Don Maxwell

 

By Don Maxwell
MAPA LOG, Mooney Airplane Pilots Association


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Brake Maintenance
 

 

 We've received a request for a “HOW TO” on replacing brake linings. Although not an approved task for owners under the preventive maintenance provision of Part 43, the task is fairly simple but will require a sign off  by an A&P.  

Tools

1.    Flat blade screwdriver
2.    Diagonal side cutters
3.    1/4" combination wrench
4.    7/16" combo wrench or socket and ratchet.
5.    Pin punch and small shop hammer
6.    Brake lining rivet tool
7.    Brake Linings
8.    Rivets
9.    5606 Brake fluid
10.  8 oz pistol grip oil can
11.  1/4" clear vinyl tubing
12.  Coffee can
13.  “C” clamp
14.  5/32 Cleco and pliers
15.  Work bench and vise
16.  .032 safety wire and pliers
 

Lining Type

Before 1967, our Mooney’s used Cleveland brake assembly part # 30-5. This assembly used a three hole lining current part # 066-11100.
(Fig. 1)

After 1967 and for a few of the 1966 Executive models, Mooney switched to the Cleveland assembly # 30-56. This assembly used a two hole lining current part # 066-10500. (Fig 2)  Both assemblies use rivets part # 105-00200.

Removal

It is not necessary to jack up the aircraft or remove a wheel to replace the linings. Fig 3.For the removal process refer to fig 8 and fig 9.

1.    First I remove the safety wire, if installed, on the two 1/4" bolts(1) that attach the brake cylinder (5) to the back plate(15).


2.    Next I place the blade of a screwdriver between the pressure plate (12) and the brake disc. Fig 4  Prying the pressure plate towards the brake cylinder will move the piston inward and allow clearance for the installation of the new linings.


3.    Remove the two bolts (1) and remove the pressure plate (15).


4.    The brake cylinder can now be removed from the torque plate(18)by sliding outward.


5.    Remove the pressure plate by sliding it off of the anchor bolts (17).


6.    Place “C” clamp over piston and brake cylinder to keep piston from coming out of cylinder.


7.   Take the pressure plate and back plate to your work bench. Using the punch and hammer, remove the rivets holding the old linings. You can also use a drill but with caution. Too large a bit and the hole in the plates can be drilled oversize and cause replacement of the plates.  These items are very expensive. 


8.   Clean oil and residue from plates.


9.   Place the rivet tool in a vise. I prefer to use the screw type tool.   Using the hammer type tool can damage the three hole 066-11100 lining which is very thin.


10. I use a 5/32 Cleco to secure the lining to the pressure plate. Insert a rivet and squeeze. Fig. 5Remove the Cleco and install the remaining rivets in both plates. Fig. 6


11.  Returning to the plane, inspect the anchor  bolts(17) for rust, wear and nicks. Polish with fine emery or scotch Brite pad. Check bore of torque plate(18) and clean as necessary. The anchor bolts must slide freely in the torque plate.


12.   Remove “C” clamp and install pressure plate over anchor bolts.


13.   Install brake cylinder by inserting anchor bolts into torque plate.


14.   Install back plate on brake cylinder using the two 1/4" bolts and torque to 90 inch pounds. Check to see that the assembly is loose and floating in the torque plate. Safety wire bolts together using .032 safety wire.


15.   Install a length of clear vinyl tubing to the vent on the hydraulic reservoir and the other end in the small coffee can. Fig7


16.   Fill the oil can with 5606 aircraft brake fluid. Automotive fluid will NOT work. Attach a small length of the clear vinyl tubing to the oil can by sliding it over the stem. Fig 8 Pump the can until the tubing is full of fluid with no bubbles.


17.  At the bottom of the brake cylinder is a bleeder valve(7). Loosen the bleeder with the 1/4" wrench one full turn. Attach the loose end of the oil can tubing over the bleeder valve. Pump about one half the contents of the oil can thru the brake system being careful not to allow bubbles to enter the clear tubing. Remove the tubing and tighten the bleeder  valve.


18.  Repeat procedure for opposite side and remove tubing from brake reservoir.


19.   Check reservoir for proper fluid level and adjust as necessary.


20.   Check brake operation before starting engine. There may be a low brake pedal on the first application.

 
Gear Doors

Later models aircraft with inner gear doors will require the loosening of the inner gear doors but not removal. Some model have a single bolt at the center axle and a brace at the forward gear leg. Others have two bolts at the axle center that are safety wired together. Removing these center bolts will allow the gear door to move away from the brake cylinder. Be aware that each of these bolts have washers as spacers between the axle and gear door. These must be replaced as installed to provide clearance between the gear door and the tire.

Dual Puck Brakes

Dual puck brakes are installed or are optional on the “K” model and up to the current models. These brakes are constructed like two of the single puck units molded as one unit. They use the same 066-105 lining just twice as many per side. Relining is done in the same manner as the single puck units.