AD 49-52-01 ACTIVE

49-52-01 LOCKHEED: Applies to All Models 49, 149, 649, and 749 Aircraft.

Compliance required as indicated.

Numerous instances of malfunctioning of the elevator booster system have been reported, causing longitudinal hunting of the airplane and, in one instance, injury to some passengers when operation of the elevator boost shifter mechanism was accomplished. Also, in other instances, it has sometimes been impossible to actuate the shifter mechanism, probably as a result of frozen moisture accumulating on the mechanism. To minimize further difficulties of these natures, the following must be accomplished:

A. Booster Unit Rework and Lubrication.

At or prior to next engine overhaul period, rework all aileron, rudder and elevator booster control valves, as follows:

1. Drill six 1/8-inch water drain holes in the valve cap;

2. Line ream the bushing, P/N 266146-3, to 0.6270-inch/0.6285-inch diameter;

3. Replace AN 913-1 plug with AN 286-2 lubricator;

4.Pack cap assembly with AN G-25 grease, or equivalent;

5. Reidentify valve and cap assemblies by adding a -2 to each part number.

Relubricate booster control valves with AN G-25 grease or equivalent at each engine overhaul period. This lubrication interval may be increased as substantiated by service experience.

B. Rework of Elevator Shifter Latches.

At or prior to the next No. 3 inspection, all elevator shifter latches, LAC P/N 278416, shall be reworked to remove the end which hooks around the anchor pin, LAC P/N 278484. (The overcenter spring on the shifter walking beam eliminates the necessity for the locking action of these hooks.) The shifter control system shall then be checked as follows: With the shifter walking beam in "boost on" position, the control system should be rigged so that (1) when the cockpit control is in full down position, the reworked latch is in firm contact with the anchor pin but acts as a stop device only; (2) when the cockpit control releasebutton is depressed, the control springback is approximately 0.25 inch.

C. Rework of Elevator Booster Power Levers.

As soon as practicable but not later than next engine change, the feel lever bolt holes in the elevator walking beam assembly shall be chamfered in accordance with LAC SD 67471.

D. Flight Manual Revisions.

To be accomplished not later than July 15, 1949. Dependent upon the airplane model involved, ascertain that the Model 49 and Model 149 Flight Manuals incorporate approved revision dated March 4, 1949, or that revised Model 649/749 Flight Manual dated February 5, 1949, is being utilized. (The 49/149 revision and Section III, paragraph 2 of the revised 649/749 Manual outline the shifting techniques to be followed when shifting is desired.)

(Lockheed Service Bulletin 49/SB-578 dated October 25, 1949, covers item A and Lockheed Service Information Letter No. 425, dated February 28, 1949, covers item D above. Item C is covered by Lockheed telegram to alloperators dated January 18, 1949, and similar information is contained in Lockheed Service Bulletin 49/SB-502. Two E. O. 4681A describes an approved method of complying with item B. The replacement link assemblies called for in LAC Service Bulletin 49/SB-502 utilize new latch hooks, P/N 303689. Installation of these new link assemblies does not preclude the necessity of removing the hook ends of the latches, as specified in item B.)

This supersedes AD 49-22-01.