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PPL AGK > Fuel > Flashcards

Fuel Flashcards

1
Q

what is the normal type of fuel used in aircraft?

A

aviation gasoline or AVGAS.

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2
Q

what are the grades of AVGAS? (4)

A

MOGAS 91 - PURPLE
MOGAS 95 - ORANGE/YELLOW
AVGAS 100LL - LIGHT BLUE/CYAN
AVTUR/JET A1 - STRAW COLOURED/CLEAR

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3
Q

how do you read OCTANE? (e.g AVGAS 100LL)

A

100 is the octane number, the higher the better resistance to detonation or knocks.

LL means low lead. low lead content is 2mL per imperial gallon or one part per 2250

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4
Q

if a fuel has a mix of 87% octane and 13% heptane normal what does this mean? and how can you improve it?

A

it’s graded as 87 octane. to improve fuel octane rating, Tetra Ethyl Lead (TEL) can be added.

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5
Q

what is the max amount of TEL that can be added?

A

5.5ml per imperial gallon or one part per 800 for avgas.

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6
Q

what does OCTANE 100/130 mean?

A

means that 100/130 AVGAS has an octane rating of 100 at the lean power settings and 130 at rich settings.

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7
Q

how does a gravity feed system work?

A

gravity moves the fuel from the tank to the carburettor.

fuel flow is maintained due to gravity and so long as the pressure provided is 150% of the maximum flow rate required there’s no need for a fuel pump.

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8
Q

fuel systems typically have what?

A

four arrangements and is normally set to both but if an imbalance occurs, manually selecting the one with more help.

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9
Q

how do pressure systems work?

A

fuel is drawn from tanks and is routed via the fuel selector valve. which is then directed to the strainer via two fuel pumps. first is electrically driven and the second is an engine-driven pump.

In normal flight engine-driven pump supplies fuel under pressure to the carburettor. a fuel line also runs to the fuel pressure gauge in the cockpit. if the engine pump fails, the engine stops so the electric pump must be switched on immediately.

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10
Q

when is the electric fuel pump switched on? and what can it do? (6)

A
  • normally during critical stages of flight like takeoff and landing and at flights below 1000ft.
  • Provides fuel for starting
  • electrically driven
  • purge fuel lines of vapour lock
  • may prime cylinders
  • supply fuel if engine driven pump fails
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11
Q

what are in the tanks of pressure systems?

A

float type content units that may have direct reading fuel quantity transmitters not requiring power that sends information to fuel quantity gauges on the instrument panel.

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12
Q

what is unusable fuel?

A

fuel in the tank(s) that is not considered to be accessible for running the engine

e.g if tank has 10 gallons, if the level falls to that of the outlet, there may be as 1 gallon left in the tank and that’s referred to as unusable fuel, so that means only 9 gallons are usable. the fuel gauges only read usable fuel

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13
Q

what do the numbers mean at the of different fuel?

A

fuel grade - below a figure of 100 they’re known as octane rating and above they’re known as performance number.

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14
Q

what are the three different types of fuel?

A

AVGAS - used for light aircraft
MOGAS - used for motor vehicles like cars
AVTUR - used by jet turbine aircraft.

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15
Q

what are the characteristics of AVGAS? (4)

A
  • Can cause damage if used in older lower compression engines.
  • labelled red
  • dyed blue
  • higher quality control than MOGAS
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16
Q

what are the characteristics of MOGAS? (4)

A
  • may cause detonation in AVGAS designed planes
  • labelled purple
  • dyed purple for 91 and yellow for 95
  • vapourises more easily than AVGAS causing vapour locks
17
Q

what are the characteristics of JET A1/AVTUR?

A
  • straw or clear coloured
  • kerosene smell
  • damage AVGAS planes
  • labelled black
18
Q

what can using MOGAS in AVGAS aircraft lead to? (3)

A
  • leads to vapour locks in the engine
  • the engine will produce less power which contributes to detonation
  • spark plugs can foul.
19
Q

what is the most common contaminant in fuel?

A

water

20
Q

how can contaminants be avoided? (3)

A

condensation can occur at night inside the tank (if near empty) so keeping them full overnight minimises the chance.

