PPRuNe Forums - Temp Error Correction USA

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Temp Error Correction USA

Notwithstanding the whys and wherefores of Temperature Error Correcting altimeters, I'm just wondering what the general procedures are in the USA in an aircraft that doesn't have FMCs that automatically correct for the error. I know the FAA publishes a list of Cold Weather airports with temperature limits (snowflake symbol), below which one must apply corrections but what about airports not on the list?

Say I was cleared the VOR 22L at JFK and it was -10decC at the field. My thinking is I'd be correcting the step heights & MDA etc for the temperature but JFK isn't on the list of Cold Weather airports so would a local operator be correcting the altitudes? Or would they not bother as the FAA had checked out the Required Obstacle Clearances at various temps and deemed that they weren't infringed so a correction wasn't necessary? The AIM suggests the latter - "e. Pilots are responsible to compensate for cold temperature altimetry errors when operating into an airport with any published cold temperature restriction and a reported airport temperature at or below the published temperature restriction."

I appreciate that RNAV approaches often have minimum temperatures for uncompensated LNAV/VNAV approaches, below which one is unable to fly the approach.

I'd be grateful for any info from those working in the States please! :)

If cold weather corrections are required, it will be listed in the notes on the approach chart (Jeppesen charts) No note, no corrections are to be applied.

The notes may also place a restriction that the approach may not be flown if the temperature is below (or above) what is indicated.

Cold weather corrections can apply to any approach - ILS or non-ILS if noted. Airports with approaches where corrections are required will “normally” have a 10-1W page (I haven’t seen one without it) Pilots are to apply the corrections (interpolation allowed from 10-1W chart) to altitudes only on the approach (IAF to MAP) based on the elevation of the altimeter reference point. Corrections are not to be applied to ATC assigned altitudes (although a query to ATC may be prudent) Pilots are to notify ATC of what cold weather corrected altitudes will be flown from approach commencement to FAF, and then on the missed. ATC need not be advised of cold wx corrected minimums.

If you want a math/cold wx correction exercise, get the plate for KMSO, RNAV(GPS) Y RWY 12 and plan a circle to 30 with a temperature of -25c.