Definition
Specific endurance is the flight time an aircraft can sustain per unit of fuel consumed, expressed as flight hours per pound of fuel (or per gallon). It measures how efficiently an aircraft converts fuel into time aloft at a given set of conditions, and is calculated as flight hours divided by pounds of fuel used.
Plain English
It is how many hours of flying you get out of each pound (or gallon) of fuel. Higher specific endurance means the aircraft stays in the air longer for the same amount of fuel.
Context Anchor
Seen in range and endurance performance discussions, especially when comparing power settings for staying airborne as long as possible.
Derivation
‘Specific’ here comes from the Latin specificus, meaning ‘relating to a particular kind or measure.’ In engineering, ‘specific’ usually means ‘per unit of something’ — in this case, per unit of fuel. ‘Endurance’ is the length of time the aircraft can remain airborne. Put together: time aloft per unit of fuel.
Why Pilots Care
It lets a pilot determine how long they can loiter, hold for weather, or divert using the fuel actually on board.
Analogy
It is like asking how many minutes a flashlight can keep shining from each battery. The concern is not distance covered, but time kept running.
Intuition Check
Specific endurance does not mean how tough or durable the airplane is. In this context, it means flight time gained from each unit of fuel.
Example Sentence 1
By reducing power and flying at the recommended endurance airspeed, the pilot improved the aircraft's specific endurance and extended holding time.
Example Sentence 2
The pilot compared specific endurance at two altitudes before choosing the lower power setting that gave more time aloft on the same fuel load.