Aircraft Fuel Systems

A fuel pressure warning switch contacts close and warning light is turned on when?

the fuel pressure drops below specified limits.

Fuel jettisoning is usually accomplished

through a common manifold and outlet in each wing

Fuel is moved overboard in most fuel jettison systems by?

Boost pumps.

What is used in many aircraft to prevent bubbles in the fuel after it leaves the tank when atmospheric pressure is lower than fuel vapor pressure?

Boost pumps.

A typical large transport aircraft fuel manifold system allows how many of the following?

- All tanks can be serviced through a single connection. - Any engine can be fed from any tank. - All engines can be fed from all tanks simultaneously. - A damaged tank can be isolated from the rest of the fuel system.

Microbial growth is produced by various forms of microorganisms that live and multiply in the water interfaces of jet fuels. Which of the following could result if microbial growth exists in a jet fuel tank and is not corrected?

- Interference with fuel flow. - Interference with fuel quantity indicators. - Electrolytic corrosive action in a metal tank.

What are the four general types of fuel quantity gauges?

- Sight glass. - Mechanical. - Electrical - Electronic.

When installing a rigid fuel line, 1/2 inch in diameter, at what intervals should the line be supported?

16 inches.

What should be used to remove flux from an aluminum tank after welded repairs?

5 percent solution of nitric or sulfuric acid.

What is the maximum vapor pressure allowable for an aircraft fuel?

7 PSI.

Which of the following would be most useful to locate and troubleshoot an internal fuel leak in an aircraft fuel system?

A fuel system schematic.

(1) A fuel pressure relief valve is required on an aircraft positive-displacement fuel pump. (2) A fuel pressure relief valve is required on an aircraft centrifugal fuel boost pump. Regarding the above statements,

A. only No. 1 is true.

What is the purpose of the pump crossfeed valve?

Allow operation of engines from one tank.

Entrained water in aviation turbine fuel is a hazard because of its susceptibility to freezing as it passes through the filters. What are common methods of preventing this hazard?

Anti-icing fuel additives and fuel heater.

How may the antiknock characteristics of a fuel be improved?

By adding a knock inhibitor

How is the outlet fuel pressure regulated on a submerged, single-speed, centrifugal-type fuel pump?

By the pump's design and internal clearances.

What should be used to inert an integral fuel tank before attempting repairs?

CO(2).

A probe or a series of probes is used in what kind of fuel quantity indicating system?

Capacitor.

Which gas is used for purging an aircraft fuel tank?

Carbon dioxide.

How does temperature affect fuel weight?

Cold fuel is heavier per gallon.

If it is necessary to enter an aircraft's fuel tank, which procedure should be avoided?

Conduct the defueling and tank purging operation in an air-conditioned building.

A transducer in a fuel pressure system serves what function?

Converts fluid pressure directly through a transmitter to the indicator.

A transmitter in a fuel pressure warning system serves what function?

Converts fluid pressure to an electrical signal

Which procedure must be followed when defueling aircraft with sweptback wings?

Defuel the outboard wing tanks first.

What is one disadvantage of using aromatic aviation fuels?

Deteriorates rubber parts.

Fuel system components must be bonded and grounded in order to?

Drain off static charges.

Fuel jettisoning past the limits prescribed by Federal Aviation Regulations is usually prevented by?

Dump limit valves or a low-level circuit.

What type of remote-reading fuel quantity indicating system has several probes installed in each fuel tank?

Electronic.

Which aircraft fuel quantity indicating system incorporates a signal amplifier?

Electronic.

Select one means of controlling the fuel temperature on turbine-powered aircraft.

Engine bleed air to a heat exchanger.

A fuel jettison system is required under certain conditions if the maximum takeoff weight exceeds the maximum landing weight. What regulations cover the requirements of fuel jettisoning?

FAR: - 23, - 25 - CAM 4b.

What is the dielectric (nonconducting material) in a capacitance-type fuel quantity indicating system?

Fuel and air in the tank

Where is fuel pressure taken for the pressure warning signal on most aircraft engines?

Fuel pressure line of the carburetor.

Which of the following would give the first positive indication that a change-over from one fuel tank to another is needed?

Fuel pressure warning.

What method is used on turbine-powered aircraft to determine when the condition of the fuel is approaching the danger of forming ice crystals?

Fuel temperature indicator.

Which of the following precautions is most important during refueling operations?

Fuel to be used must be appropriately identified.

Which statement concerning an electronic capacitance-type fuel quantity indicating system is true?

It has no moving parts in the tank.

Why is the capacitance fluid quantity indicating system more accurate in measuring fuel level than a mechanical type?

It measures by weight instead of volume.

What is the purpose of a float-operated transmitter installed in a fuel tank?

