12
PERFORMANCE
Excess power is a measure of the ability of the aircraft to accelerate or climb. Specific excess
power (P
s
) is the excess power normalized for aircraft weight, allowing the capability of aircraft
at different weights to be compared. Compared to a swept - wing jet aircraft, maximum specific
excess power for a straight - wing turbo propeller aircraft occurs at much slower speeds in the
envelope. The excess power characteristics translate to lower speeds for best angle of climb and
best rate of climb for the C-130 relative to swept -wing jet aircraft.
The following diagrams compare the notional characteristics of a swept - jet aircraft (black lines)
with a straight – wing turboprop aircraft (red lines). This chart shows the differences in total drag
between a swept wing and a straight wing aircraft. A straight wing aircraft has less induced drag
at slower speeds.