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Jason A very good point indeed. Here in the midwest (Michigan) the change has been over 2 1/2 degrees in the years I have been doing navigation of one form or another. The other question is however, can anyone fly an aircraft compass to withing 2 1/2 degrees of error. Not me. If anyone can, I bow to ya. Even in a boat with a 5 or 7 inch diameter compass, that is pretty good driving. That kind of navigational accuracy used to be expected in sailing before the advent of electronic navigation systems. Now with those we can really navigate with that level of accuracy quite easily. I haven't measured the diameter of the compass rose on my Lowrance 2000C but I'll bet it is out in the 10 or 12 inch range when its extended. bob branch N99891 ----- Original Message ----- From: "Jason J Ellingson" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, December 28, 2005 6:25 PM Subject: RE: [COUPERS-TECH] Deviation chart - engine on or off? > ----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]---- > > > <humor mode = "ON"> > > Take the prop off. Then you can leave it running while using the tow bar to > move it around. > > <humor mode = "OFF"> > > On a serious note... I wonder how many airports repaint their compass rose > to keep with magnetic drift? A local airport here has one, but it hasn't > been repainted for a long time... Yet the runways have been renumbered due > to magnetic drift. > ------------------------------------------------------------ > Jason J Ellingson > NC2273H > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Sent: Wednesday, December 28, 2005 5:17 PM > To: [email protected] > Subject: [COUPERS-TECH] Deviation chart - engine on or off? > > ----[Please read http://ercoupers.com/disclaimer.htm before following any > advice in this forum.]---- > > > Okay, on to esoteric technical problems... > > I found an airport with a compass rose and proceeded to align my airplane > over the rose, to get data to make a compass deviation card. > > Found it hard to assure good alignment with the rose, with the plane's > engine on and myself inside the plane. > > It would be more precise to have the plane off and to position it over the > compass rose by handling it from the outside. I could have the radios on > while doing this, however, I think that I would be missing significant > mangnetic fields from all those moving metallic parts in the motor, the > firing magnetos and spark plugs, and the turning generator, which's not that > far from the compass. > > IMHO you need the engine on in order to take every magnetic field into > account while gathering data for your compass deviation card. > > Am I right? > > Of course, I could position the plane while turned off, then start it and > take the reading, turn it off, reposition it, take another reading, and go > on... > However, I don't think turning the plane's engine on and off 12 times in a > short span of time is healthy for the engine, and worth it. > > So I either have the plane off and miss all those magnetic fields, or have > it on and miss accuracy in positioning it over the compass rose. > > So which one is it? How is it done in real life?? > > Eliacim Cortes > N87071 > > ============================================================================ > == > To leave this forum go to: http://ercoupers.com/lists.htm Search the > archives on http://escribe.com/aviation/coupers-tech/ > > > > > ============================================================================ == > To leave this forum go to: http://ercoupers.com/lists.htm > Search the archives on http://escribe.com/aviation/coupers-tech/ > > > ============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
