Systems Guide

Aerosoft
Twin Otter E
XTENDED
Systems
Vol
2
2-1-8
19 November 2013
FUEL TANK SELECTOR
In normal operation the aft tank feeds the left engine and the forward tank the right engine. Cross feed
operation is possible through a fuel selector on the overhead panel. The fuel selector rotary knob (FUEL
SELECTOR) has three settings
• NORM: forward tank feeds right engine, aft tank feeds left engine, Cross feed valve is closed, No1
boost pump in each tank is energized when the respective boost pump switch is on, No2 boost pump
is deactivated.
• BOTH ON FORWARD/BOTH ON AFT: cross feed valve is open, boost pumps on non-selected tank
deactivated, both booster pumps on the selected tank activated (booster pump switch overridden).
The cross feed valve is powered by the right DC bus.
BOOSTER PUMPS SWITCHES.
The two booster pump switches are located on both sides the fuel selector and control the No1 booster pump
in each tank. They have three settings
• AFT BOOST/FWD BOOST: activates the pump.
• OFF: deactivates the pump
• TEST: momentary setting to test the system
The No2 booster pumps are activated automatic on failure of the No1 pump.
BOOSTER PUMP PRESSURE CAUTION LIGHTS
Four caution lights (BOOST PUMP 1 AFT PRESS, BOOST PUMP 2 AFT PRESS, BOOST PUMP 1 FWD PRESS, BOOST
PUMP 2 FWD PRESS) light up when the pressure downstream of the fuel line drops below 2 psi. The second
caution light of each tank is then automatically switched off. Should No1 booster pump fail its caution light will
illuminate and the No2 caution light will be put online and will illuminate should the No2 booster pump fail.
STANDBY BOOSTER PUMP EMERGENCY SWITCHES
Because the tanks of the Twin Otter are located below the engines, any gravity feed is impossible and a the
No2 booster pumps can be manually activated with these switches
FUEL EMERGENCY SHUTOFF SWITCHES
An emergency fuel shutoff switch for each engine is located on the emergency panel and control firewall
shutoff valves.
FUEL LOW CAUTION LIGHTS
Two low fuel caution lights on the caution panel will light when 75 lb (aft) and 11 lb (forward) remains. This is
only accurate in level flight!
FUEL QUANTITY INDICATORS
Two fuel quantity indicators show the remaining fuel in the aft and forward tanks in LBS x 100.
FUEL QUANTITY INDICATOR TEST SWITCH
A fuel quantity indicator test switch is located close to the fuel selector. This push button (IND TEST) will cut
power to the fuel indicators and they should fall to zero
FUEL HEATERS