Conventional v tricycle gear

On Jul 8, 10:49 am, John Smith wrote:
wrote:
On Jul 7, 1:13 pm, John Smith wrote:

Be VERY, VERY careful when doing this on wet grass!
It gets real interesting when the tail is up, the brakes are on, and the
mains are sliding down the runway. :-0

Done that, in a 185, braking as hard as I could with the tail
way up. It'll stop much shorter than the POH says, even when the grass
is wet.

And the surprised look on your face at the time... priceless! :-))
(I know it probably was on mine.)

I was taught be a pro who'd been a bush pilot and a pilot in
Africa, flying with a relief organization that had high standards and
many difficult and seldom-seen techniques. They still do. He showed me
what it would do, then taught me the technique. I've used in in other
taildraggers, too, and it's not difficult if you're current, which I'm
not much anymore. Too little time flying and too much time fixing.
That's what you get when you spend an extra four years becoming an
engineer: the pilots who don't do all that extra work get to do all
the flying. Life seems unfair sometimes.

Dan

wrote in
:

On Jul 8, 10:49 am, John Smith wrote:
wrote:
On Jul 7, 1:13 pm, John Smith wrote:

Be VERY, VERY careful when doing this on wet grass!
It gets real interesting when the tail is up, the brakes are on,
and the mains are sliding down the runway. :-0

Done that, in a 185, braking as hard as I could with the tail
way up. It'll stop much shorter than the POH says, even when the
grass is wet.

And the surprised look on your face at the time... priceless! :-))
(I know it probably was on mine.)

I was taught be a pro who'd been a bush pilot and a pilot in
Africa, flying with a relief organization that had high standards and
many difficult and seldom-seen techniques. They still do. He showed me
what it would do, then taught me the technique. I've used in in other
taildraggers, too, and it's not difficult if you're current, which I'm
not much anymore. Too little time flying and too much time fixing.
That's what you get when you spend an extra four years becoming an
engineer: the pilots who don't do all that extra work get to do all
the flying. Life seems unfair sometimes.


I still don't see it shoteing the landing roll. Can't see the physics that
would make a wheel landing shorter. I'll just have to try it!

Bertie

On Jul 9, 1:24 pm, Bertie the Bunyip wrote:

I still don't see it shortening the landing roll. Can't see the physics that
would make a wheel landing shorter. I'll just have to try it!

Here are the physics:

The trike, to get maximum weight on its mains for braking
traction, has to keep its weight off the nose. We can use full up-
elevator, but the presence of the nosewheel assures us that it will
take some of the weight and that we cannot get the wing's AOA low
enough to stop it lifting. The only advantage we have in the trike is
the elevator's downforce added to the airplane's weight. Electric flas
make it worse, since we can't retract them instantly to dump their
lift.

The taildragger can get its tail way up high. If you sit in the
airplane while its tail is on a jack or some other support so that the
airplane is in level attitude, you will be astounded at how nose-low
it feels. Observe the propeller clearance in this position, too, and
make some allowance for bouncing that might lower the prop closer to
the runway. I used to do this with students who were afraid to raise
the tail to level attitude, and they always amazed at the picture out
the front.
A taildragger with long legs, like a 185, can get its tail even
higher than level. I've seen a shot of a Helio Courier with its tail
up so that the fuselage was pointed downward at 5 or 10 degrees, and
the pilot was braking hard. No lift at all in that scenario, and
manual flaps can be retracted quickly to get even more weight on the
wheels. Most taildraggers will have the main axles 15 degrees ahead of
the airplane's CG, meaning that if you pick up the tail you can raise
it until the airplane is at that 15 degree nose-low attitude and it
will be balanced there. You'd better have lots of skill if you're
going to try this in the rollout. Pilots of another humanitarian
outfit that operated Helios did this all the time, since the Helio's
short-field takeoff capabilities are of no use if you can't get into
that short little strip and get stopped in the first place.

Dan

wrote in
:

On Jul 9, 1:24 pm, Bertie the Bunyip wrote:

I still don't see it shortening the landing roll. Can't see the
physics that would make a wheel landing shorter. I'll just have to
try it!

