Definition
A unit of speed expressing the number of statute miles traveled in one hour. One statute mile equals 5,280 feet. On some airspeed indicators, particularly in older or light general aviation aircraft, airspeed is displayed in miles per hour (MPH) rather than knots.
Plain English
How many statute miles you would cover in one hour at the current speed. It's the same speed unit used on car speedometers.
Context Anchor
Seen on some airspeed indicators and in some aircraft handbooks, especially when comparing speeds shown in miles per hour with speeds shown in knots.
Derivation
Mile comes from a Latin phrase meaning “a thousand paces.” Hour comes from an older word for a period of time. Together, miles per hour simply means distance covered during one hour.
Why Pilots Care
Pilots must know whether the ASI uses miles per hour or knots to read speed correctly and apply performance data without error.
Intuition Check
Do not assume every aviation speed is in miles per hour. Many aviation speeds are given in knots, so the unit printed on the instrument or in the handbook matters.
Example Sentence 1
The Cessna 150's airspeed indicator was marked in miles per hour, so the pilot noted that cruise speed of 100 MPH equaled about 87 knots.
Example Sentence 2
The student checked the ASI in miles per hour before converting the value for the performance chart.