Reciprocating Engine Fuel Metering Flashcards by Josh Wall

Where the fuel in a float chamber system is stored

Float chamber

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The five air/fuel mixture settings

Full rich 2. idle-cutoff 3. lean best power 4. rich best power 5. best economy

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In the induction manifold, as the throttle is opened, the pressure_______

rises

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Primary cause of Pre-ignition

Hot-spot

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The two types of carburetors

Float type, Pressure injection

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Why an increase in humidity will decrease engine performance

Water is incombustible

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In Afterburning in a piston engine, fire may appear in_____

The exhaust

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An airbleed system is a vented passage with a small calibrated orifice which overcomes

Surface tension of the fuel

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Relationship between volumetirc efficiency and humidity

Inversely propotional

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Aircraft with Constant speed propellers, the _____ gauge can be used to help adjust fuel mixture

MAP

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To compare an engine to the manufactures specifications, the AMT will have to perform a(an) __________

engine run-up

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The system out of the 5 carburetor systems which allows the pilot to control the mixture

Mixture control system

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The idling system allows fuel

to continue to flow to the engine with the venturi butterfly valve in the closed position

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The name for the pilot controlled restrictor plate installed in the Venturi

Throttle valve/ butterfly valve

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The air/fuel mixture that a typical piston will generate maximum power at

12:1

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The system which provides the engine with the correct amount of fuel for all speeds above idle

Main metering system

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The ratio of fuel displaced by the piston to the piston’s swept volume

Volumetric efficiency

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The most likely condtion of an engine that continues to fire after the ignition has been shut off

Pre-ignition

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In carburetors in which a single venturi is insufficient to provide an adequate pressure drop, a(an) ________ is installed

Boost venturi

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The property that prevents a liquid from readily breaking apart based on molecular cohesiveness

surface tension

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The two methods of fuel metering in reciprocating engines

Carburetion, fuel injection

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The type of valve inside the float chamber

Needle valve

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As a general rule for AVGAS, a ratio of _______ to _______ will support combustion

8:1 to 16:1

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Condition in which an excessively rich fuel/air mixture causes a slow combustion and un-burned fuel leaves the cylinder and mixes with the air in the exhaust system and ignites

Afterfire

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The condition in which an extremely lean fuel/air mixture burns slowly which will remain burning when the intake valve opens for the next cycle, which ignites the intake air before the intake valve closes and burns in the induction manifold

Backfiring

The theoretical perfect air/fuel mixture for a piston engine in 0:0 format

15:1

Burning of the fuel/air mixture prior to the spark plug firing

Pre-ignition

The three types of fuel injection

Direct, continuous-flow, electronically controlled

The only accurate way to measure a fuel/ air ratio

By weight

The tube that connects the float chamber to the throat of the venturi

U-tube

Detonation will cause: 4 things

1. High cylnder head temperatures 2. Rough running engine 3. Higher pressure 4. Loss of power

The 5 sytems of a carburator

1. Main metering 2. Idling 3. Mixture control 4. Accelerating 5. Economizer

The amount of work done by the engine compared to the amount of heat supplied to it

Thermal efficiency

All float chambers are vented to\_\_\_\_\_\_\_

atmosphere

What needs to happen to the fuel for complete and even burning

Atomized

Best economy mixture setting refers to the ratio which provides

The greatest amount of power for the least amount of fuel

A decrease in air density for a given air/fuel mixture yields a _____ mixture

richer

The number of pounds burned per hour to produce 1 horsepower

Specific fuel consumption

The stoichiometric mixture describes

A mixture in which all oxygen is used during combustion

Aircraft with fixed pitch propellers can use the \_\_\_\_\_\_gauge to adjust fuel mixture

Tachometer

An increase in humidity _______ engine performance

Degrades

A increase in air density for a given air/fuel mixture yields a _____ mixture

leaner

The uncontrolled, explosive ignition of a fuel/air mixture in a cylinder

detonation

The most accurate parameter for gauging/ setting fuel mixture

EGT

The condition of the EGT in lean mixture condition

Higher

The condition of the EGT in rich mixture

Cooler

What he size of the pressure differential between the float chamber and the venturi will determine

The amount of fuel transferred from the float chamber to the main metering jet

In a simple float type carburetor, the maximum amount of fuel flowing through the discharge nozzle is limited by

Size of the main metering jet

The term for the 1/8" difference between the height level fuel in the float chamber and the height level of fuel at the discharge nozzle

