View Full Version : Gyromagnetic Compass System

16th Apr 2006, 17:01
Hi to all!

Very happry to find a forum whereby all pilots gather... First of all, I am vincent from Singapore, currently serving in Singapore Air Force as a pilot trainee.

Ok, I have got some questions pertaining to Aircraft instruments. I am pretty confused with some flight instrument, namely DI, AI and most importantly, the Gyromagnetic Compass System! I am totally confused over this topic, I tried to find the answers online, but useless... Can someone here explain what's the use of this compass system, the modes(SLAVED, FREE) and the components. And I am also confused over this gyro thingy...

Would appreciate if someone here can advise and will be great if there's any websites that I can refer to ...



17th Apr 2006, 05:36
I see you need a lot of information there Vincent. I can't help with all of it - actually I think a textbook from your library would be more helpful than anything here - but try the following to start with:

How Stuff Works (http://science.howstuffworks.com/gyroscope.htm) or Wikipedia (http://en.wikipedia.org/wiki/Gyroscope).

In particular, understand rigidity and precession. Wander is also important to understand. Look these up on Google if you like. (Better search for "gyroscope rigidity" rather than just "rigidity" though I think...)

As for the gyroscopic compass (I presume you mean "remote indicating gyroscopic compass"), perhaps this might help a little:

Part A: a device that detects the earth's magnetic field, and generates an electrical signal according to what direction the aircraft is pointing. This is a fluxgate detector.

Part B: an ordinary gyroscope that has a horizontal axis and works like a DI. When the aircraft turns, the gyroscope does not turn (because it has rigidity) and so the pilot can look at the gyroscope to see whether he has turned and if so, how much.

Part C: an electric motor that corrects the gyroscope so that when it suffers from wander - that is, when the gyroscope wanders off the actual heading that it should be pointing to - the fluxgate detector corrects it. If this part is working properly, the pilot gets gyroscopic accuracy during a turn just like a DI, but it is reset to actual aircraft heading continuously, which saves the pilot from having to cross-check the aircraft magnetic compass in between turns.

SLAVED - when the remote indicating gyroscopic compass is working as described above. The pilot's compass is run by a gyroscope which is slaved to the fluxgate detector.

FREE - when Part A or Part C is turned off, so the pilot's compass is not automatically corrected. He will have to manually correct it every few minutes by looking at the standby compass. Free mode is useful if Part A or Part C are not working properly.

Hope this helps,