Here are the physics:

The trike, to get maximum weight on its mains for braking
traction, has to keep its weight off the nose. We can use full up-
elevator, but the presence of the nosewheel assures us that it will
take some of the weight and that we cannot get the wing's AOA low
enough to stop it lifting. The only advantage we have in the trike is
the elevator's downforce added to the airplane's weight. Electric flas
make it worse, since we can't retract them instantly to dump their
lift.

The taildragger can get its tail way up high. If you sit in the
airplane while its tail is on a jack or some other support so that the
airplane is in level attitude, you will be astounded at how nose-low
it feels. Observe the propeller clearance in this position, too, and
make some allowance for bouncing that might lower the prop closer to
the runway. I used to do this with students who were afraid to raise
the tail to level attitude, and they always amazed at the picture out
the front.
A taildragger with long legs, like a 185, can get its tail even
higher than level. I've seen a shot of a Helio Courier with its tail
up so that the fuselage was pointed downward at 5 or 10 degrees, and
the pilot was braking hard. No lift at all in that scenario, and
manual flaps can be retracted quickly to get even more weight on the
wheels. Most taildraggers will have the main axles 15 degrees ahead of
the airplane's CG, meaning that if you pick up the tail you can raise
it until the airplane is at that 15 degree nose-low attitude and it
will be balanced there. You'd better have lots of skill if you're
going to try this in the rollout. Pilots of another humanitarian
outfit that operated Helios did this all the time, since the Helio's
short-field takeoff capabilities are of no use if you can't get into
that short little strip and get stopped in the first place.


Oh, I can do it, but I don't see it giving you any more braking. Quite
the contrary. A given braking force will apply a rotational force around
the airplane's gear. In the three point attitude, you've got more of the
airpane sitting behind the gear, so more braking should be available.
Also, if you touch down in the same spot three point as opposed to doing
a wheel landing, you should have touched down with less airspeed.
Therefore less energy to kill.
For the sake of argument, let's say that you touched down at the same
speed, though, and that you are now tail high. It would want to be very
high indeed to contribute the same amount of aerodynamic drag as the
three point attitude. OK, your Cf is a bit better because of the extra
weight on the wheels, but since the limiting factor is nosing the
airplane over as opposed to achieving max Cf that's irrelevant.


Bertie

On Thu, 10 Jul 2008 07:54:50 +0000 (UTC), Bertie the Bunyip
wrote:

wrote in
:

On Jul 9, 1:24 pm, Bertie the Bunyip wrote:

I still don't see it shortening the landing roll. Can't see the
physics that would make a wheel landing shorter. I'll just have to
try it!

Here are the physics:

The trike, to get maximum weight on its mains for braking
traction, has to keep its weight off the nose. We can use full up-
elevator, but the presence of the nosewheel assures us that it will
take some of the weight and that we cannot get the wing's AOA low
enough to stop it lifting. The only advantage we have in the trike is
the elevator's downforce added to the airplane's weight. Electric flas
make it worse, since we can't retract them instantly to dump their
lift.

The taildragger can get its tail way up high. If you sit in the
airplane while its tail is on a jack or some other support so that the
airplane is in level attitude, you will be astounded at how nose-low
it feels. Observe the propeller clearance in this position, too, and
make some allowance for bouncing that might lower the prop closer to
the runway. I used to do this with students who were afraid to raise
the tail to level attitude, and they always amazed at the picture out
the front.
A taildragger with long legs, like a 185, can get its tail even
higher than level. I've seen a shot of a Helio Courier with its tail
up so that the fuselage was pointed downward at 5 or 10 degrees, and
the pilot was braking hard. No lift at all in that scenario, and
manual flaps can be retracted quickly to get even more weight on the
wheels. Most taildraggers will have the main axles 15 degrees ahead of
the airplane's CG, meaning that if you pick up the tail you can raise
it until the airplane is at that 15 degree nose-low attitude and it
will be balanced there. You'd better have lots of skill if you're
going to try this in the rollout. Pilots of another humanitarian
outfit that operated Helios did this all the time, since the Helio's
short-field takeoff capabilities are of no use if you can't get into
that short little strip and get stopped in the first place.


