Feature Request - ICAO Cold Temperture Corrections

With the 272 new airports in the US implementing cold Wx limitations beginning January 8, 2015 what's the chance the ICAO table can be built in to the IFD540 and some automation in correcting for it?

Something similar to, but possibly better than, what the G450 does in this example would be nice?
http://code7700.com/altimeter_temperature_correction.html



Edited by roltman - 13 Dec 2014 at 4:55pm

I guess it would be an option for a user to enter a field temperature and enable ICAO adjusted approach altitudes. It looks like Honeywell/Gulfstream allow the entry all the time, but if one of the airports where loaded in the IFD540 that required it then it'd present a field to the user where they could enter the reported field temperature and get alternate minimums in the flight plan if the criteria were met.

EASA has had these conversions requirements for a few years.  The FAA is adopting them, and 272 airports beginning in the first cycle of 2015 will have cold temperature limitations applied to them.

Page 446 of http://www.faa.gov/air_traffic/publications/notices/media/12-11-14_NTAP.pdf explains it.

I do believe Jepp knows about which segments and/or airports have these limitations; however, if the limitation applies due to cold surface temperatures at the airport, the pilot now must compute new minimums based on the ICAO table and use the adjusted alternate minimum altitude.  To me this is a lot of juggling particularly since the temperatures at which they apply can be as high as 0C down to -60C depending on the airport.

For example KRUT in Vermont has a limitation at only -4C or 25F which I think it'd hit somewhat regularly in the winter months.

Further details can be found in ICAO 8168 Vol 1 chapter 4.3 along with a copy of the formula in section 4.3.4.  This formula comes from Engineering Sciences Data Unit (ESDU)'s publication called: "Performance", Volume 2, Item number 77022 for off-standard temperature atmosphere.

I couldn't find a direct ICAO link for the aforementioned document, but here's another website's copy:
http://code7700.com/pdfs/icao_doc_8168_vol_1.pdf
See page 233 of 279 for the formula that could be implemented in the FMS.

Since EASA and FAA have adopted this, I figured it'd be a nice feature to help offload some work from the pilots around the world who hit these colder climates.




Edited by roltman - 14 Dec 2014 at 11:47am

Unfortunately the way I interpret the FAA's implementation you'd have to know at what temperature it applies first. The FAA merely took the coldest temp X-years prior and determined if the approach still met the TERPs.  If not then it was flagged and  the temperature where it failed the TERPs became the temperature where the conversion was applied. 

I guess nothing would prevent a person from always applying the cold Wx minimums, but seemed like a good feature putting all those Jepp $$$s to work for us. :)


Edited by roltman - 14 Dec 2014 at 12:03pm

We started trying to implement this in the next release until we looked at each other like a couple of ding dongs so maybe you can help clarify the intent of this one.

If I understand it correctly, we're talking about altering published minimums for an approach due to cold temperatures.

Presuming that is true, the issue with the IFD540 and 440 wrt this topic is since the 540/440 don't support any notion of approach minimums, there is nothing to apply these corrections to.   So we don't have anything to do wrt this topic.  Anyone see it differently?

Sure but the 540/440 uses GPS-based altitude for FMS operations and not baro-based altitude so I still don't know of anything to correct. An EFIS/PFD would be a different story obviously but the 540/440 is unaffected.

I stumbled on this post. Was this feature ever implemented?

No, it hasn't been implemented.  Here's a link to Orest's original post.