Hello fellow 120/140 members,
Recently purchased remodeled 140 with 120 wings. The control cables for the ailerons were extremely loose and had them adjusted. The wash out on the wings was zero. I had to ride the left rudder and put in right aileron to fly straight. Now the ailerons are not loose but instead of having 1/4 a ball out the left, I have 1/2 total deflection to the right and wants to roll right. I read the wash out is a max of 1 degree. Mechanic said would probably need tweaking. I assume it needs less wash out on the right wing. Any ideas for correction or what information I need to give the mechanic? THANKs
Wing Washout
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Re: Wing Washout
Did you check the wing drag wires?
"Some people spend their entire lifetime wondering if they made a difference, the Marines don't have that problem"
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Re: Wing Washout
1. Start with the basics....
CESSNA SERVICE LETTER SLN-49
DATE: 09-26-47
SUBJECT: Instructions Wing Rigging
The dihedral and angle of incidence on the Cessna 120 and 140 wings are set up originally at the factory by the pre-determined position of the fuselage wing fittings and wing strut lengths which are set up in a jig. For informational purposes, the dihedral on the wings is 1 degree, and the angle of incidence is 1 degree in relation to the thrust line. These small angles would be difficult to measure with a protractor, and therefore, the setting up of the struts is the best and simplest way to arrive at proper wing rigging. The length of the front strut from centerline to centerline of the bolt holes is 98 13/64". The rear length measured the same way it 109 13/16".
The wing can then be set in place with the strut installed, and any additional rigging required due to wing heaviness after test flight should be rigged out by lengthening the rear strut on the light wing one rotation at a time. In doing this, there is one caution; namely, double check the length of the thread engagement in the strut adjustment. This can be done by the use of the safety hole in the fitting made for that purpose. If a wire will not go in the hole, the thread length is satisfactory.
2. As far as Aileron Cables, the POH says something like 30# tension, don't do it, that's too tight. Most of us go by feel on the tension to get good function and play without slop.
3. See attached photo of rear strut bolt attach, this bolt should not be digging into the rear spar and it's a painfully close fit. The grip of the bolt should remain in the attach arms, don't let bolt thread take the load. Let us know if it's the correct bolt, some past discussion in the Forum on making one from standard AN bolt.
4. Getting the ailerons even is by the turnbuckles and pushrods, there's a trick for wiring one of the starboard turnbuckles
CESSNA SERVICE LETTER SLN-49
DATE: 09-26-47
SUBJECT: Instructions Wing Rigging
The dihedral and angle of incidence on the Cessna 120 and 140 wings are set up originally at the factory by the pre-determined position of the fuselage wing fittings and wing strut lengths which are set up in a jig. For informational purposes, the dihedral on the wings is 1 degree, and the angle of incidence is 1 degree in relation to the thrust line. These small angles would be difficult to measure with a protractor, and therefore, the setting up of the struts is the best and simplest way to arrive at proper wing rigging. The length of the front strut from centerline to centerline of the bolt holes is 98 13/64". The rear length measured the same way it 109 13/16".
The wing can then be set in place with the strut installed, and any additional rigging required due to wing heaviness after test flight should be rigged out by lengthening the rear strut on the light wing one rotation at a time. In doing this, there is one caution; namely, double check the length of the thread engagement in the strut adjustment. This can be done by the use of the safety hole in the fitting made for that purpose. If a wire will not go in the hole, the thread length is satisfactory.
2. As far as Aileron Cables, the POH says something like 30# tension, don't do it, that's too tight. Most of us go by feel on the tension to get good function and play without slop.
3. See attached photo of rear strut bolt attach, this bolt should not be digging into the rear spar and it's a painfully close fit. The grip of the bolt should remain in the attach arms, don't let bolt thread take the load. Let us know if it's the correct bolt, some past discussion in the Forum on making one from standard AN bolt.
4. Getting the ailerons even is by the turnbuckles and pushrods, there's a trick for wiring one of the starboard turnbuckles
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Re: Wing Washout
Thanks for the outstanding technical information.