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Old 06-30-2013, 09:09 PM
NASA515 NASA515 is offline
Join Date: Nov 2011
Location: Hansville, Washington
Posts: 536

My airplane always pulls to the left during taxi -and needs either right brake tap or a fairly consistent right brake application to keep it on the center line. Other RV-12 pilots in my group have reported something similar.

I have attributed it to P-factor. I need about 2200 rpm to taxi level, and - some of KPWT taxiways climb uphill quite a bit - needing 2500-2600 pm - and figured that was the way it is.

We checked the nose wheel fork pull pressure values, and have also played with the nose tire pressures, but other than that have done nothing about toe-in or toe-out or any of the rest of this stuff.

Bob Bogash
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Old 06-30-2013, 09:57 PM
lllewis45 lllewis45 is offline
Join Date: Jun 2012
Location: Erie, CO
Posts: 45
Default Pulling to the left

With these very light aircraft, when flying solo, the extra weight on the left main gear will cause more tire friction and a tendency to turn left.
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Old 07-01-2013, 05:39 AM
BigJohn BigJohn is offline
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,587
Default A few thoughts....

Have you checked both main gear bearings - set to Matco specs? Could be uneven rolling friction. How tight is your nose wheel as far as castoring goes? If set per the plans it may be way too tight - mine was. Is your nose wheel perfectly aligned in the vertical plane?

There are a couple of theories stated above that I don't think could cause your problem. Weight of pilot on one side is balanced out by fuel on the other. Both close to center line - unlikely to cause a noticeable difference. P-factor would only come into play with nose high attitude - seems unlikely you are taxiing around at a high enough speed to get the nose up.

Here is something you could try, to isolate the left turning tendency to either the mains or the nose gear. Loosen the castoring nut way up so there is no friction and the nose wheel swivels freely. The try pushing the airplane ahead on a level surface and see if it tends to go one way or another.
John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
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Old 07-01-2013, 09:57 AM
NASA515 NASA515 is offline
Join Date: Nov 2011
Location: Hansville, Washington
Posts: 536

We checked the fork pull at about 15-16 lbs on Friday, John - less than the spec - but haven't operated since (I'm involved in a major maintenance episode, that I think will have evolved into an early Annual.)

I set the main wheel bearings VERY carefully (actually RESET them very carefully), but will give them another look.

Actually, the turning while taxiing is not a big issue for me - my Number One Issue currently is wandering during take-off due to the free-castering nose wheel, the P-factor, and maybe poor pilot technique. I've been playing with the fork pull, tire pressures, checked the rudder cables, and worked on the technique - been getting LOTS of advice from fellow pilots.

Hope to resume flying by mid-week.

Bob Bogash
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Old 07-01-2013, 10:00 PM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,729

The first few times I took off I made the mistake of not applying enough back pressure on the stick and encountered some wheel-barrowing and tendency to wander in a squirrelly (engineering term?) fashion. Since improving my technique there have been no problems.
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Old 07-02-2013, 10:23 AM
Steve Steve is offline
Join Date: Jan 2005
Location: Roy, Utah
Posts: 1,127

The taxiways are crowned for water drainage at my airport. Unless my nosewheel is rolling on the painted centerline, the plane is heading downhill.
Five Sierra Fox
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Old 07-03-2013, 07:37 AM
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f1rocket f1rocket is offline
Join Date: Jan 2005
Location: Martinsville, IN
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I just mounted my gear legs and wheels/tires this week. I found one axle to be straight but the other had some toe out so I ordered some shims from Van's. I would spend some time to get this right based upon my experience with other RVs/Rockets. I believe it has significant impact on the taxiing and landing qualities. It should be set as straight as you can get it.

Yes, there are many things that can affect the handling qualities and cause the airplane to steer one way or the other. However, you have to get the toe set to neutral first or you'll never solve it. I flew for a year with an ill-handling airplane before I took the time to get it fixed. The difference was amazing. It was a totally different airplane after that.
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Old 12-15-2018, 02:30 PM
Tacco Tacco is offline
Join Date: Jan 2017
Location: White Salmon, WA
Posts: 151

Same left pulling problem here. Put in .5 degree shim to correct a left toe-out condition, alignment is now dead nuts on. Tire pressures are identical. Even measured break away torque of wheels - 8 in lbs on both sides. My conclusion is that the cause is having a 180 pound person in the left seat. Doesn’t help there was only 50 lbs of fuel on the right side. A quick back-of-the-envelope calculation says the left wheel sees approximately 35 lbs more weight than the right under this loading. Tomorrow we’ll taxi from the other side and let you know.

Last edited by Tacco : 12-16-2018 at 02:13 PM.
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Old 12-15-2018, 06:50 PM
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Piper J3 Piper J3 is offline
Join Date: Nov 2014
Location: Hinckley, Ohio
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Originally Posted by Tacco View Post
Even measured break away torque of wheels - 8 in lbs on both sides.
I don't understand break away torque of wheels... Are you talking about main wheels? The mains should spin pretty freely indicating no bearing preload drag or excessive brake pad drag.
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Old 12-15-2018, 07:47 PM
DHeal DHeal is offline
Join Date: Sep 2006
Location: Windsor, California
Posts: 895

If you have the standard MATCO main wheels on your RV-12 they should not spin freely. MATCO specifies a certain bearing pre-load and drag for their wheel bearing assemblies. This is all explained in the MATCO on-line service literature. Note that the MATCO nose wheel uses a different kind of bearing and has a different torquing procedure.

See MATCO literature at:
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Last edited by DHeal : 12-15-2018 at 07:53 PM.
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