cold temp corrections

[flyburg]

My company adjusts the DA and MDA for cold temperature. We have table we can use or you calculate with the rule of thumb: every 1000', every degree nonstandard ads 4 feet to DA. Do other companies use the cold wtemp corrections on DA/MDA as wel? ( I know in the states you don't)

greetings

[VRThomas]

I think that the official calculation for the general rule is:

4% for every 11 Deg C.

VRT

[oldebloke]

Defiinite part of the Canadian AIP...All Alt's are compensated for cold temps in the approach and terminal(minimum radar vectors are modified)...The pro' ceedure turn,FAF DH/MDA and go-around alts should be considered in the 'briefing' :ok:

[VRThomas]

In fact...
In Canada, Jeppesen will provide you with a chart that shows the corrected alts for temps below 0 for any requested airport.

Pretty slick and no reason why they shouldn't be used EVERYWHERE!

VRT

[80/20]

Many airlines use ICAO Cold Temperature Error Tables. This is also the case in the US. Various FAA circulars and documents are discussing this issue and gives examples of how SOPs should include this information. Not too long ago the FAA iussued temperature restriction for using BARO-VNAV approaches.

[reynoldsno1]

baro VNAV approaches have a cold temperature correction built into the calculation of the final approach obstacle surface - it is normally based on the coldest forecast aerodrome temperature -5C rounded down to the next lowest 5C. This temperature is published as the lowest value for which the procedure is valid.

[flyburg]

Thanks for the replies,

Yes oldebloke, you're right not only the da/mda but all alts need to be corrected. I was just curious wether other countries applied them as wel. I used to fly for a 121 carrier in the states for 4 years and never even heard of it, definitely not part of comp sop's. Called some old buddies that have moved to the US majors (well, most are furloughed lately) and they had never heard of it either. Hence my curiousity how other countries applied them.

Thanks

P.s. I guess in Canada they become somewhat more important with the cold temps :-)

[Kilo-club SNA]

Well I can assure you that any scandinavian operator will correct their altitudes....it ends up being a thousand feet or more sometimes brrr

[mcdhu]

This is quite often hidden in the depths of the Ops Man Gen and quietly forgotten. Should be applied at or below ISA-15?

Cheers,
mcdhu

[corporal klinger]

recently during a landing at fairbanks/alaska I noticed a strong temp inversion,which basically would have been resulted in a too high altitude if we would have added a temp correction because of cold wx on the ground.

my colleague told me this is quite common in alaska/canada,I was wondering if somebody from that region could comment on that.

I don't see much sense in adding a correction on the DA,since the difference would even in extreme circumstations be minor,am I wrong?

cheers

[BLE]

The formula for correction to cold temperatures is to add 4% altitude (QFE / AGL) for every 10 C below ISA from the reporting source.

You will find it in Jepps ATC chapter, and in most JAA operators manuals.

My experience is only scandinavian + canadian operators understand and perform this correction as a part of SOP.

The number of blank stares I have received from co-pilots, training captains and examiners elsewhere in the world when briefing this procedure, is just mind boggling.

A quick example common in many airports these days:

A sea level airport reporting a temp of -10C will need a correction of 10% (ISA -25, 4+4+2%) to MSA, MEA, MORA and all altitudes below.

If your MEA is 5000`, this is now corrected to 5500.
Flying a glideslope in these conditions will easily show you how important the corrections are.
If published GS intercept is 3000`at 10 NM, maintain 3300` indicated until 10NM and you will see the GS intercepting excactly at 3300` and 10NM.

Outer marker passage on the GS will occur at 2200` instead of 2000`.
A 200`DA will only need to be corrected by 20`, which is hardly noticable.


Flying non-precision approaches in very cold temps can easily make you a CFIT statistic. Remember the MSA is 1000` regardless
of terrain below/above 5000`.
Descending to the MSA of 8000` in ISA - 10C will only give you 200` AGL clearance. Add some wind, and I hope your GPWS is capable of saving your hide!


You as a pilot better do it, ATC will not. The only exception is being radar vectored in Canada, where they correct MVA for non standard temps.

Flying baro VNAV in these conditions will require you to have the FMS correct by manually enter aiport temp if possible, or applying the corrected altitude to the approach altitudes in the FMS.

A life saving rule of thumb is to add 10% to MEA, MSA, IAF, DA , MDA etc. when the airport reports temps down to -10C. Add 20% when down to -30C. Any colder, get the book out, or stay home!:oh:

[IHL]

The Chart is from the Canadian CAP( Approach charts) Gen.

The Canadian AIP is online at : Temperature correction RAC 9-14[ hperlink does not appear to be working]




http://img.photobucket.com/albums/v633/jetboxIII/Presentation1.jpg

http://www.tc.gc.ca/CivilAviation/Regserv/Affairs/AIP/PDF/AIP-RAC-01-05.pdf (http://) [/URL]

[BOAC]

Done 'to death' many times on this forum. Try 'search' for 'cold weather altimeter' or 'altimeter corrections'. A couple of good frighteners in there too for those who doubt:eek: