Cold weather Alt
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Cold weather Alt
Hi there
I'm hoping someone can provide assistance on the following
I've been studying the cold weather alt tables. I understand how the correction to MSA is accomplished but I'm a little confused with correction to procedural altitudes (IAF,FAF, MDA etc). Should I be correcting the FMC altitudes only in this regard or am I required to set the MCP ALT to these adjusted altitudes. If so do I need to advise ATC each time I do this?
And if ATC clear me e.g. to ANY altitude am I required to set that altitude exactly with no correction?
Any info would be appreciated
I'm hoping someone can provide assistance on the following
I've been studying the cold weather alt tables. I understand how the correction to MSA is accomplished but I'm a little confused with correction to procedural altitudes (IAF,FAF, MDA etc). Should I be correcting the FMC altitudes only in this regard or am I required to set the MCP ALT to these adjusted altitudes. If so do I need to advise ATC each time I do this?
And if ATC clear me e.g. to ANY altitude am I required to set that altitude exactly with no correction?
Any info would be appreciated
Is TEMP COMP available in your FMS? If so, follow those altitudes once the temp deviation is loaded and activated. If not, compute the temp correction, advise ATC of the indicated altitude being flown for the existing temp. Canadians an d most cold weather areas, except the US, understand the need for temp comp.
You comp for all altitudes from IAF inbound. Set the ALT SEL to the corrected altitude, VNAV, if the VNAV can be temp comped, will follow temp corrected altitudes.
You comp for all altitudes from IAF inbound. Set the ALT SEL to the corrected altitude, VNAV, if the VNAV can be temp comped, will follow temp corrected altitudes.
The point is that your altimeter will overread, leading you to be lower than you think you are. If you correct all the altitudes in your FMC, but then go to lower altitudes by intervening with the MCP ... let's hope there's no terrain.
If you are being radar vectored, the altitudes ATC gives you should already be temperature corrected so no need to apply any more. If you're in doubt just ask them. Any other altitudes on approach or missed approach should be corrected, but for altitudes that could affect ATC, such as MA altitude, make sure you tell them what you are doing.
If you are being radar vectored, the altitudes ATC gives you should already be temperature corrected so no need to apply any more. If you're in doubt just ask them. Any other altitudes on approach or missed approach should be corrected, but for altitudes that could affect ATC, such as MA altitude, make sure you tell them what you are doing.
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Depends on your FMC. Our A320 and 737 FMCs do not do automatic temperature correction although they do have all the information needed. So we have to do it ourselves, however our SOP only require it if the OAT at the airport is -15°C or below.
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Different outfits, different rules...
In some cold weather correction is to be applied below 0C.
In some aircraft types it can be selected in FMC.
In all cases where it cannot it need only be applied to all MSA and below altitudes, thus anything in FMC which depicted on a chart is at or below MSA requires a cold weather correction.
For RNP approaches, different rules apply inside the FAF, where no corrections are allowed, to make it more awkward.
In some cold weather correction is to be applied below 0C.
In some aircraft types it can be selected in FMC.
In all cases where it cannot it need only be applied to all MSA and below altitudes, thus anything in FMC which depicted on a chart is at or below MSA requires a cold weather correction.
For RNP approaches, different rules apply inside the FAF, where no corrections are allowed, to make it more awkward.
As with many things in aviation, the Lawyers will get it right after the 'event'. If you currently operate a lot into very cold temps, ask your Operating Authority to simplify and explain exactly what you are required to do in all different situations you may find yourself in. Do it now, not some time later........
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Nope.
Minimum temperatures are only published for baro VNAV procedures and all of those we use are corrected to -15°C.
Apply the altitude corrections when needed:
• No corrections are needed for reported temperatures above -15°C or if the aerodrome temperature is at or above the minimum published temperature for the procedure being flown;
• No corrections are needed for reported temperatures above -15°C or if the aerodrome temperature is at or above the minimum published temperature for the procedure being flown;
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If you are being radar vectored, the altitudes ATC gives you should already be temperature corrected so no need to apply any more. If you're in doubt just ask them.
