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POWERPLANT ORALS
CHAPTER 7 - ENGINE FUEL AND FUEL METERING
Question | Answer |
---|---|
WHAT ARE SOME OF THE SOURCES USED TO HEAT THE FUEL IN A TURBINE ENGINE FUEL SYSTEM? | BLEED AIR AND ENGINE LUBRICATING OIL. |
WHAT ARE THE MOST COMMON TYPES OF FUEL METERING SYSTEMS USED ON SMALL RECIPROCATING ENGINES? | FLOAT-TYPE CARBURETORS, PRESSURE-INJECTION CARBURETORS AND DIRECT FUEL INJECTION SYSTEMS. |
WHAT FUNCTION DOES THE MIXTURE CONTROL PERFFORM? | CONTROLS THE FUEL/AIR MIXTURE. |
WHAT GENERLLY CAUSES SPARK PLUG FOULING? | OPERATING THE ENGINE WITH AN EXCESSIVELY RICH MIXTURE AT IDLE. |
WHAT IS THE PURPOSE OF AN ACCELERATING SYSTEM? | IT PROVIDES AN IMMEDIATE BUT BRIEF INCREASE IN FUEL FLOW IN THE VENTURI TO ENRICH THE MIXTURE. |
WHAT IS A CARBURETOR ECONOMIZER SYSTEM? | IT IS A POWER ENRICHMENT SYSTEM THAT PROVIDES A RICHER MIXTURE AT HIGH POWER SETTINGS, WHERE THE EXCESS FUEL AIDS IN ENGINE COOLING. THIS SYSTEM FUNCTIONS AT THROTTLE SETTINGS ABOVE CRUISE POWER SETTING. |
WHEN THE MIXTURE IS PLACED IN THE IDLE-CUTOFF POSITION, A SLIGHT RISE IN R.P.M. IS NOTED PRIOR TO THE ENGINE DECELERATING. WHAT DOES THIS INDICATE? | THE IDEL MIXTURE IS SET CORRECTLY. |
WHY SHOULD ENGINE R.P.M. BE ACCELERATED PERIODICALLY WHEN MAKING CARBURETOR ADJUSTMENTS? | TO CLEAR THE ENGINE. |
WHAT MAINTAINS THE FUEL PRESSURE IN A PRESSURE-INNJECTION CARBURETOR? | AN ENGINE-DRIVEN FUEL PUMP. |
WHAT HAPPENS IF THE MANUAL MIXTURE CONTROL OF A PRESSURE INJECTION CARBURETOR IS MOVED TO THE IDLE CUTOFF POSITION? | THE ENGINE STOPS. |
HOW DOES AN AUTOMATIC MIXTURE CONTROL (AMC) FUNCTION? | A SEALED BRASS BELLOWS CONNECTED TO THE FUEL METERING SYSTEM, EXPANDS AND CONTRACTS WITH CHANGES IN PRESSURE AND TEMPERATURE, ADJUSTING THE MIXTURE ACCORDINGLY. |
WHAT ARE SOME OF THE ADVANTAGES OF FUEL INJECTION SYSTEMS OVER CARBURETOR SYSTEMS? | LESS DANGER OF INDUCTION ICING, BETTER ACCELERATION, BETTER FUEL DISTRIBUTION, BETTER FUEL ECONOMY, REDUCED OVERHEATING OF INDIVIDUAL CYLINDERS. |
WHAT PURPOSE DO TURBINE ENGINE FUEL CONTROL UNITS SERVE? | THEY AUTOMATICALLY METER FUEL TO THE ENGINE. |
WHAT ARE THE TWO BASIC TYPES OF TURBINE ENGINE FUEL CONTROL UNITS? | HYDROMECHANICAL AND ELECTRONIC. |
WHAT ARE THE ENGINE VARIABLES DETECTED BY THE FUEL CONTROL UNIT? | POWER LEVER POSITION, ENGINE R.P.M., COMPRESSOR INLET TEMPERATURE, COMPRESSR INLET PRESSURE, COMPRESSOR DISCHARGE PRESSURE, BURNER PRESSURE. |
WHAT ARE THE TWO MAJOR COMPONENTS OF A SUPERVISORY ELECTRONICS ENGINE CONTROL? | THE ELECTRONIC CONTROL UNIT (COMPUTER), AND THE HYDRKMECHANICAL FUEL CONTROL. |
WHAT ARE SOME OF THE ADVANTAGES OF A FULL-AUTHORITY DIGITAL ENGINE CONTROL (FADEC) OVER A HYDROMECHANICAL FUEL CONTROL? | BETTER FUEL ECONOMY, IMPROVED STARTS, REQUIRES NO ENGINE TRIMMING, PROVIDES ENGINE LIMIT PROTECTION, PROVIDES CONSTANT IDLE SPEEDS, FULLY MODULATES THE ACTIVE CLEARANCE CONTROL, AND ALLOWS MORE REPEATABLE ENGINE TRANSIENTS. |
WHAT DO TURBINE ENGINE FUEL SPRAY NOZZLES DO? | THEY INJECT FUEL INTO THE COMBUSTION AREA. |
