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Fuel metering O&P
| Question | Answer |
|---|---|
| Name 2 maintenance or inspection tasks performed during routine fuel system inspection and maintenance. | drain sumps, change filters, clean filters |
| What checks of a fuel system can be made to verify proper operation? | no external leaks, fuel system controls should move freely, make sure all units are securely fastened |
| What is the function and operation of a fuel boost pump? | provide positive fuel pressure to the engine fuel system |
| What is the function of a fuel selector valve? | to select the proper tank |
| What is done to inspect an engine driven pump for leaks and security? | turn the pumps on and check for leaks |
| What is the function and operation of engine fuel filters on a turbine engine fuel system? | to remove micronic particles that may be in the fuel |
| What is vapor lock and how can it be avoided or remedied? | make sure the boost pumps are on and in working order |
| What is a possible reason for fuel running out of a carburetor throttle body? | float level must be below the level of the discharge nozzle |
| What are some indications that the mixture is improperly adjusted? | spark plug fouling, faulty acceleration |
| What is the procedure for checking idle mixture adjustment on a recip engine? | move the mixture control toward idle cutoff, observe the tachometer for a slight rise (10-50) rpms |
| What are possible causes of poor engine acceleration, engine backfiring or missing when the throttle is advanced? | a lean mixture, cracked distributor block |
| What are 3 types of fuel metering systems used on recip engines and how do they operate? | float type, pressure carbs, fuel injection |
| Name the fuel metering system components in a float type carburetor. | venturi, discharge nozzle, float and float valve |
| What is the purpose of the part power stop on some engines when accomplishing engine trim procedure? | to ensure the engine is stabilized |
| Explain the operation of a fuel flow indicating system and where it is connected into the engine. | connected to the flow divider and senses the pressure being applied by the discharge nozzles |
| What is the operation of a manifold pressure gauge? | indicates the pressure in the induction system of a recip aircraft engine |
| Where does the fuel metering system of a turbine engine discharge its fuel? | through spray nozzles into the combustion chambers. |
| What is adjusted when the fuel control unit of a turbine engine is trimmed? | The idle speed and the maximum-thrust speed. |
| What are two locations water may be injected into a turbine engine? | At the compressor inlet and at the inlet to the diffuser section. |
| What is meant by a duplex nozzle in a turbine engine fuel metering system? | one that has two fuel discharge passages. |
| What is the function of a float carburetor? | to measure airflow through the engine induction system and dispense the appropriate amount of gasoline into the airflow for all engine operating perimeters and conditions |
| Does the air-fuel mixture provided by a float carburetor become richer or leaner as the aircraft goes up in altitude? | If the mixture is not adjusted, it will become richer as the aircraft gains in altitude. |
| Does the air-fuel mixture provided by a float carburetor become richer or leaner when carburetor heat is applied? | The mixture becomes richer when carburetor heat is applied. |
| What would happen to the air-fuel mixture ratio in a float carburetor if the main air bleed were to become plugged? | The mixture would become excessively rich. |
| How does the automatic mixture control in a pressure carburetor keep the air-fuel mixture constant as the aircraft changes altitude? | It automatically, and progressively, bleeds the air between the two sides of the air diaphragm and decreases the air metering force. This leans the mixture as the aircraft goes up in altitude. |
| What are two purposes of the manifold valve (or flow divider) in the fuel injection system of a horizontally opposed aircraft engine? | It provides a constant discharge fuel pressure for idling, and it provides a positive shutoff for the fuel when the engine is shut down. |
| How does the mixture control change the air-fuel mixture ratio on the Teledyne-Continental fuel injection system? | When the mixture control is in its FULL RICH position, all fuel goes to the manifold valve. When it is in the IDLE CUTOFF position, all fuel is returned to the pump inlet. |
| Why must the diaphragms of a pressure carburetor be soaked before the carburetor is ready for flight? | restores them to the condition of flexibility that they had when the carburetor was calibrated. |
| What are two basic types of fuel controls for aircraft turbine engines? | Hydropneumatic and electro-hydromechanical. |
