User manual

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• Another source for engine failure is overheating. To monitor
engine temperatures there is a EGT gauge for each engine.
During startup they show EGT (Exhaust Gas Temperature), but
when Ng (RPM) passes 50% they shift to read TIT (Turbine Inlet
Temperature). EGT is measured with a probe in the exhaust
gas, while TIT is calculated from EGT, since no probe would last
very long at the TIT temperature. The TIT is further altered by
the SRL computer (Single Red-Line) also called the “Pilot Lier”,
since the temperature shown is different from the real TIT.
Under ISA conditions the T76 engines are limited by torque
until approximately 17.000 feet where Max Allowable EGT
normally is reached). With higher OAT this altitude becomes
lower. To be honest, the Bronco is not happy when flown that
high, it’s an aircraft designed to be flown low. Max Allowable
EGT is not a fixed value, but is a function of Ng (RPM), OAT,
Altitude and Airspeed. Using EGT to determine if you are
running the right temperatures is complex and involves many
tables and charts. That’s where TIT with the SRL correction
comes is, Max allowable TIT, compensated by the SRL, is always
approximately 1000 °C , so the pilot only needs to verify that the
needles don´t get higher than that. The TIT Warn lights are also
set to light at 996 °C. Some Broncos (the German OV-10B’s for
example) were later changed to always display EGT, but still have
the TIT warn lights that will light when the temperatures are too
high. Keep an eye on these lights. They are important.
Accumulative Engine Wear
If this option is enabled the engines will start to wear. They will
degrade over time by this schedule:
• 0-80 hours = Excellent
• 80-120 hours = Good
• 120-140 hours = Ok
• 140-160 hours = Poor
• 160 -> hours = INOP (not functional)