Wet Runway - Again

[LOKE]

What is the criteria your Airline gives you for determining if the runway is wet for Takeoff - for aircraft newly certified (such as the 737 NG) having actual certified Wet Runway Performance Data. Heard lots of fague suggestions, Standing water, Thourghly soaked, a sheen - are these actually specified in any traing manual or just passed along during training. I've also read an FAA document that says if it is not dry - then it is Wet. Apparently standards were tightened up with these new Takeoff numbers - has anything actually been produced that gives the pilot a determination on what wet is?

LL

[john_tullamarine]

FAA recommendation and general industry practice is described in draft AC 91-6B.

Ignoring the ifs, buts, and maybes ...

wet
Neither dry nor contaminated. Flight tests are done on runways with a water depth of 0.5 mm minimum

contaminated
More than 25 percent to a depth greater than 3mm standing water or slush, or has an accumulation of snow or ice

[mutt]

A wet runway is......

FAA - Neither dry nor contaminated (Draft of AC91-6B)

JAA - Shiny in appearance, depth less than 3mm of water (JAR-OPS 1.480)

Although we are an FAA operator, we use the JAR description as follows....

A runway is considered WET when the surface appears shiny with 3mm or less of water

Mutt.

[LOKE]

First – Thanks very much, MUTT & John, for your informative and prompt responses – but I’m still confused:

The old (prior to 98 in the US) RTO performance standards for a wet runway were based on “advisory” numbers – with reference to both V Speeds and performance (weights). In 1998 – FAR 25.109 is changed and seemed to say that aircraft must provide accelerate-stop distances for wet runways. In some of the most incredibly wormy and limp language I’ve ever seen (“are not being applied retroactively to either airplanes currently in use or airplanes of existing approved designs that will be manufactured in the future.”) – see the summary FAR 25.109 – it is hard to say what FAR 25.109 says.

Nevertheless, certain Aircraft Manufacturers do “voluntarily” provide operating limitations, in the Airplane Flight Manual, for wet runways, on specific aircraft models, and operators of those aircraft are presumably bound, due to FAR 121.189, to use those standards when the runway is wet.

So we now go back to defining when a runway is wet:

1. The only officially documented guidance that I have seen is from 8400 – “Any runway which is not dry is considered to be wet. Standing water, puddles, or continuous rain are not necessary for a runway to be considered wet.”
2. AC 91-6A provides no definition, nor guidance for determining when a runway is wet (as opposed to dry). This Circular was published 24 years ago.
3. AC 91-6B provides some guidance and perhaps a distinct definition of when a runway is wet. AC 91-6B was submitted for public comment 18 years ago but is not yet published. In fact AC 91-6B is presently neither listed among drafted Advisory Circulars, nor those submitted for public comment.
4. Extensive searches on FAA WEB sites (and the Ineternet) do not provide anything in the way of an official AC 91-6B document – only vague references to it.

So let me get this straight. We now have aircraft which must use wet runway data when the runway is wet. The only documented definition is over 10 years old, in 8400, (and in my opinion ridiculously restrictive), yet the industry turns to guidance in an AC which was conceived nearly 20 years ago and has completely disappeared as a real reference.

With all due respect – what am I missing here?

LL

[john_tullamarine]

I'll leave this one for Mutt .... other than to observe

(a) Part 25 is an airworthiness standard and not generally applied retrospectively.

(b) Part 121, etc., are the operating standards and will dictate just what applies to your operation if you have N tail feathers.

(c) The draft AC is available if you ask for it but basically throws it back on the manufacturer to produce some useful numbers or procedures for the ops engineers to do the sums.

[mutt]

Loke,

Welcome to the world of contaminated operations :(:(

I have looked through a number of Boeing manuals, none of them offer a wet/contaminated runway definition. In their training courses they offer the definitions from AC91-6B.

It is therefore up to your airline to harrass the local FAA to give you an acceptable definition, failing this,IMHO, its the airlines moral responsibility to set the definitions and to then support their crews in any subsequent court of law.

Mutt.

[LOKE]

Mutt:

That's good advice - thanks,

LL

[john_tullamarine]

.. took the thoughts right out of my tiny little mind ......