Aircraft Fuel System Flashcards
Fuel jettisoning is usually accomplished
through a common manifold and outlet in each wing
The primary purpose of an aircraft’s fuel jettison system is to quickly achieve a
lower landing weight
(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
Which of the following is employed to maintain lateral stability when jettisoning fuel?
Two separate independent systems
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?
Federal Aviation Regulation Part 23, 25 and CAM 4b
Fuel is moved overboard in most fuel jettison systems by
boost pumps
Fuel jettisoning past the limits prescribed by Federal Aviation Regulations is usually prevented by
dump limit valves or a low level circuit
Which procedure must be followed when defueling aircraft with sweptback wings?
Defuel the outboard wing tanks first
(Refer to Figure 17.) What is the purpose of the pump crossfeed valve?
ans. allow operation of engines from one tank
Normal fuel crossfeed system operation in multiengine aircraf
provides a means to maintain a balanced fuel load condition
What is the primary purpose of the crossfeed system?
to allow the feeding of any engine from any tank
Fuel system components must be bonded and grounded in order to
drain off static charges
A typical large transport aircraft fuel manifold system allows how many of the following?
1. All tanks can be serviced through a single connection.
2. Any engine can be fed from any tank.
3. All engines can be fed from all tanks simultaneously.
4. A damaged tank can be isolated from the rest of the fuel system
1,2,3 and 4
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
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
Which of the following precautions is most important during refueling operations?
fuel to be used must be appropriately identified
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
What flight safety-related advantage does a pressure fueling system provide?
reduces the chances for fuel contamination
Aircraft pressure fueling systems instructional procedures are normally placarded on the
fuel control panel access door
Pressure fueling of aircraft is usually accomplished through
at least one single connection
Which of the following may be used for the repair of fuel leaks on most integral fuel tanks?
riveting and resealing
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 is one purpose of a fuel tank vent?
to maintain atmospheric pressure
When inspecting a removable rigid fuel tank for leaks, what procedure should be followed?
pressure the tank with air and brush with soapy water
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
What is the recommended practice for cleaning a fuel tank before welding?
steam clean the tank interior
An aircraft’s integral fuel tank is
a part of the aircraft structure
Which gas is used for purging an aircraft fuel tank?
carbon dioxide
Why is the main fuel strainer located at the lowest point in the fuel system?
it traps small amount of water that may be present in the fuel systems
The purpose of a diaphragm in a vane-type fuel pump is to
compensate fuel pressures to altitude changes
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
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
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
The presence of fuel stains around a fuel nozzle would indicate
clogged fuel nozzle
What should be used to inert an integral fuel tank before attempting repairs?
Co2
What should be used to inert an integral fuel tank before attempting repairs?
5 percent solution of nitric or sulfuric acid
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
Why are jet fuels more susceptible to water contamination than aviation gasoline?
jet fuel has a higher viscosity than gasoline
When installing a rigid fuel line, 1/2 inch in diameter, at what intervals should the line be supported?
16 inches
The probe of a capacitance-type fuel level gauge is essentially a
capacitor with fuel and air acting as a dielectric
Which statement concerning an electronic capacitance-type fuel quantity indicating system is true?
it has no moving parts in the tank
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
A drip gauge may be used to measure
the amount of fuel in the tank
The electronic-type fuel quantity indicating system consists of a bridge circuit,
an amplifier, an indicator, and a tank unit
A probe or a series of probes is used in what kind of fuel quantity indicating system?
capacitor
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
One advantage of electrical and electronic fuel quantity indicating systems is that
several fuel tanks levels can be read on one indicator
A fuel totalizer is a component which indicates the
amount of fuel in all tanks
What is the dielectric (non-conducting material) in a capacitance-type fuel quantity indicating system?
fuel and air in the tank
A capacitance-type fuel quantity indicating system measures fuel in
pounds
What are the four general types of fuel quantity gauges?
