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Rigging step that uses a bubble protractor

Aviation Mechanic Airframe (AMA) practice question 9 of 11 on Rotorcraft Fundamentals. ACS element AM.II.N.K3 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhile rigging a helicopter, a mechanic uses a precision bubble protractor to check the angular difference between a control surface and a fixed surface on the aircraft. Which major rigging step is this?

  1. ASetting the maximum range of travel of the components
  2. BPlacing the control surfaces in a reference position
  3. CHolding the control system with pins or clamps
Show the answer and explanation

Correct answer: B. Placing the control surfaces in a reference position

  • A — incorrect That step limits the physical movement of the control system; it is not performed by measuring an angle against a fixed surface.
  • B — correct Checking the angular difference between a control surface and a fixed surface with a rigging jig, a precision bubble protractor, or a spirit level is how control surfaces are placed in a specific reference position.
  • C — incorrect Immobilizing the control system with pins, clamps, or jigs while linkages are adjusted is a separate step from measuring surface angles.

BACKGROUND

Rigging a 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. The work is not difficult but demands great precision, and the adjustments, clearances, and tolerances in the manufacturer's maintenance manuals must be followed exactly. Rigging breaks into three major steps: placing the control system in a specific position and holding it there with pins, clamps, or jigs while the linkages are adjusted; 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 against a fixed surface; and setting the maximum range of travel of the various components. After static rigging is finished, a functional check of the flight control system must be accomplished. Upon completion, all attaching, securing, and pivot points are checked and every bolt, nut, and rod end is properly secured and safetied.

STUDY TIP

Memorize the three rigging steps by the tool each one uses: pins and clamps to immobilize, a protractor or level to set a reference angle, and stops to limit travel.

KEY POINTS

  • Rigging establishes the relationship between the rotors and their controls and demands exact tolerances from the maintenance manual.
  • The three major steps are immobilizing the control system, setting control surfaces to a reference position, and setting maximum travel.
  • A rigging jig, precision bubble protractor, or spirit level measures the angle between a control surface and a fixed surface.

SOURCES

  • FAA-H-8083-31B ch02 "Rotary-Wing Aircraft Assembly & Rigging" (sources/ama-airframe/ch02.txt)
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.