Fuel Systems Flashcards
GIVEN THE FACT THAT STATIC ELECTRICITY ACCUMULATES ON THE AIRCRAFT DURING FLIGHT AND DOES NOT DISSIPATE TO THE GROUND AFTER LANDING (RUBBER TIRES); WHAT ARE THE THREE STEPS, IN ORDER, BEFORE YOU TAKE OFF THE FUEL CAP?
- Install bonding wires from truck to aircraft
- Verify proper grade of fuel, read label next to filler cap
- Connect static wire between nozzle and A/C, prior to cap removal
STATIC ELECTRICITY WILL ACCUMULATE DURING THE REFUELLING PROCESS. HOW? AND WHAT IS THE PROPER TECHNIQUE TO DISSIPATE IT?
proper grounding of aircraft, fuelling hoses, fuel trucks, fuel pit
WHAT IS THE PROPER WAY TO INSTALL A FILLER CAP WITH RESPECT TO THE DIRECTION OF FLIGHT OR RELATIVE WIND?
the vent should face forward in flight or the arrows should match.
WHAT ARE THE CONSEQUENCES OF FLYING WITH A PLUGGED FUEL CELL VENT?
fumes will build up which is fire hazard
IF YOU ARE REINSTALLING A CHECK VALVE IN THE VENT LINE OF A FUEL TANK, WHICH WAS SHOULD THE ARROW BE POINTING?
Arrow should face the direction of flow
IF THE CHECK VALVE IN A FUEL TANK VENT LINE HAS A HINGED FLAP, IS HINGE ORIENTATION A CONSIDERATION WHEN REINSTALLING?
Yes, the hinge should be installed in the highest point
GIVEN THE FACT THAT THE ACCUMULATION OF FUEL VAPOURS (FUMES) IS DANGEROUS, WHAT IS THE DISPATCH CRITERIA FOR A FUEL LEAK IN A CONFINED AREA?
Ground the aircraft
A LEAK IN THE FUEL TANK VERSUS A LEAK IN THE METERED FUEL SUPPLY: WHICH ONE CAUSES A REDUCTION IN ENGINE POWER? AND A REDUCTION IN ENGINE POWER CAN LEAD TO WHAT?
A leak in the metered fuel supply will cause a reduction in engine power. It can lead to lost of engine efficiency or worst case scenario lose the engine.
LARGER AIRCRAFT MEASURE THE ONBOARD FUEL IN TERMS OF WEIGHT.
WHICH TYPE OF FUEL MEASURING SYSTEM CAN SEND A WEIGHT SIGNAL TO THE FUEL GAUGE? WHAT PROPERTY OF ELECTRICITY IS IT BASED ON?
WHAT EFFECT WOULD WATER IN THE FUEL HAVE ON THE ACCURACY OF THE FUEL QUANTITY MEASURING SYSTEM?
Capacitance type sends weight signal to the fuel gauge and is based on di-electric property. water would cause the capacitance type probe to not be accurate.
WHAT IT IS OR WHAT IT DOES IS WHAT THEY CALL IT. WHY DO THEY CALL IT A BOOST PUMP? WHAT PRESSURE IS IT BOOSTING? WHERE IS IT DELIVERING THIS PRESSURIZED FUEL?
boosts fuel pressure then delivers the pressurized fuel to the engine driven pump.
ONCE THE CAUTION LIGHT CIRCUIT BREAKER IS PUSHED IN ALL THE LIGHTS ARE SUPPLIED WITH POWER. THEY NEED A PATH TO GROUND TO ILLUMINATE. THE PATH TO GROUND IS PROVIDED BY A SWITCH. THE TYPE OF SWITCH DEPENDS ON THE NATURE OF THE CAUTION. FOR EXAMPLE IF THE CAUTION LIGHT SAYS DOOR THEN IT WOULD BE A DOOR ACTIVATED SWITCH. THE SWITCH WOULD BE OPEN WHEN THE DOOR IS PROPERLY CLOSED (NO LIGHT) AND THE SWITCH WOULD BE CLOSED IF THE DOOR IS LEFT OPEN IN FLIGHT (PATH TO GND LIGHT ON
ONE FUEL SYSTEM CAUTION LIGHT IS: LOW FUEL PRESSURE (BOOST PUMP)
WHAT KIND OF SWITCH IS IT? BOOST PUMP PRESSURE OPENS OR CLOSES IT?
It is a pressure switch and the boost pump closes the pressure switch when it’s low pressure
WHEN YOU TURN ON THE BATTERY MASTER AND THEN PUSH IN THE CAUTION LIGHTS CIRCUIT BREAKER BUT YOU HAVEN’T TURNED ON THE BOOST PUMP YET; THE LOW FUEL PRESSURE CAUTION LIGHT SHOULD BE ON BECAUSE THERE IS NO FUEL PRESSURE. ONCE THE BOOST PUMP IS TURNED ON THERE IS A SHORT TIME INTERVAL WHEN THE LIGHT IS OFF BUT WHEN THE PUMP SPINS UP TO MAX RPM THE LIGHT GOES OUT. WHAT DOES IT MEAN IF OVER TIME, IT TAKES LONGER AND LONGER FOR THE LIGHT TO GO OUT?
boost pump is failing
ANOTHER CAUTION LIGHT IN THE FUEL SYSTEM IS “LOW FUEL”.
WHAT TYPE OF SWITCH WOULD OPEN OR CLOSE AT A CERTAIN FUEL LEVEL IN THE TANK? WOULD THIS SWITCH HAVE AN INSTALLATION ORIENTATION (ONE END OF THE SWITCH MUST BE FACING UP)?
Float type or other mechanically operated switch closes to ground when fuel volume goes below a preset and illuminates the fuel light.
IF A FUEL FILTER IS STARTING TO CLOG BECAUSE OF ACCUMULATED CONTAMINATION THE FUEL HAS DIFFICULTY FLOWING THROUGH THE FILTER ELEMENT. THIS CREATES A PRESSURE DIFFERENTIAL ACROSS THE FILTER i.e. THE BEFORE FILTER PRESSURE INCREASES AT THE SAME TIME THE AFTER FILTER PRESSURE DECREASES. IF YOU WANT TO DESIGN A FILTER CLOGGING CAUTION LIGHT, WHAT TYPE OF SWITCH WOULD USE TO TURN ON THE LIGHT WHEN THE FILTER IS STARTING TO CLOG?
Differential pressure switch would turn on if the filter is clogged
THE CRJ FUEL SYSTEM VIDEOS SHOW THAT EJECTOR PUMPS ARE USED TO TRANSFER FUEL FROM THE WING TANKS TO THE COLLECTOR BAY (SCAVENGE FUNCTION) AND FROM THE COLLECTOR BAY TO THE ENGINE (MAIN ENGINE FEED). EJECTOR PUMPS ARE CONSTRUCTED USING A VENTURI. LOOK AT THOSE VIDEOS AGAIN. GIVEN THE FACT THAT FUEL TANKS CAN HAVE DIRT CONTAMINATION WHAT IS ONE WEAKNESS OF AN EJECTOR PUMP i.e. COULDN’T PERFORM IT’S FUNCTION PROPERLY?
Dirt could build up in the venturi causing a blockage to the ejector pump
