By Don Maxwell
Published MAPA, Volume 24, Number 4 ~ April 2001


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SERVICE BULLETIN M20-202
The Eight-Second Ride
G MODEL MOONEYS


No, I’m not talking about Bull riding, but if your nose gear ain’t right, it can be just as exciting!
Mooneyville....

Saturday morning, the weather is clear and the early morning coffee crowd, on the bench in front of the terminal, is ready to critique the landings of the local flight school.

On final approach is a modified 1966 M20E owned by Gerry Graham. Today, Terry Bewley, the owner of a 1964 M20C, is at the controls. Gerry has installed a new GPS in his panel and asked Terry to fly him around as he tries to figure it all out.

Terry and Gerry have similar aircraft ownership backgrounds. Both owned Cessna 150's before they bought their Mooney’s. Both bought their Mooney’s about the same time and both installed every commercial mod they could purchase. Their Mooney’s were also the only one’s they had flown and Terry was about to make his first landing in Gerry’s.

The coffee crowd expects nothing as the mains touch. Shortly after the nose wheel makes contact, the plane veered to the left, too much correction and across the runway to the right narrowly missing a runway light, back to the left and now it’s almost sideways. Finally, under control, they make the turnoff. As they taxi by our bench headed for the hangar, there is a lot of finger pointing and conversation in the cockpit.

After they put the plane up, they came to the terminal for their ribbing. We hear from Gerry that he was aware that his steering was overly sensitive, but he understood that “Mooney’s were like that ”and his was normal.
I assured Gerry that it was not normal and that his plane should track straight with little effort during landing.

 SB M20-202
In July of 1977 Mooney issued this service bulletin that could affect every Mooney built prior to 7-6-77. A note to the SB stated that all aircraft manufactured after 7/6/77 have been checked prior to licensing. “The purpose of this bulletins to provide instructions for checking the location of the nose wheel and instructions for adjustment of the nose gear assembly, if necessary, to locate the nose wheel in the position to obtain optimum tracking and nose gear steering during the high speed ground operations or take-offs and landings. It is recommended that this check and modification, if required, be accomplished if control difficulties have been encountered during these operations.

 SB Instructions
To check for proper tracking, place jacks under the wing. With the nose wheel on the ground, place a level, on the seam above the access door to the tail cone

Jack the aircraft up until the bubble is centered. You will notice that the main wheels are several inches above the floor and the horizontal stabilizer is nearly shoulder high.

This is a good time to stand back and look at the attitude of your plane in a level attitude. This particular plane is an early “F” model that shared the “Twist wing” with it’s big brother the Mustang.

Now you know why it’s so important to use the proper airspeed and attitude while landing to avoid porpoising and prop strikes.  With the aircraft in this level attitude, a plumb bob, is placed over the front of the nose gear trunnion. The plumb bob should fall in the center of the axle. If the line falls behind the axle, you need to add the spacer provided in the kit, and be prepared for a pleasant experience on your next landing.

If the line falls in front of the axle, you have probably been experiencing some shimmy, and the shock disc need replacement.

Visual Checks
This nose gear problem is very common ,but apparently the word is not out. First of all, if your plane does not track straight on landing; if it darts, usually to the left, it’s not right. Another check is to measure the distance between the hangar floor and the tip of the prop in a vertical position.

This distance should be between 9-1/2 & 10". Less than 9-1/2 and you probably need shock disc. More than 10" and you need the SB kit.
Another check I use is to pull the plane in the hangar and see if the rudder and nose gear are aligned.

A few months ago, a Doctor in Louisiana called and complained that the G model he had recently purchased was a dream to fly, but a bear to land. We checked the alignment per the SB and installed the spacer. Previous owners had tried to compensate for the swerve to the left by adjusting the nose gear to the right. MAN, what a ride!

This past month, I had a 65 “E” model in for a new tach. As I pulled it in the shop, I checked the track. Nose gear was several degrees to the left and the rudder was 3 degrees right. I asked how long he had owned the plane and if he noticed any problem with the steering on landing. Said he had owned it for 30 years, then he and his wife laughed and said they were always exciting. Again the phrase, “I thought Mooney’s were like that.” We rigged the nose gear and rudder, along with the ailerons and flaps. His wife E-mailed me when they got home and said that for the first time since she had been flying with him, 11 years, that the plane would fly hands off, and that darn crosswind on landing had disappeared.

 Gear Doors
After you and your favorite mechanic get your Mooney to track right, be sure and check to see that your gear doors close properly. Complying with the service bulletin will not affect gear rigging or preload, but it can affect the travel of the nose gear up into the nose well. If you add the spacer, then your nose wheel will travel a little farther up into the gear well.

I see a lot of nose gear doors that do not close properly. The adjustment is a little intimidating if you or your mechanic have never adjusted one, and it will affect the preload on the nose gear. There are 4 eccentrics on the gear operating rods that rotate to adjust the height of the gear in the nose well. Most of the problems are with the wheel not going up high enough, and allowing the gear door to rub the wheel. Not knowing how to adjust the travel, most owners or mechanics run lower nose tire pressure, or in some instances, actually grind the bottom edge of the gear door for clearance. The correct adjustment will allow your nose wheel doors to close completely and, who knows, you might gain a few knots. It’s all in the service manual.

 Service manual
Two things you must have if you own a Mooney.
1. A parts book for your model.
2. A service manual for your model.

Both are available, for all models, from Mooney, or any of your Mooney service centers. If you or your mechanic do not have a service manual, then your plane cannot be serviced properly.

Next Article
Now that we know how to make our Mooney’s behave on the ground, we’ll discuss how to make them fly straight thru the air. And yes they will fly hands off without the PC.

 TIP
Gas caps too tight? Do you need a screwdriver to pry the center latch up?
Next time you check your oil, lift the latch on the fuel caps , take your dipstick and let a few drops of oil drip on the center shaft. Works great.