3 Degree Kelvin Split for Landing Performance.

[Smokie]

Does anyone have official reference for the 3 Degree Kelvin Split used for Landing Performance ? Either JAR Ops and or EASA. I know TCX has used this previously, do they still use it? Are there any other Airlines that use this calculation?
I seem to recall something about TALPA ARC ?
I have done a search but nothing seems official in any Regs for EASA or JAR Ops.
Thanks.

[Smokie]

236 views but no info. That is a shame as I was hoping that some of our more knowledgable members could steer me in the right direction.

[FlightDetent]

Something is on Google for TALPA ARC. Your 3 Degree Kelvin Split yields no results apart for the post above. Me googling "go figure" now...

[B737900er]

Smoke its a rule of thumb not an exact science that may be the reason.
Our Scandinavian brothers have found a correlation between temp/dew point, and reported braking action, and what was experienced by flight crew. They found most incidents/accidents occurred when braking action was given but reality was a worst. The common dominator was the temp dew point spread.

[FakePilot]

Maybe try 3 degree C split? Kelvin is the same as Celuis just 0 is absolute 0.

[nick14]

We have an awareness programme for the 3 kelvin spread rule for braking actions.

[gustl]

Hi Smokie, perhaps this link is helpful:
Runway Surface Friction - SKYbrary Aviation Safety (http://www.skybrary.aero/index.php/Runway_Surface_Friction)
gustl

[Jwscud]

My airline also uses the 3K spread rule for braking action awareness and includes this in its internal performance and winter operations material.

The rule it gives is that in the following conditions:

- Temperature less than 3°C
- Dewpoint spread 3°C or less

Snow or ice covered runways may be slipperier than reported so plan landing and stopping requirements with caution and use more conservative braking action when doing so.

[safetypee]

“The ‘3-Kelvin-spread-rule’: Moisture in combination with contaminated runways plays a more significant role in relation to ‘slipperiness’ than previously understood. In most occurrences the difference between the air temperature and dew point (at 2 m height above the runway surface - METAR values) was ≤ 3 Kelvin. This is referred to as the ‘3-Kelvin-spreadrule’ and indicates that the humidity is 80 % or more.”

http://www.aibn.no/Aviation/Reports/2011-10?iid=8169&pid=SHT-Report-Attachments.Native-InnerFile-File&attach=1 Page 3

IIRC this was published as a recommendation (main report page 10, Winter Operations, Friction Mesurements and Conditions for Friction Predictions | aibn (http://www.aibn.no/Aviation/Reports/2011-10?)) / advisory information and circulated by ICAO/EASA/UK CAA; I don’t have the references immediately to hand.

[Superpilot]

Smokie,

Airlines introduced some of the findings from the FAA TALPA ARC, ref:

http://www.faa.gov/regulations_policies/rulemaking/committees/documents/index.cfm/document/information?documentID=302

TCX pulled it back in November citing, amongst other things, the fact that no approved methodology for calculating the effect on landing run for such conditions exist and therefore an arbitrary amount without regulatory or industry evidential support would be difficult for the organisation to justify.

[Smokie]

A bit late getting back into this but thanks for all the replies guys. 👍

[A Squared]

Maybe try 3 degree C split? Kelvin is the same as Celuis just 0 is absolute 0.

I'm with you, why on earth make it Kelvin? For temperature differences, thee is no difference between Celsius and Kelvin, and the use of Kelvin can only be confusing for those who don't know what it is.

[peekay4]

The rule of thumb was probably derived from scientific literature. It's very common in the scientific world to express temperature differences in Kelvin -- the official SI unit for temperature and temperature intervals -- even when using degrees Celsius for measurements. Part of the reason is because the Celsius scale is not zero based (not an absolute scale), but it's really a matter of custom/tradition than anything else.

E.g., OAT measurement of 15 degrees C, +/- 3 K.

[Matvey]

Because if you say 3 degree rule, you'll get some American (or an old Canadian) pilot who will hear 3 degrees and think Fahrenheit. By saying Kelvin, you make it clear that it's 3 Celsius degrees. Though I also think it's weird phrasing.

[A Squared]

By saying Kelvin, you make it clear that it's 3 Celsius degrees.

I suspect that peekay4 probably has the answer, but in respons to this, I would argue that saying it was Celsius would make it a bit clearer that it was Celsius. ;)