Slips and skids

On Mar 16, 8:13 pm, "Bob F." wrote:
--
Regards, BobF."Dan" wrote in message

...

On Mar 16, 6:44 pm, wrote:

I'd say that the rudder controls yaw, period.

You can change heading using the rudder. I've done it (hah, especially
a lot as a student trying to practice power on stalls), and it stands
to reason considering the force vectors acting on a fuselage that is
yawed into the relative wind. I've never tried to do what Bertie
describes though. But I will next time I'm up.

Nevertheless I follow the school that says the elevator is really the
main turn control (Langewiesche, Stowell, and many others).

Yes, but (oh those exceptions)...

Rudder comes in handy for very small changes in course (such as
required on an ILS).

You know, yaw right! Seriously, I've used this technique a lot. Works
particularly well on large airplanes. I get mixed responses from DFE's
however and check with them before I turn a student loose on him. Some
don't mind it and another ripped one of students apart because of it.

It's nearly impossible to bank 2 degrees, but very easy to correct 2
degrees with rudder.

Dan Mc

Exactly right -- it's the "wrong technique" that works perfectly.

The tiny amounts of input pose no threat to stability.


Dan Mc

On Mar 16, 6:03*pm, "Bob F." wrote:
Let's see what is it that you are experiencing. *Before flight with the
plane sitting on level ground (at least as much as you can tell). *Is the
ball centered? *As you taxi and make small heading changes, does the ball
move freely in the raceway? * In the practice area. *Slow to 60 Kts, pitch
up and add full power, maintain 60 kts. *You should immediately notice the
ball go right and you will need right rudder to center the ball. *Keep the
plane from changing heading. *Be sure to keep the wings level. *Now notice
as you enter into a left turn, you DO NOT need to step on the left rudder
(you only maintain enough left rudder pressure to keep slack out of the
cable system) until you have released all the pressure from the right
rudder, then as you increase bank further you can add left rudder. *In fact
you MIGHT not need left rudder at all. *Keep the ball centered all the time.
Is that what you are seeing?

I do understand the scenario you are describing as letting the p-
factor and torque supply the yaw movement instead of the rudder.

Now, *In a glide situation, *things should be more symmetrical. *Lower the
nose, reduce power to say 1200 rpm, maintain 60 kts. *As you bank right and
left the rudder pressures required to keep the ball centered each way should
be about the same. *Do you see this effect? *Please report if you know, or
try it the next time you go out.


The situation I experienced was this:

1) With moderate to low power in cruise, wings level, the ball
indicates skid unless right rudder is applied.
2) Turning left, idle power, level or descending, requires pretty
substantial right rudder to overcome skid. If you use any left rudder
at all, the ball is way out of center.

The airplane is a C150. I took my checkride in it, and it's behavior
also threw off the DE who was demonstrating how he liked to handle
approaches. Standard left hand pattern, each turn was a pretty wild
skid, even for him. At the time I didn't yet understand what was going
on.

Before my checkride I spent most of my hours in a C152 which behaved
as you are describing -- ie, normally -- in low power, without p-
factor & torque interfering, rudder pressure same for both turns.
However next time (if ever) I choose to fly that C150 again I'll try
out what you suggest, along with some things some others have brought
up.

On Sun, 16 Mar 2008 13:47:41 -0700 (PDT), Andrew Sarangan
wrote:

Banking rotates the airplane about its
longitudinal axis. Yawing rotates about its vertical axis. Neither of
these causes the airplane to change heading. It is the aerodynamic
forces that streamlines the airplane with the relative wind is what
makes it turn (ie weather vaning).

And here I always thought it was the lift vector being tilted to one
side of vertical that caused the airplane to turn. :-)

wrote in message
...
On Mar 16, 6:03 pm, "Bob F." wrote:
Let's see what is it that you are experiencing. Before flight with the
plane sitting on level ground (at least as much as you can tell). Is the
ball centered? As you taxi and make small heading changes, does the ball
move freely in the raceway? In the practice area. Slow to 60 Kts, pitch
up and add full power, maintain 60 kts. You should immediately notice the
ball go right and you will need right rudder to center the ball. Keep the
plane from changing heading. Be sure to keep the wings level. Now notice
as you enter into a left turn, you DO NOT need to step on the left rudder
(you only maintain enough left rudder pressure to keep slack out of the
cable system) until you have released all the pressure from the right
rudder, then as you increase bank further you can add left rudder. In fact
you MIGHT not need left rudder at all. Keep the ball centered all the
time.
Is that what you are seeing?

I do understand the scenario you are describing as letting the p-
factor and torque supply the yaw movement instead of the rudder.

