REVO, Inc. 

SERVICE BULLETIN B-78 R2

Page 2 of 4

IN-SITU INSPECTION 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 angles, and any contact of the fitting with the skin. (See below). Both left and 

right stabilizer halves, top and bottom, must be checked for adequate clearance and any evidence 

of cracking where the inboard stabilizer beam channel and the stabilizer fitting meet. 

1. Measure the clearance between the horizontal stabilizer skin and the fitting. If there is less than 

1/16” clearance, trim the edge of the skin to provide at least 1/16” clearance. 

2. Measure the gap between the horizontal stabilizer rear beam doubler angle and the fitting. The 

shank of a 5/32” drill bit may be used to check the gap. 

3. If the gap is at least 5/32”: 

a) Clean the top and bottom of the fitting and visually inspect the top and bottom of the 

fittings using a magnifying glass or boroscope. Pay extra attention to the front edge of the 

fitting in the area noted on the Figure on page 1 of this bulletin. Repeat this inspection 

every 50 hours until 850 hours of time is reached on the fitting. 

b) If cracks, fretting or corrosion is evident or suspected in this area, the fitting must be 

removed from the airplane (follow the removal instructions found in the APPENDIX of 

this bulletin) and inspected in accordance with the “DETAILED INSPECTION and 

REPLACEMENT” section of this bulletin. If cracks, fretting or corrosion are present, 

the fitting must be replaced with a new fitting (follow the replacement instructions in the 

“DETAILED INSPECTION and REPLACEMENT” section of this bulletin). 

4. If the gap is less than 5/32”, it will be necessary to remove the fitting in order to properly inspect 

it. Remove the fitting by following the removal instructions found in the APPENDIX of this 

bulletin and Inspect, and replace if necessary, in accordance with the “DETAILED INSPECTION 

and REPLACEMENT” section of this bulletin. At the next 50 hour inspection the inspections in 

Item 3 above may be followed. 

5. When the part reaches 850 hours time in service the part must be removed from the airplane and 

replaced with a new fitting (follow the removal and replacement instructions in the APPENDIX 

and the DETAILED INSPECTION and REPLACEMENT sections). 
REVO, Inc. 

SERVICE BULLETIN B-78 R2

Page 3 of 4

DETAILED INSPECTION and REPLACEMENT 

1. 2200-14, 1-2200-14 and 2-2200-21 fittings have a life limit of 850 hours T.I.S. If a fitting has 

over 850 hrs TIS, or total time cannot be determined, it must be replaced; proceed to step 3. 

2. With the fitting removed, inspect its forward face and edge 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-I-6866B or equivalent, is also recommended. If cracks, fretting or corrosion are 

present, the fitting must be replaced with a new 2-2200-21 fitting. 

3. New fittings may come with or without the (20) 0.191” rivet holes. This is to allow the holes 

to be drilled in the field for improved alignment and fit. 

4. Before drilling these (20) rivet holes in the field, center the new fitting midway between the 

upper and lower beam and doubler flanges, with the centerline of the 3/8” bolt holes 15/16” 

(± 1/16”) inboard of the beam end. Check to assure that the fitting location meets the 

inspection requirements of items #1 and #2 of the “IN-SITU INSPECTION PROCEEDURE” 

above. 

5. Locate the rivet holes on the fitting by marking the forward face of the fitting through several 

of the rivet holes in the stabilizer beam. Remove the fitting from the beam and mark the 

remaining rivet holes using the old fitting as a template. Check holes for minimum edge 

distance of 5/16”. 

6. Drill the (20) rivet holes with a #11 drill bit, using the old fitting as a drill template. 

7. Before installing any fitting, trim the inboard edge of the stabilizer skin if necessary to keep 

at least 1/16” clearance between the skin and the fitting. Trimmed edges should be filed 

smooth with no sharp edges. 

8. Prior to reassembly, use brush Alodine and primer on all bare metal exposed during the 

inspection and repair processes. 

9. Install the new 2-2200-21 fitting using AN470AD6 rivets. 
REVO, Inc. 

SERVICE BULLETIN B-78 R2

Page 4 of 4

 APPENDIX

REMOVAL and REINSTALLATION of HORIZONTAL TAIL HALVES: 

1. Disconnect the pushrod from the elevator horn inside the vertical tail. Allow the pushrod 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. 

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. (Existing bolts and hinges in good condition 

may be reused.) 

9. Install all seals and access covers. (Existing parts may be re-used.) 

10. Check travels and operation of elevator, trim surfaces, and rudder. 

 

MODELS> 

SURFACE 

Colonial 

C-1 

Colonial 

C-2 

Lake 

LA4, LA4A, LA4P, LA4-200 

Elevator UP 18.5° 26° ±1° 26° ±1....° 

Elevator DOWN 20°... 23° ±1° 23° ±1°.... 

Trim Tab UP -- -- 36° +2°/-1° 

Trim Tab DOWN -- -- 24° +2°/-1° 

Rudder Left & Right 25° ±1° 25° ±1° 25° ±1....° 

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