Wet runway performance problem

[giladal]

Hi Guys,

Having an issue with completing this following problem. The issue is, I dont know if there is a special requirement for every country or this is just a standard ICAO requirement.

What would you use to calculate wet runway landing distance. 115% or ? Maybe even a different method.

Problem:
Assuming that VIENNA is your destination alternate, according to the MET forecast and your turbojet powered aircraft calculated landing distance of 6,200 feet, what is the minimum runway length required at VIENNA?
TAF VIENNA: 0018 28015KT 2000 SHRA SCT025

Looking forward to hearing from you guys,
CG

[hollingworthp]

I would go at this from the other direction (the runway length is clearly fixed so you can only limit your landing weight).

As far as I am aware, there is no standard factor to apply to dry distances as it would depend on a number of factors.

You will need to dive into your AFM and check out the performance section.

For my type, you determine the Dry landing distance required (taking into account the usual approach climb / brake limit etc). Once you have this figure, you then go into a simplified table against the dry distance and read off the contaminated column depending on the conditions (wet, 0.125 / 0.2 / 0.3 / 0.4 / 0.5 inches water depth and so on for slush, snow, wet ice etc).

On the basis of your example, assuming the runway at Vienna is not grooved (and hence treated as dry) then Wet runway would be 9450' if landing at VRef and 10950' if landing at VRef + 10 (without reversers or tailwind and from 50' screen height). Goes to show how important speed control is!

However, we rarely get out the AFM as we have a route performance manual and Flygprestanda showing the max landing weight for each runway and contaminated condition.

[giladal]

Thanks for your reply.

I thought as well that this should be linked to a performance chart, but it isn't linked to any chart or figure. It seems as if it is a general jet question not pertaining to any specific model or chart.


Any other takers?

CG

[whiskey1]

If you need 6200 feet (Dry test pilot figures) then to plan to land you will need:

6200 x 1.67 (regulatory factor turbo jet) x 1.15 ( wet) = 11908 feet of actual runway at destination.

W1

[giladal]

Hi Guys,
Thanks for all the replies.

So, the solution that brings me closest to the provided answer is to multiply the LDR by 1.67. I guess since it is it Alternate airport, the wet factor doesnt apply for planning purposes.

6,200 * 1.67 = 10,354

Provided answer: 10,333

So pretty close. I will stick with that rule for the test.

Thanks again guys until next time ;) Really appreciate all your replies.