Diagnosing your Wing Leveler


So you have a wing leveler in your Mooney. Also; known as Positive Control. You don’t have money to upgrade to the latest S-Tec and would like help on those long cross countries. And your mechanic suggests “Take the damn thing out”. What do you do?

Well! Here are some tips and my experience as I revived this old but reliable system….

What to expect?

First of all; here is what to expect. This is a basic wing leveler and will keep your plane level for the most part. It is not a nav hold or heading hold. So don’t expect it to do that.

If you are debating its worth; I am listing down the prices based on my experience. You get to make your own choice 🙂

What kind of system is it?
It is a vaccum driven system driven by vaccum boots in each wing and in the tail cone. So for the most part; you need to make sure that you vaccum stuff is working like it should.

Where to diagnose?

Look at the service manual and see where the boots are located (they are also called servos per Brittain). You want to make sure that they are all in good condition. If not; you will need to get them replaced. Most MSCs (Like Lasar) as well as Brittain Autpilots will carry exchange units.

The second part to look at is looking at the little vaccum lines which go from the panel to wing and the tail cone. Make sure that they are in good condition.

If all the above looks good then you want to check for leaks. You can disconnect the vaccum lines from the panel and use any thing that will create vaccum and confirm that there are no leaks.

Besides these items the Turn Co-Ordinator and the controller in the tail cone might have issues and they can be adjusted or Overhauled.

Who can help?

Brittainautopilots.com – The people at Brittain are really helpful. I talked Cecilia and was pleasantly surprised on the level of support and co-operation she provided. I got all questions answered and got a lot of help (including manuals)

Costs? (These are the estimates I got when I changed my servos. Check with a MSC or Brittain for the current price)

90-100 $ per servo (upto 4 servos might require to be changed)
TCControl unit in the tail cone can be overhauled in less than 500$ each.

Future upgrades?

There are three key upgrades that can be done to this system. You can add heading hold, nav hold and altitude hold at very reasonable prices. The big problem is the availibility; these systems are overhauledused and hard to come by. Wait of 1 – 2 yrs is not un-common. I am still on the waiting list. I will post my review when I get one of the upgrades installed.