was the alternator cable connection to the breaker that was not well connected and was generating noiseSent from my iPhone using Tapatalk Pro 1 Quote Link to comment Share on other sites More sharing options...
takair Posted March 22, 2021 Report Share Posted March 22, 2021 1 hour ago, RDuplechin said: I recently had my compass swung and made my first flight this weekend since the work was done. It appears to be reading accurately on the ground with all radios, lights, electronics powered up. I flew from Grand Prairie to San Angelo (west southwesterly) and it appeared to be reasonably accurate in flight. On the return trip later the same day the compass indicated about 30-35 degrees all the way home. That should have been 74 degrees minus a few for the northerly winds...say 65 degrees for discussion. Any idea what's happening here? I’m assuming some sort of magnetized airframe maybe, but why would it not show up on the ground and not show up in flight for a few hours. My airplane has original panel configuration, KX-155s, Garmin 327 xpndr, Garmin 796...nothing new or unusual. IPad mini with a cooling deck plugged into cigar lighter. The only electrical work I have done in the last year is to put in a 406 ELT, put in a tail beacon ADS-B, put in LED nav/strobes, wire up the pitot heat, put in an electric step motor. Nav lights stay on all the time since it powers the ADS-B. Thanks for any insight. Kind of what Oscar said. The compass swing should be performed with essentially the same configuration you will fly. Things like landing lights and pitot heat are major contributors. Basically look at the loads. Portable equipment on the glare shield also make a difference. Quote Link to comment Share on other sites More sharing options...
RLCarter Posted March 22, 2021 Report Share Posted March 22, 2021 Just a quick look, KSJT > KGPM looks to be more like 60° with no wind correction. What were the winds aloft and what does your compass correction card say for 60° heading? Quote Link to comment Share on other sites More sharing options...
RDuplechin Posted March 22, 2021 Author Report Share Posted March 22, 2021 Yes, engine was running. All lights and electrical systems were on...take off configuration...xpndr to ALT...the works. Engine is at 1800 or so during the run up with a known heading. During run up, I generally check vacuum then verify the DG matches the compass and make sure both agree with my actual heading (taxi way line, 90 degrees to the runway, etc). Only thing not on at that particular time is the boost pump...but that isn't on in flight either, so that shouldn't be the culprit. All that was fine at GPM on flight 1 and at SJT on the return flight. From SJT to GPM the winds were out of the north northwest, but based on the Star Wars chart they would have had to be close to 50 knots to give me that drastic of a crab angle. They were actually more like 12-15 knots. Forgot to mention...just for fun I did 30 degree (roughly) turns left and right just to see if the compass would move at all. It moved a few degrees but not as much as one would expect. I am familiar with lead/lag and accelerate/decelerate tendencies. That normal compass behavior is not what I experienced. The compass correction card calls for 2 degrees at that heading. This far exceeded that. This was more like it was stuck magnetically very close to 030. Once I got closer to GPM, I got real busy dodging the parade of 172s full of future airline pilots who don’t speak English and I admittedly stopped paying attention to the compass. Same after landing...I forgot to note what it was doing on the ground. Quote Link to comment Share on other sites More sharing options...
47U Posted March 22, 2021 Report Share Posted March 22, 2021 Do you have a vertical card compass? The mechanism in those have been known to eventually wear out. Generally takes years and years, though. Quote Link to comment Share on other sites More sharing options...
RDuplechin Posted March 22, 2021 Author Report Share Posted March 22, 2021 No, it is the original style. Might be the original one. i cant find a reference to it being replaced. Quote Link to comment Share on other sites More sharing options...
hammdo Posted March 24, 2021 Report Share Posted March 24, 2021 Was the IPad close to the center of the panel or compass? -Don Quote Link to comment Share on other sites More sharing options...
carusoam Posted March 24, 2021 Report Share Posted March 24, 2021 The next time you go flying... Try performing a standard rate timed turn... while watching the compass... If something magnetized the airframe... the compass will not behave smoothly... you can watch it stop, then accelerate to catch up... at certain headings, it can get stuck... as it doesn’t have much strength to break through the odd magnetic force... Then, you will be looking for info on degaussing... PP thoughts only, not a mechanic... Best regards, -a- 1 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.