AES3

• Engine Operations – Fuel Characteristics

  • For the engine to operate at its optimal performance, we must ensure that we use the correct GRADE as well as TYPE of fuel.

  • Most single engine piston powered aircraft use AVGAS type fuel. This simply is an abbreviated way of saying “aviation gas”

  
• Engine Operations – Fuel Characteristics

  • Properties of good fuel

  • Burns slowly and expands evenly

  • Fuel has two main components

  • OCTANE - has minimum detonating qualities

  • HEPTANE - has maximum detonating qualities

  • The GRADE of fuel is a ratio of octane to heptane

  • “80 octane” is 80% octane & 20% heptane
• Engine Operations – Fuel Characteristics

  • Some fuel will have additives placed in them to help with freezing and performance enhancement

  • Anti-icing fuel additives inhibit the formation of ice crystals

  • Other additives scavenge lead and reduce lead fouling of spark plugs
• Engine Operations – Grades of Fuel

  • Grades may be indicated by 2 numbers (80/87)

  - The first number is octane at lean mixture

  - The second number is octane at rich mixture

  • The higher the grade of octane, the higher the lead content

  
• Engine Operations – Grades of Fuel

  • LEANING – means that we are using the mixture control lever inside the cockpit to reduce the air to fuel ratio.

  • Leaning means to reduce the amount of fuel being mixed with the air.

  • Why lean the mixture? - As we climb to higher altitudes the air density decreases, this results in an unnecessarily rich mixture which wastes fuel and can create excessive carbon deposits on spark plugs and engine combustion chambers.
• Engine Operations – Grades of Fuel

  • ENRICHING or RICH – means that we are using the mixture control inside the cockpit to increase the air to fuel ratio.

  • Making the fuel RICHER means to increase the fuel amount.

  • Rich mixture is used in full power situations and just prior to commencing a descent to lower altitudes where air density increases.
• Engine Operations – Contamination and Deterioration

  • One of the most common contaminants is water.

  • Water often forms in fuel tanks overnight. If the tank is not full of fuel, there will be air contained in the top space of the tank. As night, as temperature decreases, any water vapor may condense into water droplets and contaminate the fuel.

  • Pilots can avoid this by filling the tanks and putting the aircraft inside a hangar out of the weather.

  
• Engine Operations - Detonation

  • Detonation is an undesired state and occurs when fuel explodes inside the cylinder instead of the normal consistent even burning of the fuel.

  • Detonation results in a rapid rise in cylinder pressures and temperatures.

  • Causes stress to engine parts resulting in overheating, warped valves and piston damage.

  
• Engine Operations – Detonation Symptoms

  • Light detonation may not be recognizable by the pilot.

  • Moderate to severe detonation could be noticed as engine roughness, vibration, and loss of power

  
• Engine Operations – Detonation Causes

  • Using the incorrect grade of fuel (Too low octane)

  - Remember that low octane means low detonation qualities

  • Excessive leaning of the mixture at high power settings

  - This will cause the temperature to be too hot in the combustion chambers

  - Fuel is cold – cold fuel helps keep the combustion temperature low

  
• Engine Operations – Detonation Causes

  • Overheating (prolonged climb with high nose attitude) - If airflow cannot adequately cool the engine, the entire system will overheat

  • Cracked or damaged spark plugs

  
• Engine Operations – Pre-Ignition

  • The strokes of the engine are timed to ensure that a spark will ignite the fuel air mixture at the correct time.

  • If the mixture ignites before the spark plug sparks it, we call this "pre-ignition“.

  • Can cause serious damage such as warped pistons and cracked cylinders prior to the timed spark from the spark plug.

  Piston Damage:

  
• Engine Operations – Pre-Ignition

  • Pre-ignition can happen as a result of detonation or by glowing hot carbon.

  • Glowing carbon particles are a buildup of leftover fuel components that have clung to the walls of the combustion chamber.

  • These local hot spots in cylinders cause the fuel/air mixture to ignite prior to the spark plug doing so.