1. Sight glass.
2. Mechanical.
3. Electrical.
4. Electronic.
5. Bourdon tube.
6. Vane-type transmitter.
1,2,3,4
How does temperature affect fuel weight?
a cold fuel is heavier per gallon
One advantage of electrical and electronic fuel quantity indicating systems is that the indicator
can be located any distance from the tanks
When fuel quantity is measured in pounds instead of gallons, the measurement will be more accurate
because fuel volume
varies with temperature change
An electrical-type fuel quantity indicating system consists of an indicator in the cockpit and a
float- operated transmitter installed in the tank
What is the purpose of a float-operated transmitter installed in a fuel tank?
it sends electric signal to the fuel quantity indicator
In an electronic-type fuel quantity indicating system, the tank sensing unit is a
capacitor
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
What unit would be adjusted to change the fuel pressure warning limits?
pressure sensitive mechanism
Select one means of controlling the fuel temperature on turbine-powered aircraft.
engine bleed air to a heat exchanger
What is the purpose of flapper-type check valves in integral fuel tanks?
to prevent fuel from flowing away from the boost pumps
What unit is generally used to actuate the fuel pressure warning system?
pressure sensitive mechanism
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 would give the first positive indication that a change-over from one fuel tank to
another is needed?
fuel pressure warning
A fuel pressure warning switch contacts close and warning light is turned on when
the fuel pressure drops below specified limits
A transmitter in a fuel pressure warning system serves what function?
converts fluid pressure to an electrical signal
Where is fuel pressure taken for the pressure warning signal on most aircraft engines?
fuels pressure line of the carburetor
Which of the following is necessary to effectively troubleshoot a fuel pressure warning system?
the manufacturer’s maintenance manuals
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
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
(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) 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) 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,
only no. 1 is true.
The primary purpose of a fuel tank sump is to provide a
place where water and dirt accumulation in the tank can collect and be drained
Why are integral fuel tanks used in many large aircraft?
reduce weight
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
Aircraft defueling should be accomplished
in the open air for good ventilation
Integral fuel tanks on transport aircraft are
formed by the aircraft structure
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
The purpose of the baffle plate in a fuel tank is to
resist fuel surging within the fuel tank
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 one disadvantage of using aromatic aviation fuels?
deteriorates rubber parts
Fuel-boost pumps are operated
to provide a positive flow of fuel to the engine
Flapper valves are used in fuel tanks to
act as check valves
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
Why is it necessary to vent all aircraft fuel tanks?
to limit pressure differential between the tank and the atmosphere
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
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
What type of fuel-booster pump requires a pressure relief valve?
sliding vane
To prevent vapor lock in fuel lines at high altitude, some aircraft are equipped with
booster pumps
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
When inspecting a fuel system, you should check all valves located downstream of boost pumps with
the pumps
operating
The 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
(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
When routing a fuel line between two rigidly mounted fittings the line should
have at least one bend between such fittings
(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
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?
1. Interference with fuel flow.
2. Interference with fuel quantity indicators.
3. Engine seizure.
4. Electrolytic corrosive action in a metal tank.
1,2,4
The vapor pressure of aviation gasoline is
lower than the vapor pressure of automotive gasoline
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 is the maximum vapor pressure allowable for an aircraft fuel?
7 PSI
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
How may the antiknock characteristics of a fuel be improved?
by adding knock inhibitor
A digital fuel totalizer automatically indicates the amount of fuel used, fuel remaining, current rate of
consumption, and fuel
weight , aboard at takeoff
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
How many engine driven fuel pumps per engine are required for engines requiring fuel pumps?
one fuel pump for each engine
A fuel system must be designed to prevent fuel-vapor ignition caused by
lightning
What is the minimum distance allowed between a fuel tank and the fire wall separating the engine?
one-half inch
Fuel baffles are installed in tanks to prevent ______________________ caused by changes in the
attitude of the aircraft.
surging
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
Fuel heaters are used with fuel systems for turbine engines to prevent ____________ in the fuel from
clogging system filters.
ice crystals
A transducer in a fuel pressure system serves what function?
converts fluid pressure directly through a transmitter to the indicator