It sends an electric signal to the fuel quantity indicator.

Why is the main fuel strainer located at the lowest point in the fuel system?

It traps any small amount of water that may be present in the fuel system.

Why are jet fuels more susceptible to water contamination than aviation gasoline?

Jet fuel has a higher viscosity than gasoline.

The use of turbine fuels in aircraft has resulted in some problems not normally associated with aviation gasolines. One of these problems is?

Microbial contaminants.

The location of leaks and defects within the internal portions of the fuel system can usually be determined by?

Observing the pressure gauge and operating the selector valves

How many engine driven fuel pumps per engine are required for engines requiring fuel pumps?

One fuel pump for each engine.

What is the minimum distance allowed between a fuel tank and the fire wall separating the engine?

One-half inch.

What method would be used to check for internal leakage of a fuel valve without removing the valve from the aircraft?

Place the valve in the OFF position, drain the strainer bowl, and with boost pump on, watch to see if fuel flows to the strainer bowl.

What unit is generally used to actuate the fuel pressure warning system?

Pressure-sensitive mechanism

What unit would be adjusted to change the fuel pressure warning limits?

Pressure-sensitive mechanism.

Normal fuel crossfeed system operation in multiengine aircraft?

Provides a means to maintain a balanced fuel load condition.

What flight safety-related advantage does a pressure fueling system provide?

Reduces the chances for fuel contamination.

Which of the following may be used for the repair of fuel leaks on most integral fuel tanks?

Riveting and resealing.

What type of fuel-booster pump requires a pressure relief valve?

Sliding vane.

As a general rule, which statement is true regarding fuel leaks?

Stains, seeps, and heavy seeps, (in addition to running leaks) are considered flight hazards when located in unvented areas of the aircraft.

What is the recommended practice for cleaning a fuel tank before welding?

Steam clean the tank interior.

Which of the following is necessary to effectively troubleshoot a fuel pressure warning system?

The manufacturer's maintenance manuals.

What precautions must be observed if a gravity-feed fuel system is permitted to supply fuel to an engine from more than one tank at a time?

The tank airspaces must be interconnected.

Before fueling an aircraft by using the pressure fueling method, what important precaution should be observed?

The truck pump pressure must be correct for that refueling system.

According to Part 23, what minimum required markings must be placed at or near each appropriate fuel filler cover for reciprocating engine-powered airplanes?

The word 'Avgas' and the minimum fuel grade.

What minimum required markings must be placed on or near each appropriate fuel filler cover on utility category aircraft?

The word 'Avgas' and the minimum fuel grade.

What is the primary purpose of the crossfeed system?

To allow the feeding of any engine from any tank.

Why is it necessary to vent all aircraft fuel tanks?

To limit pressure differential between the tank and atmosphere.

What is one purpose of a fuel tank vent?

To maintain atmospheric pressure.

What is the purpose of flapper-type check valves in integral fuel tanks?

To prevent fuel from flowing away from the boost pumps.

Why are integral fuel tanks used in many large aircraft?

To reduce weight.

Why are centrifugal-type boost pumps used in fuel systems of aircraft operating at high altitude?

To supply fuel under pressure to engine-driven pumps

How many vents, arranged so that they are not likely to become plugged at the same time, must be used in multiengine fuel systems?

Two

Which of the following is employed to maintain lateral stability when jettisoning fuel?

Two separate independent systems.

What can be done to eliminate or minimize the microbial growth problem in an aircraft jet fuel tank?

Use anti-icing and antibacterial additives.

What must each fuel quantity indicator be calibrated to read during level flight when the quantity of fuel remaining is equal to the unusable fuel supply?

Zero

In some aircraft with several fuel tanks, the possible danger of allowing the fuel supply in one tank to become exhausted before the selector valve is switched to another tank is prevented by the installation of?

a fuel pressure warning signal system.

An aircraft's integral fuel tank is?

a part of the aircraft structure.

Flapper valves are used in fuel tanks to?

act as check valves.

A fuel totalizer is a component which indicates the?

amount of fuel in all tanks.

The electronic-type fuel quantity indicating system consists of a bridge circuit?

an amplifier, an indicator, and a tank unit.

If an aircraft is fueled from a truck or storage tank which is known to be uncontaminated with dirt or water, periodic checks of the aircraft's fuel tank sumps and system strainers?.

are still necessary due to the possibility of contamination from other sources.

Pressure fueling of aircraft is usually accomplished through?

at least one single point connection.

To prevent vapor lock in fuel lines at high altitude, some aircraft are equipped with?

booster pumps.

