SkyDrill

Function of the push rod checknut

Aviation Mechanic Airframe (AMA) practice question 12 of 16 on Flight Controls. ACS element AM.II.C.K5 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONOn a push rod used in a flight control system, what is the function of the checknut?

  1. AIt retains the ball race in the rod end bearing
  2. BIt locks the push rod to the bellcrank
  3. CIt keeps the rod end or clevis from loosening
Show the answer and explanation

Correct answer: C. It keeps the rod end or clevis from loosening

  • A — incorrect The ball races are retained by peening of the rod end, which is a separate concern from the checknut.
  • B — incorrect Attachment to control system parts is made by the rod end or clevis and its pin or bolt, not by the checknut.
  • C — correct The checknut, when tightened, prevents the rod end or clevis from loosening on the threaded end of the tube.

BACKGROUND

Push rods, also called control rods, are used as links in the flight control system to give push-pull motion. A push rod consists of a tube with threaded rod ends, and an adjustable antifriction rod end or a rod end clevis attaches at each end of the tube; adjustment may be provided at one or both ends. The rod end or clevis permits attachment of the tube to flight control system parts, and the checknut, when tightened, prevents the rod end or clevis from loosening. Rods should be perfectly straight unless designed otherwise, and when installed the assembly should be checked for correct alignment and free movement. Control rods fitted with bearings can become disconnected if the peening that retains the ball races fails, which is why the rod end flange is installed between the ball race and the anchored end of the attaching pin or bolt.

STUDY TIP

Learn the parts of a push rod in order — tube, threaded rod end or clevis, checknut — and what each one does.

KEY POINTS

  • A push rod gives push-pull motion and may be adjustable at one or both ends.
  • The checknut prevents the rod end or clevis from loosening.
  • Peening retains the ball races; install the rod end flange to guard against bearing failure.

SOURCES

  • sources/ama-airframe/ch02.txt "Push Rods (Control Rods)"
Practice the Aviation Mechanic Airframe (AMA) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON FLIGHT CONTROLS

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.