Temp correction for ALL approaches??

[777AV8R]

Temperature Corrections...

ALL CAT I altitudes must be corrected down to and including the DH. It is true that the glideslope is 'fixed', however; on a CAT I approach, all altitude and fix crossing references are based on the pressure altimeter hence, all fixes must be corrected as well. These may seem minuscule corrections but for the sake of being 'right', they must be done. The most important correction on a CAT I is the DH, where the DH/DA is predicated on the use of the pressure altimeter. The correction must be added to the altimeter otherwise, for an uncorrected altimeter, you will reach your true DH at a lower true altitude. In essence, an uncorrected altimeter will always lead you to a lower DH in cold temperatures which has the affect of 'busting limits'.
On the other hand, CAT II and CAT III limits are all based on RA in which case no correction is required at the DA, BUT the intermediate and final fix crossings must be corrected because these altitudes are all based on pressure altimeter readings hence, you will have a correct altimeter reading as you pass by the fix.

Under radar control, maneuvering altitudes are not required to be corrected as ATC is supposed to apply temperature corrections to the vectoring altitudes. As a good situational awareness procedure, you will want to correct the MSA and procedure turn altitudes just to make sure that ATC isn't vectoring you below safe altitudes. If in doubt, you can always ask ATC if they have made the corrections.

Missed approach altitudes must be corrected as well as these altitudes are based on pressure altimeter. If you do carry out a MAP under radar, the controller will provide you with the correct altitude in most cases but again for situational awareness, the MAP altitude should be corrected.

If you are carrying out a VNAV approach, the crossing altitudes shown on the legs page must be corrected, however; do NOT change the fix itself.

From the TC AIP:

With respect to altitude corrections, the following procedures apply:
1. 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.
2. IFR assigned altitudes accepted by a pilot shall not be adjusted to compensate for cold temperatures, i.e., if a pilot
accepts “maintain 3 000”, an altitude correction shall not be applied to 3 000 ft.
3. Radar vectoring altitudes assigned by ATC are temperature compensated and require no corrective action by pilots.
4. 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.



My two cents as a check airman and having flown the arctic for many years.