Temperature error correction - or lack of....
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Temperature error correction - or lack of....
Could anyone point me towards a link on the web which details any aircraft accidents which were attributed to low temperatures and the altimeter errors associated with them. I have tried but no luck
Cheers RA
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If ATC were to give pilots QFE rather QNH info for landing,would that help since QNH doesnt take temperature (only uses ISA) into consideration?
Qfe being more acurate on the ground(msl that is).
Otherwise well have to use the 96K divided by 1013 to find out how many feet equals to 1 mb..as not charts exist for the safe side(high temps..)
Could be more specific/exact but not much time now..
M.85
Qfe being more acurate on the ground(msl that is).
Otherwise well have to use the 96K divided by 1013 to find out how many feet equals to 1 mb..as not charts exist for the safe side(high temps..)
Could be more specific/exact but not much time now..
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M.85
It wouldn't make any difference, as QNH is measured at the airfield, then adjusted (using ISA) to sea level. Thus it reads airfield elevation at touchdown, as the altimeters are calibrated to ISA too.
The TEC is designed to account for the anomalies in altimeter readings when in the air above an airfield. In this instance the atimeter in calibrated in ISA, but the atmosphere between the airfield and the aircraft is not!
It wouldn't make any difference, as QNH is measured at the airfield, then adjusted (using ISA) to sea level. Thus it reads airfield elevation at touchdown, as the altimeters are calibrated to ISA too.
The TEC is designed to account for the anomalies in altimeter readings when in the air above an airfield. In this instance the atimeter in calibrated in ISA, but the atmosphere between the airfield and the aircraft is not!
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Dear Pub,
I understand QNH is using ISA but not actual temp....
Maybe I should go back to my books...in any case the difference wont be larger than 80 ft...so if in extreme cold weather you dont go below DH,youll be alright..maybe time time to use the rad alt??
Safe flying,
M.85
I understand QNH is using ISA but not actual temp....
Maybe I should go back to my books...in any case the difference wont be larger than 80 ft...so if in extreme cold weather you dont go below DH,youll be alright..maybe time time to use the rad alt??
Safe flying,
M.85
Here are details from an unpublished internal investigation by a major European operator re failure to apply low temperature altimeter correction for take-off.
When operating from an airfield in Norway which only provided advisory ATC, an EGPWS alert was given after take off during the flap retract level segment (2500ft aal). The altitude error was approx 500ft low; (-32C at 2500ft above altimeter setting reference) local terrain SSAs 6000-7500ft!
The significant issues here are:
Uncontrolled airport, no ATC to apply the correction or adjust cleared altitudes.
No specific SID identifying terrain clearance.
Do not forget takeoff corrections for these circumstances.
When operating from an airfield in Norway which only provided advisory ATC, an EGPWS alert was given after take off during the flap retract level segment (2500ft aal). The altitude error was approx 500ft low; (-32C at 2500ft above altimeter setting reference) local terrain SSAs 6000-7500ft!
The significant issues here are:
Uncontrolled airport, no ATC to apply the correction or adjust cleared altitudes.
No specific SID identifying terrain clearance.
Do not forget takeoff corrections for these circumstances.
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Alf5071h
Thanks v.much. This is the sort of thing I'm looking for. TEC is something of a bugbear of mine and I'm looking for incidents or accidents to help bring the message home to people. Anyone aware of any other accident reports (available on the net) which point to a lack of TEC as a causal factor.
Thanks v.much. This is the sort of thing I'm looking for. TEC is something of a bugbear of mine and I'm looking for incidents or accidents to help bring the message home to people. Anyone aware of any other accident reports (available on the net) which point to a lack of TEC as a causal factor.
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Maybe I should go back to my books...in any case the difference wont be larger than 80 ft...so if in extreme cold weather you dont go below DH,youll be alright..maybe time time to use the rad alt??
If the controlling obstacle is in the final approach segment, you will only clear it by the height loss margin! The further away from the landing THR that this obstacle is located, the larger your TEC will be and, therefore, the less clearance you're likely to have.
The situation is much worse if the obstacle is in the precision missed approach segment because, while you still won't know where the obstacle is, you may only just barely clear it, in the event of a missed approach. Thus, an error of even 80 feet, as you put it, could ruin your day if you have to go missed approach.
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temp
Dear Ozexpat,
I believe flying an ILS is just following Glide Slope info...so temp doesnt get into the equation doest it?
About the missed approach,I ,once again ,have to read the books..but i believe once a pos climb:end of first seg) and at 400ft (2nd segment) it provides you with 200ft clearance,the 3rd segment (acceleartion segment,1.1%climb min)gives you 400ft clearance..
