Definition
A unit expressing a required climb or descent gradient as the number of feet of altitude change per nautical mile of horizontal distance flown along a procedure track. Used on instrument procedure charts to specify minimum climb performance for departures and required descent performance for arrivals and approaches.
Plain English
How many feet you must climb or descend for every nautical mile you travel forward along the route. It is a slope, written as a number of feet for each mile.
Context Anchor
Seen on instrument procedures such as STARs, where a published route may require a certain climb or descent gradient.
Derivation
A simple ratio notation: feet (vertical) divided by nautical mile (horizontal). The slash is read as 'per.' The form follows the same pattern as 'mph' (miles per hour) — a vertical quantity over a horizontal one to describe a rate.
Why Pilots Care
Allows precise compliance with altitude restrictions and ensures terrain clearance on arrivals and departures.
Grounding Statement
Picture a ramp: for every nautical mile you move forward, the ramp rises (or falls) a fixed number of feet. A gradient of 300 ft/NM means a 300-foot altitude change for each mile along the track.
Intuition Check
Do not confuse ft/NM with feet per minute. ft/NM is based on distance traveled, not time.
Example Sentence 1
The departure procedure required a minimum climb gradient of 250 ft/NM until reaching 3,000 feet.
Example Sentence 2
After takeoff the procedure calls for a minimum climb gradient of 250 ft/NM to clear obstacles.