Speculation re BAe position: damp=wet.
Apparently the UK CAA commented on the EASA draft of “4027 B. II. Draft Decision - Part- OPS - Subpart B – Section III – AMC OPS.CAT.316.A(a)(3) Performance General – Aeroplanes”, recommending that the damp alleviation be deleted; i.e. damp=wet. This recommendation was not accepted by EASA, with arguments re definition; resulting the current EASA view.
Of note there was a similar case re wet-grooved runways, where subsequently the EASA ruling was ‘clarified’ by the UKCAA, where they required depth of proof which essentially prohibits UK operators from using the EASA alleviation; FODCOM 03/2009 – interestingly titled “THE IMPORTANCE OF USING PERFORMANCE DATA APPROPRIATE TO THE EXISTING RUNWAY CONDITIONS”.
Whereas ‘wet-grooved’ is an operational issue for which the national authorities have responsibilities in implementation and safety supervision, such action for aircraft performance might not be appropriate as it would contravene internationally agreed CS25 certificated performance.
However, a manufacturer can clarify the basis of certificated performance to best represent how the data should be used; i.e. clarify any confusion between regulatory requirements, ill-defined terms, or for specific operations.
Thus a national authority and manufacturer are able to ‘politely’ disagree with EASA (regulatory two fingers) to ensure that the required level of safety, in their view, is maintained. This probably relates to historical agreements and interpretations of previous documents.
This form of disagreement is slightly disturbing as it questions the EASA process where a majority of less-well qualified (relatively new) authorities in certification matters can override a more experienced opinion. Furthermore that an operational view of performance (EU-OPS) can override a certification aspect (CS25) – normally two separate entities in EASA, i.e. a lack of joined-up thinking.
The result is that without clarification the issue resides with operators and individual crews. Irrespective of EU-OPS, Ops manuals, etc, it remains a crew’s decision at the time to judge ‘damp’, which can be questioned after an event.
For the current EASA text, the thread title might be better worded as how to determine a damp runway. And don’t quote an EASA definition or ATC report as neither will prevent an incident; only the crew can do that at the time and of course bear responsibility of any investigation finding.
Thus I choose damp=wet.
If the actual performance requires dry, find out what is the limiting factor and how might this be better mitigated as opposed to quoting some ‘get-out’ clause of a regulation.
Do any manufacturers quote damp performance? How has this been justified?