52-15-02 MARTIN: Applies to All Models 202 Airplanes With Hamilton Standard Reversing Propeller Installations.
I. Prior to reactivation of the reversing feature of the propellers:
A. Modify the following terminal strips and pin connector assemblies as specified in items 1 and 2 of Attachment A (see AD 52-13-02 Lockheed):
(1) Terminal strip at nacelle firewall junction box.
(2) Terminal strip at center wing panel.
(3) Terminal strip at fuselage Section 225.
(4) Terminal strip at nose junction box.
(5) 19 pin connector assembly at the propeller control relay box.
B. Modify Hamilton Standard propeller reversing relay box at the front of the control pedestal to shield the reversing solenoid circuit 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 beso installed that it is not possible inadvertently to interchange any connectors on the two relay boxes.
C. Rewire the feathering button circuit so that the wire from the feathering button to the fixed terminal for the auxiliary pump on the "A" relay is not energized when feathering is being accomplished and so that the hold in coil on the feathering button is inoperative during unfeathering. Isolate reversing circuit relay contacts in the propeller control relay box in a manner equivalent to the change specified in item I.B. Protect the exposed relay terminals as specified in items 3. of Attachment A.
D. Modify the reversing solenoid circuit wiring in accordance with item 4. of Attachment A.
E. Revise the reversing circuits to comply with Hamilton Standard Service Bulletin No. 236.
F. In order to prevent reversing of a normally operating propeller when unfeathering the other propeller: If the reversing solenoid circuits for the two propellers are adjacent toeach other in any connectors, at terminal strips, in wire bundles, or any other points where contact may occur between the two circuits due to a fault, isolate the two circuits from each other as specified in Attachment A and observe the maintenance practices in item II.A.
G. The "reverse operable" warning device shall be clearly visible when the lock is open just a sufficient amount to permit moving the throttles into the reverse regime. It shall not be possible for the flap to catch on its track or on the control pedestal and remain held in the up position.
H. Incorporate throttle pedestal cover plate No. 2021A19719 which has a steel track to prevent lifting the throttles before they reach the idle position.
I. If an alternate manually controllable ground circuit is installed to permit unfeathering in case of an open blade switch circuit, the alternate circuit shall be removed.
J. Increase the height of the throttle quadrant stop at the positive idle positionso that a lift of at least 1/4-inch is required to lift the pin over the stop.
II. Maintenance practices (to be instituted when reversing is reactivated):
A. At each nearest scheduled service to 350 hours:
(1) Inspect all points specified in I.A.(1) through I.A.(4) unless the modifications made to the system conform to item 1(a) or 1(b) of Attachment A.
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 faultoccurs 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.)