Once again i may be wrong..but if an AC doesnt allow you an extra 80ft of clearance on a missed app...we may not be flying it at the first place..just to make us think..
M.85
I believe flying an ILS is just following Glide Slope info...so temp doesnt get into the equation doest it?
About the missed approach,I ,once again ,have to read the books..but i believe once a pos climb:end of first seg) and at 400ft (2nd segment) it provides you with 200ft clearance,the 3rd segment (acceleartion segment,1.1%climb min)gives you 400ft clearance..
Once again i may be wrong..but if an AC doesnt allow you an extra 80ft of clearance on a missed app...we may not be flying it at the first place..just to make us think..
M.85
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.85
I do not know how much experience lies under your 'ATPL(A)'? Perhaps if you took the time to read the rest of the threads on this you would realise there is more to operating an aircraft than flying an ILS down to 200' AAL or less with which you seem pre-occupied. With an ILS DH of 200' I would suggest your walk-round would be more hazardous than any temperature error correction. Think of Non-precision apps, some with high DAs, and - of course - enroute MSAs which can be in error by over 2000' in extreme cases. The actual errors at a DH of 200' are lost in other altimeter errors, and of course the rad alt can NOT be used for minima unless so specified, can it?
I do not know how much experience lies under your 'ATPL(A)'? Perhaps if you took the time to read the rest of the threads on this you would realise there is more to operating an aircraft than flying an ILS down to 200' AAL or less with which you seem pre-occupied. With an ILS DH of 200' I would suggest your walk-round would be more hazardous than any temperature error correction. Think of Non-precision apps, some with high DAs, and - of course - enroute MSAs which can be in error by over 2000' in extreme cases. The actual errors at a DH of 200' are lost in other altimeter errors, and of course the rad alt can NOT be used for minima unless so specified, can it?
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BOAC – Before making the first post I searched high and low all round the web for an actual incident report or accident investigation report that gave Temperature Error as a causal factor. I’m afraid I have failed to locate such a report.
What I wasn’t looking for is a thread on TEC, which usually involves more general discussions of the subject. I’ve operated in Canada and Northern Norway in winter enough times over the last 12 years to have a reasonably sound understanding of the subject.
I can also do a search of forums.
alf5071h’s information was just the sort of thing I was looking for. However, this is difficult to use as it’s an unpublished internal investigation so something published by the CAA, FAA etc would be good.
I think my original post was reasonably clear so I regret that you feel it necessary to ridicule me in this way.
What I wasn’t looking for is a thread on TEC, which usually involves more general discussions of the subject. I’ve operated in Canada and Northern Norway in winter enough times over the last 12 years to have a reasonably sound understanding of the subject.
I can also do a search of forums.
alf5071h’s information was just the sort of thing I was looking for. However, this is difficult to use as it’s an unpublished internal investigation so something published by the CAA, FAA etc would be good.
I think my original post was reasonably clear so I regret that you feel it necessary to ridicule me in this way.
Last edited by RoboAlbert; 25th Nov 2003 at 23:09.
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temp
Dear Boac,
I will go to my books..time to read i guess..
My ATPL..i got it in a cornflakes pack at oxford where i passed all subj the first time..that was a year ago.
Flyingwise..most of my flying was done in areas where there was barely any trees sticking out..except DIA where they made sure to shop them for me..
Seriously i hope you get what you are looking for.
M.85
I will go to my books..time to read i guess..
My ATPL..i got it in a cornflakes pack at oxford where i passed all subj the first time..that was a year ago.
Flyingwise..most of my flying was done in areas where there was barely any trees sticking out..except DIA where they made sure to shop them for me..
Seriously i hope you get what you are looking for.
M.85
RoboAlbert
I have been told that the takeoff event was published by BAE SYSTEMS as an ‘All Operators Message’ Flight Safety Bulletin Ref 01/022V dated 12 Oct 2001. You should be able to get a copy from a friendly BAe146 / Avro RJ operator – they should be able to access the BAE SYSTEMS support web page where all AOMs are held.
The following extracts are from “Terrain II” a summary of CFIT accidents and incidents (limited distribution), published by Honeywell. With thanks to Don Bateman.
MD-80 Kelowna BC Jan 1998
While flying level at 6300 ft inbound to ‘LW’ beacon the charter flight from Vancouver BC received a GPWS terrain warning. The pilot immediately began a go around. The radio altimeter dipped to below 200 ft. The aircraft was 800-900 ft too low due to cold temperature (-30C).
