AD 83-23-05 ACTIVE

83-23-05 GENERAL DYNAMICS (Convair): Amendment 39-4773. Applies to Model 240 series and all military models eligible or to be made eligible for civil use under Type Certificate A- 793 and all such model airplanes converted to turbo propeller power, certificated in all categories, equipped with a forward right hand cabin "Main Entrance Door and Stairs - Mechanism Installation," P/N 240-3110695, regardless of whether or not the stairs have been replaced with a crew ladder.

Compliance is required as indicated unless already accomplished.

To prevent separation of the main entrance door in flight due to a malfunction of the door latching systems, accomplish the following:

A. Within the next 30 days or 100 hours time in service, whichever occurs first after the effective date of this AD, perform a visual inspection and functional test of the forward right hand cabin main entrance door primary and secondary latch mechanisms, linkages, switch plungers, and switches to insurethat these elements function properly. Accomplish this using paragraphs (1) and (2), below, and the instructions as specified in
paragraph 2, "Accomplished Instructions," of General Dynamics, Convair Division Service Bulletin 600 (240D) No. 53-6 dated May 25, 1983, or equivalent means approved by the Manager, Western Aircraft Certification Office, FAA, Northwest Mountain Region.

(1) In the primary latching mechanism, the main entrance door latch link attaching arms must be thrown up, inboard, then down and over-center on both forward and aft door hooks. Each hook will move a plunger and lever to actuate separate warning switches to indicate that the primary latching mechanism is in the closed position.

(2) In the secondary latching mechanism a forward moving linkage rod will guide separate pins through each door hook in the closed position, then up against stops in the aft and forward latch housings. This action simultaneously activates a door open warning switch to indicate that the secondary latching mechanism is in the closed position, and that the main entrance door is now securely closed and locked.

NOTE 1. Failure of the primary latching mechanism to operate as designed may be caused by numerous conditions. One condition defeating the warning light exists when the main entrance door lock indicating pin or plunger is restricted in the depressed position. This may be due to rust, corrosion, a weak or broken pin spring, grease that has aged and hardened, or an accumulation of dirt and sand in the latch housing. Refer to appropriate Convair-Liner maintenance manual for other conditions.

NOTE 2. Failure of the secondary latching mechanism to operate as designed may also be caused by numerous conditions. One condition exists when a linkage rod fails to move the pins completely through the door hooks due to a bent rod, loose adjustment nuts or actuating linkage out of adjustment. Refer to appropriate Convair-Liner maintenance manualfor other conditions.

B. Defective units of the primary and secondary main entrance door latch locking mechanism discovered during accomplishment of paragraph A, above, must be repaired or replaced prior to further flight.

C. Repeat the inspections and tests specified in paragraph A. of this AD at intervals not to exceed twelve calendar months since the last such inspection.

D. Prior to issuance of a Certificate of Airworthiness for military aircraft being converted for civil certification, the airplane must be inspected and tested in accordance with paragraph A. of this AD.

E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes unpressurized to a base in order to comply with the inspections and tests required by paragraph A. of this AD.

F. Alternative means of compliance providing an equivalent level of safety may be used when approved by the Manager, Western Aircraft Certification Office, FAA, Northwest MountainRegion, Hawthorne, California.

All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to General Dynamics, P.O. Box 80877, San Diego, California 92138, ATTN: Mr. Larry Hayes, Manager, Product Support, Convair Division. These documents also may be examined at Regional Rules Docket, Office of Regional Counsel, FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or Western Aircraft Certification Office, FAA, Northwest Mountain Region, 15000 Aviation Blvd., Hawthorne, California.

This amendment becomes effective November 28, 1983.