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low temperature correction

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low temperature correction

Old 24th Mar 2004, 11:20
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low temperature correction

Can anyone point me to a chart that shows the relationship of temperature to QNH at cold weather airports, for approach corrections. Tried jeps tables and codes, but no joy...Thanks. Bumz
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Old 24th Mar 2004, 15:01
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Bumz_Rush Try search – low temperature correction.
Also see:
http://www.faa.gov/language/accold.pdf
http://www.bluecoat.org/reports/Long_98_Cold.pdf
http://www.fmcguide.com/media/calgary.pdf

It is surprising how often this subject appears in this forum; this begs the question is the subject taught, and if so how or when is it remembered. Was it fully understood? Furthermore, the many links and references tell what the corrections are, but few tell where or when to use them. Is the industry complacent in these matters, who next will to be caught out by the failure to correct the altimeter and what risk is there of a CFIT event if EGPWS is not fitted?

A recent FSF conference paper reviewed the use of geometric altitude (GPS based) in the EGPWS; this facility shows the true altitude on the EGPWS display (ND), but does not correct the main altimeters. Thus if there is a difference between geometric and the main altimeters then start thinking about cold temp correction or recheck that you have the correct pressure setting. The speaker at FSF also noted the poor understanding that crews have of the actual equipment fit – EGPWS with or without geometric altitude, navigation input GPS or FMS RNAV (FMS RNAV operators beware of potential errors - Addis Ababa event). Also of note were the poor updating of software standards and terrain databases; all free from the manufacturer http://www.egpws.com.

Do the issues above suggest that operators are under strain in the training and knowledge area?
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Old 24th Mar 2004, 16:18
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Thanks Alf

I also thought they were in Jeps, but never managed to find the. However the first URL from Alf on page 7 is the ball park figures.
I managed to find the formulae on a previous search. but this is the bogs d*******s. Thanks guys.
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Old 24th Mar 2004, 17:34
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Jepp CA19

The Cold Temp correction chart is published by Jeppesen. It's page CA19, but I believe you have to have a Canadian subscription to get it.

The link posted by Mike Jenvey appears to be correct (I didn't check all the values), but it doesn't have the text to clarify how it's used.

In a nutshell, if you "hear" the altitude, i.e., an altitude given by ATC, fly it without correction. They've already done the math.

If you "read" it, i.e., from a Jepp chart, then you must apply the corrections.

In the USA, the AIM now has a section on cold weather altitude corrections.
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Old 25th Mar 2004, 10:30
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bumz - use 'search ' to look for it. There are many threads -
'temperature error' is a good starting phrase
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Old 26th Mar 2004, 17:15
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The tables for temperature error correction are in the Jepp'es we use in Europe - Flight Procedures Part VI. The tables are there but lack in any real instructions on how to use them my advice would be....

If the airfield temperature is below 0ºC the following altitudes are corrected for temperature error:

a. The DA or MDA.

b. For a non-precision approach, all step down fixes inside the FAF or procedure turn.

c. All altitudes in the missed approach procedure.

If the airfield temperature is below 0ºC and the airfield lies in mountainous terrain (3000' or above), the following altitudes are corrected for temperature error:

a. MSA values.

b. All altitudes in the procedure, including those within STARs and SIDs.

c. All altitudes in the missed approach procedure.

Any thoughts anyone?
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Old 26th Mar 2004, 18:39
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When to use temperature correction.
In addition to the suggestions from RoboAlbert, do not forget the initial descent altitudes, and step downs at non controlled airports. Also remember to temperature correct altitudes during takeoff from non controlled airports, flap retract, acceleration, and turning altitude, etc.

How does this work in the US for a controlled airport by day, but uncontrolled by night; or controlled by a remote centre? I guess it depends firstly on the reference for the pressure setting and second, the type of procedure (precision / non precision) to be flown.

From memory, some time ago, the helpful ATC controllers in Europe would always annotate a temperature corrected altitude clearance. i.e. descent into Innsbruck would be given as “descend to x.yyy ft temperature corrected” (where the lower procedure altitude was x.xxx ft), is this still the approved phraseology?
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Old 1st Jan 2006, 12:28
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'Tis now the season

Recent experience as follows:

Several Russian Airports, in Moscow give the corrected QFE setting, as perhaps there is no need to correct a setting that has been read directly from the reference mesuring device.

Next time I will compare the advised QNH, and QFE. Expect optortunity tomorrow....

So does the problem only manifest itself in NON controlled airports, that are working on QNH settings.

Recently been to a Russian airport at 3am, local temp was -30C, (deep inversion layer, at 1000 ft QFE only -10), Not surprising the QFE displayed zero on touchdown.

Bumz,
sorry for not actually helping to clear the fog...
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Old 1st Jan 2006, 13:14
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Exclamation

...and the GS check altitude and FAP if a DME is used, if I may add to RoboAlberts' list.

As alf5071h pointed out, it is surprising to see the question re-appear year after year - but encouranging to see that people at least [I]know[I] that a correction must be applied & ask the question. Still, it's found in every OPS1-airlines OM Part A, Chapter 8 - and should be part of the winter LPC/OPC session.