Fuel metering head

The function of the fuel metering head distance

The prevention of fuel leaking from the carburetor into the venturi

The function of idle jets in a float type carburetor

Ensure consistent engine operation at idle speed

The term for a system which uses sealed bellows to move a variable orifice, so that during a climb, when atmospheric pressure decreases, the bellows expand which leans the fuel/air mixture

AMC (automatic mixture control)

When the throttle valve is opened rapidly, the condition of the fuel/air mixture\_\_\_\_\_\_ due to \_\_\_\_\_\_\_\_\_

leans, due to fuel discharge nozzle lagging

The typical method of preventing problem of the mixture momentarily leaning out during rapid opening of the throttle/ butterfly valve

Using of the accelerator pump

Heat generated by operating at maximum power, which can be more than air cooling can dissipate, can be dissipated by power enrichment. Another term for power enrichment can be Economizer. Why

It also permits the pilot to use a leaner mixture at cruise

2 cons of using a float type carburetor

1. Ice formation 2. Unusual body attitudes

the 2 types of carburetor icing

1. Fuel evaporation ice 2. Throttle ice

The first place on a piston engine aircraft (non fuel injection) to start accumulating ice during flight

Carburetor

The process of fuel evaporation ice

Fuel vapor inside the venturi absorbs heat which drops the overall temperature

Typical temperature range and humidity percentage which carburetor ice will start to form

40-50 F, 60%

The very specific area in a (non fuel injection) piston engine where throttle icing first accumulates

Behind the partially closed throttle valve

The description of a pressure balance duct in a carburetor system

A duct which balances pressure between the float chamber and the venturi

The type of system, also named by anti-detonation injection system, used on piston engines with pressure injection, that produce

Water Injection system

The composition of the fluid injected into a pressure injection carburetor system

Water and alcohol

The term given for a fuel injection system which has the fuel directly injected into the combustion chamber

Direct fuel injection

The most commonly used type of fuel injection system used on piston engines

Continuous-flow fuel injection system use in piston engines

The fuel system in which fuel is delivered to the outside of the intake valves of the cylinder before being sucked into the cyilinder for combustion

Continuous-flow fuel injection

The 2 types of continuous-flow fuel injection systems used in the US

1. Precision Airmotive RSA 2. Teledyne Continental Motors

The 5 components of the RSA Fuel metering system

1. Venturi housing 2. Fuel metering unit 3. Fuel regulator 4. Fuel divider 5. Fuel Nozzle

The system in a carburetor which increases fuel flow at high power settings

Power enrichment/ Economizer

The 2 types of Economizers found on piston engines

1. Needle type 2. Air bleed type

Identify

Economizer needle

The measure of the vacuum pressure between the throttle and the cylinders

MAP pressure

The more the throttle is opened, the ________ that manifold pressure \_\_\_\_\_\_\_to atmospheric pressure.

closer, returns

Desribe what is happening

Manifold pressure is lower because there is not a large amount mass flow into the engine

Desribe what is happening

Since the throttle is being opened and there is more mass flow entering the intake, there is a greater density of fuel/air mxiture per same volume so there is an incrase in pressure

The 3 types of mixture control in float type carburetors

1. Variable Orifice 2. Back suction 3. Automatic mixture control (AMC)

With the Back-suction mixture control, describe operation during idle/ cutoff position

The float chamber is vented to the low pressure side of the venturi to elimiate any potential pressure gradient between the float chamber and the discharge nozzle

For idle mizture adjustment in a float carburetor, the engine should be run until the cylinder head

Cylinder head temperature is within normal range

The required action in order to check the idle mixture control on a float carbureator and what to watch for (3 conditions- too lean, too rich, just right)

Pull mixture aft and watch tachometer 1. RPM will increase slightly before dropping rapidly (just right) 2. Immediate drop in RPM (Too lean) 3. Momemtary increase of more than 50 RPM (too rich)

Typical idle speed for float type carburetors engines

600- 800 RPM

The checmical used to clean a carburetor of grease, oil and varnish from gasoline additives

Stoddard Solvent

What not to use to dry carburetors with after cleaning with Stodard Solvent and why

Shop rags, lint can clog up metering jets

How to float clearance between the gasket and float on some carburetors is measured

With the shank of a drill bit

Most carburetor bodies are constructed out of

cast aluminium

Since carburetor bodies are very soft (cast aluminium) the method for protecting any threaded openings from damage upon insertion

Insert the first thread, followed by application of thread lubricant to the threads

The mechanical control stops on a carburetor should be reached before

The controls reach their stops in the cockpit

The amount of control travel possible between the engine component's stop and the cockpit stop is termed

Spring back