Fuel Systems and Landing Gear

Purpose Of Fuel Systems

Stores, distributes, and controls fuel to meet engine demand and performs operations for refuel, defuel, and fuel transfers between tanks

Fuel Management Panel

Centralized means of controlling fuel movement. Located in the flight deck

Fuel Tanks/Cells

Provide fuel storage. Vary in design, size, and shape based on aircraft

Integral Fuel Tanks/Cells

Built as part of the wing or fuselage (main body) structure and are formed by sealing off structural areas with fuel resistant sealants

Bladder Fuel Tanks/Cells

Installed in compartments called cavities and can be made of rubber or nylon

External Fuel Tanks/Cells

Attached to the aircraft exterior to extend aircraft range may be jettisoned (dropped) from certain aircraft during combat or emergency situations

Tank Filler Caps

Provide access for: gravity (over-the-wing) refueling of individual tanks and visual or dip stick checks of fuel quantity in tank (secured in place with locking mechanism)

Fuel Pumps

Provide necessary pressure to move fuel through the system plumbing and can transfer fuel from tank to tank (mounted in fuel tanks: electrically powered and submerged in fuel for cooling purposes)

Boost Pumps

Ensure a positive fuel supply to engine driven pumps (can be used to defuel a tank; electrically driven, cooled and lubricated by fuel)

Transfer Pumps

Transfer fuel from tank-to-tank (can be used to defuel a tank; electrically driven, cooled and lubricated by fuel)

Ejector Pumps

Operates by fuel being forced through a narrow area resulting in pressure reduction and velocity increase (known as the Venturi principle) to move fuel from tanks

Fuel Valves

Control movement of fuel through the airframe and engine fuel systems

Engine Feed Valve

Controls flow of fuel from a main tank to its respective engine

Cross Feed Valve

Permits interconnection between the left and right sides of the aircraft and engine feed lines. Allows routing of fuel from any tank to any engine and tank-to-tank on either side of aircraft

Engine Firewall Shutoff Valve

Shuts fuel flow to the engine during emergencies but normally stays open to allow free flow (controlled by emergency push button/T-handles on/above forward instrument panel)

Check Valve

Allows fuel to flow in one direction only

Fuel Level Control Valve

Located internally at top of each fuel tank and controls filling of tanks and prevents overfilling (electronically positioned by one of two methods: selectively using switches on refuel management panel and fuel float rises when tanks are full)

Pre-Check Selector Valve

Checks the shutoff operation of the fuel level control valve

Condensation Drain Valve (Sump Drain)

Located at lowest part of tank (drains water)

Fuel Manifolds

Transport (carry) fuel from place to place within fuel system

Single Point Refueling (SPR) Manifold

Routes fuel from SPR receptacle to each tank

Engine Feed Manifold

Delivers fuel to engines from selected tank(s)

Fuel Filters

Remove foreign particles from the fuel and contain bypass valve to allow flow if filter is clogged

Heat Exchangers

Heats fuel for better atomization and cools oil or hydraulic fluid

Vent System

Routes air into or out of fuel tanks as it is displace by fuel and allows air to enter tanks to displace fuel being removed during engine operation, transfer, or defuel (relieves effects of temp/altitude changes on fuel and air in tank)

Pressurization System

Controls amount of positive pressure entering the tank

Pressure Relief Valve

Relieves excessive negative and positive air pressure in the tanks

Fuel Dump System

Provides emergency means of dumping fuel overboard in flight to lighten aircraft

Dump Mast

At rear of aircraft or on wing trailing edge routes fuel overboard

Tank Sensor/Probe Unit

Electrically measures amount of fuel in a tank and sends signal through an amplifier to fuel quantity indicator

Fuel Quantity Indicator

Receives/decodes the signal from tank sensor/probe unit and shows the amount of fuel in each tank (indication provided in pounds of fuel)

Total Indicator

Shows total amount of fuel in all tanks

Indicator Test Switch

Depressing test switch initiates a self-test of the indicator

Low Pressure/Sump Warnings Lights

Indicate fuel level/pressure is below required minimum (located on fuel management panel)

Single Point Refueling (SPR) Receptacle (Refuel)

Provides for rapid fueling of all tanks by connecting a hose to a quick disconnect

Gravity (Over-The-Wing) (Refuel)

Provides for individual tank filling through a tank filler cap

In-Flight Refueling (IFR)/Aerial Refueling Receptacle (Refuel)

Located to provide in-flight refueling access

Single Point Receptacle (Defuel)

Provides for rapid defueling of all tanks by connecting a hose to a quick disconnect

Gravity (Defuel)

Provides for draining of individual tanks

Siphon (Defuel)

Provides for suctioning fuel out of individual tanks through a filler cap using a hose from a defuel truck

Where is maintenance not allowed?

During fueling operations

Who is allowed in refuel/defuel area?

Authorized refuel personnel ONLY

Which TO ensures aircraft and equipment are statistically grounded?

