View Full Version : Slips and skids
William Hung[_2_]
March 15th 08, 08:38 PM
I have heard definitions for both, but I'm still confused. Anyone
care to elaborate?
Wil
WingFlaps
March 16th 08, 12:49 AM
On Mar 16, 9:38*am, William Hung > wrote:
> I have heard definitions for both, but I'm still confused. *Anyone
> care to elaborate?
>
In a skid the ball is deflected to the outside of the turn and in a
slip it's to the inside. Since you "step on the ball" with the rudder,
it foillows that a skid occurs when there is too much yaw in the
direction of turn (like a car rear end breaking away) and a slip when
there is not enough.
Hope this helps.
Cheers.
On Mar 15, 7:49*pm, WingFlaps > wrote:
> On Mar 16, 9:38*am, William Hung > wrote:
>
> > I have heard definitions for both, but I'm still confused. *Anyone
> > care to elaborate?
>
> In a skid the ball is deflected to the outside of the turn and in a
> slip it's to the inside. Since you "step on the ball" with the rudder,
> it foillows that a skid occurs when there is too much yaw in the
> direction of turn (like a car rear end breaking away) and a slip when
> there is not enough.
>
> Hope this helps.
>
> Cheers.
Heh.
Except when the control system is misrigged like a plane I flew
recently. In order to get a coordinated turn, I had to give "top"
rudder in a turn. That's wrong.
Of course the actual rudder must have been bottom, but, it was bad.
If you want a great explanation (and a GREAT) book on flying, get Rich
Stowell's "Emergency Maneuver Training". It has nice drawings
illusatrating rudder and aileron positions in both slip and skid. Plus
an explanation about why your life depends on knowing the difference
when you're in the pattern or otherwise low to the ground and at
relative high AoA.
Roger[_4_]
March 16th 08, 05:38 AM
On Sat, 15 Mar 2008 13:38:20 -0700 (PDT), William Hung
> wrote:
>I have heard definitions for both, but I'm still confused. Anyone
>care to elaborate?
To me the easiest analogy is to think of a road that has a steep
banked turn covered with ice. If you go around it too fast you will
"skid" to the outside. If you go too slow you will slip down hill to
the inside.
In the case of the airplane too much rudder to the inside will make
you fell like you are being pushed to the outside and the plane will
be skidding to the outside.
Not enough rudder and the nose will drop in the turn. so you add
rudder to raise the nose and you feel like you are pressed against the
lower side of the plane which is now slipping down hill.
>
>Wil
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
> Not enough rudder and the nose will drop in the turn. so you add
> rudder to raise the nose and you feel like you are pressed against the
> lower side of the plane which is now slipping down hill.
>
Are you sure?
I think the more bottom rudder you give in a turn, the more the nose
will appear to move lower against a given horizon. All the rudder does
is pull the plane around an axis from ear-to-ear. So if you give too
much bottom rudder, the nose will appear to drop in a turn. If you
give top rudder, you'll have the nose "rise" against the turn.
The classic case of skid is when too much bottom rudder is given, the
nose swings around the ear-to-ear axis, yawing past coordinated turn;
and if the pilot pulls back on the elevator to "raise" the nose back
up, it increases AoA, things could be getting dangerous ...
Roger[_4_]
March 16th 08, 07:28 AM
On Sat, 15 Mar 2008 22:57:41 -0700 (PDT),
wrote:
>> Not enough rudder and the nose will drop in the turn. so you add
>> rudder to raise the nose and you feel like you are pressed against the
>> lower side of the plane which is now slipping down hill.
>>
>
>Are you sure?
I phrased tht badly but it is an anology. Stick with the car on the
sliper y road<:-))
>
>I think the more bottom rudder you give in a turn, the more the nose
>will appear to move lower against a given horizon. All the rudder does
>is pull the plane around an axis from ear-to-ear. So if you give too
>much bottom rudder, the nose will appear to drop in a turn. If you
>give top rudder, you'll have the nose "rise" against the turn.
>
>The classic case of skid is when too much bottom rudder is given, the
>nose swings around the ear-to-ear axis, yawing past coordinated turn;
>and if the pilot pulls back on the elevator to "raise" the nose back
>up, it increases AoA, things could be getting dangerous ...
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
Bob F.
March 16th 08, 01:41 PM
You guys are talking about airplanes. You have to think about all the other
factors associated with engines, like "p" factor and torque, and then wing
wash in and out, offset rudder, etc. Then consider the differences in
shallow, medium and steep turns (please look up the definitions, if it's
unclear) where control forces are again difference. It is helpful to take
some glider lessons which removes some of these variables.
