Definition
The power delivered by an engine at its output shaft, measured in horsepower, before any losses from the propeller or accessories. In a turboprop, SHP represents the mechanical power the gas turbine sends through the reduction gearbox to turn the propeller shaft.
Plain English
It is how much turning power the engine produces at the spinning shaft that drives the propeller.
Context Anchor
Seen in turboprop engine discussions, aircraft performance charts, and engine power ratings.
Derivation
Horsepower originated with James Watt in the 1700s as a way to compare steam engines to draft horses. 'Shaft' specifies that the measurement is taken at the rotating output shaft itself — not at the propeller, and not as thrust.
Why Pilots Care
It tells the pilot how much usable power is available for takeoff, climb, and cruise performance calculations.
Intuition Check
SHP is not the total push of the whole engine. It is the power delivered to the propeller through the shaft.
Example Sentence 1
The PT6A-67 is rated at approximately 1,200 SHP at takeoff.
Example Sentence 2
During climb the pilot keeps SHP within limits to avoid exceeding temperature or torque values.