Flashcards in EMB-120 Fuel System Deck (54):
The Main Jet pumps are “powered” by?
Motive Flow (venturi)
What hazard is there in single point refueling with no power on the aircraft?
Overpressure- power allows vent valve to operate.
The Main Jet pumps can be shut down how?
• Pull the fire handle- closes firewall shutoff valve just before the pump.
• Opening the Crossfeed- closes the motive flow valves.
• Condition Levers- FUEL CUT OFF- shuts off fuel at the HMU.
What three valves are controlled by the Fuel Crossfeed Switch?
• 2 Motive Flow Valves. Otherwise, main jet pump output of 35 psi would override 20 psi boost pump output.
• Crossfeed Valve
For AUTOMATIC refueling, what conditions must exist?
• Power ON
• Hose connected
• Vent Valve CLOSED light extinguished
• Refueling Shutoff Valve CLOSED light extinguished
• Set bugs to desired fuel level
• Place switch in AUTO and begin fueling
Where is the Main Jet Pump located and what does it do (except when)?
The Main Jet Pump is located in each wing collector tank and supplies the required fuel flow and pressure to their respective engine, except engine start and cross feed operations.
Where are the Transfer Jet Pumps located and what do they do?
The Transfer Jet Pumps are located in each inboard tank and maintain the collector tanks at the proper operating level, regardless of aircraft flight attitude.
What is the total fuel per tank? Total?
2,866 x 2 = 5,732 lbs.
What is the max allowable fuel imbalance?
How much unusable fuel is there per wing?
Add ______ to the unusable fuel in the corresponding wind when the main ejector booster pump is inop?
Why add ______ to the unusable fuel in the corresponding wind when the main ejector booster pump is inop?
The Main Ejector Pump sits lower in the tank than the electric pumps. The electric pumps leave more unusable fuel in the hopper tanks.
When are you required to declare “Emergency Fuel”?
In flight, if you determine that you will land with less than 30 minutes of fuel.
How much can you reduce release fuel before you need to contact Dispatch?
200 lbs or 50% of contingency fuel, whichever is more restrictive.
What is MINTO fuel?
Fuel required at the start of the takeoff roll. It’s the minimum FAR fuel required to complete a leg and reach the farthest alternate.
How is fuel measured in each wing?
Six capacitance probes measure fuel quantity.
How do you measure fuel if the fuel gauge is inoperative?
Each wing has four dripless sticks; the most inboard is #1, outboard #4.
Where do you find the procedure for cross feeding?
What happens when you place the crossfeed switch to OPEN?
o Cross feed valve opens.
o Both HMU motive flow valves close (to allow proper crossfeed operation).
When would the electric fuel boost pumps be needed?
o Engine start.
o Backup to main ejector (jet) pump.
o Cross feeding fuel.
o To start/operate APU if right engine not running.
o Transfer fuel on the ground.
The only things that work regarding the fuel system in electrical emergency mode are:
o Two front electric boost pumps.
o Motive flow pumps.
The rest of the system is Normal DC powered, including the fuel gauge panel.
Which tank has all of the fuel pumps (electric and ejector pumps)?
Collector Tank (part of the hopper tank).
How does the main ejector pump work?
Motive flow (venturi)
What do the NACA vents do?
Let air in as fuel is consumed.
What do the refueling vents do?
Let air out as tank is fueled
How does the scavenge pump work and what does it do?
Works via motive flow. Keeps the collector tank fuel at a level that provides a constant source of fuel for the main ejector pump and electric boost pumps.
How do you convert fuel from lbs. to gallons?
Subtract what you have from what you need. Drop the last 0. Multiply by 1.5
Need 2,400; have 1,400. 2,400 – 1,400 = 1000. 100 x 1.5 = 150 gallons.
What happens when you lose the main ejector pump?
o FUEL light on MAP.
o LOW FUEL PRESS light on overhead panel flashes ON.
o Electric fuel boost pumps cycle ON, with switch is in AUTO.
o No motive flow, scavenge pumps inop.
o Add 79.6 lbs. of unusable fuel per tank to the already 24 lbs. of unusable fuel.
Why is power needed for single point refueling?
Safety, it’s a failsafe so the vent valve is operational to prevent overpressure.
Where do you find the De-Fueling procedure?
What is checked on the Fuel System during the Descent Checklist?
o Fuel quantity and balance- both analog and totalizer gauges.
o Overhead panel- fuel pumps in auto and crossfeed closed.
What happens when you pull the fire handle?
It closes the Firewall Shutoff Valve just before the pump. This is the only way to close this valve.
What happens when you when condition levers get placed in FUEL CUT OFF?
Shuts fuel off at the HMU.
What are the positions of the master refuel switch and which do we use?
o AUTO, MANUAL, OFF.
o AUTO, set bug to the total desired for each tank.
Which fuel tank feeds the APU?
Right tank; the line to the APU is on the right side of the crossfeed valve.
How much fuel does the APU consume? Generator and Bleed / Generator only?
o Generator and Bleed: 130 pph.
o Generator only: 70 pph.
On FFOD Taxi Check, you place all fuel pump switches to OFF and open the crossfeed valve. With no tank pumps operating why doesn't the engine flameout?
The engine driven fuel pump on the TMM has enough suction to operate up to 15,000’.
Where does the Totalizer receive its information about fuel flow?
Turbine Flow Transmitter. It subtracts from the fuel remaining.
What does the fuel LOW TEMP light indicate and what do you do if it comes on?
o Fuel temp is at or below 5°.
o Descend to warmer temp.
o Acceptable if illuminated after a cold night before engine start.
At what pressure does the Low Press light illuminate?
How many fuel filters and caution lights are there?
2 filters but only 1 light. There is no way to tell which until MX investigates.
Is the aircraft’s fuel heated?
Yes, via a fuel / oil heat exchanger.
Loss of the engine driven fuel pump will result in?
Will the engine quit if all tank pumps are inop?
No, main engine fuel pump can suck enough out below 15,000. Low Press lights ON.
Is refueling plumbing different than crossfeed?
How does the vent valve work?
When fuel is supplied to the adapter, a small amount is applied to the vent valve assembly. The fuel pressure unseats the normally closed valve and vapor is vented from the fuel tanks.
Does the vent valve require electrical power?
What two ways can the pilot valve be closed?
By raising the fuel level lifting the float until it closes automatically and power being applied to the solenoid which pulls down on the arm of the float.
When the pilot valve is closed during refueling what happens?
Fuel back pressure is created to assist the spring in closing the SOV that goes to the fuel tank.
A low press is an indication that what has failed?
Main Jet Pump
At what pressure will the electric fuel pumps turn on if in AUTO?
Where is low fuel pressure sensed?
After the fuel tank, just prior to the Main Engine Fuel Pump.
What is happening during the FFOD Test when the fuel pumps are off and the crossfeed is open?
Motive flow ceases and a low pressure condition is created.