Helicopter Flight Control Assembly and Rigging Guide

Proper assembly and rigging are essential to safe helicopter operation. Rigging ensures that pilot control inputs are accurately transmitted to the main and tail rotor systems, allowing the helicopter to respond correctly throughout its operating range. Precise adjustment and inspection of all control components are necessary to maintain flight safety and performance.

The flight control units located in the flight deck of most helicopters are generally similar. All helicopters have either one or two of each of the following: collective pitch control, throttle grip, cyclic pitch control, and directional control pedals. [Figure 1]

Figure 1. Controls of a helicopter and the principal function of each

These control units perform the same basic functions regardless of helicopter type; however, the operation of the control system varies considerably by helicopter model.

Rigging the helicopter coordinates the movements of the flight controls and establishes the relationship between the main rotor and its controls, and between the tail rotor and its controls. Although rigging procedures are straightforward, they require great precision and attention to detail. Strict adherence to rigging procedures described in the manufacturer’s maintenance manuals and service instructions is a must. Adjustments, clearances, and tolerances must be exact.

Rigging of the various flight control systems can be broken down into the following three major steps:

1. Placing the control system in a specific position—holding it in position with pins, clamps, or jigs, and then adjusting the various linkages to fit the immobilized control component.
2. Placing the control surfaces in a specific reference position—using a rigging jig, a precision bubble protractor, or a spirit level to check the angular difference between the control surface and some fixed surface on the aircraft. [Figure 2]
3. Setting the maximum range of travel of the various components—this adjustment limits the physical movement of the control system.

Figure 2. A typical rigging protractor

After completion of the static rigging, a functional check of the flight control system must be accomplished. The nature of the functional check varies with the type of helicopter and system concerned, but usually includes determining that:

1. The direction of movement of the main and tail rotor blades is correct in relation to movement of the pilot’s controls.
2. The operation of interconnected control systems (engine throttle and collective pitch) is properly coordinated.
3. The range of movement and neutral position of the pilot’s controls are correct.
4. The maximum and minimum pitch angles of the main rotor blades are within the specified limits. This includes checking the fore-and-aft and lateral cyclic pitch and collective pitch blade angles.
5. The tracking of the main rotor blades is correct.
6. In the case of multirotor aircraft, the rigging and movement of the rotor blades are synchronized.
7. When tabs are provided on main rotor blades, they are correctly set.
8. The neutral, maximum, and minimum pitch angles and coning angles of the tail rotor blades are correct.
9. When dual controls are provided, they function correctly and in synchronization.

Upon completion of rigging, a thorough check should be made of all attaching, securing, and pivot points. All bolts, nuts, and rod ends should be properly secured and safetied as specified in the manufacturer's maintenance and service instructions.

Quick Review: Helicopter Flight Control Rigging

What are the three major steps involved in rigging a helicopter flight control system?

The rigging process consists of: 1) immobilizing the control system in a specific position using pins, clamps, or jigs to adjust linkages; 2) placing control surfaces in a reference position using tools like bubble protractors to check angular differences; and 3) setting the maximum range of travel to physically limit control system movement.

What critical checks must be performed during the post-rigging functional inspection?

Technicians must verify that the direction of main and tail rotor blade movement matches pilot inputs, ensure collective and throttle interconnection is synchronized, confirm the maximum and minimum blade pitch angles are within limits, and verify proper main rotor blade tracking.

How are multi-rotor aircraft handled differently during the rigging process?

In multi-rotor configurations, the rigging procedures must ensure that the movements and pitch angles of both rotor systems are perfectly synchronized to maintain balanced aerodynamic control and prevent physical or mechanical interference between the systems.

What final safety precautions are required before returning a rigged helicopter to service?

Upon completing all physical adjustments, a comprehensive physical inspection must be performed on all attaching, securing, and pivot points. Every single bolt, nut, and rod end must be properly secured and safetied strictly according to the manufacturer's maintenance manual instructions.

Helicopter Assembly, Rigging, and Rotor System Setup →

Rotorcraft Design Configurations of Rotary-Wing Aircraft Review the major rotary-wing aircraft configurations and their assembly characteristics. Open Article → Rotor Systems Types of Rotor Systems Examine the rotor system designs that require precise assembly and rigging procedures. Open Article → Rotorcraft Controls Rotorcraft Controls Learn how rigging affects the operation of collective, cyclic, throttle, and antitorque controls. Open Article → Rotor Tracking Stabilizer Systems Explore rotor blade tracking, vibration analysis, and stabilization procedures used after rigging. Open Article → Rotorcraft Dynamics Forces Acting on the Helicopter Understand how proper assembly and rigging influence helicopter aerodynamic forces and handling. Open Article → Flight Operations Helicopter Flight Conditions See how accurate rotor system rigging contributes to safe and efficient helicopter flight. Open Article →