Why do we still use magnetic north?
Thread Starter
Join Date: Sep 2007
Location: Some sunny place with good wine and good sailing
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
Why do we still use magnetic north?
Why are runways, VORs etc still referenced to ever-drifting magnetic north? Of course, it made sense when we used compasses to navigate (remember those days?) but the compass nowadays is largely irrelevant except in dire emergency. If true north were used as a worldwide reference it would save a lot of hassle and money.
Join Date: Dec 2000
Location: on the golf course (Covid permitting)
Posts: 2,131
Likes: 0
Received 0 Likes
on
0 Posts
Richatom
I wouldn't disagree with you - the majority of large commercial aircraft use IRS's which derive all headings in true and then apply variation as a function of position to derive magnetic heading.
The problem is that the majority of the rest of aviation still relies on the magnetic compass.
The question is how to transition from where we are to where we want to be.
I wouldn't disagree with you - the majority of large commercial aircraft use IRS's which derive all headings in true and then apply variation as a function of position to derive magnetic heading.
The problem is that the majority of the rest of aviation still relies on the magnetic compass.
The question is how to transition from where we are to where we want to be.
Thread Starter
Join Date: Sep 2007
Location: Some sunny place with good wine and good sailing
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
I don't buy that argument. Do the majority of GA really still use magnetic compass? I don't know of many GA pilots that don't have at minimum a portable GPS on the yoke. And anyway, as they are generally flying short distances where there is no significant change in magnetic declination then they need only learn on number and they can convert to true north in a flash. Why penalise the rest of the aviation world for a handful of GA who still fly on compass?
There would be significant cost savings and safety improvements if magnetic north were abandoned. For a start, it would avoid having to redesignate runways every few years as magnetic north drifts around.
Has there ever been any serious studies into the implications of making the change? Surely it has got to happen sooner or later...
There would be significant cost savings and safety improvements if magnetic north were abandoned. For a start, it would avoid having to redesignate runways every few years as magnetic north drifts around.
Has there ever been any serious studies into the implications of making the change? Surely it has got to happen sooner or later...
Magnetic North.
If we change to True North with all this new techie stuff to make it easy on normal days, what happens on that day when the screens go blank?
We now have a Magnetic compass but have an extra job to correct it to True North. Not a good idea in an emergency.
Old saying :-
"If it ain't broke, don't fix it."
P.S. We have a mix of old and new kit on our birds.
If we change to True North with all this new techie stuff to make it easy on normal days, what happens on that day when the screens go blank?
We now have a Magnetic compass but have an extra job to correct it to True North. Not a good idea in an emergency.
Old saying :-
"If it ain't broke, don't fix it."
P.S. We have a mix of old and new kit on our birds.
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
Why are runways, VORs etc still referenced to ever-drifting magnetic north? Of course, it made sense when we used compasses to navigate (remember those days?) but the compass nowadays is largely irrelevant except in dire emergency. If true north were used as a worldwide reference it would save a lot of hassle and money.
And yes, in the USA at least, there are far more general aviation aircraft movements per day than all the airline and military flights...combined (by a factor of at least four).
It ain't gonna change, folks, nor should it.
Get off your airline high horses and leave the little guys alone.
There are far more of them than you, and they have a much stronger lobby with the regulatory authorities than many might realise...in the USA anyway.
Join Date: Apr 2006
Location: UK
Age: 35
Posts: 359
Likes: 0
Received 0 Likes
on
0 Posts
The UK situation is quite different to what you say. We use the compass a lot, GPS is there as a backup, a just incase item. I know a few pilots with GPS units that prefers navigating the proper way. I'd have to agree with the above poster.
Thread Starter
Join Date: Sep 2007
Location: Some sunny place with good wine and good sailing
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
I'm frankly rather amazed at the objections to conversion to TN on here! I would have thought that most GA pilots were able to read a magnetic compass and convert a magnetic heading to a true heading. Obviously not and so I stand corrected!
In case you microlight pilots etc haven't realised, all airline pilots also learnt to fly on light aircraft, microlights and gliders etc. Do you really think we don't know how to use a compass? Or that we don't have compasses in the aircraft?
