Does the elevator/stabilator generate upward force?

Ok, this is a followup to the previous discussion about forward control
pressure during the landing rollout. Can someone tell me if the
elevator/stabilator can actually generate an _upward_ force, or does it
simply generate a downward force for climbing and less downward force
for a decent?

Does the nose fall due to the CG being forward of the center of lift,
or does the elevator actually push the tail up?

We are talking about tricycle gear planes, not taildraggers... The PA28
series specifically.

--Dan

You tell me...

Next time you are doing your run up.. hold the brakes and move the control
foward and aft.. is the nose rising and falling because of action of wind
(prop wash) over the elevator position? Granted in a heavy PA28, it may not
be very noticable, but try it in a Cessna 152/172.

you are mixing apples in oranges when talking about "the nose falling due to
CG and center of lift".
IIRC the original thread was concerned with pushing the nose down to put
more weight on the nose wheel for cross wind control,
in the example you mention, it involves the nose falling forward because the
elevator/wings combination cannot generate enough "lift" in their respective
direction to keep the nose up.

Now.. lets expand on that a bit.. when performing an outside loop maneuver,
is the nose being pushed around the loop because the elevator is creating
less "lift" or because the elevator is forcing the nose around.

Why would a tricycle gear airplane behave any differently than a tail wheel
as far as elevator effectiveness. Other than possible physical limits
allowed to elevator travel.

In the only Piper POH I have avalible to be right now, On landing... ""After
ground contract hold the nose wheel off as long as possible. Braking is most
effective when back pressure is applied to the control wheel. In high wind
conditions, particularly in strong crosswinds, it may be desirable to
approach the ground at highter than normal speeds with partial or no flaps."

Funny, it says nothing about pushing forward on the stick for directional
control.

B

"Dan" wrote in message
ups.com...
Ok, this is a followup to the previous discussion about forward control
pressure during the landing rollout. Can someone tell me if the
elevator/stabilator can actually generate an _upward_ force, or does it
simply generate a downward force for climbing and less downward force
for a decent?

Does the nose fall due to the CG being forward of the center of lift,
or does the elevator actually push the tail up?

We are talking about tricycle gear planes, not taildraggers... The PA28
series specifically.

--Dan

The tail can produce forces in either direction, although in
flight forces are mostly in the down direction at the tail.

The wing lift is concentrated aft of the CG so that there is
a nose down moment when the airplane becomes stalled. This
is for static stability. The initial movement for
statically stable airplanes must be toward a unstalled angle
of attack and flying speed. This happens with the tail
moment leveraging the turning moments to a balanced dynamic
position, which will decrease at lower speeds, causing the
static pitching moment downward.

But it can produce an upward force if the airplane is aft of
the CG range, in order to balance the airplane in flight.
But if you stall, the nose will pitch up into a deeper
stalled condition.
On landing the airplane will rotate [pitch] around the main
wheel axles and even the nose wheel which is wheel
barrowing.

The magnitude all depends on the center of gravity in
relation to the CG range and the amount of travel exerted.
Normal flight is very small movements and acrobatics, and
control forces below stall speed on the ground use control
displacements for gross changes.

The issue is not tail draggers, but tail or canard, the
location of the wheels in relation to the CG [wing chord]
only has to do with finer details, like rolling.



"Dan" wrote in message
ups.com...
| Ok, this is a followup to the previous discussion about
forward control
| pressure during the landing rollout. Can someone tell me
if the
| elevator/stabilator can actually generate an _upward_
force, or does it
| simply generate a downward force for climbing and less
downward force
| for a decent?
|
| Does the nose fall due to the CG being forward of the
center of lift,
| or does the elevator actually push the tail up?
|
| We are talking about tricycle gear planes, not
taildraggers... The PA28
| series specifically.
|
| --Dan
|

Think loop: outside or inside.



"Dan" wrote in message
ups.com...
| Ok, this is a followup to the previous discussion about
forward control
| pressure during the landing rollout. Can someone tell me
if the
| elevator/stabilator can actually generate an _upward_
force, or does it
| simply generate a downward force for climbing and less
downward force
| for a decent?
|
| Does the nose fall due to the CG being forward of the
center of lift,
| or does the elevator actually push the tail up?
|
| We are talking about tricycle gear planes, not
taildraggers... The PA28
| series specifically.
|
| --Dan
|

"you are mixing apples in oranges when talking about "the
nose falling due to
| CG and center of lift".
| IIRC the original thread was concerned with pushing the
nose down to put
| more weight on the nose wheel for cross wind control,"

Increased weight on the nose wheel makes the nose wheel the
pivot point and is guaranteed to cause loss of direct
WHEELBARROWING

Page 8-32
http://www.faa.gov/library/manuals/a...lane_handbook/
chap 7-9
When a pilot permits the airplane weight to become

concentrated about the nosewheel during the takeoff or

landing roll, a condition known as wheelbarrowing will

occur. Wheelbarrowing may cause loss of directional

control during the landing roll because braking action is

ineffective, and the airplane tends to swerve or pivot on

the nosewheel, particularly in crosswind conditions.

