AIM 8/15/19  7/16/20  Although not all altitudes on the approach will be corrected back to standard day values, a safe distance above the terrain/obstacle will be maintained on the corrected approach segment(s). Pilots may calculate a correction for each fix based on the fix altitude if desired. “Reported Temperature” row. Round this number as applicable and then add to the final MA altitude only. (b) Aircraft with temperature compensating system: If flying an aircraft equipped with a system capable of temperature compensation, follow the instructions for applying temperature compensation provided in the AFM, AFM supplement, or system operating manual. Ensure the temperature compensa- tion system is on and active prior to the segment(s) being corrected. Manually calculate an altimetry correction for the MDA or DA. Determine an altimetry correction from the ICAO table based on the reported airport temperature and the height difference between the MDA or DA, as applicable, and the airport elevation, or use the compensating system to calculate a temperature corrected altitude for the published MDA or DA if able. Pilots may use Real Time Mesoscale Analysis (RTMA): Alternate Report of Surface Temperature, for computing altitude corrections, when airport temperatures are not available via normal reporting. The RTMA website is http://nomads.ncep.noaa.gov/pub/data/nccf/com/rtma/ prod/airport_temps/. NOTE − g. Communication: Pilots must request approval from ATC whenever applying a cold temperature altitude correction. Pilots do not need to inform ATC of the final approach segment correction (i.e., new MDA or DA). This request should be made on initial radio contact with the ATC facility issuing the approach clearance. ATC requires this information in order to ensure appropriate vertical separation between known traffic. Pilots should query ATC when vectored altitudes to a segment are lower than the requested corrected altitude. Pilots are encour- aged to self − announce corrected altitude when flying into a non towered airfield. f. Acceptable Use of Table for manual CTA altitude correction: (See TBL 7 − 3 − 1.) Pilots may calculate a correction with a visual interpolation of the chart when using reported temperature and height above airport. This calculated altitude correction may then be rounded to the nearest whole hundred or rounded up. For example, a correction of 130 ft. from the chart may be rounded to 100 ft. or 200 ft. A correction of 280 ft. will be rounded up to 300 ft. This rounded correction will be added to the appropriate altitudes for the “Individual” or “All” segment method. The correction calculated from the table for the MDA or DA may be used as is or rounded up, but never rounded down. This number will be added to the MDA, DA, and all step − down fixes inside of the FAF as applicable. 1. The following are examples of appropriate pilot − to − ATC communication when applying cold − temperature altitude corrections. (a) On initial check − in with ATC providing approach clearance: Missoula, MT (example below). GLYPH<C0083> Vectors to final approach course: Outside of IAFs: “ Request 9700 ft. for cold temperature operations.” GLYPH<C0083> Vectors to final approach course: Inside of ODIRE:  “Request 7300 ft. for cold temperature operations. ” GLYPH<C0083> Missed Approach segment: “ Require final holding altitude, 12500 ft. on missed approach for cold temperature operations. ” (b) Pilots cleared by ATC for an instrument approach procedure; “Cleared the RNAV (GPS) Y RWY 12 approach (from any IAF)”. Missoula, MT (example below). GLYPH<C0083> IAF: “ Request 9700 ft. for cold tempera- ture operations at LANNY, CHARL, or ODIRE. ” 2. These techniques have been adopted to minimize pilot distraction by limiting the number of entries into the table when making corrections. 1. No extrapolation above the 5000 ft. column is required. Pilots may use the 5000 ft. “height above airport in feet” column for calculating corrections when the calculated altitude is greater than 5000 ft. above reporting station elevation. Pilots must add the correction(s) from the table to the affected segment altitude(s) and fly at the new corrected altitude. Do not round down when using the 5000 ft. column for calculated height above airport values greater than 5000 ft. Pilots may extrapolate above the 5000 ft. column to apply a correction if desired. 7 − 3 − 5 Cold Temperature Barometric Altimeter Errors, Setting Procedures and Cold Temperature Airports (CTA)