I fly GA aircraft, gliders, and microlights for fun - I don't see any problem at all using true north. I know the declination of the area I am flying and it takes a demisecond to calculate true north by reading the compass.
Anyway, I defy any microlight/light aircraft pilot to fly on their wobbly compass at an accuracy that is greater than the difference between magnetic and true north (ok in parts of canada where declination is large maybe - but certainly not in Europe where declination is of the order of a couple of degrees).
And if adding a couple of degrees of declination to your compass heading is too much workload for you "in an emergency" then I am somewhat surprised, even for a low time GA pilot.
But OK, if it is too difficult for GA pilots to convert between true and magnetic north on their compasses, then we'll all just have to carry on with the status quo. So every few years airports will still have to repaint their runway numbers and recalibrate their navaids (no wonder landing fees are so high!), Jeppesen will still have to reprint all their approach cards to cope with drifting magnetic north, pilots will still have to spend ages faffing around updating their approach cards, etc, etc, etc -all just because the GA pilots can't cope with converting between true and magnetic from their wobbly compasses!
In case you microlight pilots etc haven't realised, all airline pilots also learnt to fly on light aircraft, microlights and gliders etc. Do you really think we don't know how to use a compass? Or that we don't have compasses in the aircraft?
I fly GA aircraft, gliders, and microlights for fun - I don't see any problem at all using true north. I know the declination of the area I am flying and it takes a demisecond to calculate true north by reading the compass.
Anyway, I defy any microlight/light aircraft pilot to fly on their wobbly compass at an accuracy that is greater than the difference between magnetic and true north (ok in parts of canada where declination is large maybe - but certainly not in Europe where declination is of the order of a couple of degrees).
And if adding a couple of degrees of declination to your compass heading is too much workload for you "in an emergency" then I am somewhat surprised, even for a low time GA pilot.
But OK, if it is too difficult for GA pilots to convert between true and magnetic north on their compasses, then we'll all just have to carry on with the status quo. So every few years airports will still have to repaint their runway numbers and recalibrate their navaids (no wonder landing fees are so high!), Jeppesen will still have to reprint all their approach cards to cope with drifting magnetic north, pilots will still have to spend ages faffing around updating their approach cards, etc, etc, etc -all just because the GA pilots can't cope with converting between true and magnetic from their wobbly compasses!
Last edited by richatom; 12th Mar 2008 at 14:55.
Thread Starter
Join Date: Sep 2007
Location: Some sunny place with good wine and good sailing
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
If we change to True North with all this new techie stuff to make it easy on normal days, what happens on that day when the screens go blank?
Thread Starter
Join Date: Sep 2007
Location: Some sunny place with good wine and good sailing
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
Here we have (I would presume) an airline guy trying to tell the rest of the aviation community, how it should be done.
And yes, in the USA at least, there are far more general aviation aircraft movements per day than all the airline and military flights...combined (by a factor of at least four).
And yes, in the USA at least, there are far more general aviation aircraft movements per day than all the airline and military flights...combined (by a factor of at least four).
I don't see where you are coming from, describing this as a GA versus airline issue.
When the day comes when everyone is flying new aircraft with computer based navigation systems then that would be the day we should change to true north. One software update and everyone is on true north. Until such time the cost of changing every magnetic slaved gyro in the world to know where it is and correct for declination would be astronomical.
Without changing the avionics to read true north instead of magnetic north the concept of changing the standard to make things more complicated, requiring mental arithmetic for every ATC vector, turn, intercept, etc ad nauseum is misguided at best.
Lets look at an aircraft flying KLAX to RJAA. Departing, the crew would have to subtract 13 degrees from all headings. Enroute the crew would continually be updating the amount to add or subtract. By the time they arrive the crew is now adding 7 degrees to all headings. Changing the standard in order to complicate the approach at the end of a several hour flight would be well ... stupid. All so that we don't have to repaint the runway numbers every 25 to 50 years?
Without changing the avionics to read true north instead of magnetic north the concept of changing the standard to make things more complicated, requiring mental arithmetic for every ATC vector, turn, intercept, etc ad nauseum is misguided at best.
