Systems Guide

Aerosoft
Twin Otter E
XTENDED
Systems
Vol
2
2-1-4
19 November 2013
ENGINE FAILURES
The following failures are simulated:
• Excessive T5 temperature: Whenever the T5 temperature gauges goes into the red area, an over
temperature situation exist. Depending on the amount of over temperature, the engines will fail after
some time.
• Ice ingestion: When icing conditions exist, ice might build up near the engine air-intakes which might
break off and get ingested to the engines, thus causing a flameout. To prevent flameouts, turn on
intake heaters and extend the inertial separators.
• Hot-start: Hot-starts occur if fuel is introduced before Ng (Gas-producer RPM) has reached 12%. The
combustion chambers gets flooded with fuel with insufficient airflow. You will see that T5
temperature gets very hot.
• Engine over torque: Engine over torque occurs when torque is set higher than maximum allowed
continuous torque. The torque gauges has a red mark at approximately 49% for the PT6A-27. This
only marks the maximum to be reached under ISA conditions (15°C, 1013 mbar) at sea level. When
outside temperature increases or as you climb, this value will decrease. In this chart the actual
maximum allowable torque can be found: (Chart to be inserted for PT6A-27). You can also open the
checklist and look on page 1 where a blue bug indicates actually maximum torque on the torque
gauges found there. The engines will fail after a certain time as a function of over torque amount.
Failure due to over torque and over temperature will trigger an engine fire. Shut off fuel and pull the fire
handle to activate the fire extinguisher.
STARTING SYSTEM
The starting system for each engine combines a starter/generator, start switch and starter relays. With the DC
Master switch on and the starter switch held to the start position, the starter motor will rotate the gas
generator turbine. When it reaches sufficient RPM the engine will light-up. The starter switch can then be
released and the starter motor will start to function as generator..
START SWITCH
A three positioned start switch is located on the left overhead panel. The spring loaded LEFT and RIGHT
positions energize the left and right engine starter systems.
ENGINE INSTRUMENTS
TORQUE PRESSURE
The main thrust indicator as it shows the portion of total thrust to the propeller. This gauge requires 26 volts
to operate. It is your primary trust indicator as it indicates how much of the total power is delivered to the
propeller.
PROPELLER RPM
This mechanical gauge (does not require electrical power) indicates the revolution per minute of the propeller.
It indicates in percentage of maximum RPM (around 2200).