High altitude cold weather corrections

[pelmet]

Anybody using the formulas in the AIM for their high altitude enroute cold weather corrections. Over the Rockies, the Antarctic, anywhere else.

Does the high altitude affect the corrections significantly?

[The De-Icer]

It's always cold at high altitude.

[DrSpaceman]

Set standard

[switchflicker]

Please don't correct enroute altitudes.

[Rockie]

Please don't correct enroute altitudes.

Ditto.

[AuxBatOn]

If you are assigned an altitude by ATC, adhere to this. If you feel you need higher, request and get a clearance.

If you are flying uncontrolled IFR, correct the MEA for temperature and use the next highest altitude for the direction of flight. (Example: MEA is 7,800 ft, correction is 2,000 ft that makes it 9,800 ft corrected MEA. Fly at 10,000 ft going West or 11,000 ft going East)

[PostmasterGeneral]

How freakin cold is it that you're adding 2000' to your altitudes??

[trampbike]

Around 4' per 1000' AGL per degree below ISA at the SFC. Around -40 would almost do it.

[PostmasterGeneral]

Begs the question though, anywhere you'd be uncontrolled IFR in Canada, chances are you're in the standard pressure region. Even with a couple thousand hours flown in the Baffin region in the coldest of temperatures, I can't remember ever having to correct high altitudes enroute.

[pelmet]

Please don't correct enroute altitudes.

Ditto.

Really? it surprises me abit to see that anser given here.

I'm sorry, but there are situations where I believe that it is very appropriate to correct an enroute altitude in mountainous terrain during the winter time. Some of these situations can involve mountains with peaks well over 10,000'. Aside from the examples given above there are other situations as well. They may be out of the ordinary situations but are worthy of consideration by some of us depending on the operation.

I found it difficult to understand the formulas in the AIM and figured with the large number of pilots here that have cold weather experience, I figured that there might be someone who has done this.

Anyone have experience with this?

[polar one]

I have some experience in cold weather operations. Seems to me the answers by Switchflicker, Rockie, and aux bat were correct. Don't mess with enroute altitudes. Use a higher one if the temperature correction on a lower altitude brings you to close to terrain...or a lower pressure for that matter.
But fly the enroute altitude chosen.

[pelmet]

I have some experience in cold weather operations. Seems to me the answers by Switchflicker, Rockie, and aux bat were correct. Don't mess with enroute altitudes. Use a higher one if the temperature correction on a lower altitude brings you to close to terrain...or a lower pressure for that matter.
But fly the enroute altitude chosen.

I am not sure why would you agree with Switchflicker, Aux Bat On and Rockie. They gave mostly opposing advice. The first two said not to correct enroute altitudes, which seems a little dangerous to me in certain cases. Aux Bat on said to request a higher altitude if I feel I need it, which I believe can be the case, especially in certain rare circumstances.

You did bring up an important part of the whole terrain clearance thing with your mention of altimeter setting.

My concern is really more in a non-ATC environment out in places where you are on your own.

I would like to get back to the original question though, and that is.....has anyone ever used the formulas that are presented in the AIM with perhaps a little detail.

[Rockie]

RAC 2.12 and 8.5 give guidance on how to handle cold weather en route altitudes. No need to make this more complicated than necessary because if you're going to calculate temperature corrections from ISA you'll also have to incorporate pressure differences, and you'll have to do it regularly throughout the flight as conditions change. If it's a concern bump it up a level, but do not fly at a temperature corrected altitude of say, 7300 feet IFR.

[atphat]

so you'd rather fly at 13880' than 15000'?

[atphat]

but do not fly at a temperature corrected altitude of say, 7300 feet IFR.

Absolutely. that should easily go without saying.

[pelmet]

Once again...

My concern is really more in a non-ATC environment out in places where you are on your own.

I would like to get back to the original question though, and that is.....has anyone ever used the formulas that are presented in the AIM with perhaps a little detail.

[Rockie]

People know what you're asking Pelmet and are answering you, but if you insist on a short answer so far it would seem to be "no".

[pelmet]

People know what you're asking Pelmet and are answering you, but if you insist on a short answer so far it would seem to be "no".

Thanks, that does appear to be correct so far, but if anyone has had chance to use it(it talks about spreadsheets and computer programming), I would be interested in further info.

Perhaps this sort of thing has been use by people down in the antarctic with its cold temperatures and high mountains/base elevations.

For me, I was wondering if it could be used for decompression escape routes which can be above 20.000 feet.

[Rockie]

Jeppesen publishes grid minimum off route altitudes (MORA) on their enroute charts that provide 1000' clearance above terrain and man made obstacles up to 5000', and 2000 feet above terrain over 5000'. If the data is provided by the state it provides 1000', and 2000' clearance in designated mountainous areas (think Canada). That should be enough, but as mentioned the AIM provides guidance to increase the minimum by 1000' if cold weather altimeter errors are a concern.

In the Antarctic I have no idea. It seems to me that if there are no accurately surveyed obstacle clearance altitudes available on IFR charts the minimum altitudes will be very conservatively high. Anybody actually flying down there IFR will also probably have very specific company/military procedures to follow.

PS. I just looked at my JeppFD Pro over the Antarctic and grid MORA's are provided down there as well.

[trampbike]

If you really want to bother adjusting altitudes (like most people, I don't understand why you would though), just use the formula I mentionned earlier: 4' per 1000' AGL per degrees below ISA temperature at the surface altitude.