Lets look at an aircraft flying KLAX to RJAA. Departing, the crew would have to subtract 13 degrees from all headings. Enroute the crew would continually be updating the amount to add or subtract. By the time they arrive the crew is now adding 7 degrees to all headings. Changing the standard in order to complicate the approach at the end of a several hour flight would be well ... stupid. All so that we don't have to repaint the runway numbers every 25 to 50 years?
Last edited by ahramin; 12th Mar 2008 at 20:04.
Thread Starter
Join Date: Sep 2007
Location: Some sunny place with good wine and good sailing
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
When the day comes when everyone is flying new aircraft with computer based navigation systems then that would be the day we should change to true north. One software update and everyone is on true north. Until such time the cost of changing every magnetic slaved gyro in the world to know where it is and correct for declination would be astronomical.
True North is used universally when north of 75N, - it would be interesting to hear from pilots up there as to whether there are any practical disadvantages.
It is inevitable that aviation will have to make the change one day - I'm surprised there have not been serious studies by ICAO into when and how it should be done.
Join Date: May 2005
Location: Abroad
Posts: 1,172
Likes: 0
Received 0 Likes
on
0 Posts
My take on it:
It's just a reference, about as arbitrary and elusive as any other. It's not easy to come up with a nice, stable reference system in what is essentially a wrinkled-up, slushy, eggish-shaped kind of ball, wobbling and stumbling about in space.
The current system has advantages and disadvantages (examples of both have been given here), just like the alternatives, but that's what we use.
If you can excuse the trivia, of the 11 navaids north of 75N showing up in Eurocontrol's database as of 2007, 10 are NDBs, with the remaining one VOR (THT - Thule AFB) being, indeed, aligned to True North (as in, geodetic North). There are a few more True North aligned VOR south of 75N in Canada, but not so in Europe or Russia (reason presumably being magnetic North pole being just north of Canada, about 500nm south of the CTNP)
And some pedantism...
It will if that's what it's designed to do. Do a search for "gps heading sensor" or "gps gyro".
It's just a reference, about as arbitrary and elusive as any other. It's not easy to come up with a nice, stable reference system in what is essentially a wrinkled-up, slushy, eggish-shaped kind of ball, wobbling and stumbling about in space.
The current system has advantages and disadvantages (examples of both have been given here), just like the alternatives, but that's what we use.
that is the way all navaids are aligned (at least south of 75N)
And some pedantism...
A GPS receiver won't tell you your heading
Last edited by LH2; 13th Mar 2008 at 12:28. Reason: typo
Join Date: Jul 2007
Location: West Britain
Age: 74
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts
Actually guys, there have been some very serious studies into the matter in recent years. I had the privilege of chairing a meeting organised by the Royal Institute of Navigation on the subject. The outcome was that both the airline industry and the aerospace industry would support such a move but it was recognised that there would be mass objections from the GA organisations, particularly American AOPA which is a very powerful lobbying outfit, unless a cheap, practical alternative to the 'whiskey compass' could be offered. The manufacturers took this on board and went away promising to look at developing such a device but, to my knowledge, have not reported back.
The bottom line is that not everyone wants or needs to use GPS. For my recreational flying I still happily rely on needle, ball, airspeed and compass. I agree that N(T) is a far more logical reference, especially given that the earth's magnetic field is far more complex and unpredictable than the 'bar magnet through the planet' example given in most basic textbooks. As an aside, the magnetic field can and does swap ends occasionally and such an event is (geologically) not too far away.
I'm afraid we're stuck with magnetic for the foreseeable future.
The bottom line is that not everyone wants or needs to use GPS. For my recreational flying I still happily rely on needle, ball, airspeed and compass. I agree that N(T) is a far more logical reference, especially given that the earth's magnetic field is far more complex and unpredictable than the 'bar magnet through the planet' example given in most basic textbooks. As an aside, the magnetic field can and does swap ends occasionally and such an event is (geologically) not too far away.
I'm afraid we're stuck with magnetic for the foreseeable future.
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
....mass objections from the GA organisations, particularly American AOPA which is a very powerful lobbying outfit...
It protects the rights and privileges of the private general aviation pilot, which are under constant threat by the airlines and the military.