Begs the question if people remember to apply high wind corrections to their MEA/MOCA/MORA when flying over muntaineous terrain - that correction is often in the region of 2000 ft., and if luck is not on your side, it will remove all obstacle clearance margin if not applied. Mind you, a 1200 ft. correction to the MSA alone due to temperature would also do the trick

Happy new year to all - and congrats to Danny & the crew, this looks ubercool!

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Old 1st Jan 2006, 16:42
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Re: low temperature correction

EC,

Do you have any web references for high wind corrections and how to apply them ?
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Old 1st Jan 2006, 18:19
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fish Re: low temperature correction

Hi Stator!

No, no weblinks, but should be found in your OM. My outfit operates with the following rule: With winds above 30 kts, add 500 ft. to all altitudes above the MSA pr. 10 kts above 30 kts. - with a max. correction of 2000 ft.

Would be interesting to see if anyone had a reference in a MET textbook or on the web

Brgds fm
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Old 1st Jan 2006, 18:52
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Re: low temperature correction

Statorblade Altimeter error due to wind speed, see ICAO PANS OPS Vol1 Doc 8168 Part 3 Chapter 4. The text starts on Page 242 and the tables are on Page 245.
This reference also has low temperature corrections and mountainous area corrections.
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Old 1st Jan 2006, 19:01
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Re: low temperature correction

alf5071h

Just what was needed -thanks!
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Old 2nd Jan 2006, 05:55
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Re: low temperature correction

4*alt above ground/1000 * ISAdev gives you (roughly!) the correction.
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Old 2nd Jan 2006, 08:22
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Re: low temperature correction

Following along from the original thread.

What is the correct RT when using temp correction?

For example if UK ATC clear you to descend to altitude 4000' on QNH .... What is the correct response if the temperature correction is 300'?

It is an important subject yet after spending 10 years flying around Scandinavia I have yet to hear someone actually correct for Temperature Error over the airwaves. In my experience the airlines that I flew with never corrected for Temperature, although it was written in the Ops Manual. Everyone was aware of it but no one actually did anything about it! Our check altitude at the marker would normally mention 'altitude high due temperature' and the initial brief would mention the fact that we would appear high at the marker due to temperature correction, but thats it.

The thing that really puzzles me is why I didn't hear the local airlines mention this in there replies to ATC. Quite a few winters would see the temperature on the ground fall to -20 degrees. You'd think that if any one would know the correct way of operating in these temps it would be the local national carriers?

From what I can see, there is no published procedure for Temperature Correction in CAP413.

The posters response above sounds like an excellent idea whereby ATC factor the correction into their calls. I'd not heard of this but no that in the places that I fly to the onus is on the pilots to make the correction.
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Old 2nd Jan 2006, 08:28
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Re: low temperature correction

Well, the problem only arrises when you are flying procedural approaches (e.g. N. Sweden or Norway) when there is no radar coverage. In those cases, I have sometimes had to inform ATC "Cleared the VOR?DME approach 23, be advised we will commence the procedure from non-standard 3300 ft. today due to temperature". Has never been a problem - although sometimes, the ATCO would need an explaination as to why this was so (good way to spend the 12 NM outbound leg! )

Brgds
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Old 2nd Jan 2006, 08:43
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Re: low temperature correction

Thanks to all for the wind correction references - sorry to deviate from the original topic.
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Old 2nd Jan 2006, 12:55
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Re: low temperature correction

And not all controllers give you the correction as required as I found out two nights ago at Beijing with a temperature of ISA -18. Being radar vectored to the north of the airfield, we descended to 1200M (3970') as instructed only to almost immediately get a EGPWS 'Terrain, Terrain - Pull Up' which of course we followed. The 1200M was mentioned on procedure for that runway and had we followed the procedure, we would have added 400' as my company makes the corrections easy so we add 10% for ISA -15 to ISA-30. The 1200M is based on an obstuction of 2881'. With a real altitue of 3700' ish, we were now less than 1000' from the obstacle - hence the pull up.

With everything in aviation, don't assume - check. I will be asking if altitudes are temp corrected from now on!
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Old 2nd Jan 2006, 20:54
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Re: low temperature correction

Originally Posted by Dan Winterland
And not all controllers give you the correction as required as I found out two nights ago at Beijing with a temperature of ISA -18. Being radar vectored to the north of the airfield, we descended to 1200M (3970') as instructed only to almost immediately get a EGPWS 'Terrain, Terrain - Pull Up' which of course we followed. The 1200M was mentioned on procedure for that runway and had we followed the procedure, we would have added 400' as my company makes the corrections easy so we add 10% for ISA -15 to ISA-30. The 1200M is based on an obstuction of 2881'. With a real altitue of 3700' ish, we were now less than 1000' from the obstacle - hence the pull up.

With everything in aviation, don't assume - check. I will be asking if altitudes are temp corrected from now on!
Very, very interesting. I shall be extra careful going into PEK in two days time although I don't know what the Cantonese is for "do you correct for low temperature?"
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Old 3rd Jan 2006, 14:35
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Re: low temperature correction

They actually speak Mandarin in PEK so Cantonese will be of little use. Their Engrish however, is reasonably good and the ATC fairly good as well. The problem highlighted stemmed not just from their failure to apply a temperature correction, but also as a result of the new procedures introduced a couple of months ago. Everyone is getting to grips with them and our incident may just have highlighted a problem which needs ironing out.

But be careful of those 18 procedures. They take you close to some fairly high ground.
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