Jump to content

stdby fuel boost


peter131176

Recommended Posts

From the Twin Otter Extended Manual Vol.2 (You really should read it from start to finish, but still don´t hesitate to ask questions, that is what this forum is about):

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.

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.

Finn

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Privacy Policy & Terms of Use