Cessna 172 compass drift 30 deg in 10 mins
After many years in jets, I've finally had time for a reunion with the 172, the bird most of us started in. I line up the compass with the glareshield whiskey compass on my runup on the ramp and on taxi out, I see it drifting but ignored it for now. Now before T/O I line up the compass with the whisky compass again, the runway HDG was 210, the whisky said 210, the compass was around 240 so it set it back to 210 and took off. Leaving controlled airspace, I see the compass drifting again and mismatching again. To makes things worse, the attitude gyro also seemed particulary drunk and drifted around (at one point i was making a constant 300 feet/min climb straight ahead with the gyro showing 6 deg pitch down and 10 deg bank... i was only at 90 knots!).
Any ideas to why the compass was drifting so much, it might be my bad memory but I'm sure it shouldn't drift that fast. There was no mentioning of it in the aircraft log, just a note saying don't trust attitude gyro too much its a bit drunk (yes the mech wrote that!), flight into IFR prohibited until gyro replaced. That explains the gyro but the compass is still a mystery. I have all electronic devices turned off (except the aircraft lights, avionics and radios obviously). There were lots of telecom attenas in the area though, might this affect the compass?
P.S. to make matters worse that flight, the vis went down to 4000 with haze, i was 1500 AGL, gonna request vectors but the big jets and military guys keep buzzing on the tower and approach frequencies that i don't get a chance to squawk a word. Saved 7700 for later (luckily did not have to use it), and used VOR (yes! luckily it worked flawlessly), to get back to visual range of airport. Got told to orbit as the big jets approach and takeoff... tons of birds in my orbiting area, most of em vulture sized... like dogfighting with em, looking out and maneuvering. Thought the tower forgot me, then they say for me to make a dash for the runway in the traffic gap. (amazing that i only lined up with the runway at the point I get the miniums callout in the jets i fly in) Luckily on the ground in one piece. Should I write up about the compass? Seems the pilots yesterday had no issue with it...