3 Degree Kelvin Split for Landing Performance.
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3 Degree Kelvin Split for Landing Performance.
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.
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.
Only half a speed-brake
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...
Last edited by FlightDetent; 21st Jan 2016 at 11:59.
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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.
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.
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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.
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.
“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/...-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) / advisory information and circulated by ICAO/EASA/UK CAA; I don’t have the references immediately to hand.
http://www.aibn.no/Aviation/Reports/...-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) / advisory information and circulated by ICAO/EASA/UK CAA; I don’t have the references immediately to hand.
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Smokie,
Airlines introduced some of the findings from the FAA TALPA ARC, ref:
http://www.faa.gov/regulations_polic...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.
Airlines introduced some of the findings from the FAA TALPA ARC, ref:
http://www.faa.gov/regulations_polic...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.
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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.
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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.
E.g., OAT measurement of 15 degrees C, +/- 3 K.
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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.
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