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Powerplant > Fuel Metering > Flashcards

Fuel Metering Flashcards

1
Q

What are the air/fuel mixture ratios that support combustion?

A

8:1 - 17:1

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2
Q

What is the leanest air/fuel mixture?

A

17:1

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3
Q

What is the richest air/fuel mixture ratio?

A

8:1

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4
Q

What air/fuel mixture ratio is considered maximum power?

A

12:1

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5
Q

What is Stoichiometric?

A

The perfect air/fuel mixture in which both ingredients can be used up completely

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6
Q

What is the stoichiometric ratio?

A

15:1

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7
Q

What is the hottest air/fuel mixture?

A

Stoichiometric

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8
Q

What is the richest mixture ratio?

A

Idle mixture
(Because of poor air flow)

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9
Q

What is the SECOND richest mixture ratio?

A

Take off ratio
(Extra fuel is needed for cooling)

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10
Q

What is the leanest fuel/air mixture?

A

Cruise mixture
(Engine is running at reduced power & higher altitude)

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11
Q

What 2 reasons are why engines are shut down with the mixture control?

A

To prevent the un-burnt fuel from
washing away the oil film off the
cylinder wall
&
Safety (no accidental start ups)

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12
Q

What 3 instruments are used to monitor engine power?

A

Manifold Absolute Pressure (MAP) - airflow

Fuel Flow

Tachometer (RPM)

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13
Q

Where can manifold pressure be taken?

A

Anywhere after the throttle valve or before the intake valve

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14
Q

The manifold gauge measures pressure where?

A

In the inlet manifold which relates to the engine power

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15
Q

The fuel flow gauge measures what?

A

The amount of fuel delivered by the fuel system which relates to the engine power

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16
Q

What is the tachometer used to monitor?

A

Engine power and to ensure the engine is operated within certified limits

17
Q

What air/fuel mixture burns the slowest?

A

Lean

18
Q

Some aircraft use ________ ignition timing.

A

Staggered

19
Q

What does a float carburetor do?

A

Provides a uniform air/fuel mixture as the airflow varies
Has an internal reservoir for fuel that maintains a constant level with a float/valve mechanism

20
Q

What does the Venturi do?

A

Converts potential energy to kinetic energy or pressure to velocity
-Proportions the fuel/air mixture
-Decreases the pressure at the discharge nozzle
-Limits the airflow at full throttle

21
Q

Where does the fuel level inside of a float bowl need to be adjusted to?

A

Slightly below the discharge nozzle outlet

22
Q

Where is the discharge nozzle located?

A

In the Venturi

23
Q

What is Air Bleed?

A

Aids in atomizing by increasing surface area of fuel.
Keeps a constant air/fuel ratio as air flow varies

24
Q

What does the Metering Jet do?

A

Restricts maximum amount of fuel

25
Q

What are the two types of mixture control?

A

Variable orifice
&
Back suction

26
Q

How does a variable orifice work?

A

Restricts fuel leaving float bowl

27
Q

How does back suction work?

A

Reduces float chamber pressure reducing fuel metering force

28
Q

What is an economizer?

A

Power Enrichment System
Adds additional fuel at high power settings for cooling purposes

29
Q

What is the purpose of the acceleration system?

A

Allows fuel to be fed from nozzle until flow can be generated
(Because fuel lags behind the airflow)

30
Q

Can an A&P overhaul a pressure carburetor?

A

No, it is considered a major repair

31
Q

What is the function of Chamber A in a pressure carb?

A

Impacts air pressure

32
Q

What is the function of Chamber B in a pressure carb?

A

Venturi Pressure

33
Q

What is the function of Chamber C in a pressure carb?

A

Metered fuel

34
Q

What is the function of Chamber D in a pressure carb?

A

Unmetered fuel

35
Q

What keeps a constant pressure inside of a pressure carburetor?

A

The discharge nozzle needle valve

Powerplant (18 decks)

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