Now, In a glide situation, things should be more symmetrical. Lower the
nose, reduce power to say 1200 rpm, maintain 60 kts. As you bank right and
left the rudder pressures required to keep the ball centered each way
should
be about the same. Do you see this effect? Please report if you know, or
try it the next time you go out.


The situation I experienced was this:

1) With moderate to low power in cruise, wings level, the ball
indicates skid unless right rudder is applied.
2) Turning left, idle power, level or descending, requires pretty
substantial right rudder to overcome skid. If you use any left rudder
at all, the ball is way out of center.

ok, this sounds like a little manual bend in the rudder trim tab should do
it. Most schoold don't like their renters to deal with it, however. And
unfortunately, this adjustment is good only for a particular configuration.
Piper's have a nice rudder trim to help out. This situation is not tool
unusual. I've climbed into many an airplane with rigging not precise. You
learn to recognize and deal with it.

The airplane is a C150. I took my checkride in it, and it's behavior
also threw off the DE who was demonstrating how he liked to handle
approaches. Standard left hand pattern, each turn was a pretty wild
skid, even for him. At the time I didn't yet understand what was going
on.

Before my checkride I spent most of my hours in a C152 which behaved
as you are describing -- ie, normally -- in low power, without p-
factor & torque interfering, rudder pressure same for both turns.
However next time (if ever) I choose to fly that C150 again I'll try
out what you suggest, along with some things some others have brought
up.

ok, I'm glad to hear you understand it all. This won't be the last time
you run into a airplane that's slightly out of rig. Some worse than others.
I just wanted to make sure you weren't expecting too much from the
technology these days.
--
Regards, BobF.

On Mar 16, 5:44 pm, "Bob F." wrote:

ok, I'm glad to hear you understand it all. This won't be the last time
you run into a airplane that's slightly out of rig. Some worse than others.
I just wanted to make sure you weren't expecting too much from the
technology these days.

That airplane isn't slightly out of rig. What he described
couldn't be fixed with rigging or bending a trim tab, but it's the
classic symptom of a broken rudder bar spring.
150s and 172s have two rudder bars, parallel to each other
and running across the front of the cockpit under the floor. The
rudder pedals are mounted on vertical tubes welded to those rudder
bars. The pilot's left pedal and the copilot's left pedal are on each
end of one of those bars, and both right pedals are on the other bar.
The bars are mounted in plastic bearings bolted to the aircraft
structure. Each bar has a vertical bellcrank on it near the aircraft's
centerline inside the console. The bellcranks have the rudder cables
attached to them; thos run back to the rudder control horn. The
bellcranks also each have a spring attached, and the other end of the
spring is hooked on a bracket up near the firewall. The springs keep
some tension on the cables and keep the pedals from possibly flopping
back toward the pilot.
Those springs are cheap and they break. They get a lot of
flexing, and eventually one will let go. In sockpuppet's case, the
right spring is probably broken and the left spring is pulling pretty
hard on the left rudder bar and cable so that right pedal has to be
applied to balance it and center the ball. Skidding left turns would
be expected.
It's usually the left spring that breaks more often. It gets
stretched on every takeoff and climb as the pilot applies right rudder
(left pedal pulls back against its spring) to keep straight and
coordinated.
Another thing that's appearing on old Cessnas: the nosewheel
steering rods are sprung affairs. They have a tube with a compression
spring inside that works against a washer to apply tension on the
steering rod that sticks out of it and which is connected to the
steering yoke. The washer's extension stop is a crimp around the tube.
The washer and crimp wear, the washer sneaks past the crimp, and
instead of letting the rod move against the spring in flight once the
nosewheel cam has locked it at center, it jams against the wrong side
of the crimp and stops completely any rudder deflection in that
direction. Now that's a *bad* deal. When taxiing out in one of these
old birds, beware if it has the usual springy/sloppy/ineffective
steering in one direction and rapid, rigid steering in the other.
Don't take off, for Pete's sake.


Dan

The washer's extension stop is a crimp around the tube.
The washer and crimp wear, the washer sneaks past the crimp, and
instead of letting the rod move against the spring in flight once the
nosewheel cam has locked it at center, it jams against the wrong side
of the crimp and stops completely any rudder deflection in that
direction. Now that's a *bad* deal. When taxiing out in one of these
old birds, beware if it has the usual springy/sloppy/ineffective
steering in one direction and rapid, rigid steering in the other.
Don't take off, for Pete's sake.

* * * * Dan

Wow thanks for that info. Whatever problem that plane has, I don't
think its the last one, as right rudder is effective still. But that
good to know for sure.