AIM ¶ 4-2-11 — Speed Phraseology
AIM 4-2-11: How pilots and ATC say airspeeds and Mach numbers on the radio. Examples, phraseology rules, and oral exam prep for student pilots.
AIM 4-2-11 explains how to say airspeeds and Mach numbers correctly on the radio. Clear, standardized phraseology prevents misunderstanding between pilots and controllers — especially during speed adjustments in busy airspace.
Knots:
- Speak each digit separately, followed by the word "KNOTS."
- Examples: 250 → "two five zero knots"; 190 → "one niner zero knots."
- Controllers may omit "KNOTS" when issuing speed adjustments, e.g., "REDUCE SPEED TO TWO FIVE ZERO."
Mach Number:
- Precede the digits with the word "Mach" and speak each digit individually.
- Examples: 1.5 → "Mach one point five"; 0.64 → "Mach point six four"; 0.7 → "Mach point seven."
Why it matters: using standard phraseology keeps frequencies efficient and reduces readback errors. Even though AIM is non-regulatory, controllers expect this format, and using it cleanly on your checkride demonstrates professional radio discipline.
Five FAA-written-style questions. Instant explanations, every answer cites its source — no account needed.
You are flying VFR in Class E airspace at 8,500 feet MSL during the day. What are your minimum visibility and cloud clearance requirements?