00-25-172

Aircraft needs to be parked at least __ feet from buildings.

50

AGE equipment will not be operated within __ feet of refuel/defuel area.

50

No smoking within __ feet.

50

No radio transmission within __ feet of aircraft.

10

Aircraft/ground radar will not e operated within ___ feet.

300

Fuel Leak Classifications

Determines conditions/repair requirements for system and ensures leak point is located and marked prior to performing repair maintenance

(Leak Classifications) Class A

Slow seep, 0-1/4 of an inch

(Leak Classifications) Class B

Seep, greater than 1/4 to 3/4 of an inch

(Leak Classifications) Class C

Heavy seep, greater than 3/4 to 8 inches and/or less than 4 drops per minute

(Leak Classifications) Class D

Running leak, greater than 8 inches or 4 drops per minute

Landing Gear

Supports and provides steering and braking action, while the aircraft is on the ground

3 Types Of Landing Gear

Bicycle, tricycle, and quadricycle

Shock Strut

Supports the aircraft on the ground and absorbs shock during take-off, landing, and ground operation

Pneudraulic Unit (Shock Strut)

Serviced with hydraulic fluid and nitrogen

Trunnion

Attaches the strut to the aircraft/acts as a pivot point when raising or lowering the landing gear

Charging Valve

Servicing point for nitrogen

Upper Cylinder

Attached to aircraft by the trunnion

Lower Cylinder (Piston)

Slides in and out of the upper cylinder to help absorb shock

Torque/Scissor Links

Connects the upper and lower cylinders and aligns the wheels

Tow Point

Connection point for tow bars

Jack Points

Location for axle jack placement

Landing Gear Control Lever/Handle

Provides the means to select landing gear position (up/down)

Landing Gear Control/Selector Valve

Directs hydraulic pressure to and from the gear and door actuators

Landing Gear and Door Actuators

Utilized to raise and lower the landing gear and opens and closes the gear doors

Landing Gear Doors

When closed, creates a smooth surface to reduce turbulence when the gear is up and locked

Landing Gear Restrictor Valves

Reduces the speed of the gear and door actuators when in motion

Landing Gear Sequence Switch

Controls the order in which the gear and doors operate

Landing Gear Ground Safety Switch

Prevents operation of the landing gear to prevent unintended retraction of the gear while on the ground

Landing Gear Ground Safety Pins

Locks and prevents accidental collapse of the landing gear while aircraft is on the ground

Uplocks and Downlocks

Locks the gear in either UP or DOWN position

Emergency Extension System

When operated, forces the gear into the lower position

(Gear Position Indicating System) Green Light On / Picture Of A Wheel

Indicates each gear is down and locked

(Gear Position Indicating System) Green Light Off / (Tell-Tale Indicating System) Picture Of The Word "UP"

Indicates each gear is up and locked

Picture Of Diagonal Stripes (Barber Pole Image)

Gear is in transit, in unsafe position, or no power applied to aircraft

Landing Gear Warning System

Warns pilot during landing approach if gear is not down and locked (uses a warning horn or audible tone/voice)

Landing Gear Warning Light

Illuminates when gear is in transit or is unsafe (light in gear control handle/lever)

Nose Wheel Steering System

Allows pilot/co-pilot to maneuver the aircraft on the ground

Rudder Pedals and/or Steering Wheel

Used to select the direction and degree of turn

Wheel Brakes

Slows or stops the aircraft wheel and tire assemblies

Parking Brakes

Hydraulically locks system pressure to keep brakes engaged. Prevents aircraft movement when: wheel chocks are not installed, during aircraft towing preparations, engines runs, and refueling/defueling operations.

Arresting Gear

Used to stop fighter aircraft in emergencies by catching a runway cable (danger area exists at the rear of the aircraft)

(Brake Components) Rudder Pedals

Applies brake pressure using toe pressure to the top of the rudder pedals

Brake Control Valve

Directs fluid to the brake assemblies

Brake Assembly

Slows or stops aircraft using pressure to create friction between rotor disc and stator disc

Brake Housing

Contains hydraulic pistons that push on pressure plate

Pressure Plate

Transfers pressure developed in the housing to the rotors and stators causing friction

Rotors

Rotate with the wheel

Stators

Stationary discs located between the rotors

Backing Plate

Surface at the end of the brake assembly against which rotors and stators are pressed

Anti-Skid System

Prevents wheel and tire assemblies from skidding during maximum braking

Brake Bleeding

Removes air from hydraulic fluid in the brake system (required when brakes are changed or maintenance is performed)

What TO do you use for the inspection of tires for serviceability?

TO 4T-1-3

Split Wheels

Two halves are bolted together (most common type)

What is the most common type of tire?

Tubeless

(Tire Markings) Wear Indicators

A layer of fabric (normally red) used to identify the maximum wear limit

(Wear Limits) Cut Limits

Identifies the max allowable cut limit for the tire

What do you use to measure cuts in tires?

Depth Gauge