| How does the exhaust gas temperature of a reciprocating engine tell anything about the air-fuel mixture being burned by the engine? | A stoichiometric mixture (a mixture in which all of the constituents of the air-fuel mixture are burned) produces the highest exhaust gas temperature. |
| What two things are adjusted when adjusting the idling of a reciprocating engine? | The throttle stop, to get the proper idling RPM, and the idle mixture control, to get the smoothest operation. |
| What is controlled by the adjustment of the orifice in the fuel pump of a Teledyne-Continental fuel injection system? | The high unmetered fuel pressure. |
| What is the significance of the letters that are stamped on the flats of a fuel injection nozzle? | These letters designate the relative size of the orifice in the injector nozzle. The lower the letter in the alphabet, the smaller the amount of fuel the nozzle will flow. |
| What is the function of the derichment valve in a pressure carburetor used on an aircraft engine with an antidetonation injection system? | The derichment valve automatically closes to lean the air-fuel mixture when ADI fluid is flowing. |
| What is the function of the economizer system in an aircraft engine carburetor? | allows the engine to operate with an economically lean mixture for all conditions other than full power |
| In what position is the mixture control placed for starting an engine that is equipped with a pressure carburetor? | In the IDLE CUTOFF position |
| In what position is the carburetor heat control placed when starting an aircraft engine? | In the COLD position. |
| Why is an aircraft reciprocating engine killed by placing the mixture control in the Cutoff position, rather than by using the magneto switch? | the combustion chambers are left full of air with no fuel. |
| Where is the fuel from a continuous-flow fuel injection system discharged? | through injector nozzles screwed into the cylinder heads near the intake valves. |
| In which direction relative to the wind should a turbine-powered aircraft be positioned when the fuel control is being trimmed? | it should be trimmed facing into the wind. |
| What engine parameters are sensed by the fuel control unit of a turbine engine? | Engine RPM, inlet air pressure, compressor discharge pressure, burner can pressure, and inlet air temperature. |
| When does the acceleration system operate on an aircraft carburetor? | When the throttle is suddenly opened. |
| What is the purpose of the bypass valve in an engine-driven fuel pump? | allows fuel to flow around the engine-driven pump for starting and for emergency operation if the engine-driven pump should fail. |
| On which side of the firewall is the engine fuel shutoff valve located? | the side of the firewall away from the engine. |
| What are three purposes for the boost pumps in an aircraft fuel system? | To provide fuel pressure for starting the engine, to pressurize the fuel lines to prevent vapor lock, and to transfer fuel from one tank to another. |
| What kind of boost pump is used in most aircraft fuel systems? | Electrically operated centrifugal pumps. |
| Where does an engine-driven fuel pump direct the excess fuel from its pressure relief valve? | Back to the inlet side of the pump. |
| What causes a vapor lock in an aircraft fuel system? | The fuel becomes hot enough that it boils |
| What is done in most aircraft fuel systems to prevent vapor lock? | Boost pumps in the fuel tank pressurize the fuel in the lines and force the fuel into the fuel metering system. |
| What is meant by a compensated relief valve in an engine-driven fuel pump? | A pressure relief valve that is acted upon by a diaphragm as well as a spring. |
| What is the purpose of the pressurizing and dump valve in the fuel system for a turbine engine? | acts as a flow divider, directing the fuel into the main or pilot manifold |
| What should be done to an aircraft reciprocating engine if it has been operated on turbine engine fuel? | fuel should be drained, oil changed, compression check, cylinders and oil filter should be examined |
| What are the two basic types of turbine engine fuel? | Jet A Jet B |
| Why do some turbine engine fuel systems incorporate a fuel heater? | keeps the fuel warm enough that any water that precipitates out of the fuel will not freeze on the filters. |
| What are two reasons Prist is used in turbine engine fuel? | acts as a biocidal agent that kills the microbial growth that forms scum in fuel tanks. |
| Why do some aircraft fuel filters have a built-in relief valve? | it will open and allow unfiltered fuel to flow to the fuel control device if the filter should become plugged with ice or other contaminants. |
Created by:
possumslopper2000
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