Slippery/Contaminated Runways

[jumbojohn]

Just what is the definition of a slippery or contaminated runway?

[m&v]

no braking action(reaction)at all is true general definition of 'slippery'..
Keep in mind,that although one reffers to'slippery'in the everyday concept,there is no reference to 'slippery' requirements
during 'certification'-ergo if one is on a slippery runway,there is nothing to refer to..Contaminated Runway is any runway with more that 3mm of standing water,slush,snow etc:p

[None]

jumbojohn: Just what is the definition of a slippery or contaminated runway?


If my memory is correct, Slippery-Wet data is used when something on the runway is a factor for stopping, but not so much for accelerating. Typically this could be a thin layer of water on a non-grooved runway, ice, or compact snow. The data varies from one airport to another, and from one runway to another.

A cluttered runway may be snow, slush, or standing water. This affects both stopping and accelerating performance. The depth
and type of clutter is an important discriminator.

I think both can be called contaminated, but they have different effects on takeoff data. Additionally, crosswind limitations change based on the state of the runway.

[Captain Stable]

UK AIP MET 3-5 to 3-7 provides a decode of the METAR or SPECI 8-figure Runway State Group. This shows how a runway state is reported.

I can't find a specific breakdown on decelerometer readings into "good/medium/poor" categories, but 1 is the best, 0 you need to be Tonya Harding.

[Spitoon]

There's a UK AIC (http://www.ais.org.uk/uk_aip/pdf/aic/4P195.PDF) that says 'For JAR-OPS performance purposes, runways reported as WATER PATCHES or FLOODED should be considered as CONTAMINATED'.

Here in the UK, when there's snow or ice on the runway, we give a plain language report of the surface conditions including braking action usually based on a mu-meter reading as below
mu 0.40 and above = Good
mu 0.39 - 0.36 = Medium/Good
mu 0.35 - 0.30 = Medium
mu 0.29 - 0.26 = Medium/Poor
mu 0.25 and below - Poor

I have heard pilots saying that if they are told that braking action is poor they have to use performance tables for icy runways but that the friction co-efficient marked on those tables is much lower than .25.

Mu-meters are unreliable in slush or wet snow so only plain language reports of runway conditions are passed to pilots.

Don't know whether that helps at all.

[DontSink]

Well, a Slippery runway is a contaminated one...

Runways can have 4 states, dry, damp, wet and contaminated. Damp can be considered dry for performance according to the JARs and wet when contamination on the runway is inferior to 3mm of standing water, slush or lose snow.

By definition a contaminated runway is when more than 25% of the runway area (in isolated areas or not) is covered by more than 3mm of lose snow, water, slush and compact snow and ice, or melting snow or ice independent on depth.

The slippery definition (if I`m not mistaken) came from SAS on the 50s, to make things easier, instead loosing 20 minutes decoding the snowtam, and that was adopted by everyone. Boeing says that a slippery runway is when you have info about braking action good, medium or poor. If no info on braking action, you can`t use the slippery performance, but the slush/standing water equivalence performance (contaminated performance, that is)

The braking action good is more or less the equivalent to a wet runway and poor to an ice or compact snow contaminated runway. The good, medium and poor terms are used according to braking coefficients obtained after runway examination…

Cheers!
;)

[downfourgreen]

Contaminated runway: A runway where more than 25% of the required field length within the width being used is covered by standing water or slush more than 0.125 in (3.2 mm) deep, or that has an accumulation of snow or ice. However, in certain other situations it may be appropriate to consider the runway contaminated. For example, if the section of the runway surface that is covered with standing water or slush is located where rotation and lift-off will occur, or during the high speed part of the takeoff roll, the effect will be far more significant than if it where encountered early in the takeoff while at low speed. In this situation, the runway might better be considered 'contaminated' rather than 'wet' only.

[jumbojohn]

Okay, this has in my experience always beem a bit of a grey area, my company ops manual says, quite rightly that is is difficult to define some of these conditions. But in these days of litigation.....

So lets see if I can summarise so far; more than 25% of the runway and more than 3mm of water or slush appears to be the figures that most operators consider contaminated. Dry snow is often another matter.

The runway can be classified as dry, damp, wet of contaminated (or flooded).

The actual braking action can be measured be a variety in instruments.

So what about these phases such as "slippery when wet" and "rubber deposits" and their effect on operation?

(LGW was promulgated as slippery when wet ´cos of resurfacing)

What if a previously landing pilot reports the runway as "slippery", is that then legally binding, ie slippery landing data, cross wind limits etc?

What if you are the first to land for some time and no pilot reports are available?

Are ATC responsible (around the world) to notify the crew of the state of the runway?

[john_tullamarine]

You pays your money and takes your chances .. and, if you are sensible, you will err very much on the side of caution ... that's the way it is ... no guarantees ...

[m&v]

As I said in the former note,there is no 'definition'in Cert' of slippery.It's a common sense saying there is 'verybad-no' braking action.As John says you can take your chances!!!If you slide off,after you received a 'poor' braking report-your on your own(inevery sense of the word).Should you receive a 'slippery'report,query the tower as to the last arrivals braking report,after all if he didnt slide off the end-he must have had some braking.In canada the tower will stipulate the Type giving the report,which is something to go on???Remember the crosswind limit is reduced drastically(preferably nil) with a slippery report......:rolleyes: