# 2 April 3, 1998 DATE ISSUED



### SUBJECT: 

### REVO, INC. 

## SERVICE BULLETIN B-78

Horizontal Tail AttachmentFittings Airplanes Affected: All Colonial C-2, Lake LA-4 & 

### LA-4-200 Models Compliance: Description:



## t 

# t- 

# + Within next 5 hours offlight time A recent incident involving failure ofthe attachment fitting ofthe lefthand horizontal stabilizerto the vertical fin has shown that a cause for initiation ofa crack in thefitting can exist. The area in questions 

### is shown below
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### PROCEDURE: The fitting in the area ofits attachment to the horizontal stabilizer rear beam may be initially inspected by raising theelevatorand determining the distance between the fitting and the flanges ofthe beam doubler anglel, and any contact ofthe fitting with the skin. (See below). Both left and right stabilizer halves, top and bottom, must be checked.

The shankofa 5/32 drill bit may be used to check the gap. 1. If

### the gap is at least 5/32", and the stabilizer skin is 

### not contacting the fitting, no further action is necessary. 2. If

### the gap is at least 5/32", but the skin has less than 1/16" clearance, simply trim offthe skin edge to provide at least 1/16" clearance. 3. If

### the gap is less than 5/32", at any fitting, it will be necessary to remove the fitting in orderto properly inspect it. This entails removal ofthe horizontal tail halffrom the airplane. (A 

### guide to this procedure is in the appendix to this Bulletin.)

2 

### of 4INSJ•ECTION and REPAIR: \Vith the fitting removed, inspect its forward face for evidence ofactual contact with the stabilizer beam or any adjacent structure. Ifcontact has been present, the fitting will show signs offretting or possibly the start ofa crack
. Removal ofpaint (by light sanding) will be necessary for this inspection. Inspect the area with a magnifying glass. Dye checking, per MIL-1-68668 or equi\alent, is also recommended. Ifcracks, fretting, or corrosion are present, the fitting must be replaced with a new 2-2200-21 fitting. Before installing any new fitting, trim the end ofthe stabilizer beam doubler flange and bend radius area to provide positive clearance for the fitting. Also, use brush Alodine and primer on all areas where metal has been removed befoa·e re-assembly and re-installation ofthe horizontal tail. Check these before riveting the fitting in place. When installing a new fitting, center the fitting midway between the upper and lower beam and doubler flanges, with the 3/8" bolt hole 15116" (+- 1/16") inboard ofthe beam end.



### 3 of 4APPENDIX

Removal ofhorizontal tail halves:
I. Disconnect the pushrod from the elevator horn inside the vertical tail. Allow the pushrod to lower out ofthe way. 2. Disconnect the trim surface torque tubes near the inboard end ofthe horizontal tail. 3. Unbolt the elevator from the elevator horn welded assembly. 4. Remove the elevator from the stabilizer by pulling the hinge pin. 5. With the horizontal tail supported, remove the AN4 bolt from the forward beam attach point, and remove the two AN6 bolts from the rear beam attach fitting. 6. Remove the fitting from the stabilizer by carefully drilling out the AN470AD6 rivets. (Provide adequate support to the forward side ofthe aft beam when driving out the old rivet shanks.) 7. Repeat the procedures 2 through 6 for the other stabilizer halfifnecessary. 8. After installing a new or corrected fitting onto the stabilizer rear beam, reverse the above procedure for reinstallation ofthe horizontal tail. (Exisiting bolts and hinges may be re-used.) 

### 9. Install all seals and access covers. (Exisiting parts may be re-used.) 10. Check travels and operation ofelevator, trim surfaces, and rudder. Elevator: up 16 +-1 down 23 +-1 Trim Surfaces: up 36 deg. +2 deg. -1 deg. down 24 deg. +2 deg. -1 deg. Rudder: left 25 deg. +-I deg. right 25 deg. +-I deg.

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