WHAT ARE THE DIFFERENT ENGINE INDICATIONS USED FOR TRIMMING A TURBINE ENGINE? | EITHER EPR OR RPM IS USED DEPENDING ON THE PARTICULAR ENGINE. |
WHAT MAINTENANCE ADJUSTMENTS ARE NORMALLY ALLOWED ON AN INSTALLED HYDROMECHANICAL FUEL CONTROL? | SPECIFIC GRAVITY FOR FUEL, IDLE RPM, AND MAXIMUM RPM (OR MAXIMUM EPR), |
WHAT TYPE OF PUMP CAN VARY THE AMOUNT OF FUEL DISCHARGED REGARDLESS OF SPEED? | A VARIABLE DISPLACEMENT PUMP. |
WHAT IS USED TO KEEP WATER, SEDIMENT, AND FOREIGN MATTER OUT OF THE CARBURETOR? | THE MAIN FUEL STRAINER. |
WHAT IS THE PURPOSE OF A PRESSURE RELIEF VALVE IN A CONSTANT DISPLACEMENT PUMP? | IT RETURNS EXCESS FUEL THAT IS NOT REQUIRED BY THE ENGINE TO THE INLET SIDE OF THE PUMP. |
WHAT TYPE OF ENGINE-DRIVEN FUEL PUMP IS WIDELY USED OTHER THAN GEAR OR PISTON PUMPS? | A ROTARY VANE TYPE. |
WHAT FUNCTION DO FUEL BOOST PUMPS PERFORM? | THEY SUPPLY PRESSURIZED FUEL TO THE FUEL PUMP, WHICH HELPS PREVENT VAPOR LOCK AND CAVITATION. |
WHAT IS A COMMONLY USED TYPE OF FUEL BOOST PUMP? | THE CENTRIFUGAL TYPE. |
WHAT CAUSES VAPOR LOCK AND WHY IS IT OF CONCERN? | VAPOR LOCK IS CAUSED BY INSUFFICIENT FUEL PRESSURE, HIGH FUEL TEMPERATURES AND EXCESSIVE FUEL TURBULENCE, WHICH MAY COMPLETLY BLOCK ANY FUEL FLOW RESULTING IN ENGINE FAILURE. |
WHAT FUNCTION DOES THE ENGINE-DRIVEN PUMP ON A TURBINE ENGINE PERFORM? | IT PROVIDES A CONTINUOUS SUPPLY OF FUEL AT THE PROPER PRESSURE WHILE THE ENGINE IS RUNNING. |
NAME THE TWO CATEGORIES OF TURBINE ENGINE PUMPS. | CONSTANT AND VARIABLE DISPLACEMENT. |
WHAT CATEGORY IS A GEAR-TYPE PUMP CLASSIFIED IN? | CONSTANT DISPLACEMENT. |
WHEN PERFORMING AN EXTERNAL INSPECTION OF AN ENGINE-DRIVEN FUEL PUMP, WHAT SHOULD YOU LOOK FOR? | LEAKS AND SECURITY OF MOUNTING. |
WHAT IS THE PURPOSE OF A SHEAR SECTION OF THE DRIVESHAFT IN A DUAL ELEMENT CONSTANT DISPLACEMENT PUMP. | IF ONE ELEMENT SEIZES, A PORTION OF THE DRIVESHAFT SEIZES, ALLOWING THE OTHER ELEMENT TO CONTINUE TO OPERATE. |
WHERE IN A TURBINE ENGINE FUEL SYSTEM IS ICE FORMATION LIKELY TO OCCUR AND HOW IS IT PREVENTED? | THE FUEL FILTER IS MOST SUSCEPTIBLE TO ICE FORMATION, SO A FUEL HEATER IS USED THAT CONSIST OF A HEAT EXCHANGER USING EITHER ENGINE OIL OR BLEED AIR TO WARM THE FUEL. |
WHAT IS THE PURPOSE OF A BYPASS VALVE IN AN ENGINE FUEL SYSTEM MICRON FILTER? | IT IS A SAFETY FEATURE THAT ALLOWS FUEL TO FLOW TO THE ENGINE IF THE FILTER BECOMES BLOCKED. |
WHAT IS THE PURPOSE OF A DUPLEX FUEL NOZZLE? | A DUPLEX FUEL NOZZLE DISCHARGES TWO DIFFERENT SPRAY PATTERNS. THE SPRAY PATTERN IS WIDER DURING START UP AND ACCELERATION AND NARROWS WHEN ENGINE SPEED INCREASES ABOCE IDLE. |
WHAT ARE THE FUNCTIONS OF THE PRESSURIZING AND DUMP PORTIONS OF A PRESSURIZING AND DUMP VALVE? | THE PRESSURIZING PORTION PROVIDES PRIMARY AND SECONDARY FUEL FLOW TO DUAL-LINE DUPLEX FUEL NOZZLES, AND THE DUMP PORTION ALLOWS FUEL TO DRAIN FROM THE MANIFOLDS AFTER ENGINE SHUTDOWN. |
WHAT PURPOSE DO FUEL SELECTOR VALVES SERVE? | THEY ALLOW TANK AND ENGINE SELECTION, AND PROVIDE A MEANS FOR SHUTTING OFF FUEL FLOW. |