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aircraft brakes were never designed for stopping aircraft.



 
 
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  #1  
Old July 19th 08, 11:54 AM posted to rec.aviation.homebuilt
Stealth Pilot[_2_]
external usenet poster
 
Posts: 846
Default aircraft brakes were never designed for stopping aircraft.


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
  #2  
Old July 19th 08, 12:27 PM posted to rec.aviation.homebuilt
Vaughn Simon
external usenet poster
 
Posts: 735
Default aircraft brakes were never designed for stopping aircraft.


"Stealth Pilot" wrote in message
...
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


  #3  
Old July 19th 08, 02:23 PM posted to rec.aviation.homebuilt
denny
external usenet poster
 
Posts: 14
Default aircraft brakes were never designed for stopping aircraft.

On Jul 19, 7:27�am, "Vaughn Simon"
wrote:
"Stealth Pilot" wrote in message

...

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


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
  #4  
Old July 19th 08, 02:38 PM posted to rec.aviation.homebuilt
[email protected]
external usenet poster
 
Posts: 472
Default aircraft brakes were never designed for stopping aircraft.

On Jul 19, 3:54*am, Stealth Pilot
wrote:


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
  #5  
Old July 19th 08, 08:38 PM posted to rec.aviation.homebuilt
Alan Baker
external usenet poster
 
Posts: 244
Default aircraft brakes were never designed for stopping aircraft.

In article ,
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.

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
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg
  #6  
Old November 8th 08, 05:55 AM posted to rec.aviation.homebuilt
Highflyer
external usenet poster
 
Posts: 102
Default aircraft brakes were never designed for stopping aircraft.


"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)


  #7  
Old November 8th 08, 10:01 PM posted to rec.aviation.homebuilt
Alan Baker
external usenet poster
 
Posts: 244
Default aircraft brakes were never designed for stopping aircraft.

In article , "Highflyer"
wrote:

"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.


Wow. This is so wrong.

The expander tube expands because when you push on the brake pedals you
force fluid into it. If that fluid is heated, it will try to expand but
since the pressure in the system is determined by your feet on the
pedals, what will happen is that the pedals will push back on your feet.
If you don't push any harder, they will move back until the reduction in
pressure once again balances the system. If that moves the pedals all
the way back to the stops, then the orifice to the reservoir will open
and fluid will get pushed back into it.


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. :-)


Then I suggest that there is something wrong with your brakes...


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


Ummm... What model Stinson weighs two tons? You're not claiming you fly
a Stinson Reliant, are you?


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.


And you don't have to. The kinetic energy of a 1,000kg light aircraft at
a landing speed of 27.8 m/s is 1/2 mv^2 = 386420 Joules

The specific heat of steel is 500 Joules per kg*K (degrees Kelvin).

So if you have two brakes weigh -- say -- 10kg each, then the rise in
temperature (dT) is

386420 = 20(dT)(500); dT = 386420/10000 = 38.64 K degrees. Even if the
brakes weigh a half of my estimate, the temperature rise is still only
77 K, or 139 F.


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.


Sorry, but you won't stop a Stinson in 290 feet on aerodynamic drag
alone.


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! :-)


You only scrape off much rubber if you brake close to the threshold of
adhesion.


Highflyer
Highflight Aviation Services
Pinckneyville Airport (PJY)


--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg
  #8  
Old November 11th 08, 12:44 AM posted to rec.aviation.homebuilt
[email protected]
external usenet poster
 
Posts: 1,130
Default aircraft brakes were never designed for stopping aircraft.

On Nov 8, 3:01*pm, Alan Baker wrote:
In article , "Highflyer"
wrote:







"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.


Wow. This is so wrong.

The expander tube expands because when you push on the brake pedals you
force fluid into it. If that fluid is heated, it will try to expand but
since the pressure in the system is determined by your feet on the
pedals, what will happen is that the pedals will push back on your feet.
If you don't push any harder, they will move back until the reduction in
pressure once again balances the system. If that moves the pedals all
the way back to the stops, then the orifice to the reservoir will open
and fluid will get pushed back into it.



