Altimeter Cold Temperature Correction Policy

[kijangnim]

Once your sensors have measured values, which after all are just digital data, appropriate software will do the magic.

[Challenger 605]

The sensors still do not know what the temperature is at the altimeter setting source. Isn't it that temperature that is the important one when calculating the error of an altimeter at a minimum IFR altitude??

[kijangnim]

Greetings the temperature is a part of the measured data, SAT, TAT, etc...most systems consider tropopause as soon as temp is 56.5 deg. so anything below that altitude is computed as delta ISA

[bookworm]

The sensors still do not know what the temperature is at the altimeter setting source. Isn't it that temperature that is the important one when calculating the error of an altimeter at a minimum IFR altitude??

No, it's the mean temperature deviation of the column of air between the altimeter and the altimeter setting source that matters. Thus it might be approximated by the SAT and a standard lapse rate.

[Challenger 605]

Let me see if I got this correct. The ADRU will temperature correct the altimeter. But how does the ADRU know if I am operating at the minimum IFR altitudes (which are the ONLY ones that must be corrected for cold temperature)? Will the ADRU correct ALL aircraft altitudes? If not, what mechanism instructs it to not correct non-min IFR altitudes?

[kijangnim]

Greetings,

The task of the ADRU is to measure data, the FMS (which is a supplemental, advisory device) to use and display these data, and the task of the crew is to be sure that the aircraft is not flying below IFR......

[Challenger 605]

OK. I still don't get it. The crew still must ensure that they do not fly below the min IFR altiitude but the ADRU will correct for cold temperature errors of the aircraft's altimeter. Let's say that the crew chooses to fly at the min IFR altitude (let us assume that the published min IFR altitude is 3700 feet). The crew descends to 3700 indicated on the altimeter but that is OK because the ADRU compensates for the the cold temperature error and the procedure designed obstacle clearance is not violated. What happens if the crew chooses to fly at 4000 feet? Is that atitude compensated for cold temperature by the ADRU and if it is that aircraft is not at the same atitude as other aircraft without compensation at 4000 feet! At what point does the ADRU not affect the altimeter reading in the cockpit due to temperature (below or above ISA)???

[kijangnim]

Greetings,
I have drifted away from my thoughts, Airway corridors are surveyed for minimum Radio nav reception altitude and terrain protection, the terrain protection takes into account lowest pressure/temperature. Now my argument about ADRU concernes approaches only, particularly NPAs.

[kijangnim]

Greetings
Now having said what is above, I personnaly compute the temperature effect on altitude, for single engine ceiling, driftdown, and emergency descent, 4 feet X delta ISA X N(1000)Feets + Indicated.
Where in operate we do have high Mora ...

[Zeffy]

The incident (a near-CFIT statistic) involving an MD-80 at Kelowna, BC occurred during the procedure turn.

http://www.bluecoat.org/reports/Long_98_Cold.pdf

Cold temp corrections should be applied to all minimum IFR altitudes, not just those inside the FAF.

[kijangnim]

Greetings

During vector radar should take care of it, during the approach, Procedure turn included (Procedure turn to be flown on heading for the Airbus) we should have a minimum temperature for that praticular approach,

[john_tullamarine]

During vector radar should take care of it

You place great trust in those who don't risk dying in the event of a miscalculation ... most pilots would opine that a better solution is to be ahead of the radar and KNOW where you are both laterally and vertically ..

[galaxy flyer]

J_T

My humble experience is that a generation younger than ours puts touching faith in radar controllers. It has been pointed out to me that the controller is responsible for terrain clearance, I've fired back, "but he won't die for his mistake."

GF

[john_tullamarine]

GF,

The acknowledged benefits of being raised by PacMan, I guess ....

I'm just glad that I got to play a lot on the 733 ... if it all looked like it was working, one could leave it on and still fly with an eye on the steam data but with some add-ons to make a few mental processes easier ... otherwise the "OFF" button worked real fine and we went back to flying a la DC3 and one definitely was responsible for one's success in life ...

My simplistic view is

(a) under the surgeon's knife, you don't have a choice

(b) in an aeroplane, you can tell the controller what you are going to do, albeit that it might get up his/her nose a tad .. and, of course, most of us have had the occasional need to do just that ... ATCers (and I have more than a few mates in that discipline) are no less immune from errors than the rest of us ..

[kijangnim]

Greetings,

In my humble opinion, we have to leave people to do their jobs, weither they die or not from their mistakes, because we cannot handle ATC, FO and our own mistakes or errors. Yes human are error making machines, but we have to handle it under error management concept, that is to use methods (SOP) to minimize them. If you do ATC's job on top of your flying tasks, I think you are overloaded, we have safety nets on board ,they are mandatory, such as TAWS, TACAS and it is not a luxury we all know that. BTW I have been flying for 28 years

[john_tullamarine]

The PacMan comment was not directed to your good self but was a tongue-in-check comment on the differences betwixt us older folk and the young folk starting off in the Industry ...

I concur in part with your comments .. however, in the same way I like to know what the steam gauges are telling me (real stuff) while looking at the pretty pictures (much more processed ..) a basic is knowing where you are and what you are doing .. if you agree with ATC's apparent plan .. then, well and good .. if not .. voice your opinion .. to the extent of diverging from clearance and declaring an emergency if appropriate. I was not concerned about doing ATC's job .. only looking after my own neck to the best of my ability ...

Sitting back and watching the world go by was a fail item in the good old days ... and I can see no reason for the philosophy to have altered ?

[kijangnim]

Greetings

[BANANASBANANAS]

Slight thread creep here.

I believe some airports that suffer consistently long periods of cold weather publish approach charts that are 'corrected' down to a nominal temperature and that this cold temperature is published on the chart - hence no temp correction required if the actual OAT is warmer than the cold limit OAT published on the chart.

I dont seem to be able to find an example of such a chart though. Would any of our experienced cold weather operators out there be able to give an example - preferably Jepp?

Thanks.

[DBate]

I believe some airports that suffer consistently long periods of cold weather publish approach charts that are 'corrected' down to a nominal temperature and that this cold temperature is published on the chart

Personally I have not come across any of those already corrected charts (not using Jepp Charts though). But I know that at some airports with very low temperatures during winter period the controllers give you clearances to already temperature corrected values (I think Helsinki is one for example).

But to be honest - I would not count on that. We always correct the values ourselves and advise ATC accordingly if needed. I remeber we had some problems doing that in Kasakhstan; ATC always cleared us to the lower, not corrected altitudes, and complained if we did not comply . And they did not even understand why we used corrected values. A short visit of one of our liason pilots to that ATC unit solved the problem.

[aztruck]

Plenty of cold places in civilisation with no radar and non precision approaches. You better have the back of an envelope handy before top of descent. Fagernes (Norway)being a prime example. Cold wx corrections as per the Jepps table worked out spot on. Flew it once in VMC and got a good view. Next time to minimums(300 agl or thereabouts in blowing snow)and not applying corrections would have been suicide.
Caution best exercised in kasakhstan and other Eastern countries. Double whammy cross checking metric altitude tables AND seeing if they make sense as having been temp corrected for vectoring, especially if QNH requested and they normally use QFE.