The fuel system typically has a sump at the bottom of each tank collecting any contaminants that are heavier than fuel can collect. a check of fuel via taking fuel samples through the fuel drain should be done before each flight and after refuelling to check for contaminants.

if present show check with instructor or engineer.

21
Q

what are the disadvantages to a gravity feed system?

A
  • extreme attitude changes can affect fuel flow. if gravity can’t assist the fuel into the carburettor, it’ll be deprived of fuel and cause engine failure.
  • vapour locking. where fuel vapourises in the fuel lines prevent fuel from flowing.
22
Q

what is the use of the priming system?

A

to assist with starting the engine when it’s struggling to do so such as during cold days.

23
Q

how does a priming system work?

A

pumping fuel into most of the cylinders. operated from the cockpit with either a hand pump or electric activated it bypasses the carburettor and injects fuel directly into the cylinders.

24
Q

what is incorporated into most fuel systems and what do they do?

A

fuel filters and fuel strainers.

they are the last opportunity to stop impurities from entering the carburettor.

25
Q

what is normally at the bottom of each fuel tank?

A

sumps where any impurities heavier then fuel can collect.

drain cock fitted at the lowest point allowing pilots to collect samples of fuel to find potential contaminants.

26
Q

why are fuel vents important?

A

allow atmospheric pressure to be maintained above the fuel as its being consumed during the flight.

preventing a partial vacuum from developing in the tank which could lead to the collapse of the tank or fuel starvation.

27
Q

during pre-flight what should be done with fuel vents and filler cap?

A

check if secured tightly.

vents aren’t blocked or obstructed.

28
Q

what do baffles do?

A

stop fuel from sloshing and moving quickly from one end to the other.

As if they were to move around it would mean the COG to suddenly move and would cause problems.

29
Q

Fuel lines from each tank will meet together where?

and what does this allow a pilot to do?

A

meet together at the fuel selector which is operated from the cockpit.

allows the pilot to choose whether the fuel is on or off and in some aircraft will allow for the pilot to select individual tanks.

30
Q

what does a fuel quantity gauge do? and how does it work?

A

tells you how much fuel remains in the tank.

some might have a mechanical float with an arm or it may have a system that measure the capacitance from sensors in the tank.

31
Q

what does a fuel flow metre or fuel pressure gauge do?

A

allows a pilot to assess the fuel flow from the tanks to the engine.

32
Q

what is a cross feed system?

A

a system where if you have two or more fuel tanks and two engines you can decide whether to draw from one tank or both to engine 1 or 2.

33
Q

what are the general rules when refuelling? (7)

A
  • park brake let off so that in the event of a fire it can be pushed away.
  • nobody inside aircraft if refuelling with avgas
  • engine and ignition off
  • no smoking
  • earth aircraft
  • hold nozzle in a way so that the weight of the hose is not resting on the aircraft and stressing the skin
  • look at nozzle and make sure its clean before putting in.
34
Q

what is the general procedure when conducting a fuel drain check?

A

during pre-flight inspection check for any fuel contaminants using an approved container to take a sample from fuel drain. any water will be seen at the bottom.

never tip fuel sample back in, for the risk of contaminating the fuel. if contaminants are visible take another two samples and check if still present, if so consult engineer.

35
Q

when should a fuel drain check take place?

A

before flight and after refuelling, but refuelling you should wait 20 minutes to let contaminants work their way to the bottom.

36
Q

what should be considered when using drumstocks? (3)

A

fill drum up so minimal air is left in the sum as fuel can be contaminated by water, dust and rust.

store drum on its side so that the bung is completely covered with fuel.

when uplifting fuel from a drum, the use of a filter can help keep contaminants out of your fuel system.

37
Q

refuelling from drumstocks what should you consider

A

stand drum upright but tilted slightly and chock it with the high side positioned at 12 o’clock, bung at 3 and vent at 9.

allow drum to stand undisturbed for at least 10 minutes prior to fueling to let any internal contaminants settle out.

connect the bonding lead from the drum to the aircraft before opening any fuel caps, and leave it in place until all fuel caps have been replaced.

38
Q

what are the considerations with non approved plastic containers?

A

with non approved plastic containers, a static charge can build on the container and this charge can then jump to another object causing a spark.

this spark can ignite the fumes of the fuel being used.

PPL AGK (29 decks)

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