TURBOPROP ENGINE RATINGS
In turboprop engines, power is measured in
Equivalent Shaft Horse Power (ESHP) and
Shaft Horse Power (SHP). SHP is determined
by propeller rpm and torque applied to turn
the propeller shaft. The hot exhaust gases also
develop some kinetic energy as they leave the
engine, similar to a turbojet engine. This jet
thrust amounts to about 10% of the total en-
gine power. ESHP is the term applied to total
p owe r d e l ive re d, i n c l u d i n g th e j e t th r u s t .
Turboprop engine specif ications usually show
both ESHP and SHP, along with limiting am-
bient temperatures.
ENGINE TERMS
To properly understand the operation of the
PT6A series engines, there are several basic
ter ms you should know:
• N
1
or N
G
-Gas generator r pm is per-
cent of turbine speed
• N
2
or Np-Propeller r pm
• NF-Power turbine r pm (not indicated
on engine instr uments)
• P
3
-Air pressure at station three (the
source of bleed air)
• ITT or T
5
-Interstage Turbine Tempera -
ture in degrees of temperature at sta-
tion 5
Review and remember these terms. They will
be used often to describe PT6A engines.
KING AIR C90GTi/C90GTx
PILOT TRAINING MANUAL
7-3
FOR TRAINING PURPOSES ONLY
7
POWERPLANT
ENGINE OIL COOLER
INLET LIP HEAT (HEATED BY EXHAUST)
INTAKE
AIR
INERTIAL SEPARATOR VANES
COMPRESSOR BLEED VALVE
OIL FILLER AND DIPSTICK
ENGINE AIR INLET
COMBUSTION CHAMBER
EXHAUST
PROPELLER GOVERNER
COMPRESSOR SECTION
Figure 7-2. Engine Installation
Summary of Contents for C90GTi
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