A B737 following the MD-80 had applied cold temperature correction.
(Also see B727 Salt Lake City Feb 1977 ASRS)
MD-80 Windsor Locks CT USA 12 Nov 1995
While on a non precision VOR approach the aircraft flew through trees approx 586 ft above the field level. A go around was initiated but aborted when engine thrust rapidly diminished and the runway lights became visible. The pilots managed to get within 50 ft of the runway threshold taking out the localizer antenna.
Contributing factors:
The flight crew failed to request an updated altimeter setting with a fast moving low pressure storm, giving at least 70 ft error from the previous setting. Probable additional altimeter error from wind flow over mountain, reading 40-90 ft high, and down draught of 300 – 1200 fpm.
Steep instrument approach.
Late night, delays, long duty time, little rest.
I also recall incidents in Alaska and Norway but I cannot locate the reports.
I have been told that the takeoff event was published by BAE SYSTEMS as an ‘All Operators Message’ Flight Safety Bulletin Ref 01/022V dated 12 Oct 2001. You should be able to get a copy from a friendly BAe146 / Avro RJ operator – they should be able to access the BAE SYSTEMS support web page where all AOMs are held.
The following extracts are from “Terrain II” a summary of CFIT accidents and incidents (limited distribution), published by Honeywell. With thanks to Don Bateman.
MD-80 Kelowna BC Jan 1998
While flying level at 6300 ft inbound to ‘LW’ beacon the charter flight from Vancouver BC received a GPWS terrain warning. The pilot immediately began a go around. The radio altimeter dipped to below 200 ft. The aircraft was 800-900 ft too low due to cold temperature (-30C).
A B737 following the MD-80 had applied cold temperature correction.
(Also see B727 Salt Lake City Feb 1977 ASRS)
MD-80 Windsor Locks CT USA 12 Nov 1995
While on a non precision VOR approach the aircraft flew through trees approx 586 ft above the field level. A go around was initiated but aborted when engine thrust rapidly diminished and the runway lights became visible. The pilots managed to get within 50 ft of the runway threshold taking out the localizer antenna.
Contributing factors:
The flight crew failed to request an updated altimeter setting with a fast moving low pressure storm, giving at least 70 ft error from the previous setting. Probable additional altimeter error from wind flow over mountain, reading 40-90 ft high, and down draught of 300 – 1200 fpm.
Steep instrument approach.
Late night, delays, long duty time, little rest.
I also recall incidents in Alaska and Norway but I cannot locate the reports.
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Robo - your skills in 'Search' SHOULD have produced this link
compressor stall
posted 13th February 2003 01:04
--------------------------------------------------------------------------------
GlueBall
No consideration given to the effects of temperature on your altimeter?
You might want to read this FAA advisory circular.
http://www2.faa.gov/language/accold.pdf
And you might want to read this article, then have a stiff drink...
http://www.bluecoat.org/reports/Long_98_Cold.pdf
The second URL would then have taken you to the first incident to which 'alf' kindly points you. Sadly no 'official' report, though.
This topic 'TEMPERATURE ERROR' goes back years on pprune and there is a stack of good stuff there for those who seek it.
.85 - one of the things I look for is a pilot who applies TEC to his enroute MSA - and I hope I do get it too.
Hopefully we all know now that the errors at 200' are insignificant, and that there are far bigger traps waiting for us as alf's two found out?
compressor stall
posted 13th February 2003 01:04
--------------------------------------------------------------------------------
GlueBall
No consideration given to the effects of temperature on your altimeter?
You might want to read this FAA advisory circular.
http://www2.faa.gov/language/accold.pdf
And you might want to read this article, then have a stiff drink...
http://www.bluecoat.org/reports/Long_98_Cold.pdf
This topic 'TEMPERATURE ERROR' goes back years on pprune and there is a stack of good stuff there for those who seek it.
.85 - one of the things I look for is a pilot who applies TEC to his enroute MSA - and I hope I do get it too.
Hopefully we all know now that the errors at 200' are insignificant, and that there are far bigger traps waiting for us as alf's two found out?
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BOAC
The point I sought to make about a forum search was that I knew how to do one.
However it is not a precise science and you won’t always find the things you want. I therefore feel it not unreasonable to ask any of my fellow ppruners if they can give me any helpful pointers.
Now what I find ironic on a CRM forum is that two people had some useful information but only one chose to share it. The other seemed to prefer not to.
RoboAlbert
The point I sought to make about a forum search was that I knew how to do one.
However it is not a precise science and you won’t always find the things you want. I therefore feel it not unreasonable to ask any of my fellow ppruners if they can give me any helpful pointers.
