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AMT1220
Fuel Metering
| Question | Answer |
|---|---|
| What is not a factor in the operation of an automatic fuel control unit used on turbine engines? | Mixture control position |
| How is the fuel control adjusted when trimming a turbine engine? | Set to idle RPM and maximum speed |
| How does an EEC obtain the most effective engine operation? | By adjusting a standard hydro mechanical fuel control unit |
| What is generally turned off when trimming an engine> | All accessory bleed air |
| What causes the automatic mixture control to respond in reciprocating engines? | Changes in air density due to changes in altitude or temperature |
| What is the fuel metering force of a conventional float-type carburetor in its normal operating range? | the pressure acting on the fuel in the float chamber and the discharge nozzle |
| How would the engine run if the main air bleed of a float-type carburetor becomes clogged? | Rich at rated power |
| How would you adjust the level of the float in a float-type carburetor? | Add or remove shims under the needle-valve seat |
| How would you achieve better fuel vaporization and control of fuel discharge, especially at lower engine speeds? | Have a calibrated orifice in a main air bleed |
| How does the back-suction type mixture control system operate? | By varying the pressure acting on the fuel in the float chamber |
| What occurs when a back-suction type mixture control is placed in IDLE CUTOFF? | The float chamber will be vented to a negative pressure area |
| On an engine equipped with a pressure-type carburetor, how is fuel supply in the idling range insured? | by the inclusion in the carburetor of a spring in the unmetered fuel chamber |
| If the bellows of the automatic mixture control (AMC) in a pressure carburetor ruptures while the engine is operating at altitude, how will the mixture be affected? | It will become richer |
| Where do you NOT measure the fuel level of a float-type carburetor? | the edge of the float |
| What component measures the amount of air delivered to the engine? | Venturi |
| If the engine is not running and the carburetor leaks fuel, what is the likely cause? | worn or otherwise not seated float needle valve |
| From where is fuel discharged during idling speeds on a float-type carburetor? | The idle discharge nozzle |
| When air passes through the venturi of a carburetor, what three changes occur? | Velocity increases, temperature decreases, and pressure decreases |
| The carburetor venturi does not do what? | regulate the idle system |
| How is idle cutoff accomplished on a carburetor equipped with a back-suction mixture control? | By introducing low pressure (intake manifold) air into the float chamber |
| What is the primary purpose of an air bleed in a float-type carburetor? | To decrease fuel density and destroy surface tension |
| Where is the measurement usually made to determine the float level in a float-type carburetor? | From the top of the fuel in the float chamber to the parting surface of the carburetor |
| What device controls the ratio of fuel/air mixture to the cylinders? | mixture control |
| What device controls the volume of fuel/air mixture to the cylinders? | throttle valve |
| What causes the pressure drop in the carburetor venturi? | air velocity |
| At what engine speed does the main metering jet actually function as a metering jet in a float-type carburetor? | All RPM's above idle range |
| What is the purpose of the carburetor accelerating system? | Temporarily enrich the mixture when the throttle is suddenly opened |
| What carburetor component actually limits the desired maximum airflow to the engine at full throttle? | Venturi |
| What will happen to the mixture on a carburetor without an automatic mixture control as you ascent to altitude? | It will become enriched |
| How is the desire idle speed and mixture setting adjusted? | With the engine warmed up and operating |
| What component in a float-type carburetor aids in emulsifying the fuel at idle speeds? | The idling air bleed |
| What would be considered as the most desirable conditions for trimming a turbine engine? | No wind and low moisture |
| In air-cooled reciprocating engines, when will the mixture be richer? | At rated power and at idle |
| (During idle mixture adjustments) How do you know the correct mixture has been achieved? | Changes in RPM or manifold pressure |
| When the mixture control is moved to IDLE CUTOFF, the manifold pressure decreases and RPM increases momentarily before the engine stops. What does this indicate? | The optimum idle mixture has been obtained |
| When checking the idle mixture on a carburetor, how much of an increase in RPM should there be if the idling mixture is correct? | 10-50 |
| What will happen if the idling jet becomes clogged in a float-type carburetor? | The engine will not idle |
| What are benefits of using water injection? | Increase engine power and control detonation and preignition |
| What will an excessively lean fuel/air mixture cause? | Increased cylinder head temperature |
| How much air to fuel is a mixture of 11:1? | 1 part fuel to 11 parts air |
| What system in a float-type carburetor increases the fuel/air ratio at high power settings? | The economizer system |
| What does the dump portion of the valve do in turbine engines that use a pressurization and dump valve? | Drains the engine manifold lines to prevent fuel boiling |
| What has little to no effect on the operation of a jet engine? | humidity |
| What position will the pressurization and dump valves be in when the engine is shut down? | Pressurization valve closed, dump valve open |
| What would a ruptured balance diaphragm cause? | A lean mixture and high cylinder temperature |
| What occurs when the air/fuel mixture burns too fast? | Detonation |
| When should the needle valve and seat be replaced? | When the carburetor is found to be leaking fuel from the discharge nozzle |
| When operating a gas turbine engine fuel control unit, what factor is NOT used? | Mixture control position |
| Fuel control manufacturers recommend all final adjustments increase direction in order to stabilize what? | Cams, springs, and linkages |
Created by:
Ms.Fietzek
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