AD 52-16-01 ACTIVE

52-16-01 MARTIN: Applies to All Model 202A Airplanes.

Item I is to be accomplished by means of a progressive modification program to be submitted to and approved by the FAA. The program shall begin no later than August 10, 1952, and shall be completed no later than May 1, 1953.

I. In order to prevent inadvertent actuation of the propeller reversing solenoid valves, Protect the reversing solenoid circuits from all other electrical circuits and protect the reversing solenoid circuits from each other. This is to be accomplished in accordance with Attachment A (see AD 52-13-02 Lockheed) and the following instructions which pertain to specific features to be considered in isolation of the circuits. Other features which are not specifically referred to in this list shall be treated in an equivalent manner.

A. Comply with TWA Engineering Orders 5686, 5776, and 5887.

B. Modify the 19 pin connector at the propeller control relay box as specified in item 2 of attachment A.

C. Modify the Hamilton Standard relay box on the front of the control pedestal to shield the reversing solenoid relay contacts, etc., from all other circuits which are energized at any time except when reversing is desired. Reversing relay boxes which have separate pin connectors for the reversing solenoid wire and the remaining circuits, shall be so installed that it will not be possible inadvertently to interchange any connectors between the relay boxes.

D. Modify the configuration of the propeller control relay box in a manner equivalent specified in item I.C.

E. Modify reversing solenoid circuit wiring in accordance with item 4 of attachment A.

II. The following maintenance practices are to be instituted not later than August 10, 1952.

A. At each nearest scheduled service to 350 hours:

(1) Inspect all points covered by TWA Engineering Orders 5686 and 5776.

(2) Perform an electrical check of the reverse safety switches in the pedestal assembly to assure that the switch is open when the throttles are moved forward out of the reverse position, unless it is shown that failure of any of the reverse safety switches to open will be clearly apparent to the flight crew by reason of improper operation of the propeller control system. Because of the many technical considerations involved, analyses showing that the objective of this revision has been accomplished should be referred to the FAA for engineering evaluation and approval.

B. At any time that an electrical fault occurs in a circuit which is carried in the same bundles or the same conduits as the reversing solenoid circuit, representative terminal points in the faulty circuit are to be inspected to determine whether any damage may have occurred within the bundles or conduit. If there is evidence of possible damage, all the wiring involved is to be removed and inspected. Damaged wiring is to be replaced as necessary.

III. Operating instructions: Comply with item 5 of attachment A.

IV. (Note: Propeller governor design changes which are under development and whose purpose is to provide a high pressure hydraulic circuit bypass to safeguard against inadvertent reversing and to provide ability to feather even when the reversing solenoid is energized, are still under consideration and may be the subject of a future directive.)