aircraft brakes were never designed for stopping aircraft.

On Aug 5, 5:17 am, Stealth Pilot
wrote:

when I put new pads on earlier this year I broke one so I actually
have one of the pads sitting 2inches from my space bar as I type.
I calculated that it has a surface area of no more than 1.57 square
inches. when you brake hard in the aircraft they get fitted to you are
using no more than 6 and a quarter square inches of pad to stop a one
thousand five hundred pound weight aircraft.
as for standing on the brakes sure it can be done but at some
considerable abuse to the braking systems.
the concept is one of half m vee squared's worth of energy being
converted to heat by 6 or so square inches of pad.

Plenty of area to stop a 1500 lb airplane. As I said before, my
4500 lb car has brake pads that are no more than three times as large
as the pads you have there, and those car brakes are used to stop the
car from 80 MPH, are used on long downhills, are used hundreds of
times every day in traffic, and so on. They're designed to do that.
The light aircraft brakes are used to hold the airplane during runup
and to stop it at the end of a taxi or landing roll, neither of which
are anywhere near as brutal as the auto's brakes have to deal with.
Many older light aircraft had pads even smaller, yet they worked
just fine. The bigger issue is heat dissipaton from the disc, since
excessive disc temperature will cause brake fade no matter how large
the pads. Kinetic energy is transformed into heat, and when the discs
are hot they can't absorb much more energy and will lose their
effectiveness. Aircraft brakes are out in the breeze and get better
cooling than car brakes.
Occasional hard braking in your airplane won't hurt the brakes
and will maybe keep the airplane out of the rhubarb. Brake pads are
cheaper than airframe damage any day.
Dan

On Wed, 6 Aug 2008 13:14:10 -0700 (PDT),
wrote:



On Aug 5, 5:17 am, Stealth Pilot
wrote:

when I put new pads on earlier this year I broke one so I actually
have one of the pads sitting 2inches from my space bar as I type.
I calculated that it has a surface area of no more than 1.57 square
inches. when you brake hard in the aircraft they get fitted to you are
using no more than 6 and a quarter square inches of pad to stop a one
thousand five hundred pound weight aircraft.
as for standing on the brakes sure it can be done but at some
considerable abuse to the braking systems.
the concept is one of half m vee squared's worth of energy being
converted to heat by 6 or so square inches of pad.

Plenty of area to stop a 1500 lb airplane. As I said before, my
4500 lb car has brake pads that are no more than three times as large
as the pads you have there, and those car brakes are used to stop the
car from 80 MPH, are used on long downhills, are used hundreds of
times every day in traffic, and so on. They're designed to do that.

The light aircraft brakes are used to hold the airplane during runup
and to stop it at the end of a taxi or landing roll, neither of which
are anywhere near as brutal as the auto's brakes have to deal with.

Dan are we separated by a common language?
the 3 lines above contain exactly the point I was making in my
original post. the brakes in a light aircraft are not intended for
decelerating an aircraft. we have runways and make use of drag for the
slowdown after landing.
I dont know whether these guys approach aviation as some sort of
outlet for egotism or what.
In my country the piloting skills taught to pilots tend to emphasise
gentle but effective control of an aircraft. that has been the case
for all the years since WW2.
slamming the brakes on during a normal landing is as frowned on as
landing on the nose wheel.
short field landings are only an occasional technique not to be used
for every landing.
I guess piloting finesse is a lost concept with the americans.
if you teach pilots to fly and land intelligently, the aircraft they
fly will last a lot longer and in better condition.
if the americans are too stupid to use any finesse in their flying at
least they arent flying in my country (or yours) and I do appreciate
them keeping the parts supply going.

the word in my country is aeroplane!
long may it remain so.
Stealth Pilot

"Stealth Pilot" wrote in message
...
the 3 lines above contain exactly the point I was making in my
original post. the brakes in a light aircraft are not intended for
decelerating an aircraft.

Actually you just have to read the title of this thread, because you are the
OP. What you said was light "aircraft brakes were never designed for stopping
an aircraft", and you have been shown to be dead wrong. You can read the design
requirements for USA certified light aircraft at 14 CFR part 23 Sec. 23.735. I
am sure that the European standards are similar.

You have tried to make this thread about piloting style, but your words which
started this thread are quite different. We are discussing aircraft design, not
piloting.


Vaughn

On Aug 7, 4:57 am, Stealth Pilot
wrote:

slamming the brakes on during a normal landing is as frowned on as
landing on the nose wheel.
short field landings are only an occasional technique not to be used
for every landing.

And that's what Cessna and Transport Canada and a whole lot of
instructors teach. You had insisted that brakes were only for holding
and airplane that's already motionless, and that's not true at all. We
could use simple axle locks for that, similar to the Park lock on an
automatic transmission, not heat-creating friction brakes.

Dan

On Thu, 07 Aug 2008 12:11:20 GMT, "Vaughn Simon"
wrote:


"Stealth Pilot" wrote in message
.. .
the 3 lines above contain exactly the point I was making in my
original post. the brakes in a light aircraft are not intended for
decelerating an aircraft.

Actually you just have to read the title of this thread, because you are the
OP. What you said was light "aircraft brakes were never designed for stopping
an aircraft", and you have been shown to be dead wrong. You can read the design
requirements for USA certified light aircraft at 14 CFR part 23 Sec. 23.735. I
am sure that the European standards are similar.

You have tried to make this thread about piloting style, but your words which
started this thread are quite different. We are discussing aircraft design, not
piloting.


