53-05-01 BOEING, CONVAIR, DOUGLAS and LOCKHEED: Applies to All Boeing 377, Convair 240 Series, Douglas DC-6 Series, and Lockheed 749 Series Airplanes With Curtiss Reversing Propellers.\n\n\tItems I through IV are to be accomplished by means of progressive modification program to be submitted to and approved by the FAA. This program shall begin no later than September 1, 1953, and shall be completed no later than March 1, 1954. (For Boeing 377 completion must be no later than July 1, 1954.) The replacement program in item III and the maintenance and inspection program in item V shall be instituted no later than April 1, 1953.\n\n\tI.\tRevise propeller slip rings, brush cap connector plug and harness to provide isolation of the reverse slip ring and brushes by relocating them between the "Common" and "Bonding" slip rings and brushes, which are both maintained at ground potential. Curtiss Information Reports have been issued to cover this subject, as follows: Convair 240 Series, Report No. 245S dated November 5, 1951; Douglas DC-6 Series, Report No. 249S dated December 4, 1951; Boeing 377, Report No. 258S dated March 21, 1953; Lockheed 749 (C634S Propeller), Report No. 250S dated April 15, 1952; Lockheed 749 (C632S Propeller), Report No. 267S dated May 14, 1952.\n\n\tII.\tA. Install Curtiss brush cap P/N 148764, which has provisions for a separate brush cap connector for the reversing lead. This change may be accomplished after or simultaneously with I, and in accordance with Curtiss Information Report No. 273-S, dated January 15, 1953.\n\n\t\tB.\tIsolate the reversing circuit from the propeller brush cap to (and including) the "I" terminal on the reverse pitch relay, in the manner described below. Where applicable, the same isolation shall be provided for the extension of the reversing circuit to the secondary reverse lock relay.\n\n\t\t\t(1)\tTerminal strips. Any one of the following methods of isolation may be used:\n\n\t\t\t\t(a)\tElimination of connections at terminal strips by using continuous wiring.\n\n\t\t\t\t(b)\tProviding separate covered terminal strip for reversing lead connections.\n\n\t\t\t\t(c)\tIsolating the reversing lead stud, terminals, and associated hardware from all nearby components in an insulating cover which is so designed or secured to the wiring that the wire will stay in place in case of breakage of the terminal; or so that the broken wire and terminal will remain insulated by the cover from contact with other circuits if the wire comes off its terminal. The nature of the cover design or provisions for its attachment must be such that its installation will not be overlooked during maintenance. \n\n\t\t\t\t(d)\tRemoving or grounding studs adjacent to the reversing lead stud and securing all adjacent wiring and the reversing lead to prevent contact of broken leads with reversing terminal or contact of broken reversing lead with other terminals. If the adjacent studs are grounded, rather than removed, the studs must be identified distinctively so that they will not inadvertently be used for the attachment of wires serving other circuits.\n\n\t\t\t(2)\tMultiple pin connector assemblies. Any one of the following methods of isolation may be used:\n\n\t\t\t\t(a)\tElimination of connectors by using continuous wiring.\n\n\t\t\t\t(b)\tProviding separate connectors for each reversing circuit.\n\n\t\t\t\t(c)\tDeactivating all pins adjacent to the one carrying the reversing circuit. These pins are to be retained in the connector but identified distinctively so that they will not be used inadvertently. When distinctively identified, these pins may also be used for circuits which cannot supply sufficient energy to drive the pitch-change motor or to release the pitch change motor brake, or for circuits which are energized only when reversing is desired. At the points where wires are attached to the connector pins, all exposed metal parts are to be protected with insulating covers so secured that contact between circuits cannot occur in case of failure of the connection or in case foreign material is left in the connector assembly.\n\n\t\t\t(3)\tExposed terminals on relays or switches.\n\n\t\t\t\t(a)\tAs specified in item B(1)(c) for terminal strips, or\n\n\t\t\t\t(b)\tIf the terminal is a type which cannot be protected as specified above, cover all exposed metal components with insulating material and secure all wires so that no wire can touch another terminal if the wire breaks or falls off its own terminal. Install insulating barriers as necessary to prevent inadvertent contact between broken or loose wires and other terminals.\n\n\t\t\t(4)\tReverse circuit wiring. Modify in one of the following ways:\n\n\t\t\t\t(a)\tPhysically isolate the reverse wire from all other circuits.\n\n\t\t\t\t(b)\tIf the wiring is run in bundles with other wires, a shielded wire is to be used. The shielding shall be grounded at both ends, and a protective cover shall be provided over the shielding. The shielding shall be carried as close as possible to all terminal points.\n\n\t\t\t(5)\tNacelle filter. If the reverse wire and, where applicable, the lead to the secondary reverse lock relay, is enclosed in conduit or shielding for its entire length from the brush cap to the "I" terminal of the reverse pitch relay, the lead may be routed so as to bypass the nacelle filter thus eliminating the need for isolating the condenser terminals. If the reverse wire is isolated in such manner that filtering is still necessary, provide an additional filter which is physically separated from the existing nacelle filter.\n\n\tIII.\tComply with AD 56-08-01.\n\n\tIV.\tAn unmodified C632S Series propellers which have both the reverse pitch circuit and the feathering circuit opened by the same limit switch when the propeller blades are at the reverse pitch position modify the propeller limit switch arrangement so that it will be possible to energize the increase pitch circuit by operating the feathering control even when the propeller is in reverse pitch. Curtiss Information Reports have been issued to cover this subject, as follows: CV-240 Series, Report No. 245S, dated November 5, 1951;DC-6 Series, Report No. 249S, dated December 4, 1951; L-749 Series, Report No. 267S, dated May 14, 1952.\n\n\tV.\tMaintenance practices.\n\n\t\tA.\tAt each nearest scheduled service to 350 hours:\n\n\t\t\t(1)\tInspect all points specified in items II.B.(1) and II.B.(3). The inspections of item II.B.(1) may be discontinued if the modifications made to the system are of the type described in items II.B.(1)(a) or II.B.(1)(b).\n\n\t\tB.\tAt any time that an electrical fault occurs in a circuit which is carried in the same bundles or the same conduits as the reverse wing, 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 for inspection. Damaged wiring will be replaced as necessary.\n\n\t\tC.\tAt each scheduled service nearest to 350 hours, perform an electrical check of the reverse safety switches in the pedestal assembly to assure that the switches open when throttles are moved forward out of the reverse position. \n\n\t\tD.\tAt any time that operations are performed which may affect the relative position of the solenoid lock and throttle switches, but in any event at intervals not to exceed 1,500 hours: Check the relationship between the position of the pedestal strikers when they are: (a) in contact with the solenoid latch; (b) at the point where the detent roller contacts the first detent cam; and (c) when the reversing microswitches are actuated. It shall not be possible for the switches to be actuated before the latch and the detent engage the striker and the cam. This determination shall be made by positive measurements rather than observation of engine r.p.m. at which these actions take place.