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Wojtus
1st Feb 2009, 19:14
Hello!

I had some discussion regarding breaking action recently and I'd like to clear it up.
So, is it true to say a plane needs better breaking for departure (possible high-speed abort) than landing? Do your friction coefficient minimums differ for each third of the runway? Does weak braking action causes more trouble with decceleration or rather stability/steering? Does paint used for runway markings significantly reduces friction locally in wet conditions?

Opinions may vary between different airframes, so if possible - please state the bird you're flying in replies. Thanks a lot.

Wojtus

hoover1
1st Feb 2009, 19:24
i fly the 737. braking is more important on the reject than on landing since the reject is at maximum breaking. landing, depending on length may not require any brakes. runways usually will report braking action in thirds. our charts do not allow us to divide up the runway this way we just use the most restrictive. wet braking plays more of a factor in deceleration than steering. steering is achieved by use of the rudder and nose wheel. about paint, i don't know but riding my bike i stay off the paint when it rains.

Olabade
1st Feb 2009, 19:34
Sir,

I fly the A32s family and yes the low friction coefficients are sometimes a trouble. For both T/O and landing. It lenghtens the required rwy distances hence reduces the weights allowed for the T/O or landing but also reduces the x-wind component which might call for a diversion sometimes with only one rwy or only parallel rwy's.

t. Olabade

Capot
1st Feb 2009, 19:50
Aircraft normally much heavier on departure, too. Plus the point where the RTO occurs is probably much closer to the far end than the point of touch-down.