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Old 28th Sep 2022, 18:11
  #5 (permalink)  
safetypee
 
Join Date: Dec 2002
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Thinking that additional knowledge doesn't matter - grooved or not - has no effect on published landing distance, seriously misjudges the pilots responsibilities in operations.

Heed the advice of the master of the dark art of performance, JT #3.

Landing distance is a conservative calculation of expected performance, which involves many assumptions that pilots should be aware of, but not always referenced as such (AMC CS 25.1592).

Wet performance is based on a single calculation; this has to accommodate a wide range of runway states defined as RCC 5; frost, snow, slush, and wet ranging from damp to 3mm of standing water. All of which involve varying degrees of uncertainty in measuring, interpreting and reporting. Thus the assumed accuracy of landing distance is highly variable.
Furthermore, there is a wide range of runway surfaces - material and texture, which can have a significant effect on braking performance. Grooved or not, porous texture or smooth concrete, can significantly challenge the assumptions and margins in the published performance. Then there is tyre tread condition.
Add to this the reality of operations; blocked grooves, rubber, dirt, wind ‘dammed’ water drainage.

A further (oft hidden) assumption is that the pilot will adjust operations according the conditions (i.e.what is meant by the assured ‘safe’ landing required by the pre-landing check, EU OPS).

https://www.icao.int/EURNAT/Other%20...hp%20PPT06.pdf

25.1591-1592 relevant amendment
https://www.easa.europa.eu/en/downloads/134260/en
N.B. Check for FAA differences; requirements vs advisory.


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