Pilot Exam Coach

US Private Pilot

Switch to Canada PSTAR
Aircraft systems and instrumentsQuestion 531 of 934

What is the rule of thumb to find the approximate TAS from CAS?

  1. Add 10 percent to CAS for each 1,000 feet of altitude
  2. Subtract 2 percent from CAS for each 1,000 feet of altitude
  3. Add 2 knots to CAS for each 1,000 feet of altitude
  4. Add 2 percent to CAS for each 1,000 feet of altitude
Show answer

Correct answer: Add 2 percent to CAS for each 1,000 feet of altitude

A pilot can also use a flight computer for the most accurate method.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 8: Flight Instruments — Airspeed Indicator (ASI), page 211

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026