Now what I find ironic on a CRM forum is that two people had some useful information but only one chose to share it. The other seemed to prefer not to.
RoboAlbert
Ppruners don’t forget that FMS BARO - VNAV approaches also require TEC. (TERPS and PANS OPS procedures). Don’t always believe the computers!
The rough correction is a 4% height increase with every 10C below standard or from the tables given in earlier links. Baro VNAV approaches are not permitted when the temperature is below the lowest published temperature for the approach, but a conventional LNAV approach is allowed. Reference “From Takeoff to Landing” a look at the criteria for the design of instrument procedures; Olle Akerlind (Ex SAS) and distributed by Honeywell EGPWS team.
The rough correction is a 4% height increase with every 10C below standard or from the tables given in earlier links. Baro VNAV approaches are not permitted when the temperature is below the lowest published temperature for the approach, but a conventional LNAV approach is allowed. Reference “From Takeoff to Landing” a look at the criteria for the design of instrument procedures; Olle Akerlind (Ex SAS) and distributed by Honeywell EGPWS team.
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Robo, perhaps you might try looking at it as BOAC trying to help you by training you to stand on your own two feet?
As moderators, we very often see the same question time after time after time. In some cases, it is clear that the questioner can't be bothered with actually looking for the answer at all, instead wanting to be spoon-fed with all the answers.
I don't accuse you of this - but it might go some way to explain why BOAC just pointed you in the right direction instead of going to look for the answer himself (initially) to post for you.
Let's face it - if two people know how to find the answer, but the one who actually wants to know can't be bothered to look for himself, why should the other do the legwork if he isn't particularly interested in it?
I stress that I'm not levelling accusations at you - merely trying to explain, and perhaps this could also stand as a plea to other people as well:-
As moderators, we very often see the same question time after time after time. In some cases, it is clear that the questioner can't be bothered with actually looking for the answer at all, instead wanting to be spoon-fed with all the answers.
I don't accuse you of this - but it might go some way to explain why BOAC just pointed you in the right direction instead of going to look for the answer himself (initially) to post for you.
Let's face it - if two people know how to find the answer, but the one who actually wants to know can't be bothered to look for himself, why should the other do the legwork if he isn't particularly interested in it?
I stress that I'm not levelling accusations at you - merely trying to explain, and perhaps this could also stand as a plea to other people as well:-
- DO A SEARCH
- If you don't find the answer, try a slightly different search
- Ask the question on the forum
- Don't get annoyed if people don't have time to do your work for you
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Captain Stable
Whilst I see you go to great lengths to stress that no accusations are being levelled at me, you nevertheless go on to make your points 1 to 4. I therefore think it fair to point out that far from going straight to step 3. I did spend a good deal of time moving through steps 1. and 2.
As to step 4. I think that whatever his intentions might be, his tone was inappropriate. Phrases like "I say again" and “I'll help. Here's the link. Try 'temperature error'” demonstrate a rather condescending attitude to a relative stranger to the tech forum. I’ve personally always steered clear of the use of sarcasm as an instructional aid.
Now to go back to my original post I don’t believe this was a repeat question. The temperature error threads contain few if any references to incidents or accidents reports related to temperature error. As I have said it was to incidents or accidents reports I was interested in, not a discussion on the application of TEC. The fact that BOAC includes the FAA document, which although very interesting to read again, makes no reference to a specific incident - demonstrating that he has still failed to understand my original question.
This kind of welcome to the tech forum is hardly likely to engender a lively and open debate.
RoboAlbert
Whilst I see you go to great lengths to stress that no accusations are being levelled at me, you nevertheless go on to make your points 1 to 4. I therefore think it fair to point out that far from going straight to step 3. I did spend a good deal of time moving through steps 1. and 2.
As to step 4. I think that whatever his intentions might be, his tone was inappropriate. Phrases like "I say again" and “I'll help. Here's the link. Try 'temperature error'” demonstrate a rather condescending attitude to a relative stranger to the tech forum. I’ve personally always steered clear of the use of sarcasm as an instructional aid.
Now to go back to my original post I don’t believe this was a repeat question. The temperature error threads contain few if any references to incidents or accidents reports related to temperature error. As I have said it was to incidents or accidents reports I was interested in, not a discussion on the application of TEC. The fact that BOAC includes the FAA document, which although very interesting to read again, makes no reference to a specific incident - demonstrating that he has still failed to understand my original question.
This kind of welcome to the tech forum is hardly likely to engender a lively and open debate.
RoboAlbert