  Piston Damage:

  
• Fuel Systems – Vapour Lock

  • In the fuel system, we have fuel lines that are dedicated to bring fuel from the tanks to the engine.

  • When fuel evaporates inside these fuel lines, we refer to it as vapour lock.

  • Evaporation leaves bubbles of air in the line.

  
• Fuel Systems – Vapour Lock

  • The gas bubble blocks fuel flow to the engine.

  • This can be caused by high temperatures.

  • More common with some types of MOGAS.

  • May also be caused by low atmospheric pressures (very high altitudes) or by low fuel pressure.

  
• Fuel Systems – Fuel tanks

  • Fuel tanks are often found in the wings of the aircraft as it gives a better center of gravity position.

  • Fuel tanks are usually made from aluminum.

  
• Fuel Systems – Gravity Feed

  • Gravity fed fuel systems use gravity to move fuel from the tanks (located above the engine) to the intake manifold.

  • Only suitable for low power, high wing aircraft, such as a Cessna 172.

  
• Fuel Systems – Pressure Feed

  • Low wing aircraft require pumps to force the fuel up to the engine.

  • This may necessitate switching between tanks during flight.

  • Mechanical engine driven pumps are used for normal flight and electrical boost pumps are used for takeoff and landing to ensure sufficient fuel pressure is maintained.

  
• Fuel Systems – Basic Components

  Fuel Lines

  • Constructed of aluminum alloy metal tubing and flexible rubber or Teflon hoses.

  • The purpose of these lines is to bring the fuel from the tanks to the engine.

  
• Fuel Systems – Basic Components

  Fuel Filters

  • Because we cannot always remove fuel contaminants, there is a fuel filter located at the lowest point of the system.

  • The filter will prevent foreign matter from entering the carburetor/injectors and to trap small amounts of water which may be present.

  
• Fuel Systems – Basic Components

  Fuel Drains

  • Located at the lowest point of the fuel tank and fuel system to remove any contaminants.

  • Contaminants will sink to the bottom of the tank and hopefully removed when pilots complete the fuel straining procedure.

  
• What is the colour of 100LL AVGAS? B

  a) Green

  b) Blue

  c) Clear

  d) Straw colored
• Which of the following is not a way to help reduce detonation? A

  a) Increase power

  b) Increase mixture

  c) Reduce power

  d) Lower nose
• In a low wing, fuel tank, what is required to get the fuel to the engine? C

  a) A fuel filter

  b) A fuel bypass

  c) A fuel pump

  d) A fuel primer
• Oil Usage – Major Types of oil

  1. Mineral Oil

  - Typically used for the engine break-in period.

  2. Ashless Synthetic

  - Used as a replacement for mineral oil in prolonged uses.

  - Typically used for the engine break-in period on turbocharged engines.

  3. Synthetic

  - Ideal for prolonged use.

  - Can be used in harsher conditions and at higher engine temperatures.
• Oil Usage – Viscosity

  • Viscosity is resistance to flow (thickness of the fluid).

  • Oil which flows slowly is viscous or is said to have high viscosity.

  • Free flowing oil has a low viscosity.

  • An oil is designated by a viscosity index number by the S.A.E. (Society of Automotive Engineers)

  
• Oil Usage – Grades and Seasonal Use

  • Classified according to grades 10, 30, 50, 60, 80, 100, etc.

  • “W” in front of the grade number indicates it is suitable for winter use .

  • In order to eliminate the need to change oil seasonally, multi-grade synthetic oils are commonly used, such as 10W30.

  • Always consult your POH/AFM or the engine manufacture as to what grade to use.

  
• Electrical System – Generator

  • Generators produce direct current (DC) in order to charge the battery and run electrical systems.

  • In order to generate this power, the engine must be turning.

  • In light aircraft, generators have typically been replaced by alternators because they are lighter and more efficient.

  • Generators create Direct Current (DC) while alternators create Alternating Current (AC).