Vaughn


what you discuss is entirely up to you.

my comment is that it is bad piloting technique to stop an aircraft on
landing using the tiny brakes. it is better to use aerodynamic forces
and the runway length to stop the aircraft.

dan was waxing eloquent about stamping on the brakes on landing and I
thought that his comments were a little amiss. poor technique in fact
given the small size of the brakes involved.
read into that whatever you will.

btw wtf is 14 CFR etc etc ??
....never mind we'll have to agree to disagree.
Stealth Pilot

On Aug 10, 5:26*am, Stealth Pilot
wrote:
On Thu, 07 Aug 2008 12:11:20 GMT, "Vaughn Simon"





wrote:

"Stealth Pilot" wrote in message
.. .
the 3 lines above contain exactly the point I was making in my
original post. the brakes in a light aircraft are not intended for
decelerating an aircraft.

* Actually you just have to read the title of this thread, because you are the
OP. *What you said was light "aircraft brakes were never designed for stopping
an aircraft", and you have been shown to be dead wrong. *You can read the design
requirements for USA certified light aircraft at 14 CFR part 23 Sec. 23.735. *I
am sure that the European standards are similar.

* You have tried to make this thread about piloting style, but your words which
started this thread are quite different. *We are discussing aircraft design, not
piloting.

Vaughn

what you discuss is entirely up to you.

my comment is that it is bad piloting technique to stop an aircraft on
landing using the tiny brakes. it is better to use aerodynamic forces
and the runway length to stop the aircraft.

dan was waxing eloquent about stamping on the brakes on landing and I
thought that his comments were a little amiss. poor technique in fact
given the small size of the brakes involved.
read into that whatever you will.

btw wtf is 14 CFR etc etc ??
...never mind we'll have to agree to disagree.
Stealth Pilot- Hide quoted text -

- Show quoted text -

You have the option of disagreeing with 99% of the people who know
what brakes are for. Don't hold your breath waiting for someone to
agree with your cockamamie theory.

Harry K

"Stealth Pilot" wrote in message
...

btw wtf is 14 CFR etc etc ??

So you haven't bothered to educate yourself? I thought not.

Actually, I have told you what it is. The relevant passage can be on your
screen seconds from now. Google is your friend.

Vaughn

"Vaughn Simon" wrote in message
...

"Stealth Pilot" wrote in message
...

btw wtf is 14 CFR etc etc ??

So you haven't bothered to educate yourself? I thought not.

Actually, I have told you what it is. The relevant passage can be on
your screen seconds from now. Google is your friend.


Well, he is from a place where the U.S. C.F.R. doesn't apply. But then, a
significant percentage of the aircraft in the world were designed with
those regulations in mind...

Of course, now he is claiming it isn't a design issue, but a good piloting
style issue - contrary to what was originally written.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

On Sun, 10 Aug 2008 20:26:19 +0800, Stealth Pilot
wrote:

my comment is that it is bad piloting technique to stop an aircraft on
landing using the tiny brakes. it is better to use aerodynamic forces
and the runway length to stop the aircraft.

I've seldom had the pleasure to read bull**** of such a magnitude on
the internet yet.

Congratulations! You made my day!


Bye
Andreas

"Alan Baker" wrote in message
...
In article ,
Stealth Pilot wrote:

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.

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
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg


Right. Almost. Maybe.....

My Stinson has 9 inch diameter drum brakes and has lots of
area on the brakes, but low pressure applied. It uses a largish
master cylinder to pump fluid into an "expander tube" under the
brake shoes inside the drum.

They work great for holding the airplane for runup and are essential
for ground handling and taxiing because the tailwheel is a swivel and in not
connected to anything that could allow it to be used for
steering. As a result, all steering is by differential braking.

You can apply the brakes on the landing roll and it will quickly slow the
airplane. However, if you do so, you may not be able to
leave the runway. Rubbing all that shoe area inside the drum makes
it quite hot inside the drum. My little infrared laser guided remote
reading thermometer gives temperatures in the 400 to 600 degree
range. It takes a while to dissipate that heat from inside the drum
and until it does the brake fluid inside the "expander tube" gets quite
warm. When it does it expands and the brakes tend to remain quite
"ON" until things cool down.

Even a long and complicated taxi, like into a parking spot at Oshkosh, will
generally result in a noticeable loss of "differential"
in the braking activity and a substantial increase in the power
required to taxi. I have found that it is wise to NOT attempt a
takeoff if it requires over 1000 RPM to maintain a reasonable taxi
speed. :-)

Of course, this airplane weighs generally two tons and lands at 70 mph at
touchdown in a three point attitude. :-)

The general limiting factor in ALL aircraft brakes is heat dissipation. The
wheels are relatively small and the brakes are
in a small space. The more effective the brakes are, the more heat
they produce. All that energy they are dissipating when they slow
you down has to go somewhere. Thermodynamics tells us that most
wasted energy appears as heat! Randomized molecular activity. :-)
To stop the airplane you have to waste the energy. 1/2 M V^2.
You can't get around it.

Fortunately, a taildragger with the flaps down and the tail on the
ground takes a LOT of energy to keep moving, so you can waste a
lot of the energy you have to get rid of by stirring up the air. Then
apply the brakes to turn off the runway after you have slowed down
without them.

FWIW Department. You scrape a lot more rubber off you tires by
landing and applying brakes vigorously while little weight is on
the wheels than you would in many many miles of taxiing around or
rolling out with the brakes off! :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport (PJY)