PPL exam compass errors

[UV]

Quote:
Isnt it time we got rid off all this nonsence?

Not quite sure what you mean UV. Are you suggesting that we just ignore the compass errors, or pretend they don't exist?


MJ

No, what Im saying is that people dont need to be examined on this bullsh1t.
All a student needs to know is that the aircraft must be in stable straight and level flight to avoid compass errors. End of.
KISS...remember!

[fireflybob]

So when the gyro stabilised HSI fails how are you going to turn onto a heading using the compass?

It's nonsense to say a pilot shouldn't have a working knowledge of compass errors.

[lasseb]

So when the gyro stabilised HSI fails how are you going to turn onto a heading using the compass?

Std IFR procedure is to fly a rate-1 turn and time it.
So note your heading (when straight and level); figure out how many degrees you want to turn. Then start stopwatch and start turning at rate-1.
This works a LOT better than trying to figure out a heading from a magnetic compass, and is the only procedure I teach IFR students.
That said, its always good to have the knowledge as to why you should not rely on the magnetic compass during turns/acc..

[dubbleyew eight]

all this because there is a tiny blob of solder on one of the magnets to make it sit level. sheesh.

[fireflybob]

Std IFR procedure is to fly a rate-1 turn and time it.
So note your heading (when straight and level); figure out how many degrees you want to turn. Then start stopwatch and start turning at rate-1.
This works a LOT better than trying to figure out a heading from a magnetic compass, and is the only procedure I teach IFR students.
That said, its always good to have the knowledge as to why you should not rely on the magnetic compass during turns/acc..

Yes that's the way I've taught it for several decades but that's not the point - you still need to start off and finish with a heading reference. Also Turn Coordinates/Needles are not always calibrated correctly.

Pilot's need to have an appreciation and basic understanding of compass errors - is it really that difficult?

[Mach Jump]

Pilot's need to have an appreciation and basic understanding of compass errors - is it really that difficult?

It's about VFR flying with just a compass. I'm with you, Bob.

...there is a tiny blob of solder on one of the magnets to make it sit level.

Errrrm, No there isn't.

(I wonder if you wrote this with your tongue in your cheek and I'm taking it a bit too literally?)

The errors are caused by the horizontal displacement of the magnets due to the pendular suspension system used to reduce the 'dip angle' at higher latitudes.


MJ

[Big Pistons Forever]

Flying instruction theory, particularly ab initio instruction, should concentrate on items which have a practical significance.

The test on whether a particular item of theory should be taught ought be " is there a potential circumstance where the student can apply the bit of knowledge I am about to teach "

So going back to the OP's question, knowing a mag compass has errors and learning how to compensate for those errors has obvious practical significance.

Teaching the design of the compass and how/ why the design produces those errors has zero practical use so IMO it is waste of time. That training/ study time could be used to teach things that are actually useful.

I think there is far too much emphasis on theoretical subject which have absolutely no use in the real world of flying an airplane. The UK is IMO particularly bad in this respect

Here is a heretical thought. Given the, on average, once a month carb ice induced engine failure and resultant forced approach maybe ground school less time should be spent on the theory of compass errors and more time on
recognizing the symptoms of carb icing and knowing those conditions when it is most probable

Hat, Coat, Door ....

[what next]

...knowing a mag compass has errors and learning how to compensate for those errors has obvious practical significance...

The "knowing a mag compass has errors" part of this statement is really all that is required. In ten years, this thing will have disappeared from aeroplanes. If one really wants to look at a magnetic compass, he can use his smartphone...

[fireflybob]

Here is a heretical thought. Given the, on average, once a month carb ice induced engine failure and resultant forced approach maybe ground school less time should be spent on the theory of compass errors and more time on
recognizing the symptoms of carb icing and knowing those conditions when it is most probable

BPF,

For me nothing heretical at all about it - I've been teaching such for decades.

There is a huge difference between doing things right and doing the right thing.

[Mach Jump]

Here is a heretical thought. Given the, on average, once a month carb ice induced engine failure and resultant forced approach maybe ground school less time should be spent on the theory of compass errors and more time on recognizing the symptoms of carb icing and knowing those conditions when it is most probable

No problem with this at all. I just don't think they are mutually exclusive.


MJ

[fireflybob]

Well we could have an even more philosophical debate as to what the instructor's job is about.

The root of the word education is from the Latin "educo" meaning to "draw out" or another one is "educere" meaning to "draw out from within" or to "lead forth".

