Cessna 150 requires left rudder during straight and level

W

wtreisinger

Guest
I noticed when flying today that I had to hold nearly constant left rudder when in straight and level flight and descents-- I had to do this to keep the nose straight and to keep the ball centered. I have only flown this plane a couple times, and I have not noticed this issue in any other plane that I've flown. Any thoughts on what this issue could be?
 
The cam that makes certain the nosewheel is locked in the straight ahead position (when fully extended, e.g, no weight) isn't catching. If the nose wheel/nosepant is turned, it's a powerful turner for which considerable rudder pressure will be required. It's in the blast of the prop!
 
.....or maybe its just your typical mis-rigged crooked trainer put together from the pieces of 2 separate wrecks back in the 70s. Check for a logbook entry: 'installed l/r wing from serial no xxxxx following Cessna maintenance manual. Replaced tailplane following drawing x.x.y with factory new parts).

A couple of months ago I rented a 172. Turns out it had electric aileron trim with the CB zip-tied in the off position. Apparently this has been the approved solution to a crooked main spar.
 
wtreisinger said:
I noticed when flying today that I had to hold nearly constant left rudder when in straight and level flight and descents-- I had to do this to keep the nose straight and to keep the ball centered. I have only flown this plane a couple times, and I have not noticed this issue in any other plane that I've flown. Any thoughts on what this issue could be?
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Did you check that someone may have straighted the manual rudder trim tab? Ask the mech to look at it.
 
Most common cause of this problem in the Cessnas is a broken rudder bar spring. You can mess all you like with trim tabs and nosewheels stuff but if the $6 spring isn't replaced it won't fix the problem.

To confirm it, pull back on each rudder pedal. If one pedal flops back easily you have a broken spring. In this case, the left one will be broken. It breaks most commonly, as right pedal needed for takeoff and climb stretches the left spring more often.

The springs are found in the forward end of the tunnel. Real fun getting at them.

Dan
 
Most common cause for this actually is that someone has bent the trim tab over to relieve right rudder pressure on take off and climb which leaves it requiring left rudder when straight and level.
 
I had a centering spring break on our 172, 2 years ago. The rudder was way out of trim and very ineffective. I knew something was wrong when I found no tension on the rudder cables. Changing the springs is not my favorite job. Just give me a Malibu to work on.

Kevin
 
Henning said:
Most common cause for this actually is that someone has bent the trim tab over to relieve right rudder pressure on take off and climb which leaves it requiring left rudder when straight and level.
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I would guess this is the answer. I learned in a 150, after about 6 lessons the CFI finally got the trim tab bent right to be able to fly hands off.
Look on the rudder and see how bent the tab is. It looks like a piece of plastic, but you can bend it.
 
The thorough rigging procedure that Cessna outlines (can't find right now) takes about 2 days. (you can see why so many folks try to fix it by bending the trim tab or 'putting in a little more washout'). I did it once. You have to do some measurements first to check for bent airframe etc, inspect all flying surfaces closely, check all the cable tensions, set everything to factory specs. and then reassemble and fly it. Then, based upon findings, you go step by step to correct things.
Too often someone will bend the tab to 'add rudder', and fix a crab - but it ends up in a constant wing low @ cruise.
 
Let'sgoflying! said:
The thorough rigging procedure that Cessna outlines (can't find right now) takes about 2 days. (you can see why so many folks try to fix it by bending the trim tab or 'putting in a little more washout'). I did it once. You have to do some measurements first to check for bent airframe etc, inspect all flying surfaces closely, check all the cable tensions, set everything to factory specs. and then reassemble and fly it. Then, based upon findings, you go step by step to correct things.
Too often someone will bend the tab to 'add rudder', and fix a crab - but it ends up in a constant wing low @ cruise.
Click to expand...


Or they'll bend the tab to overcome the assymetry caused by a broken rudder bar spring.

It shouldn't take two days to rig the rudder, but it can take a while to undo all the wrong stuff you might find. Got to figure out, by flying it, whether it's a rudder issue or wing issue. If it flies straight and level when you hold the ball centered with the rudder, it's a rudder problem. If you hold the ball centered and one wing still wants to drop, its a wing incidence problem. Resetting wings can take a long time, for sure. Did one last week. Change the eccentrics and you have to re-rig the ailerons and flaps, too, because it changes the cable lengths and tensions. Big hassle.

Sometimes a heavy wing is caused by someone having squeezed the aileron skins. If the lower skin gets shoved up a bit, the concavity can act like a trim tab and raise that aileron (which lowers the other, of course).

There's another hazard associated with 150/172 rudder/nosewheel steering systems: The steering bungee rods between the rudder bars and nosewheel steering collar have compression springs inside them, retained by a washer that's held in the tube by a crimp in the tube wall. When these things get old, or are worn from a lot of flight training, or have been jiggled a little too often by nosewheel shimmy, the washer wears against the crimp, slides past it and then jams against the backside of the crimp and jams the rod. The result is a jammed rudder. Not pretty when it's time to land.
http://www.tc.gc.ca/eng/civilaviation/certification/continuing-advisory-2007-04-424.htm

Dan
 
Henning said:
Most common cause for this actually is that someone has bent the trim tab over to relieve right rudder pressure on take off and climb which leaves it requiring left rudder when straight and level.
Click to expand...
Definitely the most common cause is a misadjusted rudder trim tab. Start there. If the rudder spring is busted, that should be obvious just the way the rudder feels on preflight.
 
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