In an airplane, holding top rudder in a turn was probably not your
imagination. In one direction this is normal and you can experience it also
in one end of the Lazy eight exercise. I think it is also a commercial
written exam question and It will almost certainly come up on the commercial
oral. Hint: Think "P' factor, low speed, high angle of attack, high power
setting. I'll leave it to you guys to discuss this further.
--
BobF.
"Roger" > wrote in message
...
> On Sat, 15 Mar 2008 22:57:41 -0700 (PDT),
> wrote:
>
>>> Not enough rudder and the nose will drop in the turn. so you add
>>> rudder to raise the nose and you feel like you are pressed against the
>>> lower side of the plane which is now slipping down hill.
>>>
>>
>>Are you sure?
>
> I phrased tht badly but it is an anology. Stick with the car on the
> sliper y road<:-))
>
>>
>>I think the more bottom rudder you give in a turn, the more the nose
>>will appear to move lower against a given horizon. All the rudder does
>>is pull the plane around an axis from ear-to-ear. So if you give too
>>much bottom rudder, the nose will appear to drop in a turn. If you
>>give top rudder, you'll have the nose "rise" against the turn.
>>
>>The classic case of skid is when too much bottom rudder is given, the
>>nose swings around the ear-to-ear axis, yawing past coordinated turn;
>>and if the pilot pulls back on the elevator to "raise" the nose back
>>up, it increases AoA, things could be getting dangerous ...
> Roger Halstead (K8RI & ARRL life member)
> (N833R, S# CD-2 Worlds oldest Debonair)
> www.rogerhalstead.com
On Mar 15, 10:57 pm, wrote:
> I think the more bottom rudder you give in a turn, the more the nose
> will appear to move lower against a given horizon. All the rudder does
> is pull the plane around an axis from ear-to-ear.
The rudder is intended to control adverse yaw, not to turn the
airplane. Banking the airplane turns it. Some airplanes, the "idiot-
proof" ones, sometimes need no rudder at all in a turn.
Dan
On Mar 15, 9:23 pm, wrote:
> Except when the control system is misrigged like a plane I flew
> recently. In order to get a coordinated turn, I had to give "top"
> rudder in a turn. That's wrong.
Is that the one in which I suggested a broken rudder bar spring?
Anything come of that?
Dan
Andrew Sarangan
March 16th 08, 08:47 PM
On Mar 16, 3:41 pm, wrote:
> On Mar 15, 10:57 pm, wrote:
>
> > I think the more bottom rudder you give in a turn, the more the nose
> > will appear to move lower against a given horizon. All the rudder does
> > is pull the plane around an axis from ear-to-ear.
>
> The rudder is intended to control adverse yaw, not to turn the
> airplane. Banking the airplane turns it. Some airplanes, the "idiot-
> proof" ones, sometimes need no rudder at all in a turn.
>
> Dan
Actually, I beg to differ. 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).
For comparison, think of the space shuttle banking or yawing in orbit.
This does not change its heading because there is no streamlining
effect.
Bertie the Bunyip[_24_]
March 16th 08, 09:27 PM
Andrew Sarangan > wrote in news:2a91a319-e4ad-48a0-
:
> On Mar 16, 3:41 pm, wrote:
>> On Mar 15, 10:57 pm, wrote:
>>
>> > I think the more bottom rudder you give in a turn, the more the
nose
>> > will appear to move lower against a given horizon. All the rudder
does
>> > is pull the plane around an axis from ear-to-ear.
>>
>> The rudder is intended to control adverse yaw, not to turn the
>> airplane. Banking the airplane turns it. Some airplanes, the "idiot-
>> proof" ones, sometimes need no rudder at all in a turn.
>>
>> Dan
>
> Actually, I beg to differ. 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).
>
> For comparison, think of the space shuttle banking or yawing in orbit.
> This does not change its heading because there is no streamlining
> effect.
>
>
>
>
Also because there's no lift under the wings!
You can happily do a flat turn in a lot of airplanes. Wings level and
stomp on the rudder and around it will come. Some will even do it faster
with the outboard wing down a bit. I sued to do this in supercubs and
citabrias when towing so's i could enter the pattern at some insane
speed on base and then scrub it off base to final
Bertie
On Mar 16, 1:47 pm, Andrew Sarangan > wrote:
> On Mar 16, 3:41 pm, wrote:
>
> > On Mar 15, 10:57 pm, wrote:
>
> > > I think the more bottom rudder you give in a turn, the more the nose
> > > will appear to move lower against a given horizon. All the rudder does
> > > is pull the plane around an axis from ear-to-ear.
>
> > The rudder is intended to control adverse yaw, not to turn the
> > airplane. Banking the airplane turns it. Some airplanes, the "idiot-
> > proof" ones, sometimes need no rudder at all in a turn.
>
> > Dan
>
> Actually, I beg to differ. 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).
>
> For comparison, think of the space shuttle banking or yawing in orbit.
