An icy question....
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An icy question....
1. Until what brake action (poor,medium,etc) do you land???
2.If you know it`s snowing and the brake action is reported 99 (unreliable or not available)....What`s your decision??
2.If you know it`s snowing and the brake action is reported 99 (unreliable or not available)....What`s your decision??
Our SOPs-
Planning- Min is Medium
In Flight- Min is Med/Poor (Poor = Divert)
As to the second point, not covered in our book, but my opinion would be not to land.
Planning- Min is Medium
In Flight- Min is Med/Poor (Poor = Divert)
As to the second point, not covered in our book, but my opinion would be not to land.
Join Date: Sep 2004
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Interesting.
We're no longer allowed to quote friction values as it is now regarded that there is no direct correlation between friction values derived from the current measuring devices and braking action. ALL UK SNOWTAM should now be annotated 99. Looking through those airfields that actually bother to publish SNOWTAM these days, most are either blank or showing 99.
At LGW, if we need to carry out treatment on the runway in adverse wx, we work until we can open it as 'wet, wet, wet' or better.
Cheers,
TheOddOne
We're no longer allowed to quote friction values as it is now regarded that there is no direct correlation between friction values derived from the current measuring devices and braking action. ALL UK SNOWTAM should now be annotated 99. Looking through those airfields that actually bother to publish SNOWTAM these days, most are either blank or showing 99.
At LGW, if we need to carry out treatment on the runway in adverse wx, we work until we can open it as 'wet, wet, wet' or better.
Cheers,
TheOddOne
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We do have performance data for poor braking.So you'll have to consider weigth,rwy length...and very important also the xwind.
Usually we take 93 as a minimum,but the book allowes you to land also on 92 rwys,if you are in the right ldg parameters.
One question though:
What you'll be your max xwind,on contaminated rwy ,slush >3mm,braking medium-they say-?
Ours is 5kt/10kt on ungrooved/grooved rwy.
But what will you do if xwind is,i.e. min+2kt?Hold for a while? What wind report you'll take? Actual from the twr,I guess?
Brgds Alex
Usually we take 93 as a minimum,but the book allowes you to land also on 92 rwys,if you are in the right ldg parameters.
One question though:
What you'll be your max xwind,on contaminated rwy ,slush >3mm,braking medium-they say-?
Ours is 5kt/10kt on ungrooved/grooved rwy.
But what will you do if xwind is,i.e. min+2kt?Hold for a while? What wind report you'll take? Actual from the twr,I guess?
Brgds Alex
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At one time ,In canada,we advocated querying the TWR as to where the proceeding flight had 'cleared' the runway..
This was some sort of guide despite the type/weight of the proceeding flt..
There's too much talk of operations on 'Slippery' runways-remember there's no Cert' accountability for slippery only 'poor'coefficient of friction..In Canada that means anything below .3 one is in dragon country(who knows)
This was some sort of guide despite the type/weight of the proceeding flt..
There's too much talk of operations on 'Slippery' runways-remember there's no Cert' accountability for slippery only 'poor'coefficient of friction..In Canada that means anything below .3 one is in dragon country(who knows)
I agree oldebloke; there are some runway conditions for which a landing should not be attempted.
From Transport Canada report TP 14273E
So far this year there have been at least 10 large / commercial aircraft runway overruns; presumable these were using runway performance calculated with factors of 1.92. Thus if you encounter a ‘slippery’ runway – and in reality neither you or ATC can reliably detect this, then you will probably wish you had used factors of 2.2 or 2.4 as you slip off the end of the runway.
Also see UK CAA AIC 61 99 “Risks and factors associated with operations on runways affected by snow, slush or water” via http://www.ais.org.uk/aes/login.jsp free access but log in required.
Also AC 121-195 Operational Landing Distances for Wet Runways; Transport Category Airplanes
From Transport Canada report TP 14273E
On a smooth, wet concrete runway surface close to the minimum maintenance standard, the Falcon 20 tire-to-ground effective braking coefficient was found to be less than the aircraft certification requirement for a fully modulating anti-skid system. Based on this finding, the current operational dispatch factor of 1.92 for turbojet aircraft landing on wet runways at destination or alternate airports would have to be increased to a value of 2.2 to 2.4 in order to achieve the same level of safety as that which is currently accepted for dry runway operations.
Also see UK CAA AIC 61 99 “Risks and factors associated with operations on runways affected by snow, slush or water” via http://www.ais.org.uk/aes/login.jsp free access but log in required.
Also AC 121-195 Operational Landing Distances for Wet Runways; Transport Category Airplanes