One of the most common causes of wheelbarrowing

during the landing roll is a simultaneous touchdown

of the main and nosewheel, with excessive speed,

followed by application of forward pressure on the

elevator control. Usually, the situation can be corrected

by smoothly applying back-elevator pressure.

However, if wheelbarrowing is encountered and

runway and other conditions permit, it may be advisable

to promptly initiate a go-around. Wheelbarrowing will

not occur if the pilot achieves and maintains the correct

landing attitude, touches down at the proper speed, and

gently lowers the nosewheel while losing speed on

rollout. If the pilot decides to stay on the ground rather

than attempt a go-around or if directional control is

lost, the throttle should be closed and the pitch attitude

smoothly but firmly rotated to the proper landing

attitude. Raise the flaps to reduce lift and to increase

the load on the main wheels for better braking action.






"BT" wrote in message
...
| You tell me...
|
| Next time you are doing your run up.. hold the brakes and
move the control
| foward and aft.. is the nose rising and falling because of
action of wind
| (prop wash) over the elevator position? Granted in a heavy
PA28, it may not
| be very noticable, but try it in a Cessna 152/172.
|
| you are mixing apples in oranges when talking about "the
nose falling due to
| CG and center of lift".
| IIRC the original thread was concerned with pushing the
nose down to put
| more weight on the nose wheel for cross wind control,
| in the example you mention, it involves the nose falling
forward because the
| elevator/wings combination cannot generate enough "lift"
in their respective
| direction to keep the nose up.
|
| Now.. lets expand on that a bit.. when performing an
outside loop maneuver,
| is the nose being pushed around the loop because the
elevator is creating
| less "lift" or because the elevator is forcing the nose
around.
|
| Why would a tricycle gear airplane behave any differently
than a tail wheel
| as far as elevator effectiveness. Other than possible
physical limits
| allowed to elevator travel.
|
| In the only Piper POH I have avalible to be right now, On
landing... ""After
| ground contract hold the nose wheel off as long as
possible. Braking is most
| effective when back pressure is applied to the control
wheel. In high wind
| conditions, particularly in strong crosswinds, it may be
desirable to
| approach the ground at highter than normal speeds with
partial or no flaps."
|
| Funny, it says nothing about pushing forward on the stick
for directional
| control.
|
| B
|
| "Dan" wrote in message
|
ups.com...
| Ok, this is a followup to the previous discussion about
forward control
| pressure during the landing rollout. Can someone tell
me if the
| elevator/stabilator can actually generate an _upward_
force, or does it
| simply generate a downward force for climbing and less
downward force
| for a decent?
|
| Does the nose fall due to the CG being forward of the
center of lift,
| or does the elevator actually push the tail up?
|
| We are talking about tricycle gear planes, not
taildraggers... The PA28
| series specifically.
|
| --Dan
|
|
|

"Dan" wrote in message
ups.com...
[...]
We are talking about tricycle gear planes, not taildraggers... The PA28
series specifically.

Where the landing gear is mounted has nothing to do with the forces that the
elevator creates. Several designs are basically identical, except for the
position of the landing gear (Pacer and Tri-Pacer, for example).

And yes, the elevator can create an upward force.

I'm kind of alarmed to hear that an instructor didn't explain to you
that the elevator generates lift.

wrote in message
ps.com...
I'm kind of alarmed to hear that an instructor didn't explain to you
that the elevator generates lift.

To whom are you replying? If me, I have no idea what you're talking about.
Your reply has nothing to do with what I wrote.

If you're not replying to me, then I suggest you learn how to reply to the
message to which you intend to reply, or at a minimum learn how to *quote*
the text to which you're replying, so that people can tell what the heck
you're talking about.

Pete

Peter Duniho wrote:
wrote in message
ps.com...
I'm kind of alarmed to hear that an instructor didn't explain to you
that the elevator generates lift.

To whom are you replying? If me, I have no idea what you're talking about.
Your reply has nothing to do with what I wrote.

If you're not replying to me, then I suggest you learn how to reply to the
message to which you intend to reply, or at a minimum learn how to *quote*
the text to which you're replying, so that people can tell what the heck
you're talking about.

Pete

Not you... Dan.

wrote:
Peter Duniho wrote:
wrote in message
ps.com...
I'm kind of alarmed to hear that an instructor didn't explain to you
that the elevator generates lift.

To whom are you replying? If me, I have no idea what you're talking about.
Your reply has nothing to do with what I wrote.

If you're not replying to me, then I suggest you learn how to reply to the
message to which you intend to reply, or at a minimum learn how to *quote*
the text to which you're replying, so that people can tell what the heck
you're talking about.

Pete

Not you... Dan.

Plus I'm pretty sure my statement was pretty odvious in it's direction
to the original author... just like you said... your post had nothing
to do with it. Sorry if I've caused irrperable offense.