57-11-01 CURTISS-WRIGHT: Applies to all C-46 Series aircraft.
Compliance required as indicated.
Numerous instances have been found where unapproved nonconformity Elevator Spring Tab Cartridge Assemblies, Curtiss-Wright P/N 20-530-5710, or portions of this assembly, have been installed on C-46 aircraft. Use of these unapproved assemblies or parts of assemblies can prove to be hazardous.
Accordingly, an inspection should be made of these assemblies for conformity to approved data. This inspection should be accomplished not later than August 31, 1957.
It will be necessary to remove and disassemble the unit to make the inspection. Listed below are the drawing numbers of the assembly and its component parts, with a brief discussion of each. Copies of these drawings are available upon payment of reproduction costs from the Chief, Aircraft Engineering Division, Civil Aeronautics Administration, P.O. Box 1689, Fort Worth 1, Texas. It is not necessary to obtain these drawings for the required inspection but in cases of doubt they are available.
20-530-5710 - Cartridge Assembly Elevator Spring Tab.
20-530-5716 - Barrel - Elevator Spring Tab Cartridge Material - 8630 Normalized Seamless Steel Tubing I.D. - 1.125 (+ .001, -.000) lapped or honed, unplated. O.D. 1.312 threaded both ends 1 5/16 - 18NEF-3. Between threaded ends part may be machined to 1.242 diameter or stock size, machined to clean up. Outside cad-plated.
20-530-5712 - Cap - Elevator Spring Tab Cartridge Material - 1.500 hex. 23ST.
20-530-5711 - Cap - Elevator Spring Tab Cartridge Material - 17ST forging (Curtiss- Wright). These caps are also approved to be machined from 24ST bar stock. It has also been noted that these caps have been made from cast aluminum which is unapproved. These unapproved parts can be identified by their rough appearance and will show a tensile strength of approximately 32,000 p.s.i. under a hardness test and should be destroyed.
20-530-5717 -Spring - Elevator Spring Tab Cartridge. This is a single spring (Curtiss- Wright). Material - 0.124 diameter, music wire (cad-plated). Tensile strength 260,000 p.s.i. O.D. 1.004 + .03 free length 4.09 + .08 inch. Spring rate 40 + 2.4 pounds per inch.
There is also a satisfactory dual spring installation. Outer Spring - Same dimensions and material as Curtiss-Wright Spring except it has more coils and a spring rate of 35+2.4 pounds per inch. Inner Spring - .675 O.D. .076 diameter music wire. Free length 3.56+ .08 inch. Spring rate 10.6 pounds per inch. Both inner and outer spring are cad-plated.
20-530-5743 - Shaft Assembly Elevator Spring Tab Cartridge. This assembly is made up of the following parts:
20-530-5714 - Shaft - Elevator Spring Tab Cartridge. Stock material 0.625 diameter x 5.20 8630 steel. Tensile strength 65,000 p.s.i.
For use with the single spring the shaft is ground and polished to .3101 (+ .0000, - .0005) diameter except for a .600 diameter collar,0.150 wide, 2.863 inches from one end. The shaft has 5/16 - 24NF-3 threads .750 long at each end. With the exception of the threads the shaft is hard chrome plated with a finish diameter of .3110 (+ .0009, -.0000). For use with the dual spring the 2.863 dimension is 2.782, the 0.150 dimension is .312 and the .600 dimension is .500, all other dimensions and finishes are the same.
20-530-5713 - Clevis - Elevator Spring Tab Cartridge. Material 24ST. The lugs have a thickness of .100 (+ .000, - .010). The threaded portion is .500 O.D. This part is pinned to the 20- 530-5714 shaft with a .125 or a .093 dia. x .75 in. 1020-1025 steel pin peened on both ends.
20-530-5715 - Plunger - Elevator Spring Tab Cartridge. Material S. B. 1100 x .870 manufactured by Chrysler Corp. Amplex Div. This material is known as Super-Oilite and is made of powdered iron and copper and has the appearance of iron. In no case should steel or any other solid material be used.
For use with the single spring the plunger has a single taper while for use with the double spring an additional shoulder is machined on the taper for the center spring.
The inspection should primarily cover the material, dimensions, and the required finishes listed. Care should be taken to inspect for rust, corrosion, or interference which may affect the operation of the cartridge. The springs should also be checked dimensionally and for proper spring rate. All assemblies or portions of assemblies which do not conform should be removed. Only approved parts obtained from a reputable source, with evidence of approval should be installed.