> This does not change its heading because there is no streamlining
> effect.
http://www.av8n.com/how/htm/4forces.html#note64 Section 4.3
http://www.av8n.com/how/htm/yaw.html#sec-yaw-stability Section 8.2
The bank moves the airplane sideways. The fin, moved sideways,
points the airplane in the new direction. The rudder controls adverse
yaw, which tends to drag the nose away from the turn.
Dan
On Mar 16, 5:41*pm, wrote:
>
> http://www.av8n.com/how/htm/4forces.html#note64* * *Section 4.3
>
> http://www.av8n.com/how/htm/yaw.html#sec-yaw-stability* Section 8.2
>
> * * *The bank moves the airplane sideways. The fin, moved sideways,
> points the airplane in the new direction. The rudder controls adverse
> yaw, which tends to drag the nose away from the turn.
Overcoming adverse yaw is only one of the reasons your reference gives
for using the rudder in a coordinated turn. The other is "You use the
rudder to change your heading (i.e. to overcome yaw-wise inertia, i.e.
to provide yaw-wise acceleration)" (section 8.8).
As the reference you cite explains, even apart from adverse yaw,
relying on weathervaning to realign the plane would not result in as
smooth a turn as properly coordinated use of the rudder.
William Hung[_2_]
March 16th 08, 10:16 PM
On Mar 15, 4:38*pm, William Hung > wrote:
> I have heard definitions for both, but I'm still confused. *Anyone
> care to elaborate?
>
> Wil
A lot of good inputs, I'm going to need some time...
Thanks all,
Wil
On Mar 16, 2:42*pm, wrote:
> On Mar 15, 9:23 pm, wrote:
>
> > Except when the control system is misrigged like a plane I flew
> > recently. In order to get a coordinated turn, I had to give "top"
> > rudder in a turn. That's wrong.
>
> * * Is that the one in which I suggested a broken rudder bar spring?
> Anything come of that?
>
> * * * Dan
Yeah, I think so. Another person also emailed me private and said the
same.
The chief pilot and other instructors at the FBO got an email from me.
Never heard anything back. Maybe they checked it out and decided I was
wrong; or maybe I found a problem and they don't want to comment on it
in a traceable way. I think I'll switch to their 172, rather than fly
that 150.
On the other hand maybe they have fixed it and I just don't know about
it.
> * * *The bank moves the airplane sideways. The fin, moved sideways,
> points the airplane in the new direction. The rudder controls adverse
> yaw, which tends to drag the nose away from the turn.
>
> * * * Dan- Hide quoted text -
>
> - Show quoted text -
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).
Bob F.
March 16th 08, 11:03 PM
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?
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.
--
Regards, BobF.
> wrote in message
...
On Mar 16, 2:42 pm, wrote:
> On Mar 15, 9:23 pm, wrote:
>
> > Except when the control system is misrigged like a plane I flew
> > recently. In order to get a coordinated turn, I had to give "top"
> > rudder in a turn. That's wrong.
>
> Is that the one in which I suggested a broken rudder bar spring?
> Anything come of that?
>
> Dan
Yeah, I think so. Another person also emailed me private and said the
same.
The chief pilot and other instructors at the FBO got an email from me.
Never heard anything back. Maybe they checked it out and decided I was
wrong; or maybe I found a problem and they don't want to comment on it
in a traceable way. I think I'll switch to their 172, rather than fly
that 150.
On the other hand maybe they have fixed it and I just don't know about
it.
On Mar 16, 3:44 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).
Which makes a lot of sense.
It's just that numerous authors hold the theory that if the left
vector is angled, the direction of flight is altered and the fin
points the nose in the new direction. And as I said, some airplanes
are so "well" designed (read: simple to fly) that no rudder input is
needed at all to keep the ball centered while going into the turn, or
keeping it there once established in the turn. Aileron geometry is
such that adverse yaw is completely eliminated. Elevator is still
necessary to counter the nose-drop as drag piles up, and there's no
argument from me that it contributes to the turn, especially a steep
turn.
I can just imagine that some clever engineer will soon design
an airplane that needs no elevator input in a turn. The R182
(colloquially known as the 182RG) is already a really tame airplane in
a steep turn; I don't know how they did it, but steep turns in it are
so easy, with an absolute minimum of back pressure. And that's with a
forward CG, too.
Dan
Dan[_10_]
March 17th 08, 12:06 AM
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).
It's nearly impossible to bank 2 degrees, but very easy to correct 2
degrees with rudder.
Dan Mc
Bob F.
March 17th 08, 12:13 AM
--
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
Dan[_10_]
March 17th 08, 12:16 AM
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.
Larry Dighera
March 17th 08, 12:28 AM
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. :-)
Bob F.
March 17th 08, 12:44 AM
> 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.
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