METEOROLOGICAL TERMINOLOGY
ISA - International Standard Atmosphere – Atmospheric conditions in
which:
1. The air is a dry, perfect gas.
2. The temperature at sea level is 15° Celsius (59° Fahrenheit).
3. The pressure at sea level is 29.92 inches of mercury (1013.2 mb).
4. The temperature gradient from sea level to the altitude at which the
temperature is -56.5°C (-69.7°F) is -0.00198°C (-0.003564°F) per foot and
zero above that altitude. This translates to -1.98°C (-3.56°F) per thousand
feet in altitude.
OAT - Outside Air Temperature – The free air static temperature, obtained
either from in-ight temperatures or ground meteorological sources,
adjusted for instrument error and compressibility effects.
Pressure Altitude – The altitude read from a pressure altimeter when the
altimeter’s barometric scale has been set to 29.92 inches of mercury or
1013.2 mb.
ENGINE POWER TERMINOLOGY
Beta Mode – The engine operational mode in which both the propeller blade
angle and the engine power are controlled by the power lever. Beta mode
may only be used during ground operations.
Flameout – The unintentional loss of combustion chamber ame during
engine operation.
Gas Generator RPM (
) – Indicated in percent of gas generator RPM based
on a scale in which 100% equals 37,500 RPM.
Hot Start – An engine start, or an attempted engine start, which results in an
ITT that is more than 1090°C.
ITT - Inter-Turbine Temperature – A measurement of the temperature
between the compressor turbine and the power turbine stator.
Maximum Climb Power – The maximum power approved for a normal climb.
Use of this power setting is limited to climb operations. This setting relates
to the power developed at the maximum torque limit relative to propeller
RPM, ITT (765°C), or
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