Aircraft Fuel Systems Overview

Aircraft Fuel

• Aircraft fuel systems serve piston and gas turbine engines.
• Piston aircraft fuel types include AVGAS 82 UL, AVGAS 100 LL, and AVGAS 100.
• Gas turbine engine aircraft fuel types include AVTUR, JET A1, JET A, AVTAG, and JET B.
• Aircraft fuel is composed of hydrocarbons with a higher sulphur content than gasoline.
• Additives such as FSII (Fuel system icing inhibitor), HiTec, static dissipater, corrosion inhibitors, and metal de-activators are used.
• Water, wax, and boiling are detrimental to the fuel system.
• Fuel storage types include integral, rigid, and flexible tanks.
• Fuel jettisoning is the intentional release of fuel to reduce weight or manage emergencies.
• Fuel tanks have level sensors and vents to equalize pressure and drains to remove contaminants.
• A Fuel Selector Valve allows to choose the fuel source.

Aircraft Fuel System Components

• Engine-driven fuel pump is the main fuel pump.
• Electric fuel pump assists or replaces the engine-driven pump for starting and switching tanks.
• Fuel strainer filters contaminants.
• Carburetor mixes fuel with air.
• Throttle controls engine power.
• Mixture control adjusts fuel-to-air ratio.
• Priming pump injects fuel directly into the inlet manifold for cold engine starts.
• Fuel gauges and indicators display fuel levels, pressure, and other engine monitoring data (oil temperature and oil pressure).

Aircraft Fuel System Monitoring & Indication

• Monitoring and indication systems display fuel levels, pressure, oil temperature, oil pressure for engine monitoring, and other essential data.
• A primary flight display (PFD) consolidates various instruments into a single display.

Aircraft Fuel Flow

• Selected fuel flows from the fuel selector valve.
• Fuel passes through the fuel strainer to remove contaminants.
• The fuel is then pressurized by the electric or engine-driven pump.
• Fuel reaches the carburetor where air-fuel mixture is created.
• The air-fuel mixture is then delivered to the engine cylinders for combustion.

Aircraft Fuel System Safety Features

• Redundancy in fuel pumps (electric and engine-driven).
• Vent system to prevent fuel tank vacuum and ensure steady fuel flow.
• Fuel strainer minimizes contaminants from entering engine.

Flight Instruments

• The 6-pack includes Airspeed Indicator (ASI), Altimeter, Attitude Indicator (AI), Heading Indicator (HI), Turn Coordinator (TC), and Vertical Speed Indicator (VSI).
• Pitot-static Instruments use relative air pressure readings to determine altitude and speed.
• Gyroscopic instruments use spinning gyros and gimbals to register changes in aircraft headings and attitude.
• The turn coordinator indicates slip or skid.
• Attitude indicator shows the aircraft position around its roll and pitch axis.
• Heading indicator acts like a compass.
• A Primary Flight Display (PFD) shows all instruments in a consolidated display.

Aircraft Emergency/Safety Equipment

• Emergency equipment is positioned and utilized following regulations (standards).
• Emergency equipment location, usage, and marking vary by aircraft type.
• Emergency equipment is often organized for use during ditching or crash landings, easily accessible, clearly located, and protected from damage.

Public Address System

• At least one microphone is provided at each passenger compartment exit for use by the flight attendant/cabin crew during necessary occasions such as power failures.
• Flight crew may also communicate via normal headset communications.

Emergency Lighting

• An emergency lighting system runs independently from the main lighting system.
• The system includes illuminated emergency exit markings and location signs, external emergency lighting, emergency exit signs, and emergency escape path markings.
• This system is powered by individual Nicad batteries with a charging circuit, monitoring, and voltage regulation circuits.
• The system provides up to 20 minutes of power.
• Cockpit and cabin attendant control switches control the lighting system.

Aircraft Interior Lighting

• Locations include aisle illumination from stowage bin bullnoses, entry/service/overwing hatches, ceiling for exit identification, self-illuminating exit signs (forward, middle, and aft cabin sections), and floor proximity lights.
• Floor proximity lighting is helpful in smoke-obscured conditions.
• Different types of emergency exit and pathway lighting are used throughout the plane.

Aircraft Exterior Lighting

• Exterior lighting illuminates escape slides and overwing exits.
• Lights are near forward/aft service entry doors and overwing escape routes.

Megaphones

• Megaphones are situated in strategic locations (front/rear, upper/lower decks).
• Cabin staff may use them to communicate with passengers during power failures.
• The megaphon units use battery power and require checking before each flight.
• Serviceability is confirmed by a 'click' sound or a neon light.
• The number of megapones varies according to the number of passenger seats.

Torches

• Torches are legally required on public transport aircraft.
• They are located at crew stations, flight decks, and floor-level exits.
• Torches aren't rechargeable and are secured with Velcro straps.
• A flashing red neon light indicates serviceability.

Emergency Exit Descent Devices

• Evacuation equipment types include ropes, slides, inertial reels, or tapes.
• Inflatable and rigid slides can double as life rafts, and are either in engage or detach modes.
• Apron slides need initial manual tensioning by the first two escapees.

Overwing Escape Hatches

• These are positioned over the wings and incorporate mechanical locks to secure the plug-type hatches.
• Hatches can be operated from inside and outside using a spring-loaded handle; seat-backs can be pushed forward for access.
• Hatches must not be removed and overwing emergency exit lights may activate when the cockpit's switch is in the ARMED position.
• To avoid blocking exits, hatches should be placed strategically during evacuation.

Cut-in-areas

• Cut-in-areas are mandatory for aircraft over 3600 kg airframe unit weight.
• These are rectangular, marked by right-angled corners, and colored red or yellow, outlined in white if contrast is needed.
• Cut-in-areas are not weak points but areas without control runs, electrical looms, or multi-stringers.

Doors/Emergency Exits

• Aside from entry, doors can be emergency exits, marked externally with contrast bands.

Locator Beacons

• Operated by pulling a red toggle.
• The "Velcro" straps release the aerial.
• The beacon will lift vertically and the neon lamp will pulse to confirm operation and to indicate transmission.
• The beacon's shape and weight provide buoyancy to maintain a vertical position above the water.

First Aid Equipment

• First aid kits are not sealed and are designed for cabin crew use in treating minor emergencies and ailments.
• Kits' contents, information, and booklet are included for passenger use.
• The quantity of kits is determined based on the number of passenger seats.

Ancillary Equipment

• Fire-proof gloves are often stowed on the flight deck and intended for use where overheating equipment is possible.

• Fire axes and jemmies are stowed for use in levering and lifting hot panels or access doors during fire situations.