  
• Electrical System – Alternator

  • Alternators create alternating current (AC), which is converted to direct current (DC) using a rectifier*

  • Found more often on light aircraft.

  • Begins producing power at very low engine power.

  * A rectifier is an electrical device that converts a two-directional alternating current (AC) into a single-directional direct current (DC). Rectifiers can take a wide variety of forms, from vacuum tube diodes and crystal radio receivers to modern silicon based designs.

  
• Electrical System – Battery

  • Batteries are used to start the airplane.

  • It stores electricity that may be required to run instruments and equipment.

  • Most small general aviation aircraft use a 12-volt direct current battery.

  • In the event of an alternator or generator failure, the battery will continue to provide electricity to equipment for a short period of time.

  
• Electrical System – Ammeter (Load Meter)

  • A positive number on an ammeter indicated that the battery is charging. A negative number means it is discharging.

  • In normal operations, the alternator or generator will power the electrical equipment PLUS charge any depleted amounts from the battery.

  
• Electrical System – Ammeter (Load Meter)

  • In the case of an alternator or generator failure, it will indicate the draw from the battery (needle moves to the left or negative indication).

  • Most single engine airplanes can last approximately 30 mins on the battery power alone. - This, of course, depends on the electrical draw and equipment onboard.

  • Measured in amps.

  
• Electrical System – Bus Bars

  • Acts as the “electrical master”.

  • Receives the current produced by the generator and battery.

  • The current is then distributed through circuit breakers or fuses to the electrical components.

  • It is a large conductive strip of metal with various electrical terminals attached.

  
• Electrical System – Circuit Breakers/Fuses

  • Circuit breakers (CB’s) will protect the electric circuit from short circuiting, which can lead to fire.

  • They also protect against overcurrent, which can damage components.

  • Circuit breakers can be reset; however, they should only be reset once.

  • Some older aircraft may use fuses which cannot be reset. They must be replaced.

  
• Electrical System – Interior Lighting

  • Interior lighting consists of instrument lights and instrument panel lighting, which may be in the form of a flood lights or post lights.

  • Sometimes the flood light is red. This is to preserve night vision.

  • Engine instruments, radio equipment, and the magnetic compass frequently have their own internal lighting.

  
• Other Aircraft Systems – Oxygen Systems

  • Some aircraft have oxygen systems.

  • In the CARS we can find that flights over 10,000 ASL for a period of more than 30 mins OR 13,000 ASL at any time will require us to have oxygen onboard (ASL – above sea level).

  • Oxygen is an important system to prevent pilots from getting hypoxia.

  
• Other Aircraft Systems – The Vaccuum System

  • On most small single-engine aircraft the vacuum pump is run by the aircraft engine and creates a partial vacuum in the system.

  • A filtered inlet on the rear-side of the instrument allows air to enter the system causing the gyro wheel to spin (gyro is the mechanism inside the instrument that spins and allows it to function).

  • Requires a suction gauge mounted on the instrument panel which indicates the proper amount of vacuum pressure.

  • Both the attitude indicator and heading indicator are often powered by the vacuum system.

  
• Oil Usage – Purpose of Engine Oil

  Cooling – Moves heat (heat transfer)

  Sealing – Helps seal the piston and cylinder

  Lubricating – Reduces friction, and cushions shock loads to bearings

  Flushing – Cleans deposits, keeps particles in suspension and protects against corrosion
• Which statement best describes AC current? D

  a) Alternating current (AC) is derived from a generator and is generally used for powering most systems in the aircraft

  b) Alternating current (AC) is derived from a generator and must be converted to direct current (DC) power by diodes

  c) Alternating current (AC) is derived from an alternator and must be converted to AC power by diodes

  d) Alternating current (AC) is derived from an alternator and must be converted to DC power by diodes.
• On an aircraft, the navigation lights must be installed. The color of these lights are __________ on the left wing, __________ on the right, and __________ on the tail section. A

  a) Red, green, white

  b) Green, red, white

  c) White, green, red

  d) White, white, red