winter ops CPH

[flyburg]

Hello Gents,

Today, I had a nightmare flight out of CPH!

Having a slot and also requiring deicing.

During preflight preparations determined rwy 04R being in use with friction qoefficients above .6. Finally after deicing we taxied out to the runway, however, friction coefficients were now .30 .22. 11.

In our documentation that equals medium/poor, poor and poor. Once again, to our documentation (and I stress, to our documentation) this is not allowed. We noticed 04L being cleaned and asked ATC how long before 04L would be available. ATC stated about 10 minutes. Long story, but due to the airport layout and operational limitations, it took us more than 40 minutes ( on top of taxiing to 04R to begin with) to get to 04L. By this time we had run out of the extra fuel we had taken and were now below min TO fuel and unfortunately had to taxi back in to refuel! We finally made it out!!

However, and this is my question, several airlines, mainly body mounted engined aircraft did take off before us and after us on the runway with the reported friction coefficients of .30, .22, .11.

One guy even took off from an intersection 1/3 down the runway!!

Having landed the evening before with similar braking coefficients we definitely experienced severe reduced braking action

Definitely not wanting to critise other airlines, I wonder if there is such a difference in operating procedures or capability in aircraft to deal with such reduced braking action?

Having great commercial pressure too leave on time(many connections) we still decided that there was no way we could legally(if not common sense) to depart on a runway with braking action poor. It was somewhat suprising to see that so many airlines did depart.

I know, 99% you take off without a glitch, but the one time you have to abort, you are f@#$%%^!!

So, once again my question? Is there so much difference in airline operating procedure or type specific procedure?

Thanks in advance

[decurion]

Hi flyburg (http://www.pprune.org/members/24093-flyburg),

The world of runway friction and how this is accounted for in takeoff and landing performance is a difficult subject which we have been studying many years now. Al lot of the performance stuff in the FCOM is advisory and its content depends on the origin of the operator and aircraft manufacture. Differences can therefore exist amongst the operators using the same aircraft. Note that the risks related to operating on contaminated runways are much higher than on dry runways.
Runway friction measurements on contaminated runways can be misleading and can give a wrong impression of what the true braking friction of the aircraft will be. There have been numerous initiatives to improve the correlation of these friction devices used by the airports and the braking friction of an aircraft. None of them gave us the best solution. The latest initiative is called TALPA ARC which to me seems to bring us closer to a better solution.
Also take a look at these publications:

http://www.nlr-atsi.com/eCache/ATS/14/919.pdf (Part Runway condition pages 23-25, and Section 5.2.4)
And
http://www.nlr.nl/smartsite.dws?id=4381

[firefish]

In our book those numbers equal medium, poor and unreliable. We are not limited by low FC's in anything but cross wind component but we have to do the math.

For landing we use the Canadian Runway Friction Index as a guide when the for certification purposes established dry and contaminated performance data isn't applicable.

For take off there are no CRFI-tables (not in our book anyway) and all we have to go by is the manufacturer supplied guidance (Cessna in this case) for water, snow, slush and ice covered runways based on JAR25X1591.
The problem is that tables in the AFM are based on type, depth and percentage of contamination and that's obviously (and unfortunately) not something that one normally gets from the ATIS or equivalent.

What I then use is a table that "translates" the FC to something that can be put into our AFM. Normal TOD for me is about 3000 feet (from the top of my head 04R is about 10500 feet) and given the FC of .30 for the first third of the runway I get a TOD of 3900 feet (we always use balanced field length). Since 3900 feet is a little more than a third I have to add some to that number since the second third has a lower FC of .22. This addition is purely based on common sense and in this case I'd add another 25% for good measure giving me a TOD of about 5000 feet. This might seem overly cautious but the FC trend is down going and why take chances?

So yes, the procedures are both company and type related. But regardless of everything else, an intersection take off a third down the runway in combo with FC of .22 and then .11 is plain stupid imo. And also, I don't think that all pilots are giving this as much thought as they really should - there are still way too many cowboys out there...