Systems Guide

Aerosoft
Twin Otter E
XTENDED
Systems
Vol
2
2-1-7
19 November 2013
Beta modes allows much faster control of the thrust. Due to the slow response to throttle setting changes in
turbo engines it is very impractical to use the throttle to control movement on the ground. You would have to
wait for the gas generator to spin up (Ng increase), providing more torque through the power turbine (PT)
increasing the prop RPM (Np). The prop CS governor would then tell the pitch control unit (PCU) to increase
the prop pitch and then you would get additional power. In beta mode, you change the pitch first instead using
the inertia in the propeller system to provide thrust, letting the Ng accelerate or decelerate in response to Np
to keep Np constant.
PROPELLER LEVERS
The propeller levers control the target propeller rpm that the systems will try to maintain regardless of the
power output through the propeller governor.
FUEL LEVERS
The fuel levers are basically just a fuel cut-off levers as there is no mixture on turbine engines.
OIL SYSTEM
Each engine has an integral oil system and consists of an oil tank, pump, filter and cooler. The heated oil is
used to warm up the fuel.
LOW OIL PRESSURE CAUTION LIGHTS
Two low oil pressure caution lights are located on the caution panel and will light when the pressure drops
below 40 psi and will go out when pressure reaches 44 psi.
OIL TEMPERATURE AND PRESSURE INDICATORS
On the Engine panel there are gauges for oil temperature and oil pressure.
FUEL SYSTEM
The Twin Otter has a simple and reliable fuel system but with the tanks low in the airframe and the engines
mounted high it is fully depended on booster pumps. Correct management of the booster pumps is therefore
very important.
FUEL TANKS
The forward and aft fuel tanks are located beneath the cabin floor. Each tank consists of 4 rubber cell, one of
which is the collector cell. The other three cell feed the collector cell through booster pumps. The collector
cells feed the engines through two booster pumps in each tank. Fuel quantity is measured in all cells and
combine into pounds for each tank.
USABLE FUEL
FORWARD TANK
AFT TANK
Fuel Grade
Density
Weight LB
Imp.Gal
U.S. Gal
Weight LB
Imp.Gal
U.S. Gal
Jet A
8.18
1235.2
151.0
181.2
1341.5
164.0
197.8
Jet A1
8.16
1232.2
151.0
181.2
1338.2
164.0
181.2
Jet B
7.80
1177.8
151.0
181.2
1279.2
164.0
181.2
JP-4
7.80
1177.8
151.0
181.2
1279.2
164.0
181.2
JP-5
8.16
1321.2
151.0
181.2
1338.2
164.0
181.2
JP-8
8.07
1218.6
151.0
181.2
1325.5
164.0
181.2