Oh, I can do it, but I don't see it giving you any more braking. Quite
the contrary. A given braking force will apply a rotational force around
the airplane's gear. In the three point attitude, you've got more of the
airpane sitting behind the gear, so more braking should be available.
Also, if you touch down in the same spot three point as opposed to doing
a wheel landing, you should have touched down with less airspeed.
Therefore less energy to kill.
For the sake of argument, let's say that you touched down at the same
speed, though, and that you are now tail high. It would want to be very
high indeed to contribute the same amount of aerodynamic drag as the
three point attitude. OK, your Cf is a bit better because of the extra
weight on the wheels, but since the limiting factor is nosing the
airplane over as opposed to achieving max Cf that's irrelevant.


Bertie

the wings stop an aircraft more effectively than tiny brake pucks.
thats why 3 pointing it achieves the shortest landing.
the actual landing speed is lower and the wing is generating lotsa
induced drag on the backside of the performance curve.

I dont believe that getting rid of flaps shortens the landing.

Stealth Pilot

On Jul 10, 9:06*am, Stealth Pilot
wrote:
On Thu, 10 Jul 2008 07:54:50 +0000 (UTC), Bertie the Bunyip
wrote:



wrote in
:

On Jul 9, 1:24 pm, Bertie the Bunyip wrote:

I still don't see it shortening the landing roll. Can't see the
physics that would make a wheel landing shorter. I'll just have to
try it!

* Here are the physics:

* * The trike, to get maximum weight on its mains for braking
traction, has to keep its weight off the nose. We can use full up-
elevator, but the presence of the nosewheel assures us that it will
take some of the weight and that we cannot get the wing's AOA low
enough to stop it lifting. The only advantage we have in the trike is
the elevator's downforce added to the airplane's weight. Electric flas
make it worse, since we can't retract them instantly to dump their
lift.

* * * The taildragger can get its tail way up high. If you sit in the
airplane while its tail is on a jack or some other support so that the
airplane is in level attitude, you will be astounded at how nose-low
it feels. Observe the propeller clearance in this position, too, and
make some allowance for bouncing that might lower the prop closer to
the runway. I used to do this with students who were afraid to raise
the tail to level attitude, and they always amazed at the picture out
the front.
* * *A taildragger with long legs, like a 185, can get its tail even
higher than level. I've seen a shot of a Helio Courier with its tail
up so that the fuselage was pointed downward at 5 or 10 degrees, and
the pilot was braking hard. No lift at all in that scenario, and
manual flaps can be retracted quickly to get even more weight on the
wheels. Most taildraggers will have the main axles 15 degrees ahead of
the airplane's CG, meaning that if you pick up the tail you can raise
it until the airplane is at that 15 degree nose-low attitude and it
will be balanced there. You'd better have lots of skill if you're
going to try this in the rollout. Pilots of another humanitarian
outfit that operated Helios did this all the time, since the Helio's
short-field takeoff capabilities are of no use if you can't get into
that short little strip and get stopped in the first place.

Oh, I can do it, but I don't see it giving you any more braking. Quite
the contrary. A given braking force will apply a rotational force around
the airplane's gear. In the three point attitude, you've got more of the
airpane sitting behind the gear, so more braking should be available.
Also, if you touch down in the same spot three point as opposed to doing
a wheel landing, you should have touched down with less airspeed.
Therefore less energy to kill.
For the sake of argument, let's say that you touched down at the same
speed, though, and that you are now tail high. It would want to be very
high indeed to contribute the same amount of aerodynamic drag as the
three point attitude. OK, your Cf is a bit better because of the extra
weight on the wheels, but since the limiting factor is nosing the
airplane over as opposed to achieving max Cf that's irrelevant.

Bertie

the wings stop an aircraft more effectively than tiny brake pucks.
thats why 3 pointing it achieves the shortest landing.
the actual landing speed is lower and the wing is generating lotsa
induced drag on the backside of the performance curve.

I dont believe that getting rid of flaps shortens the landing.

