Why do we still use magnetic north?

[TheGorrilla]

Well. Looking at the fact that (in the UK at least) lots of aircraft have the following.

1) A compass it's a legal requirement so all should have it,

2) ILS, LOC and VOR kit,

3) GPS

4) IRS (or INS for the oldies)

The first one MUST use magnetic north. Like my Cub this is all I have. An aircraft with 1 and 2 MUST still use magnetic north as this is how the ground installations are set. Till those are adjusted this aircraft has no choice.

Aircraft with 1,2, 3 and 4 have the luxury of alternating between magnetic and true. However if systems 3 and 4 fail they must revert to magnetic. Not only is it traditional to use magnetic north it's the best practice.

[richatom]

The first one MUST use magnetic north.

Yes, but the pilot sitting behind it should be able to convert the reading to True North, assuming that he knows a few basics of navigation..

[TheGorrilla]

Is there any point in that? When the runways are magnetic etc. The laat thing I would want to do when flying an airliner on the compass having experienced a total electric failure is some silly sum involving variation!!

[richatom]

Yes, and it is thus likely to remain so.
It protects the rights and privileges of the private general aviation pilot, which are under constant threat by the airlines and the military

I don't see why you see airlines and military as a "threat". What is so difficult about navigating with reference to True North for GA? As I have repeatedly written, you don't need glass cockpit to navigate with reference to True North (in fact most glass cockpit users outside of military refer to MN). All you need to know is the declination in the area you are flying and do a demi-second of arithmetic to convert from MN to TN. If you are capable of working out wind vectors then you are capable of adding/subtracting declination!

I find this stubborn luddistic attachment to MN from certain flyers quite disconcerting.

[BristolScout]

Richatom.

True enough but the pilot doesn't need unnecessary mental gymnastics. By all means, use a flight plan form which shows both if you're navigating formally but for just swanning around, stay with what the ICAO system is based on and you won't go far wrong.

411A. No need to leap to the defence (defense) of US AOPA. On this side of the ocean, we just wish our organisation was so powerful.

[TheGorrilla]

So how is that useful when flying a GA aircraft into a large international airport. Most PPLs would get very confused and be even more likely to make a mistake. Such as adding the variation on when they should have subtracted. Why make life even harder?

[richatom]

So how is that useful when flying a GA aircraft into a large international airport. Most PPLs would get very confused and be even more likely to make a mistake. Such as adding the variation on when they should have subtracted. Why make life even harder?

The average ppl is even more likely to be confused by seeing a runway heading written on the runway different to his airfield manual, because he is flying with outdated information.

Flying with reference to the vagaries of magnetic north has to change - it is just a question of when.

[LastMinute]

Originally Posted by richatom

A GPS receiver won't tell you your heading - magnetic or true.

Your point being?

My point being that a GPS receiver cannot replace a compass or heading indicator. Your post appeared to suggest that a compass is not necessary on any aircraft because some pilots have a GPS receiver.

I was under the impression that basic flying involves choosing - or being instructed - to fly a given heading in order to make good a desired track. (If I'm wrong on that, I apologise - and I clearly have a lot to learn.) Or are you also making the wider suggestion that heading is irrelevant?

Originally Posted by LH2

And some pedantism...

It will if that's what it's designed to do. Do a search for "gps heading sensor" or "gps gyro".

OK - some pedantry right back:

I'm not familiar with any portable GPS receivers of the type suggested by the OP that have dual antennae to determine heading; and if it's a gyro that's providing the heading, then it's not a GPS receiver...

[richatom]

Your post appeared to suggest that a compass is not necessary on any aircraft because some pilots have a GPS receiver.

No, my post just suggested that it might be time to consider referencing to True North in aviation. You would still need a compass - you would just need to know your local declination to correct to TN.

[TheGorrilla]

And my point is that flying on true north has a time and place. At high latitudes where a magnetic compass doesn't work where you have no choice. For some reason convention has decided it's better and more sensible to use a compass in places where it does.

I don't think this will change. I'm afraid Richtom your going to be flying around to runways with magnetic numbers on them for a long time unless you emigrate from your nice sunny place to a very cold wintery north Canadian place.