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2-7-12.  Transmission  Chip  Detectors  Fuzz  Burn- Off
SECTION  IX.  UTILITY SYSTEMS

TM-1-1520-240-10 Army CH-47D Heilcopter (EIC:RCD) Manual
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TM  1-1520-240-10            2-8-1/(2-8-2 blank) SECTION  VIII.  ROTOR SYSTEM 2-8-1.  General. Lift is produced by a rotor system consisting of two fully articulated counter-rotating rotors. Each rotor has three fiberglass blades. The forward rotor is driven by the for- ward transmission through a rotor drive shaft. The aft rotor is driven by the aft transmission through a vertical drive shaft. The  rotor  head  consists  of  a  hub  connected  to  three pitch-varying   shafts   by   three   horizontal   hinge   pins. These pins permit blade flapping. Stops on the top and bottom of the hub limit the blade flapping motion. The aft rotor head is equipped with centrifugal droop stops which provide increased blade flapping angle for ground and flight operation. Covers may be installed on the centrifugal droop stop operating  mechanism.  The  covers  prevent  ice  accu- mulation on the mechanism and ensure proper droop stop operation following flight in icing conditions. For in- formation on use of the droop stop covers, refer to Chap- ter 8, Section IV. Mounted coaxially over the pitch-varying shafts are pitch- varying housings to which the blades are attached by vertical hinge pins. These pins permit blade leading and lagging.  Each  pitch-varying  shaft  is  connected  to  the pitch-varying housing by a laminated tie bar assembly. The high tensile strength and low torsional stiffness of the tie  bar  retains  the  blade  against  centrifugal  force  and allows blade pitch changes about the pitch axis. Blade pitch changes are accomplished by three pitch- varying  links  connected  from  the  rotating  ring  of  the swashplate to the pitch-varying housing on each rotor blade. Cyclic pitch changes are accomplished by tilting the  swashplate.  Collective  pitch  changes  are  accom- plished by vertical movement of the swashplate. Com- bined collective and cyclic pitch change result from com- bined control inputs by the pilot. A direct-action shock absorber is attached to the blade and to the pitch-varying housing. When the inboard end of the shock absorber is disconnected, the blade can be folded in either direction about the vertical hinge pin. 2-8-2.  Rotor Blades. a. Each rotor blade consists of D-shaped fiberglass spar assembly and a Nomex fairing assembly bonded to the spar. The blade chord is 32 inches. b. A titanium nose cap is bonded to the leading edge of the spar. A nickle erosion cap is bonded to the blade along the outer 54 inches of leading edge. This cap pro- tects the part of the blade most vulnerable to erosion. c. The  fairing  assembly  is  bonded  to  the  trailing edge  of  the  spar.  These  fairings  are  constructed  of  a Nomex  honeycomb  core  covered  with  fiberglass  skin. Wire mesh screens are embedded in the fiberglass skin at the tip and the trim tab. the wire mesh screens provide an electrical path to the rotor hub from the metal trim tab and tip for lightning protection. Also, to provide lightning protection, each blade has two lightning cables and two straps. The cables and straps complete the path from the wire mesh to the rotor head. d. Balance and tracking weights are installed in the tip of spar and fairing assembly. The tracking weights are removable and are used for blade track and balance. 2-8-3.  Rotor Tachometers. Two rotor tachometer (16, fig. 2-1-7 and fig. 2-1-9), one mounted   on   the   pilot   instrument   panel,   the   other mounted on the copilot instrument, indicate percent of rotor revolutions per minute (RRPM). A small needle on the tachometer indicates percent RPM from 0 to 60. The large needle indicates percent RPM from 60 to 130. The RRPM sense signal is supplied by the AC generators. generator No. 1 supplies the copilot indicator and gener- ator No. 2 supplies the pilot indicator. Power to operate the indicators is supplied by the DC essential bus through the ROTOR TACH circuit breaker on the No. 1 and No. 2 PDP.







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