Contaminated Runway Takeoffs/Landings

[IdahoBoy]

It's time to get some answers to this question and I know you freight guys and gals will have some good ideas. I've searched several areas on this forum and there is very little to be said so forgive me if I've missed it. Here goes:

What "formula" or rule of thumb can be used to develop a safe operating margin in and out of a contaminated runway.

Let's assume we have a poor braking action report in mixed snow/ice on the runway. Let's further assume that the braking action report was given recently by a previous airplane of identical or near identical make and model.

I'll cut to the chase now- I operate a King Air 200 and 90 for a 135 carrier. Beech only publishes landing and Accelerate-stop distances for a dry, paved runway. I've been charged with determining a reasonable runway length for a contaminated takeoff that will keep me within accelerate-stop distances. (I know, very academic but I'm trying to humor my boss)

One idea I had would be to interpolate some numbers from a 1900 manual.

The only thing I've found after about 4 hours of internet searches is to add 120% to those numbers- which isn't a bad rule but it seems a little arbitrary.

Any thoughts on this??

[ackeight]

Originally Posted by IdahoBoy

The only thing I've found after about 4 hours of internet searches is to add 120% to those numbers- which isn't a bad rule but it seems a little arbitrary.

Any thoughts on this??

I say 120% is your best bet. It's arbitrary enough trying to guess exactly what the aircraft will perform like on the contaminated runway seeing that conditions vary widely.

[Dugie8]

http://rgl.faa.gov/Regulatory_and_Gu...E/AC_91_79.pdf

[IdahoBoy]

Hey Dugie8- thanks for the reply- but it seems the link is outdated.

Can you reference the article? The link seems to have been truncated.

[IdahoBoy]

Oops- just figured it out- AC 91-79 right?

[gomntwins]

real world is all arbitrary when it comes to this. What I actually use on a contaminated runway is no brakes. But then again, I have the luxury of reverse. In a turboprop the best thing to do is figure out how much runway you eat up in a worst case scenario (10 knot tailwind... etc.), and try your best to not use the brakes at all. This will give you a pretty close estimate on icey runways. Ice doesn't seem to affect reverse much. If you do need to use brakes, like flying a piston... your best bet is almost the same. The reason I say this... unless you know the pilot in front of you and have experienced their personal reports, you really have no clue. Some pilots will call poor no matter how bad it is just to keep traffic going in and out of the airport. They know if they call nill... very few 135 or 121 operators can land. So they just call poor. It's kindof like getting the pirep from the plane in front of you that they broke out at mins- what's that mean? Is it at mins or not? who knows. On the other end of this you've got people who slide a little bit and call it poor. It's all subjective to the individual flying- no matter if they're in the same plane as you or not. In a piston just roll to a stop, figure out how much runway you took, and that's probably the safest number on a runway calling poor.

120% seems small to me in a piston. It seems sufficient to me in a turboprop.