System 4 exam

What are the main components of an aircraft fuel system?

Storage tanks, pumps, filters, valves, fuel lines, metering devices, monitoring devices

What is the primary purpose of an aircraft fuel system?

To provide uninterrupted flow of contaminant free fuel regardless of attitude

Under which regulations are aircraft fuel systems designed?

FAR Part 23, 25, 27, 29, and 31

What must every fuel system ensure for engine operation?

Proper fuel flow rate and pressure under all operating conditions

Can a fuel pump draw fuel from more than one tank at a time?

No

What must be prevented from entering fuel system lines?

Air

What must turbine fuel systems tolerate regarding water?

They must operate with fuel containing water without interruption

What is fuel system independence?

Failure of one component cannot cause loss of power to more than one engine

What is corona discharge?

Electrical discharge due to potential difference between aircraft and atmosphere

What is streamering?

A branch-like ionized path during a lightning strike

What is the required fuel flow for gravity-fed systems?

150% of takeoff fuel consumption

What is the required fuel flow for pump systems (reciprocating engines)?

125% of fuel required at maximum takeoff power

What is required fuel flow for turbine engines?

100% of required fuel under all operating conditions

What is unusable fuel?

Fuel remaining when the first sign of malfunction occurs

What must be prevented in hot weather fuel operation?

Vapor lock

What is vapor lock?

Fuel vaporizing in lines, blocking fuel flow

What causes vapor lock?

High temperature, low pressure, turbulence

What must fuel tanks withstand?

Vibration, inertia, fluid, and structural loads

Can fuel tanks be installed on the engine side of a firewall?

No

Minimum clearance between fuel tank and firewall?

½ inch

What properties must tank enclosures have?

Fume-proof, fuel-proof, vented, and drained externally

Minimum fuel tank expansion space?

2% of tank capacity

What is the purpose of a fuel tank sump?

To collect contaminants and water

What color is 100LL AVGAS?

Blue

What color is 100 AVGAS?

Green

What color is 80/87 AVGAS?

Red

What color is 82UL fuel?

Purple

What is detonation?

Uncontrolled explosion of fuel in the combustion chamber

What sound indicates detonation?

Pinging or knocking

What is preignition?

Fuel igniting before the spark plug fires

What increases resistance to detonation?

Higher octane rating

What is the most common aviation turbine fuel?

Jet A

Freezing point of Jet A fuel?

-40°F

Freezing point of Jet A-1 fuel?

-52.6°F

What type of system do high-wing aircraft typically use?

Gravity feed system

What type of system do low-wing aircraft use?

Pump feed system

Why do low-wing aircraft need pumps?

Fuel cannot flow uphill to the engine

What is a crossfeed system used for?

Allowing one engine to draw fuel from another tank

What is a fuel jettison system used for?

To dump fuel to reduce aircraft weight

Minimum fuel jettison rate requirement?

1% of maximum weight per minute

What must fuel jettison systems avoid?

Fire hazards and fuel entering aircraft areas

What is the main difference between AVGAS and jet fuel?

AVGAS is more volatile; jet fuel has higher viscosity and boiling point

What contamination is most common in fuel?

Water

How can water enter fuel tanks?

Condensation from temperature changes

How is microbial contamination controlled?

Biocides

What problems do microbes cause in fuel systems?

Clog filters, corrode tanks, degrade fuel

What is required for each reciprocating engine fuel pump?

One engine-driven pump and one backup

What must emergency fuel pumps be?

Independent of main pump power supply

Where must an additional fuel filter be located?

Between tank outlet and fuel metering device

What is required for aircraft fuel filler openings?

Proper size and electrical bonding to ground

T or F: helicopter fuel systems are completely different than fixed wing regards to equipment

False

Turbine engine fuels have____ viscosity than reciprocating engines

lower

______ require a large access opening for replacement

Rigid tanks

Fuel strainer that incorporates a sediment collection bowl usually found on light aircraft is what:

Gascolator

What material are most fuel tanks made from?

Noncorrosive material

How are fuel tanks vented?

Cap, vent line, or both

Where is the sump located in a fuel tank?

Lowest point of the tank

What is the purpose of the sump?

Collect contaminants and water

What are the three basic types of fuel tanks?

Rigid removable, bladder, integral

What materials are rigid removable tanks made of?

Aluminum alloy or stainless steel

How are rigid tanks secured in the aircraft?

Supported by airframe with padded straps

What are bladder tanks made of?

Reinforced flexible material

Why must bladder tanks remain wet?

To prevent cracking over time

How must bladder tanks be installed?

Clipped to fuselage, smooth and unwrinkled

Where are integral tanks commonly used?

Transport and high-performance aircraft

What forms an integral fuel tank?

Sealed wing or fuselage structure

What is an advantage of integral tanks?

High volume with low weight

What is the purpose of baffles in integral tanks?

Prevent fuel sloshing

What are rigid fuel lines typically made of?

Aluminum alloy

What fittings are used with rigid lines?

Army/Navy (AN) or Military Standard (MS) fittings

Where are stainless steel fuel lines used?

Wheel wells and engine compartments

What are flexible fuel lines made of?

Synthetic rubber with reinforced braid

Where are flexible lines used?

Where vibration exists between components

What is the purpose of fuel valves?

Shut off or route fuel flow

What must all fuel valves provide?

Positive position indication

Name types of hand-operated valves.

Cone, poppet, gate

What operates motor-driven valves?

Electric motors

Why are motor-operated valves common on large aircraft?

Remote location from cockpit

What is a characteristic of solenoid-operated valves?

Open and close quickly

What is the purpose of fuel pumps?

Deliver fuel under pressure to the engine

What is the primary fuel pump on most aircraft?

Engine-driven pump

What is the purpose of an auxiliary (boost) pump?

Backup and provide positive pressure

When are boost pumps commonly used?

Starting and high-altitude operations

What is another name for a hand-operated fuel pump?

Wobble pump

What is the purpose of an engine primer pump?

Prime engine for start

What is the most common type of auxiliary fuel pump?

Centrifugal boost pump

Where are centrifugal boost pumps located?

Inside or below the fuel tank

What is the purpose of ejector pumps?

Maintain pressure, prevent cavitation

What principle do ejector pumps use?

Bernoulli's Principle

What are pulsating electric pumps used for?

Starting, backup, high altitude

How do pulsating electric pumps operate?

Solenoid-driven plunger motion

What is the purpose of fuel filters?

Remove contaminants

What does a coarse fuel filter remove?

Large debris

What does a fine fuel filter remove?

Small particles and water

What particle size do micronic filters remove?

10-25 micron particles

What is a gascolator?

Fuel strainer with sediment bowl

Where is the gascolator located?

Lowest point in system

When should the gascolator be drained?

Preflight

What type of filter is used in turbine engines?

Micronic filter

What is the purpose of fuel heaters?

Prevent icing at high altitude