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All minimum altitudes should be corrected for low temp except procedures that are designed down to a certain temp, normally -15 or -20 C. These RNP procedures are not allowed to be flown outside the minimum temperatures.
No, not all ATC units correct for low temp. If they clear you to, say 3000 ft, and this is the MSA, add the required correction and tell them you will maintain this altitude due low temp.
If your FMC autocorrects for low temp, good for you. I have never used one that could do that.
No, not all ATC units correct for low temp. If they clear you to, say 3000 ft, and this is the MSA, add the required correction and tell them you will maintain this altitude due low temp.
If your FMC autocorrects for low temp, good for you. I have never used one that could do that.
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If a procedure has a published minimum temperature there is no need to correct above that temp and it can be flown below that temp if temp correction is applied.
It's not rocket science.
It's not rocket science.
Last edited by FE Hoppy; 29th Oct 2014 at 12:38.
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No It isn't.
PANS OPS:
PANS OPS:
4.3.5.2.2 Determination of minimum promulgated temperature. Determine the minimum probable temperature (the temperature correction is obtained from Appendix A to this chapter) and round it down to the next lower 5°C increment. Then:
a) the FAS for that temperature shall be calculated (see 4.3.5.2.3) and, if less than 2.5°, the promulgated VPA shall be increased to ensure the FAS at minimum temperature is equal to or greater than 2.5°; and
b) the length of the preceding segment shall be reviewed to ensure it meets the relevant requirements for minimum distance before vertical path intercept.
Note 1.— One suitable method of obtaining the minimum temperature is to obtain the mean low temperature of the coldest month of the year for the last five years of data at the aerodrome elevation. Round this temperature down to the next lower 5°C increment for promulgation. Obtain the cold temperature correction applicable for this temperature, the aerodrome elevation, and FAP height using the criteria in the appendix to this chapter.
Note 2.— No minimum temperature restrictions apply to aircraft with flight management systems incorporating final approach temperature compensation.
Note 3.— No minimum temperature restrictions apply to aircraft with flight management systems incorporating approved final approach temperature compensation, provided the minimum temperature is not below that for which the equipment is certificated.
a) the FAS for that temperature shall be calculated (see 4.3.5.2.3) and, if less than 2.5°, the promulgated VPA shall be increased to ensure the FAS at minimum temperature is equal to or greater than 2.5°; and
b) the length of the preceding segment shall be reviewed to ensure it meets the relevant requirements for minimum distance before vertical path intercept.
Note 1.— One suitable method of obtaining the minimum temperature is to obtain the mean low temperature of the coldest month of the year for the last five years of data at the aerodrome elevation. Round this temperature down to the next lower 5°C increment for promulgation. Obtain the cold temperature correction applicable for this temperature, the aerodrome elevation, and FAP height using the criteria in the appendix to this chapter.
Note 2.— No minimum temperature restrictions apply to aircraft with flight management systems incorporating final approach temperature compensation.
Note 3.— No minimum temperature restrictions apply to aircraft with flight management systems incorporating approved final approach temperature compensation, provided the minimum temperature is not below that for which the equipment is certificated.
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aterpster
In North America, Canada does, the U.S. doesn't.
Quote:
If you are being radar vectored, the altitudes ATC gives you should already be temperature corrected so no need to apply any more. If you're in doubt just ask them.
If you are being radar vectored, the altitudes ATC gives you should already be temperature corrected so no need to apply any more. If you're in doubt just ask them.
Are you basing this on personal experience? Or is that written somewhere. If you are basing this on experience only, it might not be transparent to you that ATC is doing the correction. I.e. you might be cleared to the same altitude on a hot summer day and a cold winter night, because the minimum radar vectoring altitudes are that much lower that the procedure altitudes, to absorb the corrections.
Not all altitudes from the IAF but below the temperature corrected MSA needs to be corrected (in our company at least, EU OPS).
And you mean a t° corrected MSA right?
