View Full Version : Compass
BigEndBob
5th Mar 2024, 22:04
Has anyone ever acquired an aircraft in which the compass was accurate.
Just had back from annual aircraft with one bearing 20 degrees off.
Compass card all signed and dated.
Every single aircraft i have owned or leased, getting on for 20 plus, has required me to go out to the runway and swing the compass myself.
One aircraft came in with compass 45 degrees off on one heading.
No wonder pilots get lost or infringe airspace.
Big Pistons Forever
6th Mar 2024, 01:54
My personal experience is that once the compass was dialed in it stayed pretty close to correct. However you are correct in that some compass cards seem to be as closely tethered to reality as Donald Trump.
richardthethird
6th Mar 2024, 08:02
I was thinking that the other day. One student’s magnetic compass was 30 degrees off. Has a Garmin G5 in it too, but that doesn’t have the magnetometer in it so it only shows track. It makes teaching proper nav impossible, I think we will have to see if this compass can be swung. All well and good using track until the GPS packs up.
Fl1ingfrog
6th Mar 2024, 09:08
The maximum compass error on all headings should be no greater than 5 degrees following a swing. I have never seen such gross errors following maintenance as those reported above. If I did I would be having a serious chat with the chief engineer.
mavisbacon
6th Mar 2024, 19:38
I once flew a PA28 (cadet) that had its compass swung with the pitot heat OFF. Trouble is, pitot heat on Jesus! About 20 plus degrees difference. Massive argument ensued, ended up with all the compasses moved up from the combing away from the electrics.
My understanding is compass swing should be done with all electrics ON, and that annotated on he back of its card.
MechEngr
6th Mar 2024, 23:55
Has anyone ever acquired an aircraft in which the compass was accurate.
Just had back from annual aircraft with one bearing 20 degrees off.
Compass card all signed and dated.
Every single aircraft i have owned or leased, getting on for 20 plus, has required me to go out to the runway and swing the compass myself.
One aircraft came in with compass 45 degrees off on one heading.
No wonder pilots get lost or infringe airspace.
What you haven't noticed is that some of your buddies played a great trick and put a supermagnet into the keychain they presented you for some occasion. Or maybe a suction-cup bobble doll you keep for good luck. Buddies have done worse.
Perhaps you have a war injury with a metal plate installed? You nod off and your buddies fire up a gaussing device to see if they can get a paperclip to stick to you.
Whopity
7th Mar 2024, 22:54
When teaching Navigation I always used to demonstrate to students that switching on the Pitot Heat could move the compass by around 5 degrees, and emphasised that the compass was swung with the Pitot Heat ON. I again demonstrated this when teaching for the IMC rating.
BigEndBob
10th Mar 2024, 23:59
Problem is pitot is off on 95% of flights.
I wouldn’t consider the pitot heat to be ‘electronic’.
Its my understanding the avionics needed to be on as these are panel mounted in the vicinity of the compass.
MechEngr
11th Mar 2024, 07:24
If the pitot heat is using a resistance heating element then the wire(s) likely carry a substantial current, producing a magnetic field. If the wiring has the return current as a twisted pair back to the switch and another twisted pair from the switch to the power source, or at least far from the compass, the magnetic field in one wire should cancel that in the other. If it's a single wire, no cancellation will take place.
BigEndBob
19th Mar 2024, 18:52
See how much landing light (non led) can effect compass when lined up.