(1) Gas-turbine-engine fuel systems are very susceptible to the formation of ice in the fuel filters. (2) A fuel heater operates as a heat exchanger to warm the fuel. Regarding the above statements,

both No. 1 and No. 2 are true

(1) A fuel heater can use engine bleed air as a source of heat. (2) A fuel heater can use engine lubricating oil as a source of heat. Regarding the above statements,

both No. 1 and No. 2 are true.

(1) A fuel pressure gauge is a differential pressure indicator. (2) A fuel pressure gauge indicates the pressure of the fuel entering the carburetor. Regarding the above statements

both No. 1 and No. 2 are true.

(1) The fuel jettison valve must be designed to allow flight personnel to close the valve during any part of the jettisoning operation. (2) During the fuel jettisoning operation, the fuel must discharge clear of any part of the airplane. Regarding the above statements,

both No. 1 and No. 2 are true.

One advantage of electrical and electronic fuel quantity indicating systems is that the indicator?

can be located any distance from the tank(s).

The probe of a capacitance-type fuel level gauge is essentially a?

capacitor with fuel and air acting as a dielectric.

In an electronic-type fuel quantity indicating system, the tank sensing unit is a?

capacitor.

he type of fuel-boost pump that separates air and vapor from the fuel before it enters the line to the carburetor is the?

centrifugal-type pump.

The presence of fuel stains around a fuel nozzle would indicate?

clogged fuel nozzle.

The purpose of a diaphragm in a vane-type fuel pump is to?

compensate fuel pressures to altitude changes.

If a bladder-type fuel tank is to be left empty for an extended period of time, the inside of the tank should be coated with a film of?

engine oil.

Many fuel tanks incorporate _________________ valves to prevent fuel from flowing away from the boost pump or tank outlet when the aircraft is in a high 'G' maneuver

flapper

An electrical-type fuel quantity indicating system consists of an indicator in the cockpit and a?

float-operated transmitter installed in the tank.

Integral fuel tanks on transport aircraft are?

formed by the aircraft structure.

Aircraft pressure fueling systems instructional procedures are normally placarded on the?

fuel control panel access door.

When routing a fuel line between two rigidly mounted fittings the line should?

have at least one bend between such fittings.

Fuel heaters are used with fuel systems for turbine engines to prevent ____________ in the fuel from clogging system filters

ice crystals

A fuel temperature indicator is located in the fuel tanks on some turbine-powered airplanes to tell when the fuel may be?

in danger of forming ice crystals.

Aircraft defueling should be accomplished?

in the open air for good ventilation.

A fuel system must be designed to prevent fuel-vapor ignition caused by?

lightning

The primary purpose of an aircraft's fuel jettison system is to quickly achieve a?

lower landing weight.

The vapor pressure of aviation gasoline is?

lower than the vapor pressure of automotive gasoline.

(1) On a large aircraft pressure refueling system, a pressure refueling receptacle and control panel will permit one person to fuel or defuel any or all fuel tanks of an aircraft. (2) Because of the fuel tank area, there are more advantages to a pressure fueling system in light aircraft. Regarding the above statements,

only No. 1 is true.

(1) The function of a fuel heater is to protect the engine fuel system from ice formation. (2) An aircraft fuel heater cannot be used to thaw ice in the fuel screen. Regarding the above statements,

only No. 1 is true.

(1) If aviation gasoline vaporizes too readily, fuel lines may become filled with vapor and cause increased fuel flow. (2) A measure of a gasoline's tendency to vapor lock is obtained from the Reid vapor pressure test. Regarding the above statements,

only No. 2 is true.

When inspecting a fuel system, you should check all valves located downstream of boost pumps with the pumps?

operating.

The primary purpose of a fuel tank sump is to provide a?

place where water and dirt accumulations in the tank can collect and be drained.

A capacitance-type fuel quantity indicating system measures fuel in?

pounds.

When inspecting a removable rigid fuel tank for leaks, what procedure should be followed?.

pressurize the tank with air and brush with soapy water

The purpose of the baffle plate in a fuel tank is to?

resist fuel surging within the fuel tank.

One advantage of electrical and electronic fuel quantity indicating systems is that?

several fuel tank levels can be read on one indicator.

When moving the mixture control on a normally operating engine into the idle cutoff position, engine RPM should?

slightly increase before the engine starts to die.

Fuel baffles are installed in tanks to prevent ______________________ caused by changes in the attitude of the aircraft

surging

A drip gauge may be used to measure?

the amount of fuel in the tank

Fuel-boost pumps are operated?

to provide a positive flow of fuel to the engine.

When fuel quantity is measured in pounds instead of gallons, the measurement will be more accurate because fuel volume?

varies with temperature change.

A digital fuel totalizer automatically indicates the amount of fuel used, fuel remaining, current rate of consumption, and fuel?

weight, aboard at takeoff.