To detect and repair cracks in the four engine mount lugs.

Applies to all Model M-18L Aircraft.

Compliance required as soon as possible but not later than next 25 hours operating time and at each 25-hour period thereafter until reinforcement of engine mount lugs is accomplished.

Inspect the four engine mounts for cracks. If cracks are evident, reweld the lugs to mate with the mount holes on the engine and weld an X-4130 0.058-inch strap 1/2 x 3-inches to the lug and the side tube member. Further inspections are not necessary after the above reinforcement of the lugs is made. (Mooney Service Bulletin No. 4 covers this same subject.) Should also include the LA model, since they use the same engine mount.

To prevent the possibility of failure of the fuel line due to vibration and relative motion.

Applies to Model M-18 Series Aircraft, Serial Numbers 1 through 82 and 201 through 236.

Compliance required not later than March 15, 1951.

There have been reported failures of the fuel line due to fuel tank vibration and relative motion between the fuel tank and the fuel shutoff valve. To preclude the possibility of recurrence of this type failure, cut the fuel line at a point approximately 4 inches from the fuel tank outlet and install a 4-inch length of 3/8-inch ID approved aromatic resistant flexible hose and hose clamps at this point. Then attach a braided strap to ensure grounding of the tank. (Mooney Service Bulletin No. 6 covers this same subject.)

To prevent possible fouling of controls and the control stick by foreign objects install canvas boot P/N 22-7 around control stick and secure to floor boards.

Applies to all Model M-18 Series Aircraft.

Compliance required by October 15, 1953. (Mooney Service Bulletin No. 11 covers this same subject.)

To prevent baggage from jamming or fouling the landing gear retraction bellcranks P/N 35-1.

Applies to all models of M-18L Mite which have not had the Landing Gear Bellcrank Cover installed.

Compliance required by February 28, 1954. The main wing spar has two rectangular holes in it. These have bellcranks installed to change the direction of the push-pull tubes for the main landing gear. These bellcranks extend into the baggage compartment and can cause interference problems with baggage.

The AD requires the installation of bellcrank covers, P/N 1028-1 with installing angles P/N 1028-2 to prevent this problem. (Mooney Service Bulletin No. 12 covers this same subject).

Applies to All M-18 Series Aircraft.

Compliance required within the next 10 flight-hours but not later than December 15, 1959.

The following inspections, repairs, and replacements shall be accomplished:

(a) Empennage

(1) Remove and disassemble empennage. Remove control surfaces and hinge brackets from fin and horizontal stabilizer. Remove bolts through stabilizer main spar attach blocks. Disassemble stabilizer and fin from empennage truss and each other.

(2) Inspect all bolted joints for the following items:

(i) Wear on bolts

(ii) Wear on bolt holes in fittings and lugs

(iii) Wear on bushing

(iv) Wear of bushing on fittings, lugs and wood. (Replace parts as necessary).

(3) Remove all fabric from stabilizer and fin. Inspect all wood and glue joints including attachment of leading edge skin to main spar for deterioration.

(4) At center section of stabilizer spar inspect glue joint between attach blocks and spar for deterioration and inspect spar and blocks for cracks. Inspect fin spar for cracks at attach bolts.

(5) Any defective wood parts shall be replaced or repaired in accordance with CAM 18 and/or manufacturer's recommendations. When the fin and stabilizer are satisfactory, reinforcement of the stabilizer main spar center section and the fin and stabilizer center hinge rib-rear spar attachment shall be accomplished in accordance with Mooney M-18 Service Letter No. 16. (Kits of reinforcement parts are available from Mooney Aircraft, Inc.)

(6) Clean all empennage drain holes, and see that they are located as specified in Mooney M-18 Service Letter 16.

(7) Inspect welds at rudder and elevator hinges and control horns and at all joints on the tail truss for inadequate welds (i.e. weld which does not fill fillet cross section area) and for cracks using either method (i) or (ii) below.

(i) Magnetic particle or X-ray inspection.

(ii) Remove paint and primer and visually inspect welds with a 10-power glass. Parts with defective welds are to be replaced or repaired. A joint may be rewelded providing the old weld is removed and the surfaces thoroughly cleaned.

(8) Remove upper tail truss attach fittings from aft fuselage bulkhead and inspect as described in item (2). Inspect bulkhead front and back for cracks in area of these fittings. Inspect glue joint between bulkhead and aft fuselage skin and longerons for deterioration or separation. Repair in accordance with Mooney M-18 Service Letter No. 17. Examine trim linkage attached to lower part of aft bulkhead for worn bolts. Replace bolts as necessary.

(9) Reassemble and install empennage making sure all bolts are tight. Block airplane solidly at tail skid and inspect for empennage play as follows:

(i) Stabilizer - Move up and down at one tip and measure at opposite tip. Total allowable play 1/2-inch up and down.

(ii) Stabilizer - Move fore and aft at one tip and measure at opposite tip. Total allowable play 3/4-inch fore and aft.

(iii) Fin - Move fore and aft at top leading edge and measure at bottom rudder trailing edge. Total allowable play 1/2-inch up and down.

(b) Aft Fuselage

(1) Inspect wood around forward fuselage tubular structure attach fittings for deterioration. Clean all drain holes. Inspect all glue joints for deterioration. See that drain holes are located as specified in Mooney M-18 Service Letter 16.

(c) Wing

(1) Remove-seat, auxiliary fuel tank and belly access panel. Inspect ribs, skin and both spars at lower center section and around fuselage fittings for wood and glue joint deterioration.

