Fuel System

Question 1

Two types of fuel system

Answer 1

1. Gravity-feed system
2. Fuel-Pump System

Question 2

Gravity-feed system

Answer 2

Utilizes the force of gravity to transfer fuel
Ex. on high-wing airplanes, the fuel tanks are
installed in the wings.

Question 3

Fuel-pump system

Answer 3

main pump system is engine driven auxiliary pump (electrical, used for startup)

Question 4

Fuel injected engines

Answer 4

In a fuel injection system, the fuel is injected directly into
the cylinders, or just ahead of the intake valve.

Question 5

FI Fuel pumps

Answer 5

provides fuel from the tanks to the FCU

Question 6

Auxiliary fuel pump (electrical)

Answer 6

provides fuel under pressure to the fuel/air
control unit for engine starting and/or emergency use

Question 7

ENGINE DRIVEN FUEL PUMP

Answer 7

used after starting the engine, and provides the
fuel to the fuel/air control unit

Question 8

Fuel Control Unit (FCU)

Answer 8

replaces the carburetor, meters fuel based on the mixture
control setting, and sends it to the fuel manifold
valve at a rate controlled by the throttle.

Question 9

Fuel Manifold Valve

Answer 9

distributes the mixture to individual nozzles

Question 10

Discharge Nozzle

Answer 10

atomize fuel into fine mist and inject the fuel/air mixture directly into each cylinder intake port

Question 11

Fuel injected engines advantage

Answer 11

• Reduction in evaporative icing
• Better fuel flow& distribution
• Faster throttle response
• Precise control of mixture
• Easier cold weather starts

Question 12

Fuel Injected engines disadvantage

Answer 12

• Difficulty in starting a hot engine
• Vapor locks during ground operations on hot days
• Problems associated with restarting an engine
  that quits because of fuel starvation

Question 13

Avgas 80

Answer 13

• Color Red
• Has a Very low lead content
• Only suitable for low compression engines

Question 14

Avgas 100 color

Answer 14

• Color Green
• High lead content
• Used on high compression engines

Question 15

Avgas 100LL color

Answer 15

• Color Blue
• Contains a Low lead content

Question 16

Jet A1 color

Answer 16

colorless or straw

Question 17

Automobile gas (MOGAS)

Answer 17

Use of automobile gas to the aircraft like for Example: Petron Blaze 100 octane.

Supplemental Type Certificate (STC) issued by the Federal Aviation Administration for approval of any modification.

Question 18

If proper grade fuel type is not available….

Answer 18

use the next higher grade as a substitute

Question 19

MOGAS advantages

Answer 19

Cheaper than AVGAS

Question 20

MOGAS disadvantage

Answer 20

• It tends to cause vapor locks in pipelines at high temperature and altitudes
• Carbureted engines using this fuel are more susceptible to carburetor icing
• It has low lead content which can lead to pre-ignition and
  detonation

Question 21

Fuel Related Problems

Answer 21

• PRE-IGNITION
• DETONATION
• FUEL CONTAMINATION DUE TO
  CONDENSATION

Question 22

Pre-ignition

Answer 22

• Premature burning is usually caused by a residual hot spot in the combustion chamber, often created by a small carbon deposit on a spark plug

Question 23

Pre-ignition cause

Answer 23

• Using a lower than prescribed octane rating

Question 24

Detonation

Answer 24

Uncontrolled/ Instantaneous explosive ignition of the fuel/air mixture in the combustion chamber

Question 25

Detonation cause

Answer 25

* Use of a lower fuel grade than that specified by the aircraft manufacturer. * Operation of the engine with extremely high manifold pressures in conjunction with low rpm. * Operation of the engine at high power settings with an excessively lean mixture. * Maintaining extended ground operations or steep climbs in which cylinder cooling is reduced.

Question 26

FUEL CONTAMINATION DUE TO CONDENSATION

Answer 26

* Empty space inside fuel tanks contains moisture that condenses when the outside air temperature cools Solution: * Refilling the fuel tanks to full levels at the end of each day.

Question 27

Vapor Lock

Answer 27

* Prominent in fuel injected aircraft after shutting down a hot engine. * Atomized fuel (sprayed by the intake nozzles) evaporates into the fuel lines, preventing fuel from reaching the engine during start-up. * Solution: Use of the auxiliary fuel pump.