Airframe Mechanic Certification Aircraft Assembly and Rigging 3 — Questions and Answers
Question 1: What is the purpose of a swaged (Nicopress) sleeve on an aircraft control cable?
- To form a permanent end fitting by compressing the sleeve around a cable loop or thimble (Correct answer)
- To join two cables of different diameters in the midspan
- To provide an adjustable tension connection
- To protect the cable from chafing at fairlead exit points
Correct answer: To form a permanent end fitting by compressing the sleeve around a cable loop or thimble
Swaged sleeves are compressed (swaged) onto cable ends around a thimble to create a permanent, high-strength loop termination approved for flight control use.
Question 2: During wing-to-fuselage assembly on a high-wing strut-braced aircraft, which alignment parameter is checked using a plumb bob?
- Lateral level of the wing root attachment relative to the fuselage centerline (Correct answer)
- Dihedral angle at the wingtip
- Angle of incidence at the wing root
- Wing sweep angle
Correct answer: Lateral level of the wing root attachment relative to the fuselage centerline
A plumb bob dropped from the wing root fitting verifies that both sides are laterally level and symmetrical relative to the fuselage datum centerline.
Question 3: What is the function of a fairlead in a cable control system?
- To guide a cable through a bulkhead or structure with minimal friction and prevent chafing (Correct answer)
- To increase mechanical advantage on the cable pull
- To terminate a cable end at a fixed structure
- To adjust cable tension during rigging
Correct answer: To guide a cable through a bulkhead or structure with minimal friction and prevent chafing
Fairleads are non-metallic (or metallic) guides that support and direct cables through holes in structure, limiting side load and preventing wear.
Question 4: When is a cable guard (cable pin) required in a pulley installation?
- Whenever there is a possibility that the cable can jump the pulley groove under slack or reversed-load conditions (Correct answer)
- Only on pulleys that are larger than 3 inches in diameter
- Only on elevator and rudder systems
- When cable tension exceeds 50 pounds
Correct answer: Whenever there is a possibility that the cable can jump the pulley groove under slack or reversed-load conditions
Cable guards (pins or guards) are required to keep cables seated in pulley grooves when slack, vibration, or reversed loads could cause the cable to derail.
Question 5: After rigging a rudder control system, the rudder deflects 25° right but only 20° left. What is the most likely cause?
- The rudder stop on the left side is set too close, or the left cable is over-tensioned relative to the right (Correct answer)
- The vertical fin is misaligned to the fuselage
- The rudder hinge bolts are too tight on the left side
- The cable on the right side has too many nicks
Correct answer: The rudder stop on the left side is set too close, or the left cable is over-tensioned relative to the right
Asymmetric deflection typically results from an incorrectly set travel stop on the low-travel side or unequal cable tension causing the neutral position to be offset.
Question 6: Which of the following is a characteristic of 7×19 aircraft control cable compared to 7×7 cable?
- 7×19 is more flexible and better suited for systems with small-radius pulleys (Correct answer)
- 7×19 is stiffer and used for push-pull applications
- 7×19 has fewer total wires and therefore less strength
- 7×19 is only approved for non-primary control systems
Correct answer: 7×19 is more flexible and better suited for systems with small-radius pulleys
7×19 cable (7 strands of 19 wires each) is more flexible than 7×7 cable, making it preferred for primary flight controls and systems routed around pulleys with smaller bend radii.
Question 7: What is the purpose of checking control surface balance (mass balance) during assembly?
- To prevent flutter by ensuring the control surface center of gravity is at or forward of the hinge line (Correct answer)
- To verify that the surface is aerodynamically efficient at cruise speed
- To confirm the hinge bolts are properly torqued
- To measure the surface's maximum deflection angle
Correct answer: To prevent flutter by ensuring the control surface center of gravity is at or forward of the hinge line
Mass balancing positions the control surface CG at or ahead of the hinge line, which suppresses aerodynamic flutter that could lead to structural failure.
Airframe Mechanic Certification Aircraft Assembly and Rigging 3
What is the purpose of a swaged (Nicopress) sleeve on an aircraft control cable?