Need help from a navigator!

[Alex Whittingham]

......I'm ashamed to say.

We have a very odd ATPL question relating to the manual construction of a minimum time route using isochronic lines. I can't find a reference for the technique and none of the schools can agree on the answer. Our tame nav only goes back as far as Pembrokes and DC3s and he says he's never had to do anything like this in his life.

Its on the Wannabes forum here (http://www.pprune.org/forums/showthread.php?s=&threadid=97549) .

All contributions gratefully received.

[HectorusRex]

Copernic.com produces several 'hits' on this subject.

This is probably the most comprehensive.This (http://www.geodyssey.com/papers/tobler93.html)

[Alex Whittingham]

Thanks for that HR, but I can't find the answer on that link. Have I missed it?

[HectorusRex]

Alex, see if it makes sense to your tame Nav.
If not, then try www.google.com with the same request.:ok:

[Alex Whittingham]

Thanks, I already did. Nearly everything that comes up relates to isochrones in studies of city traffic and astronomy.

[sycamore]

Thought you were a Nav, Alex??:O

[Alex Whittingham]

Like to step outside?

[Semicolon]

Need help from a navigator, Alex, but you're ashamed? Hope you find the answer soon.

All the best,

A Navigator who knows the answer but who can't be bothered answering a pilot who is ashamed of asking a navigator.

[StopStart]

He knows the answer!!!!! He must be witch!!!!!!

BURN HIM!!!

please...

:rolleyes:

It is, however, reassuring to discover that there are still navs out there that know about this sort of mediaeval garbage. Somewhat less reassuring to see that the ATPL examiners are still asking such irrelevant and outdated questions. I smell a navigator on the examining board.....:hmm:

[BEagle]

Ah, but Stoppers, once you've got your 2000 hrs total time of which 1500 is on the Herc (with not less than 1000 as Captain), then all you'd need to do for your ATPL is to get a Class 1 medical, have an IRT watched by a CAA Examiner....and pass ATPL Air Law. Oh - and cough the dosh!:{ Say thank you to your favourite ex-QFI for starting the ball rolling which led to that!:O

So no joys of isochronic confusion - but hours spent poring over the system of lights to be displayed by airships, the dimensions of the streamers to be displayed by tethered kites and some truly riveting stuff about the various international regulations etc etc....:yuk:

[Alex Whittingham]

Aw, go on Semicolon. Pretty please?

We've dusted of our copy of the Manual of Air Navigation but we can't decipher that chapter. My ex A Cat Nav has spent the last two days poring over it with furrowed brow occasionally making little 'hoom, hoom' noises.

[2port]

working on SPHLC's theory, the answer is surely "d".

And, quite spookily it is, I think! Or maybe ...

I'll get back to you.

[FEBA]

Isochronic :confused:
Never heard of it. Is it something you find in a can of lucozade ??
I thought the construction of MTT's was a product of pressure and temperature. Such a long time ago though.
FEBA

[moggie]

D - I reckon.

You are trying to conmvert what happens in the air to what happens on the ground - this is done by adding/subtracting the effect of wind.

Mean wind is always used and, as you are looking ahead, surely it is the mean wind up to the next isochrone.

Well, that's the "applying logic" approach, anyway!

BTW - although I pilot, I reckon that having a grade B 'O' level pass in Air Navigation permits me to have Honorary Life Membership of SODCAT.

[StopStart]

Thank you favourite ex-QFI!
Nearly got all that - just 110 more hrs of the Captain stuff to go ;)

Now then.....tethered balloons you say.......

[tarbaby]

Pilots in SODCAT!! No way, not never

[FEBA]

Perfect example of the double negative

[Alex Whittingham]

Thanks for your help everyone, it looks like answer (d).