(2) Inspect all wood and glue joints in wheel well area for deterioration. Inspect both spars for cracks in area of the gear attachments.

(3) Inspect interior of wing in areas having access openings.

(4) Remove aileron and inspect hinges and control horn in accordance with part (a), item (7).

(5) Remove wing fabric locally in area of aileron hinges and at inboard corner of aileron cutout and check condition of wood and glue joints. If evidence of deterioration is found remove fabric further as necessary for complete examination of forward area of wing trailing edge. Check security of attachment of wing trailing edge in aileron area.

(6) Clean all drain holes in wing, and see that they are located as specified in Mooney M-18 Service Letter 16.

(d) Control Systems

(1) Inspect all control systems (aileron, trim, rudder, and elevator).

(i) Visually inspect all welds for cracks and inadequate welds (i.e. weld which does not completely fill fillet cross section area).

(ii) Check security of all bolted hinge and fitting attach points. (Mooney M-18 Service Letters Nos. 16 and 17 pertain to this same subject.

Amendment 39-3480 as amended by Amendment 39-4050.

Applies to Mooney M-18L S/N's 2 and up, M-18C S/N's 201 and up, M-18LA S/N's 100 through 200, M-18C55 S/N's 323 and up certificated in all categories.

Compliance required as indicated:

To prevent failure of the vertical fin spar in flight due to wood deterioration and to detect other wood and glue joint deterioration in the wood wing and wood empennage structure, accomplish the following inspections and checks or approved equivalents within the next 30 days after the effective date of this AD, unless already accomplished within the last 35 months, and thereafter at intervals not to exceed 36 months from the last inspection.:

(1) Remove all fabric from the horizontal and vertical stabilizers. Inspect all wood and glue joints including attachment of leading edge skin to main spar for deterioration.

(2) At center junction of stabilizer spar and fin inspect glue joint between attach blocks and stabilizer spar for deterioration and inspect spar and blocks for cracks. Inspect fin and spar for cracks at attachment bolts.

(3) Inspect rear bulkhead of the stabilizer for cracks and looseness in the area of the stabilizer attachments. Inspect attachment blocks for cracks or looseness at spar.

(4) Remove wing fabric locally in area of aileron hinges and at inboard corner of aileron cutout. Check condition of wood and glue joints. If evidence of deterioration is found, remove fabric further as necessary for complete examination of forward area of wing trailing edge. Check attachment of wing trailing edge in aileron area for looseness.

(5) Ensure that all drain holes in empennage and wing are clear.

(6) If any defects set forth in paragraphs (1), (2), (3), or (4) above are detected, repair in accordance with FAA Advisory Circular AC 43.13-1A or approved equivalent or replace with an identical new part or equivalent prior to further flight. Equivalent repairs, inspections, and/or parts must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

(7) A bore scope, utilizing FAA approved permanent access holes, is considered an approved equivalent means of inspecting only for the vertical and horizontal stabilizers, when satisfying the requirements of paragraphs (1), (2), and (3). The bore scope inspection shall be accomplished within the next 30 days after the effective date of this AD, unless already accomplished within the last 11 months, and thereafter at intervals not to exceed 12 months from the last inspection.

(8) Upon submission of substantiating data by an owner or operator, through an FAA maintenance inspector, the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region, may adjust the inspection time in this Airworthiness Directive.

Amendment 39-3480 was effective June 5, 1979.

This amendment 39-4050 is effective April 1, 1981.

Amendment 39-3547.

Applies to Mooney Mite models M-18L S/N's 2 and up, M-18C S/N's 201 and up, M-18LA S/N's 100 through 200, M-18C55 S/N's 323 and up, certificated in all categories.

Compliance required as indicated:

To prevent failure of structural areas due to wood deterioration and to detect other wood and glue joint deterioration in the fuselage and wood wing, accomplish the following within the next 30 days after the effective date of this AD, unless already accomplished within the last 35 months, and thereafter at intervals not to exceed 36 months from the last inspection.

(1) Remove the fabric inboard of station 12 on both wings over the main and auxiliary wing spars. Inspect spars for cracks and delaminations especially at all bolt hole locations and in the area of the landing gear attachments.

(2) If not already provided, apply a water resistant cloth or plastic adhesive such as duct tape at the wing to fuselage joint from the wing leading edge to the wing trailing edge under the metal fairing strip, to prevent entry of water at this point.

(3) Inspect all wood and glue joints in the wheel well area for cracks and wood deterioration.

(4) Remove fabric between fuselage stations 29 to 35.5. Inspect plywood joints for wood deterioration.

(5) Apply hand pressure on top of plywood turtleback in the area of fuselage station 105. If softness is detected, remove fabric and inspect for wood cracks.

(6) Inspect welds for cracks and welds which do not completely fill fillet cross section at rudder and elevator hinges and control horns with a 10-power glass.

(7) Inspect the fuel tank attachment points to the fuselage in the areas of the attachment bolts for deterioration.

(8) Inspect glue joints in the area of the battery for separation and deterioration.

(9) Clear all drain holes in fuselage.

(10) If any defects noted in paragraphs (1) through (8) above are detected, repair in accordance with FAA Advisory Circular AC 43.13-1A or approved equivalent, or replace with an identical new part or equivalent, prior to further flight. Equivalent repairs or parts must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

(11) Upon submission of substantiating data by an owner or operator through an FAA maintenance inspector, the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region, may adjust the inspection time in this Airworthiness Directive.

This amendment is effective September 3, 1979.