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Posted by Stealth Pilot on July 19, 2008, 6:54 am
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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.
from a design aspect that is the end of the use of a light aircraft's
brakes until after landing and we wish to hold the aircraft still for
shutdown and disembarkation.
of course brakes are brakes and people will use them like they were
driving cars. light aircraft brakes were never designed for slowing an
aircraft when landing.
I know that they get used for that by students of bad piloting
technique but the design intent is a fact borne out by their
diminutive size.
I'll give one concrete example. The Stinson 108 is a huge aircraft, 4
seats in 1940's luxury, yet it only has brake pucks the same size as a
5.00x5 cleveland. in fact on the one Chris M-F ownes the brakes *are*
cleveland 5.00x5 calipers.
it is quite ok to be masters of the world and fly however you like.
you'll just wear out your aeroplanes faster.
just remember though that aircraft brakes are for holding the aircraft
not stopping it.
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
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Posted by Vaughn Simon on July 19, 2008, 7:27 am
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show/hide quoted text
> just remember though that aircraft brakes are for holding the aircraft
> not stopping it.
> 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.
Apparently Cessna has also yet to realize that.
From Cessna 152 POH: (Step 6 of short field landing procedure) "6. Brakes--
APPLY HEAVILY."
Good Morning! ;-)
Vaughn
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Posted by denny on July 19, 2008, 9:23 am
Please log in for more thread options On Jul 19, 7:27=EF=BF=BDam, "Vaughn Simon" <vaughnsimonHATESS...@att.FAKE.n=
show/hide quoted text
et>
wrote:
show/hide quoted text
> > just remember though that aircraft brakes are for holding the aircraft
> > not stopping it.
> > 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.
> =EF=BF=BD =EF=BF=BDApparently Cessna has also yet to realize that.
> From Cessna 152 POH: (Step 6 of short field landing procedure) "6. Brakes=
-- =EF=BF=BD
show/hide quoted text
> APPLY HEAVILY."
> Good Morning! =EF=BF=BD;-)
> Vaughn
Where do light and heavy begin? I have a 2,000 pound gross
weight airplane. We picked the brakes based on a start braking speed
of about 70 knots. I can do multiple stops from slower speeds during
high speed taxi testing. Braking capacity is mostly a funtion of how
much mass the disk has whcih in turn determines how much heat it can
absorb. Keep the brakes small to keep the airplane light and limit
your runway options. Add some mass and stop with brakes on shorter
runways. You're experimental. Take your pick. BTW, I changed my
brake pads after about 1,200 hours because they were getting thin, but
not worn out. For me, it's cheaper and easier to change brake pads
than tires worn out by long rollouts and long taxi distances.
Denny
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Posted by veeduber@isp.com on July 19, 2008, 9:38 am
Please log in for more thread options wrote:
show/hide quoted text
> 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.
---------------------------------------------------------------------------=
-----------------
That is what I was taught. The distinction was based on breaking
surface area.
Military and commercial aircraft, meaning those having a need to bring
the loaded airplane to a full stop AND TO HOLD IT THERE during run-up
or whatever, were often fitted with brake drums rather than pucks &
rotors, since you could get more breaking surface for less weight when
using a drum & shoe arrangement.
However, modern puck & rotor systems commonly use calipers that
present a puck to each side of the rotor, allowing you to double the
breaking surface for only a modest increase in weight.
The down-side here is the need to get rid of the heat such systems can
produce when going for a full-stop.
Some modern-day systems offer a dual system, with single-pucks
intended to do the slowing/steering and dual pucks coming on-line to
provide the stoping & holding.
-R.S.Hoover
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Posted by Alan Baker on July 19, 2008, 3:38 pm
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show/hide quoted text
> 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.
>
> from a design aspect that is the end of the use of a light aircraft's
> brakes until after landing and we wish to hold the aircraft still for
> shutdown and disembarkation.
>
> of course brakes are brakes and people will use them like they were
> driving cars. light aircraft brakes were never designed for slowing an
> aircraft when landing.
> I know that they get used for that by students of bad piloting
> technique but the design intent is a fact borne out by their
> diminutive size.
>
> I'll give one concrete example. The Stinson 108 is a huge aircraft, 4
> seats in 1940's luxury, yet it only has brake pucks the same size as a
> 5.00x5 cleveland. in fact on the one Chris M-F ownes the brakes *are*
> cleveland 5.00x5 calipers.
>
> it is quite ok to be masters of the world and fly however you like.
> you'll just wear out your aeroplanes faster.
>
> just remember though that aircraft brakes are for holding the aircraft
> not stopping it.
>
> 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
Nonsense: complete and utter.
What aircraft brakes aren't designed for is stopping aircraft
*repeatedly*.
The chief advantage of putting larger brakes on any vehicle is that it
providess a greater heat sink to allow for more braking before the
brakes overheat.
Aircraft brakes need to be able to stop an aircraft *once* and then have
an essentially infinite amount of time to cool down again.
--
Alan Baker
Vancouver, British Columbia
show/hide quoted text
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
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> not stopping it.
> 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.