Stealth Pilot

In something like a Mooney, full flaps into the flare, flying the
airplane until it's out of airspeed, then sucking in the flaps just at
touchdown does shorten the landing roll -- weight gets onto the mains
a lot sooner, so frictional braking works when there's not airspeed
left to keep the nosewheel high. On the other hand, I'd not be
surprised to learn the difference is stopping distance from touchdown,
keeping the flaps extended vs retracting them, is less than 30 feet.
My goal is to touch down close enough to where I want to exit the
active so that it doesn't take much engine, or much braking, to make
the turn.


It drives me nuts to see the 172 I'm following touch down on the
numbers when the turn off is 3000 feet down the runway

Stealth Pilot wrote in
:

On Thu, 10 Jul 2008 07:54:50 +0000 (UTC), Bertie the Bunyip
wrote:

wrote in
news:801c3098-d23a-4d31-a72c-9b93ad4e5339
@m45g2000hsb.googlegroups.com:

On Jul 9, 1:24 pm, Bertie the Bunyip wrote:

I still don't see it shortening the landing roll. Can't see the
physics that would make a wheel landing shorter. I'll just have to
try it!

Here are the physics:

The trike, to get maximum weight on its mains for braking
traction, has to keep its weight off the nose. We can use full up-
elevator, but the presence of the nosewheel assures us that it will
take some of the weight and that we cannot get the wing's AOA low
enough to stop it lifting. The only advantage we have in the trike
is
the elevator's downforce added to the airplane's weight. Electric
flas
make it worse, since we can't retract them instantly to dump their
lift.

The taildragger can get its tail way up high. If you sit in
the
airplane while its tail is on a jack or some other support so that
the
airplane is in level attitude, you will be astounded at how nose-low
it feels. Observe the propeller clearance in this position, too, and
make some allowance for bouncing that might lower the prop closer to
the runway. I used to do this with students who were afraid to raise
the tail to level attitude, and they always amazed at the picture
out
the front.
A taildragger with long legs, like a 185, can get its tail even
higher than level. I've seen a shot of a Helio Courier with its tail
up so that the fuselage was pointed downward at 5 or 10 degrees, and
the pilot was braking hard. No lift at all in that scenario, and
manual flaps can be retracted quickly to get even more weight on the
wheels. Most taildraggers will have the main axles 15 degrees ahead
of
the airplane's CG, meaning that if you pick up the tail you can
raise
it until the airplane is at that 15 degree nose-low attitude and it
will be balanced there. You'd better have lots of skill if you're
going to try this in the rollout. Pilots of another humanitarian
outfit that operated Helios did this all the time, since the Helio's
short-field takeoff capabilities are of no use if you can't get into
that short little strip and get stopped in the first place.


Oh, I can do it, but I don't see it giving you any more braking. Quite
the contrary. A given braking force will apply a rotational force
around
the airplane's gear. In the three point attitude, you've got more of
the
airpane sitting behind the gear, so more braking should be available.
Also, if you touch down in the same spot three point as opposed to
doing
a wheel landing, you should have touched down with less airspeed.
Therefore less energy to kill.
For the sake of argument, let's say that you touched down at the same
speed, though, and that you are now tail high. It would want to be
very
high indeed to contribute the same amount of aerodynamic drag as the
three point attitude. OK, your Cf is a bit better because of the extra
weight on the wheels, but since the limiting factor is nosing the
airplane over as opposed to achieving max Cf that's irrelevant.


Bertie

the wings stop an aircraft more effectively than tiny brake pucks.
thats why 3 pointing it achieves the shortest landing.
the actual landing speed is lower and the wing is generating lotsa
induced drag on the backside of the performance curve.

I dont believe that getting rid of flaps shortens the landing.

Yeah, generally I agree. Depends on the airpalne, probably, but I can't
think of anything that would stop more quickly with the flaps up.
One of the things I found alarming in at least one old private pilot
course that was out there, I think it was the Jeppeson one, was advising
the pilot to push forward on the stick in a trike in order to shorten
the landing distance. The reasining was that it put more weight on the
wheels and allowed harder braking. In my experinece, if you are braking
that hard, the nosewheel is already pretty firmly on the ground and you
have enough braking already! Pushing would only put more weight on the
nosewheel at the expense of weight on the mains...
I've seen a lot of airline pilots do this, even though the Boeing
manuals specifically state to only relax up elevator enough to allow
good enough nosewheel contact in order to allow good steering.