The best instructors I have had always teased out my innate curiosity to actively go out and find out more about the subject - they didn't just tell me what they thought I needed to know.

[Big Pistons Forever]

Originally Posted by fireflybob

The best instructors I have had always teased out my innate curiosity to actively go out and find out more about the subject - they didn't just tell me what they thought I needed to know.

If they were doing ab initio insruction then they were doing it wrong. There is quite a lot of information that the student must know. Now in an Air Force or College program you have the luxury of having full time students doing nothing else but learning to fly and you can afford to gold plate the training with a lot of non essential theory.

However this is the private aircraft forum and I can say on the basis of a lot of personal experience teaching ab initio and low hour pilots, getting the time to make sure the student has mastered all the must know stuff and a reasonable amount of the nice to know stuff leaves very time for unstructured satisfactions of curiosity. In fact digressions into theory often come at the expense of study on stuff that really, really matters.

Originally Posted by Mach Jump

No problem with this at all. I just don't think they are mutually exclusive.


MJ

All knowledge in flight training is not of equal value. The challenge is teaching the right amount of information at the right time. Since flying is an innately practical exercise there is not all that much theory required to safely and efficiently fly the aircraft.

Knowing and understanding the basics of how a carburetor functions is IMO vital to fully understand how to avoid carburator icing and how to correctly use the mixture control, both of which are obviously must know areas.

Understanding the theory of why a compass has errors has no practical use in flight. So it would not be mutually exclusive only if teaching this was not at the expense of something that actually matters, which is going to be pretty much everything else. Given the time constraint realities of flight training in the private flying arena, this is IMO a tall order.....

[fireflybob]

BPF, with respect you have missed my point.

Of course at the ab initio level we need to teach the essentials but it's also a question of how you do that.

[Johnm]

The problem is, for me and many people, how much can we remember? I fly IFR most of the time with AI HSI turn coordinator and GPS. If HSI packs up the GPS tells me heading and track if HSI and GPS both pack up at the same time, then turn coordinator and stop watch are the answer and compass confirms heading when straight and level. I can't therefore remember the compass errors and would have to go and look them up if I needed to know.

[Piper.Classique]

My VFR aircraft has a compass, turn indicator, ASI and altimeter. I am entirely capable of doing timed turns but being VFR can't be **sed to do rate one turns. So I turn onto landmarks found under the wings.....
THe club aircraft have DI and radio nav. Mine doesn't.
Even so, turning on to 90 degree landmarks works well, and keeps heads out of cockpits. It works thus...
Turn 360 right? Find a landmark, bush, tree, field, farm, whatever under rigt wing. Turn until it is under left wing. That is half the turn. Repeat. That is 360.
Easy. Let aircraft settle down wings level. Check heading and adjust if needed. Vary as needed for lesser changes of heading.

I teach turning and acceleration errors, in gliders, microlights, and SEP. It takes about five minutes on the ground and ditto in the air. Compass not very useful in turns or other accelerated flight, read the book if you want to know why. Show the effects in flight. Job done.

I spend a lot longer on engine failure modes, how to diagnose and cope, full and the more insiduous partial. (yes, and some gliders have an engine.....)

Now my IMPORTANT instruments take up a bit more room. a proper glider vario, CHT and oil pressure and temperature, RPM. Would like carb temp, a CHT per cylinder, and EGT but can't find room in the panel or the money to buy them

[fireflybob]

If HSI packs up the GPS tells me heading

Johnm, how does GPS tell you the heading?

[dubbleyew eight]

mach jump, err yes it is.
the magnets are actually balanced to level by a blob of solder.
one of my mates does a very nice job of changing a northern field compass to a southern field compass just by melting off the old blob and tacking on a new one.
refilling and sitting a night in the freezer etc. etc.

[Mach Jump]

...err yes it is.

Err... No it isn't.

Field compasses may be balanced in that way, but aircraft compasses are not.


MJ

[Johnm]

Quote:
If HSI packs up the GPS tells me heading
Johnm, how does GPS tell you the heading?

Because it shows the angle I have to fly the aircraft to stay on the magenta line

[fireflybob]

Because it shows the angle I have to fly the aircraft to stay on the magenta line

Ok so it shows heading indirectly - thanks

But if ATC asked you to fly a heading (assuming drift) that wouldn't be quite as straightforward although you could offer to fly a track?