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. :-)


Then I suggest that there is something wrong with your brakes...



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


Ummm... What model Stinson weighs two tons? You're not claiming you fly
a Stinson Reliant, are you?



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.


And you don't have to. The kinetic energy of a 1,000kg light aircraft at
a landing speed of 27.8 m/s is 1/2 mv^2 = 386420 Joules

The specific heat of steel is 500 Joules per kg*K (degrees Kelvin).

So if you have two brakes weigh -- say -- 10kg each, then the rise in
temperature (dT) is

386420 = 20(dT)(500); dT = 386420/10000 = 38.64 K degrees. Even if the
brakes weigh a half of my estimate, the temperature rise is still only
77 K, or 139 F.



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.


Sorry, but you won't stop a Stinson in 290 feet on aerodynamic drag
alone.



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! *:-)


You only scrape off much rubber if you brake close to the threshold of
adhesion.



Highflyer
Highflight Aviation Services
Pinckneyville Airport (PJY)


--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg


Seems to me that the old Goodyear bladder brakes had an
expander tube and a diaphragm-type master. There was no reservoir, so
no relief hole. I think the system was filled up completely and
plugged. Any expansion of the fluid due to heat would cause some brake
drag.
As for the physics, you might have those numbers right--I
wouldn't know; I'm no physicist---but those discs are going to be much
too hot to touch. Even just maneuvering on the ramp can heat them
considerably. Shoot, just dragging them a few hundred feet while
taxiing can ruin them. I regularly see discs damaged from welding of
the semi-metallic lining due to excessive heat.

Dan
  #9  
Old November 11th 08, 05:09 AM posted to rec.aviation.homebuilt
[email protected]
external usenet poster
 
Posts: 75
Default aircraft brakes were never designed for stopping aircraft.

On Fri, 7 Nov 2008 23:55:23 -0600, "Highflyer" wrote:


"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. :-)


At about 2300 or so RPM the Deb will happily accelerate with the
brakes locked and the tires skidding. Once it starts to skid it feels
just like it hit ice as the rubber begins to melt/vaporize.


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

Man, but that's fast!. :-))
The old Deb comes down final at 80 MPH minus 1 MPH for each 100 under
gross. With me and half fuel, final is about 73 MPH. touchdown?
Gotta be in the 40 MPH range. Those big flaps slow it quickly.
Course it only weighs a ton and a half so you're hauling the
equivalent of the entire useful load of the Deb on top of the Deb's
gross.:-))

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.


Those big Cleveland's will fade if they get a lot of use, but it's
rare to ever use them that much. Even after a short field, with
maximum effort they still work. You can lock them up, but after that
the taxi gets kinda bumpy.

Steep final into the round out, firm touch down on the mains,
immediately let the nose down, get on the brakes, and go full up
elevator if the brakes will keep the nose gear down. The aerodynamic
braking with that big wing and tail is very effective giving it the
ability to stop shorter than many 172s (book figures)

I'm certainly not that proficient at present.



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)

Roger (K8RI) ARRL Life Member
N833R (World's oldest Debonair)
www.rogerhalstead.com
  #10  
Old July 20th 08, 02:07 AM posted to rec.aviation.homebuilt
Ernest Christley
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Posts: 199
Default aircraft brakes were never designed for stopping aircraft.

Stealth Pilot wrote:

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.


How does one steer a C152 while taxiing?

I was headed bopping down the downhill section of KTTA's single taxiway, when one of the LSA trainees decided that his
fuel was more important than mine. He pulled out heading straight to me. There was only one turn off, and I had about
20 feet to come to a complete stop or we'd have a mess. The old hacker that I am, I decided that using the brakes were
the best way to accomplish the task. I know that it wasn't the right thing to do. I should have cut the engine, jumped
out, and grabbed the tail to drag it to a halt like everyone is taught in groundschool. But I guess I'm just lazy.
 




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