Bertie

"Stealth Pilot" wrote in message
...
...
the wings stop an aircraft more effectively than tiny brake pucks.
thats why 3 pointing it achieves the shortest landing.
the actual landing speed is lower and the wing is generating lotsa
induced drag on the backside of the performance curve.

I dont believe that getting rid of flaps shortens the landing.

My _experience_ has been that brakes slow you down faster than floating
along the runway waiting for a three point.

Get to the end of the runway at a reasonably slow speed, plant the mains,
use the brakes, and you will be stopped before you pass the numbers.

I am told, by someone who flew them for a living, that the shortest way to
stop a DC3 is wheel land, yoke FORWARD to put the tail up and generate
negitive lift to drive the mains down against the runway, and use lots of
brakes.

Of course, with tricycle gear, you don't have this sort of option.

--
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.

"Capt. Geoffrey Thorpe" The Sea Hawk @See My Sig.com wrote in
:

"Stealth Pilot" wrote in message
...
...
the wings stop an aircraft more effectively than tiny brake pucks.
thats why 3 pointing it achieves the shortest landing.
the actual landing speed is lower and the wing is generating lotsa
induced drag on the backside of the performance curve.

I dont believe that getting rid of flaps shortens the landing.

My _experience_ has been that brakes slow you down faster than
floating along the runway waiting for a three point.

True, but you don't float if you want to land wiht little roll. Much of
your flare would have been accomplishded before you cross the fence.

Get to the end of the runway at a reasonably slow speed, plant the
mains, use the brakes, and you will be stopped before you pass the
numbers.

I am told, by someone who flew them for a living, that the shortest
way to stop a DC3 is wheel land, yoke FORWARD to put the tail up and
generate negitive lift to drive the mains down against the runway, and
use lots of brakes.

Of course, with tricycle gear, you don't have this sort of option.

True. I've flown DC 3s for a living and the reason you wheel it on is to
avoid blanking of the stab, though.
There's ample brake available to nose it over from three point, though,
so generating negative lift to plant the mains more firmly would
accompish nothing.


Bertie

"Stealth Pilot" wrote in message
the wings stop an aircraft more effectively than tiny brake pucks.
thats why 3 pointing it achieves the shortest landing.
the actual landing speed is lower and the wing is generating lotsa
induced drag on the backside of the performance curve.

I dont believe that getting rid of flaps shortens the landing.

On Jul 10, 4:28 pm, "Capt. Geoffrey Thorpe" The Sea Hawk @See My
Sig.com wrote:
My _experience_ has been that brakes slow you down faster than floating
along the runway waiting for a three point.

Exactly. The problem, Geoff, as many don't see it, is that a
three-point rollout has the wing at a high AOA. The wing does not stop
lifting just because the wheels are on the ground so that traction is
minimal, and aerodynamic braking diminishes by the square of the
airspeed---half the speed, one-quarter of the drag. So a three-point
touchdown does not allow immediate heavy braking, and since the speed
is still high the airplane covers lots of runway before the lift has
dropped to the point that the tires have enough traction for heavy
braking. If we wait for the drag to slow us down, that's what we'll
do: wait. And use up runway.
Raising the tail gets rid of lift and places weight on the
mains. Modulating brakes and elevator slows the airplane quickly right
from the touchdown point, noseover tendency being controlled with the
elevator. Once the airplane is slowed the tail is planted and braking
increased further if necessary, though the loss of elevator
effectiveness determines just how much brake one can use.
Until one tries it he has no idea what it feels like. There was
no way I could stop the 185 in anywhere near the same distance three-
point as I was able to do with the tail-high braking. I'm not talking
the normal wheel landing here; that requires a higher airspeed to
reduce AOA so that the tail is high to start with at touchdown. That
eats up runway. I'm talking minimum speed touchdown, which will be
close to the three-point attitude, if not tailwheel-first, and then
the tail is raised after touchdown to dump the lift.

Dan