Where do you find the arm of an item installed on an aircraft?

• A. The Type Certificate Data Sheets for the aircraft.
• B. The aircraft's maintenance manual.
• C. The weight and balance chart.
• D. The flight manual.

Answer: (A)

The arm is the fixed distance from the aircraft’s reference datum to where an item is installed, and that installation data is part of the aircraft’s certified design. The authoritative place to find these approved mounting positions and dimensions is the Type Certificate Data Sheet for the aircraft model. This document lays out the certified configuration, including where components are located and how far they are from the datum, so you know the exact arm for any installed item.

The maintenance manual covers procedures and checks, but it doesn’t define the official installation geometry. The weight and balance charts use arm values to calculate moments for CG, but they don’t establish the actual mounting locations—they’re used for calculations based on the approved design. The flight manual focuses on operation and performance rather than installation details.