Approaches with very low temperatures

[john miro]

I would like to know which precautions are to be taken with altimeter reading, performing a Non Precision App with temperatures like ISA - 30, and if there is any Press Altitude correction ( airport elevetion 5000 Fts ). thanks a lot, John Miro.

[rigpiggy]

add altimeter correction to all chart altitudes. try your CAP or this site http://bathursted.ccnb.nb.ca/vatcan/fir/moncton/WeeklyTopics/Archives/20040104/CurrentTopic.html

[john miro]

I's very interesting. Thanks for cooperation rigpiggy !!!

[VORDME2]

if temp is below 0°C,correct all altitude by 4% by 10°C below isa.So -3O° mean you must increase all safety altitude,outer marker,minima etc by 18%.Cold+low QNH is particulary dangerous...

[BelArgUSA]

Late 1960s. early 1970s... a Flying Tigers DC8-63F on approach to Anchorage hit mountains because of that, in the years before the problem of altitude/altimeter errors in very cold temperatures was properly addressed in training...
xxx
After (only after...) that accident, correction charts "started to appear" in my Pan Am manuals... Sadly, it takes accidents for updates in manuals.
xxx
:)
Happy contrails

[Rainboe]

I remember that, but I think it was Juneau....or somewhere between Anchorage and Vancouver.....that bit nobody knows anything about!

[Dan Winterland]

There are at least two, maybe more charts with differeing numbers. The ones published in the Jepps are the industry standard. But i fly for the same company as Rainboe and it has simplified things with a simple percentage, which is a bit generous - but safe.

[ahramin]

Cold weather corrections are a function of QFE, not QNH. The higher your altitude above ground, the larger the discrepancy. The QNH given at a particular field will already be corrected for temperature. This means that only small amounts must be added to 200' DAs no matter what the actual altitude above sea level is.

[dewarg]

I refer to a statement by “ahramin” where it’s said cold weather corrections are related to your height above ground. The height used to calculate corrections is the height above the altimeter source.

[ahramin]

Thanks dewarg. I should have said that assumes the altimeter source is at the airport, and you use the airport elevation in your height above ground calculations.

Obviously if the error is zero when the height above ground is zero then you couldn't hit a hill :eek:. And many have hit the hill.