System Review PTM CH-05 (Fuel) Flashcards
Fuel System
Two separate integral wet wing fuel tanks (one in each wing) separated by rib in the center of the tank provide fuel for the engines and APU. Fuel is automatically fed to the engines and APU during starts and while running.
The flight crew has partial control of the boost pumps and full control of crossfeed operation.
Fuel in the tank is transferred to a hopper tank in the lower section of each wing. From there it is delivered to the engines and APU through a system of pumps and fuel lines.
Fueling
The tanks can be fueled or defueled together or individually through a single point refueling (SPR) system. Individual tanks can also be filled through a filler cap on top of each wing.
Overwing Fuel Capacity
Fuel capacity is 850 gallons per wing or 1,700 gallons total. At standard density approximately 11,390 lbs.
Single Point Fuel Capacity
Fuel capacity for single point refueling is 800 gallons per wing or 1,600 gallons total. At standard density approximately 10,720 lbs.
Fuel Supply
Normally each tank supplies its respective engine with fuel. The APU gets its fuel from the right tank. Crossfeeding is possible to either engine and the APU.
Engine Feed Hopper
Close to the inboard portion of each tank is an integral engine feed hopper that houses an electrical fuel boost pump and a motive flow driven primary ejector pump. Fuel from the main tank enters the hopper through flapper valves and three scavenge ejector pumps in the main tank, which transfer fuel from specific areas into the hopper.
Wing Tank Vent System
The left and right wing fuel tanks have separate internal venting systems that vent the tanks during flight maneuvers and during SPR and defueling operations.
Vent Float Valve
Located on the inboard side of the surge tank. Primary vent during refueling and defueling.
Climb Vent Line
Extends from the inboard section of the wing tank to the surge tank. The vent line provides venting during climbs and/or wing low flight conditions and provides additional wing venting during refuel and defuel operations.
Surge Tank & Vent Scoop
A surge tank near the wing tip functions as a fuel collector and is vented to the atmosphere through a flush NACA scoop. The vent scoop is connected to the surge tank with an open-ended standpipe tube (at the high point in the surge tank), preventing fuel from siphoning or spilling overboard.
Drain Valves
Three fuel tank drain valves are in the lower surface of each wing (two drains inboard, one drain outboard of the wheel well). The drain valves are standard poppet valves, mounted semi flush externally in the wing. The valves allow unseating of the poppet to drain sediment, moisture, and/or residual fuel from the tanks.
Positive/Negative Relief Valve
Each wing fuel tank has a pressure relief valve on the underside of each wing. This valve protects the fuel tanks from excessive pressure, either positive or negative, during refueling or defueling operations. It also is a backup in case of vent system failure.
Single Point Refuel Adapter Housing
Allows refueling equipment to connect to the aircraft. The adapter contains a spring-loaded coupling valve that prevents fuel spillage during the coupling process. The housing has a port to supply precheck fuel flow to the precheck valves.
SPR Shutoff Valves
System is operated by fuel level and positive refuel or negative defuel pressure. The refuel shutoff valve is spring-loaded and is opened by positive refuel pressure. Part of the refuel flow is bypassed to the pilot line. During refueling, when the pilot port flow is cut off by the high-level pilot valve, the increased back pressure causes the valve to close. One valve is in the outboard portion of each wing fuel tank.
Precheck
Two levers that allow service personnel to run a precheck during fueling operations to ensure the system shuts off when the wing tanks are full. The levers are marked left and right. Refueling and precheck procedures are listed on a placard inside the access door
SPR Door
It is secured closed with two paddle latches and a cam key lock. The door is not monitored. Should a precheck lever be partially or fully extended, the door is designed to either stow the lever or not close at all.
Fuel Quantity Probes & Signal Conditioner
The system consists of seven compensated capacitance probes per wing with a dual-channel fuel quantity signal conditioner (FQSC), a microprocessor-based unit that consists of separate channels for each fuel tank. The amount of fuel in each tank is calculated by means of measuring how much of the probe is covered with fuel. The capacitance of the probe will change depending on the amount of fuel covering each probe. The FQSC receives a signal from each probe and processes a value that is displayed on the EIS.
Boost Pumps
One electrical fuel boost pump in the hopper of each tank supplies fuel to the respective engine driven fuel pump under certain conditions.
Boost Pump Power Source
The pump receives main DC power through 25-amp CBs in the aft J-Box
Boost Pump Activation
The pumps activate during the engine start sequence and deactivate after the engine start sequence has terminated. It also activates during cross feed or when low fuel pressure is detected. The right fuel pump may also activate during APU operations
Primary Ejector Pump
The primary ejector pump in each engine feed hopper provides a continuous supply of fuel to the respective engine-driven pump. The ejector pumps are powered by high-pressure motive flow from the engine-driven pumps. Primary ejector pumps have no moving parts and require no electricity.
Scavenge Ejector Pump
Three scavenge ejector pumps are in the forward, mid, and aft part of each inboard wing area. The pumps receive motive-flow pressure from the primary ejector pump or the boost pump. They supply fuel from isolated areas of the wing to the engine feed hoppers to ensure that they remain full during all normal flight attitudes.
Crossfeed Valve
The crossfeed valve is a main DC-powered, motor driven ball valve controlled by the crossfeed knob in the cockpit in the center pedestal. The crossfeed valve is in the fuel tank area and connects to the left and right engine supply lines.
The crossfeed system is inoperative with the loss of main DC power. The crossfeed valve remains in its last position following the loss of main DC power.
