SID Cold Weather temperature corrections

[felixthecat]

Approaches are often cold weather corrected depending on the temperature and depending on if the chart has a temperature limit on it.

However on a SID do the altitudes need to be corrected or is there a temperature that they are valid down to?

If you know the answer please provide a reference because I can't find one…..

[Piltdown Man]

My understanding is that the ATC required levels within a SIDs don't need a correction, but MSAs and any obstacles shown on charts will have to be "corrected."

TMA

[felixthecat]

Thats my understanding too but where is it written. Having asked several TRE's and received several answers it would be good so see the reference.

[Northbeach]

Approaches are often cold weather corrected depending on the temperature and depending on if the chart has a temperature limit on it.

True statement.


However on a SID do the altitudes need to be corrected or is there a temperature that they are valid down to?


I have never seen a cold weather correction on a SID, simply an observation.

Look at Jeppesen's Terminal Procedures - North America - Canada CA-19 & 20 for a source document for cold weather corrections (The Canadians know a thing or two about flying in cold temperatures; as do the Russians and Scandinavians.)

At +15C and sea level an indicated altitude of 5,000' will put you 5,000' above sea level. Drop the surface temperature to -50C with the corresponding increased air density flying the same indicated altitude of 5,000' will put you at 3,500' above sea level. Is being 1,500' lower significant? I think it is! Check the chart.

Respectfully,

Northbeach

[Checkboard]

On a SID, altitude limits are either traffic related (in which case everyone has the same error = no problem) or terrain related.

If they are terrain related (e.g. Geneva 23 departure, no turn to the right before 7000') then they have the same separation standards as MSAs etc, i.e. 1000' up to 5000' then 2000' above that. The reason for the increase above 5000' is specifically to account for cold weather corrections over large heights.

[felixthecat]

I agree Checkerboard, either a terrain or traffic issue. However the bit about all having the same error for traffic on a SID I am a little dubious about, since its not just the departing SID traffic that needs to be separated, the departing SID traffic also needs separating from the STAR traffic who won't have the same error if they are temperature corrected….

Still can't find it written down but thanks Northbeach :)

[plain-plane]

Cold weather correct ALL altitudes below the MSA STARS, APP & SID, and get ATC permission to do so (inform them)...

In the case of a SID,,, the potential problem will be your first level off restriction... I always tell ATC what I will correct this altitude to... that way I can be confident that ATC are also on the ball.

BTW not all ATC units here i Europe use cold weather temp corrections... strangely OSLO APP being one who dont cold weather their radar vectors...

[felixthecat]

No disrespect intended, but WHERE does it state the SID altitude is to be corrected or not.

There are several different theories on here already yes it should /not it shouldn't ….I want to know which is correct and the reference to back it up.

I was told by a TRE that SID altitudes are correct to -20C unless otherwise stated but still no reference….

[plain-plane]

Ultimately you will need to look at the AIP of every the country you fly into. - and/or your route manual/jeppy book- as said, not even all regions in the same "cold" country applies same procedures.

And if you work for a company who take their winter ops serious, they should include guidance in the OPS and SOP manuals...

[cldrvr]

Canadian references.

In conditions of extreme cold weather, pilots should add the values derived from the Altitude Correction Chart to the published procedure altitudes, including minimum sector altitudes and DME arcs, to ensure adequate obstacle clearance. Unless otherwise specified, the destination aerodrome elevation is used as the elevation of the altimeter source.
With respect to altitude corrections, the following procedures apply:

IFR assigned altitudes may be either accepted or refused. Refusal in this case is based upon the pilot’s assessment of temperature effect on obstruction clearance.
IFR assigned altitudes accepted by a pilot should not be adjusted to compensate for cold temperatures, i.e., if a pilot accepts “maintain 3 000”, an altitude correction should not be applied to 3 000 ft.
Radar vectoring altitudes assigned by ATC are temperature compensated and require no corrective action by pilots.
When altitude corrections are applied to a published final approach fix crossing altitude, procedure turn or missed approach altitude, pilots should advise ATC how much of a correction is to be applied.

RAC - 9.0 INSTRUMENT ARRIVAL FLIGHT RULES (IFR) ? ARRIVAL PROCEDURES - Transport Canada (http://www.tc.gc.ca/eng/civilaviation/publications/tp14371-rac-9-0-2604.htm#rac-9-17-1)

[cldrvr]

Also have a look at ICAO Doc 8168 pans-ops.

[JeroenC]

Our OPS manual says to correct all altitudes below the (temperature corrected) MSA when temp below 0, execpt ATC assigned altitudes.

My understanding is this includes all altitudes on SIDs unless they state "stop altitude by ATC".

Sorry, no official source but for me my ops manual is official ;)

[fuelevaporator]

How about this guess:

It all comes down to what one person had in her or his mind when constructing a procedure, be it an approach or a departure and it clearly is poor policy to design an obstacle critical procedure for standard temperature while thinking about lowest expected temperature AND PUBLISHING it would be regarded as normal.
Only a few procedures such as GPS- or RNAV approaches so far I have seen to show this temperature so suggest we should put on some pressure to get it on EVERY plate!

Hear myself the voices "but then we even have to be higher here and there during summertime, when performance is worse!" which is true except for obstacles taken into account for engine failure where temperature input is allways required.

Even my company requires a temperature correction only below 0 degrees Centigrade completely forgetting that this might be the standard temperature at some of our fields...

[aterpster]

The FAA has refused to take action on cold weather corrections even though the subject became an industry/FAA forum issue in 1991, or so. After a couple of years of such inaction the U.S. Air Force pulled out of the discussions and stated they would proceed with corrections, FAA on board or not.

Granted, unlike Canada, much of the U.S. doesn't need cold station corrections, but the northern states, Alaska, and the Rocky Mountains certainly do at times.

Last winter a commuter jet almost hit a mountain in Vermont on an extremely cold day.

The big issue in the U.S. is a very stubborn controllers union.

Smart folks make additives from the IAF inbound. If there is an ATC conflict you tell them what you're doing and why. It really doesn't matter that much where the IAF is 1500 or 2000 above a flat-area airport, but it sure does where there are mountains around.

[BOAC]

then they have the same separation standards as MSAs etc, i.e. 1000' up to 5000' - not forgetting that at 5000' and -35 degrees C your 1000ft has - gorn! I personally always used to correct MSA and others that were relevant in significant low temps.

[FlightPathOBN]

For the most part, 8168 refers to the final approach surface, but has a veiled reference to MSA...

Appendix A to Chapter 4
TEMPERATURE CORRECTION
1.1 Requirement for temperature correction
The calculated minimum safe altitudes/heights must be adjusted when the ambient temperature on the surface is much lower than that predicted by the standard atmosphere.
1.2 Tabulated corrections
For FAS angle calculation the cold temperature correction should be obtained from Tables III-3-4-App A-1 and III-3-4-App A-2. These tables are calculated for a sea level aerodrome. They are therefore conservative when applied at higher aerodromes (see paragraph 3)