On Sat, 19 Jul 2008 18:54:27 +0800, Stealth Pilot
wrote:


some interesting points came out of one guy's query re servicing some
old brake master cylinders.

gringomasloco commented regarding broken brake lines spraying brake
fluid over hot calipers and setting the wheels on fire. hmmmmm.

I am talking about light private aircraft here...

as I put it in the subject line aircraft brakes were never designed
for stopping aircraft. they were designed to hold aircraft.
now that may sound like semantic nonsense but it is true.

aircraft brakes were designed for use in holding the aircraft still
while the engine was started. after the taxy out and the engine has
warmed you do a run up check to make sure that the magneto circuits
are up to the bit of work that lies ahead for them. the brakes are
applied to hold the aircraft while the revs are bought up and each
maggy checked in turn.

Ahhh...I beg to differ here. First time I got someone qualified to
ride with me so I could get back in the air, they were astounded that
I could lock the brakes and acellerate.

(No, I didn't let it go very far as that's kinda hard on the tires,
but I assure you that with some planes you can take off with the
brakes locked *IF* the tires hold out. OTOH the landing and taxi are
going to be a bit bumpy:-))

BTW the brakes will hold it to do a runup IF you don't go past the RPM
listed for the runup of 2100 RPM at cycling the prop. Even the taxiway
*must* be clean and dry. It's already moving at 2400 and acellerting
when firewalled.

Those tires have a linear tread for squeezing water out and
maintaining direction. They aren't worth much for traction when it
comes to braking. Actually if you lock them up they start to
hydroplane on their own vaporized rubber.

It ain't the brakes, it's the tires and a lack of traction by those
tires. The brakes on the Deb will lock up the tires and that's as
much as you can get out of any brakes.


now brakes for commercial aircraft are different and they *are* used
for stopping, but the brakes on little lighties arent.
some people have yet to realise that.

Stealth Pilot
Roger (K8RI) ARRL Life Member
N833R (World's oldest Debonair)
www.rogerhalstead.com