Helicopter Flight Control Rigging PDF

# FLIGHT CONTROLS ## 7-1. FLIGHT CONTROLS. - Control of the helicopter is accomplished through three flight control systems: - The cyclic control system - The collective pitch control system - The tail rotor system ## 7-2. DESCRIPTION: - The cyclic control system transmits any movement of...

# FLIGHT CONTROLS ## 7-1. FLIGHT CONTROLS. - Control of the helicopter is accomplished through three flight control systems: - The cyclic control system - The collective pitch control system - The tail rotor system ## 7-2. DESCRIPTION: - The cyclic control system transmits any movement of the cyclic control stick to the main rotor hub through: - push-pull tubes - torque tubes - bellcranks - boost cylinders - swash plate - This changes main rotor attitude, to move the helicopter to either side or in a forward or rearward direction. - A synchronized elevator is linked to the cyclic control system in such a manner that the fore and aft movement of the cyclic stick controls the angle of incident of the elevator. - The collective pitch control system transmits movement of pitch control lever to the pitch change mechanism of the main rotor hub through: - push-pull tubes - torque tubes - bellcranks - By means of the collective system, the helicopter can be made to ascend or descend vertically or to hover. - The tail rotor system controls engine torque effect on the tail boom in addition to providing directional control through: - pedals - cables - pitch change mechanism - tail rotor blades. - A ventral fin is mounted on the underside of the tail boom structure to provide stability about the longi tudinal and horizontal axis of the helicopter. ## 7-3. RIGGING FLIGHT CONTROLS: - Rigging is required after installation or replacement of component parts of the control system. - Each system may be rigged independently. - However, if necessary to rig both cyclic and collective systems, it is recommended that the collective system be rigged first. ## 7-6. RIGGING - COLLECTIVE PITCH CONTROL SYSTEM WITH HYDRAULIC BOOST (Model 47G-4, figure 7-6.) ### Note: - Tolerances for all angular settings, plus or minus 1º degree (except for swashplate and blade angles which are plus or minus 1/2°) and plus or minus 0.06 inch for dimensional settings (except for collective sleeve settings 1.075 and 0.84 plus or minus 0.010). - Check low pitch blade angles before flight. ### a. Level helicopter. Check main rotor mast for vertical alignment, using a bubble protractor or square and adjusting sprag-rods and safety cables as neces sary. (Refer to section V, in the maintenance and over haul instruction handbook.) ### b. Position pitch stick in low pitch position 37.5 degrees above horizontal, adjust the low pitch stop on bracket at jackshaft, then tighten friction lock, to hold at low pitch. (See figure 7-6.) ### c. Bottom the cylinder piston and valve in the UP - direction and adjust the rod to fit (from jackshaft, to bellcrank at cylinder assembly) then shorten the rod by 1-1/2 turns, and install rod. ### d. Using the adjusting screw under collective le ver as a rigging aid, adjust screw to maintain 1.075 inch dimension, and low sleeve position. ### e. Adjust the link rod between collective lever and idler to obtain 2.97 inch dimension and their low pitch positions. ### f. With the system in low pitch position, push down on cylinder piston to bottom the valve,. adjust tube assembly to fit (between hydraulic cylinder and idler assembly) then shorten the rod by 1/2 turn. ### g. Cut safety wire and move collective pitch sleeve boot up on the mast. ### h. Hold the collective pitch lever against rigging aid screw and with a soft leaa pencil place a mark on the mast exactly at the end of the collective pitch sleeve. Make another mark on the mast 0.84 inch above first mark for high pitch position. ### i. Release friction on collective stick, move until sleeve travels to second mark on masi or 0.84 inch. ;'\djust high pitch stop on jackshaft to limit this travel. (See figure 7-6.) ### j. With collective stick at high pitch, adjust rig:. ging aid high pitch stop screw to obtain a gap of 0.20 inch between collective lever screw andsupportbelow it. With collective stick in low pitch, adjust rigging aid screws (two places) to a gap of 0.20 inch between collective lever ("A" frame) and screws.