Firewall Shutoff Valves
Engine fuel firewall shutoff valves are in the fuel tank area in each fuel supply line. The valves are DC electrical motor ball valve assemblies that shut off fuel flow to the engine when the ENGINE FIRE button is pressed.
Motive Flow Shutoff Valves
A solenoid-type shutoff valve controls the motive flow high pressure fuel used to operate the ejector pumps in each wing.
Motive Flow Shutoff Valves Power Source
The valve receives its power from the permanent magnet alternator (PMA) at speeds above 25% N2 and is normally closed.
Motive Flow Shutoff Valves Control
The full authority digital engine control (FADEC) commands it open during engine start, and closes it at engine shutdown. During crossfeed operations, the FADEC on the receiving engine signals the valve to close to stop the motive flow.
Fuel Filler Cap and Adapter
A flush-mounted fuel filler cap and adapter are on the upper surface of each wing near the wing tip. The filler cap and adapter consist of a key locking cap, adapter, and lanyard that attaches the cap to the adapter.
Fuel Oil Heat Exchanger
A heat exchanger for each engine utilizes hot engine oil to heat the fuel prior to entering the fuel filter assembly. The heat exchanger also cools the engine oil to maintain normal operating oil temperatures.
Engine Fire Button Location
LEFT and RIGHT ENG FIRE buttons are on the glareshield panel.
Engine Fire Button Operation
Pressing the buttons cause the fuel and hydraulic firewall shutoff valves to open or close. Button action activates the opposite of their current state. The buttons arm both fire bottles, disable the same side thrust reverser, and also take the same side generator offline.
Boost Pump Button Location
Two buttons are on the FUEL control panel on the center pedestal.
Boost Pump Button Operation
The buttons control the electric boost pumps and are protected with 5-amp circuit breakers on the left and right cockpit CB panels.
Boost Pump (ON)
The amber ON position indicates a manual selection.
Boost Pump (NORM)
In the cyan NORM position, the fuel boost pump automatically activates for the following reasons:
Engine start.
Crossfeed.
APU operation (if right engine is not running).
Low fuel pressure.
Crossfeed Knob Location
The CROSSFEED knob is on the center pedestal.
Crossfeed Knob Operations
Three positions:
L TANK to R ENG
OFF
R TANK to L ENG
Moving the knob from OFF to either tank position selects the tank that fuel is extracted from and the engine to be supplied. With both engines operating, the tank selected continues to supply fuel to its corresponding engine and to the opposite engine.
Fuel Indicating System
The fuel quantity indicating system measures the amount of fuel aboard the aircraft, the fuel temperature, and the fuel flow.
Crossfeed Operations (ON)
Fuel crossfeed allows the crew to supply fuel to one or both engines from either fuel tank.
Selecting L TANK or R TANK activates the fuel boost pump on the feeding tank and the FUEL BST PUMP ON L and/or R CAS message is displayed.
Once the crossfeed valve is open, the FUEL CROSSFEED CAS message is displayed to indicate crossfeed operations.
Three seconds after crossfeed selection, the motive-flow shutoff valve is commanded closed to stop motive-flow on the receiving engine.
If crossfeed is selected with 60 lbs or more imbalance in the wrong direction, the FUEL CROSSFEED CAS message will be displayed.
Fuel Transfer
Transfer of fuel from one tank to the other is not possible due to check valves in the lines preventing fuel from entering the opposite tank.
Crossfeed Operations (OFF)
Opens the motive-flow shutoff valve on the receiving engine. Three seconds later, the fuel boost pump deactivates in the feeding tank.
The FUEL BST PUMP ON L and/or R CAS message disappears.
The crossfeed valve closes and the FUEL CROSSFEED CAS message disappears.
Fuel Quantity Digital Readout
Fuel quantity indications in the EIS window. Normally green and displayed in increments of 20 lbs. If an individual tank quantity display is less than 500 pounds, the respective digital text changes from green to amber inverse video. If the total quantity is less than 1,000 pounds, the digital text changes from green to amber inverse video. The condition does not activate a CAS message.
Fuel Quantity Digital Readout Dashes
Three amber dashes display in the individual tank quantity display and the total quantity display when any capacitance probe in the respective tank fails or if any probe in that tank has failed (no associated CAS message).
Fuel Float Switch
One fuel float switch is in each tank just outboard of the hoppers to indicate low fuel quantity. The float switch activates at a decreasing fuel level of 540 ± 60 pounds of usable fuel. The fuel float switch is independent of the main fuel quantity system. The same float switch activates the FUEL LEVEL LOW L and/or R CAS message.
Fuel Flow Indication
Based on input from a fuel flow transducer on each associated engine.
Fuel Temperature Indication
Measured with fuel temperature sensors in each fuel tank. Three amber dashes are displayed when the value is invalid. Otherwise, the display is always white and shown below the respective tank quantity.
Fuel System Synoptic
A fuel system synoptic can be selected on one of the MFD display panes using the GTC.
Low Fuel Pressure
Low fuel pressure is monitored with a pressure switch between the firewall shutoff valve and the engine mechanical pump.
Fuel Filter Bypass
Fuel to the engine is filtered between the fuel/oil heat exchanger and the high-pressure engine pump. If the filter becomes contaminated and pressure differential increases, an impending bypass switch triggers the FUEL FLTR BYPASS L and/or R CAS message.
If contamination increases, actual filter bypassing occurs around the fuel filter in order to supply fuel to the HMU. The FUEL FLTR BYPASS L and/or R CAS message is not an indication that bypass is actually occurring.
