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d-m-hague(at)comcast.net
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 Posted: Sat Oct 06, 2007 6:37 pm Post subject: ultrastar rudder authority |
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Now that I've got a few extended flights on my US I'm feeling like the
rudder just doesn't have enough authority. I can get more deflection by
pushing WAY down on the rudder pedal(s) but it's quite awkward to get even
enough rudder for a normal coordinated turn, even though the seat is in a
comfortable position relative to the pedals. Of course I'm used to my
T-Craft which had great gobs of rudder authority, or the Quicksilver whose
rudder could easily overcome the ailerons.
Has anybody played with increasing the sensitivity by raising the cable
attach points on the pedals? This would give more rudder deflection for a
given amount of pedal push, and seems it'd make the plane handle much nicer.
I'm also considering lightening up the rudder pedal return springs.
Any downsides to either change?
-Dana
--
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"I'm a lawyer." "Honest?" "No, the usual kind."
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Sat Oct 06, 2007 6:55 pm Post subject: ultrastar rudder authority |
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> Has anybody played with increasing the sensitivity by raising the cable
| Quote: | attach points on the pedals? This would give more rudder deflection for a
given amount of pedal push, and seems it'd make the plane handle much
nicer.
I'm also considering lightening up the rudder pedal return springs.
Any downsides to either change?
-Dana
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Dana:
Normal rudder control of the US should be more than enough to get the job
done.
Don't know if the builder built and rigged the system correctly, according
to the plans and construction manual.
Should be able to get full rudder deflection in each direction. If not,
maybe the mechanical advantage needs a little adjustment.
Lightening up on rudder pedal return springs will encourage rudder flutter.
Strong return springs will pretty much neutralize the force required to
operate.
I'd check to insure the rudder horn is secure and rigid when operated with a
simulated flight load on it. Possiblity it is loose or flexing, preventing
full rudder deflection. Your rudder may be flexing. Do you have any broken
ribs or braces inside the rudder?
In the air, you will never come close to fully deflecting the rudder because
of its size.
The US is an aileron airplane. Rudder is used primarily for ground
handling. You can fly the US with your feet on the deck making coordinated
turns with ailerons only. Homer did a good job designing the aileron
control geometry on the US.
john h
mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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d-m-hague(at)comcast.net
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| Posted: Sat Oct 06, 2007 7:08 pm Post subject: ultrastar rudder authority |
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At 10:54 PM 10/6/2007, John Hauck wrote:
| Quote: |
Lightening up on rudder pedal return springs will encourage rudder
flutter. Strong return springs will pretty much neutralize the force
required to operate.
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Hmmm, makes sense, I hadn't thought of the flutter aspect... should have,
considering all the posts on flutter in the archives.
| Quote: | I'd check to insure the rudder horn is secure and rigid when operated with
a simulated flight load on it. Possiblity it is loose or flexing,
preventing full rudder deflection. Your rudder may be flexing. Do you
have any broken ribs or braces inside the rudder?
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It seems to flex a bit on the ground, when I apply rudder but it's being
opposed by the tailwheel. I don't think anything is broken, though, it's
something to look at.
| Quote: | In the air, you will never come close to fully deflecting the rudder
because of its size.
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I'm sure you're right... but I'm having a hard time, on the ground, getting
enough deflection for reasonably tight turns (unless I use the brakes, of
course) without really pushing my toe *way* out, and in the air it just
seems it could be a little more sensitive.
I may just try shortening the rudder cables as much as the turnbuckles will
allow, so I don't have to push as far, if that doesn't interfere with my
ability to use the heel brakes.
-Dana
--
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"I'm a lawyer." "Honest?" "No, the usual kind."
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Sat Oct 06, 2007 7:33 pm Post subject: ultrastar rudder authority |
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> It seems to flex a bit on the ground, when I apply rudder but it's being
| Quote: | opposed by the tailwheel. I don't think anything is broken, though, it's
something to look at.
>
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You probably have more tailwheel problem than rudder problem. A standard
tea cart US tailwheel and assembly was not know to turn well. A full
swiveling break away tailwheel would do a much better job. Trying to force
the US and FS to turn with rudder and power, on the ground, is very hard on
the tailpost and lower vertical stabilizer leading edge which is an alum
tube.
john h
mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Sat Oct 06, 2007 7:41 pm Post subject: ultrastar rudder authority |
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> You probably have more tailwheel problem than rudder problem. >
Forgot to add to my previous.
You may have tail wheel springs that are too weak to turn the tailwheel.
Are you sure your tailwheel is turning when you deflect the rudder?
john h
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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d-m-hague(at)comcast.net
Guest
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| Posted: Sun Oct 07, 2007 4:53 am Post subject: ultrastar rudder authority |
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At 11:31 PM 10/6/2007, John Hauck wrote:
| Quote: | You probably have more tailwheel problem than rudder problem. A standard
tea cart US tailwheel and assembly was not know to turn well. A full
swiveling break away tailwheel would do a much better job. Trying to
force the US and FS to turn with rudder and power, on the ground, is very
hard on the tailpost and lower vertical stabilizer leading edge which is
an alum tube.
|
Yes, that (the side load on the lower fin) bothers me. A swivel tailwheel
would be nice, but I've never seen one small and light enough... have you?
| Quote: | You may have tail wheel springs that are too weak to turn the tailwheel.
Are you sure your tailwheel is turning when you deflect the rudder?
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Yes, but it's back to that same issue, I have to push the rudder pedals way
down, too far to be comfortable, to get the desired effect.
-Dana
--
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"I'm a lawyer." "Honest?" "No, the usual kind."
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Sun Oct 07, 2007 5:32 am Post subject: ultrastar rudder authority |
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A swivel tailwheel
| Quote: | would be nice, but I've never seen one small and light enough... have you?
|
Call Travis at TNK. He has a nice small full swiveling tail wheel
| Quote: | Yes, but it's back to that same issue, I have to push the rudder pedals
way down, too far to be comfortable, to get the desired effect.
-Dana
|
If you have differential braking, use the brakes to help you maneuver on the
ground.
IIRC, the rudder cables on the US connect off a tab on the rudder pedal. I
may be dreaming and wrong again.
Anyhow, would insure all the measurements for attachments for cables is
correct.
Another thing to insure is not giving under load is the tail wheel horn on
the bottom of the rudder, and the hinges that attach the rudder. The hinges
on the bottom of the rudder are under heavy load when the rudder is
deflected, especially on the ground.
john h
mkIII
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Sun Oct 07, 2007 5:43 am Post subject: ultrastar rudder authority |
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>> Yes, but it's back to that same issue, I have to push the rudder pedals
| Quote: | > way down, too far to be comfortable, to get the desired effect.
>
> -Dana
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Dana:
If the tailwheel strut is still stock in length, you can shorten it until
about 4 or 5 inches of the strut are exposed. This may give you more
tailwheel authority on the ground.
john h
mkIII
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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