AD 51-24-02 ACTIVE

51-24-02 MARTIN: Applies to All Model 202 Aircraft.

Compliance required at the 3,000-hour period following the modification of the fin attachments per Martin 202 Service Bulletin No. 99 and every 3,000 hours thereafter.

To insure that the fin-to-fuselage attachments contain no structural defects, and to reduce the possibility of fretting corrosion, accomplish the following inspections and shim installations:

(1) Determine that the three fin pins (P/N 2021A11549, 2021A14243 and 2021A14244) are not worn to less than 0.292 inch in width, and are securely attached to the fin.

(2) Inspect the three fuselage receptacles (P/N 2021U27375 and 2021U27415 left and right) for the three fin pin attachments. Replace any receptacle whose slot is greater than 0.357 inch in width.

(3) Using a 4- to 6-power glass, inspect the fin forward attach plate (P/N 2021D26541), the fuselage chords (P/N 2021D25001 and 25002), and the four reinforcing straps (P/N 2021U43293, 43294 and 43295left and right) for evidence of cracks or fretting corrosion.

(4) Cracks or fretting corrosion found in item (3) should be removed with complete crack removal verified by satisfactory etch inspection. Reworked surfaces should be repfinished to a polished finish. All bolt holes should be chamfered and polished to an 0.020-inch radius. If a crack is found in a hole in any reinforcing strap, the strap must be replaced.

(5) Etch inspect the fin rear chords (P/N 2021D14234), using a 10- to 15-power glass, to detect cracks in the chords. Cracks and any surface roughness must be removed. If cracks are found in a splice hole or any splice holes have been distorted, such that the hole bushings are no longer a press fit, the holes are to be reamed oversize and oversize bushing installed. (If the hole had a crack, re-etch inspect the area to insure crack removal.) If the diameter of a hole exceeds 0.843 inch, that fin chord must be replaced.

(6) Minimum thicknesses of refinishedstructural members are:

Part
Number
Minimum Thickness (inch)
Fin attach plate
2021U43641
0.177
Fin rear chord
2021D14233 & 4
0.312
Fuselage attach plate
2021D26541
0.050
Fuselage Chord
2021D25001 & 2
0.250
Reinforcing strap
2021U43293, 4 & 5
0.187

(7) When reinstalling fin, insert shims of 1310 clear 01 vinyl sheet (or equivalent), press polished both sides, to fit between the faying service of the fin, fuselage and reinforcing straps at the fin rear spar attachment. Insert similar shims between the faying surfaces of the fuselage and fin attach plates at the fin front spar attachment.

Upon request of the operator, an FAA maintenance inspector, subject to approval of the Chief, Engineering and Manufacturing Branch, FAA Eastern Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for suchoperator.

(Martin 202 Service Bulletin No. 182 covers this same subject.)

Revised August 19, 1961.