(3)
No cable smaller than three thirty-seconds of an inch diameter may be used in any primary control system.
(4)
Pulleykinds and sizes must correspond to the cables with which they are used. The pulley cable combinations and strength values which must be used are speci.ed in Military Handbook MIL-HDBK-5C, Vol. 1 & Vol. 2 Metallic Ma-terials andElementsforFlightVehicleStructures,(Sept.15,1976, as amended throughDecember15,1978).Thisincorporationby reference was approvedby the Director of the Federal Register in accordance with 5 U.S.C. section 552 (a)and 1 CFR Part 51. Copies may be obtained from the Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, Pennsylvania, 19120. Copies may be inspected at the FAA, Rotorcraft Standards Sta., 4400 Blue Mound Road, Fort Worth, Texas, or at the O.ce of the Federal Register, 800 NorthCapitol Street, NW., suite 700, Washington, DC.
(5)
Pulleysmusthaveclose .ttingguardstopreventthecablesfrombeing displa-ced or fouled.
(6)
Pulleys mustlie close enough to theplanepassing through the cable toprevent the cable from rubbing against the pulley .ange.
(7)
No fairlead may cause a change in cable direction of more than 3'.
(8)
No clevis pin subject to load or motion and retained only by cotter pins may be used in the control system.
(9)
Turnbuckles attached to parts having angular motion must be installed to prevent binding throughout the range of travel.
(10)
There must be means for visual inspection at each fairlead, pulley, terminal, and turnbuckle.
(e)
Control systemjoints subject to angular motion must incorporate the following spe-cial factors with respect to the ultimate bearing strength of the softest material used as a bearing :
(1)
3.33 for push-pull systems other than ball and roller bearing systems.
(2)
2.0 for cable systems.
(f)
Forcontrol systemjoints,the manufacturer’sstatic,non-Brinellrating ofballand roller bearings must not be exceeded.]
Amdt. 27-26, E.. 4/5/90
FAR 27.687 : Spring devices
(a)
Each control system spring device whose failure could cause .utter or other unsafe characteristics must be reliable.
(b)
Compliancewithparagraph(a) ofthissectionmustbe shownby tests simulating service conditions.
FAR 27.691 : Autorotation control mechanism
Each main rotor blade pitch control mechanism must allow rapid entry into autoro-tation after power failure.
′
Elodie Roux. Septembre 2003
Subpart D : Design and Construction
FAR 27.695 : Power boost and power-operated control system
(a)
If apowerboost orpower-operated control system is used, an alternate system must be immediately available that allows continued safe .ight and landing in the event of–
(1)
Any singlefailureinthepowerportion of the system; or
(2)
The failure of all engines.
(b)
Each alternate system may be a duplicate power portion or a manually operated mechanical system.Thepowerportionincludes thepower source(such ashydraulic pumps), and such items as valves, lines, and actuators.
(c)
Thefailure of mechanicalparts(such aspiston rods andlinks), and thejamming of power cylinders, must be considered unless they are extremely improbable.
64.4 Landing Gear
FAR 27.723 : Shock absorption tests
The landing inertia load factor and the reserve energy absorption capacity of the landing gear must be substantiated by the tests prescribed in Secs. 27.725 and 27.727, respectively.These tests mustbe conducted on the complete rotorcraft or on units consis-ting of wheel, tire, and shock absorber in their proper relation.
FAR 27.725 : Limit drop test
The limit drop test must be conducted as follows :
(a)
The drop height must be–
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