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April 3, 1998 

DATE ISSUED 

SUBJECT: 

REVO, INC. 

SERVICE BULLETIN B-78 

Horizontal Tail Attachment Fittings 

Airplanes Affected: All Colonial C-2, Lake LA-4 & LA-4-200 Models 

Compliance: 

Description: 

t t- + 

Within next 5 hours of flight time 

A recent incident involving failure of the attachment fitting of the lefthand horizontal stabilizer to the vertical fin has shown that a cause 

for initiation of a crack in the fitting can exist. The area in questions 

is shown below. 

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PROCEDURE: 

The fitting in the area of its attachment to the horizontal stabilizer rear beam may be 

initially inspected by raising the elevator and determining the distance between the fitting and the 

flanges of the beam doubler anglel, and any contact of the fitting with the skin. (See below). Both 

left and right stabilizer halves, top and bottom, must be checked. 

The shank of a 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 

off the 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 order to properly inspect it. This entails removal of the horizontal tail half from 

the airplane. (A guide to this procedure is in the appendix to this Bulletin.) 

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INSJ•ECTION and REPAIR: 

\Vith the fitting removed, inspect its forward face for evidence of actual contact with the 

stabilizer beam or any adjacent structure. If contact has been present, the fitting will show signs 

of fretting or possibly the start of a crack . Removal of paint (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. If cracks, 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 of the 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 of the 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 of the beam end. 

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APPENDIX 

Removal of horizontal tail halves: 

I. Disconnect the pushrod from the elevator horn inside the vertical tail. 

Allow the push rod to lower out of the way. 

2. Disconnect the trim surface torque tubes near the inboard end of the 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 of the aft beam when driving out the 

old rivet shanks.) 

7. Repeat the procedures 2 through 6 for the other stabilizer half if necessary. 

8. After installing a new or corrected fitting onto the stabilizer rear beam, reverse the 

above procedure for reinstallation of the 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 of elevator, 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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