AMT 121 MIDTERMS

• Fuel, electrical, hydraulic, and oxygen systems make up the

  "airframe systems".
• The fuel system is designed to provide an uninterrupted

  flow of clean fuel from the fuel tanks to the engine. The

  fuel must be available to the engine under all conditions

  of engine power, altitude, attitude, and during all approved

  flight maneuvers. Two common classifications apply to fuel

  systems in small aircraft: gravity-feed and fuel-pump systems.
• The gravity-feed system utilizes the force of gravity to

  transfer the fuel from the tanks to the engine. For example, on

  high-wing airplanes, the fuel tanks are installed in the wings.

  This places the fuel tanks above the carburetor, and the fuel

  is gravity fed through the system and into the carburetor. If

  the design of the aircraft is such that gravity cannot be used

  to transfer fuel, fuel pumps are installed. For example, on

  low-wing airplanes, the fuel tanks in the wings are located

  below the carburetor.
• Fuel-Pump System-

  Aircraft with fuel-pump systems have two fuel pumps. The

  main pump system is engine driven with an electrically-

  driven auxiliary pump provided for use in engine starting

  and in the event the engine pump fails. The auxiliary pump,

  also known as a boost pump, provides added reliability to

  the fuel system. The electrically-driven auxiliary pump is

  controlled by a switch in the flight deck.
• Fuel primer


  1. Draw fuel from tanks

  2. Vaporize fuel directly into cylinders

  3. Prior to starting engine
• Fuel primer


  • Used in gravity-feed and fuel-pump systems
  • Helps start engines in cold weather when there is not enough heat to vaporize fuel in carburetor
• It is important to lock the primer in place when it is not in use
• If the knob is free to move

  It may vibrate out of position during flight which may cause an excessively rich fuel-air mixture
• To avoid overpriming, read the priming instructions for the aircraft
• Fuel Tanks

  The fuel tanks, normally located inside the wings of an

  airplane, have a filler opening on top of the wing through

  which they can be filled. A filler cap covers this opening.
• The

  following are the four types of engines:

  • Reciprocating powerplant

  • Turbine, propeller combination (turboprop)

  • Turbine engine incorporating a fan (turbofan)

  • Turbojet (pure jet)
• The engine oil system performs several important functions:

  • Lubrication of the engine’s moving parts

  • Cooling of the engine by reducing friction

  • Removing heat from the cylinders

  • Providing a seal between the cylinder walls and pistons

  • Carrying away contaminants
• parts that are included in the left tank of the gravity feed system are: vent, selector valve, carburetor
• parts that are included in the right tank of the gravity feed system are: strainer, primer.
• parts that are included in the left side of the Fuel-pump system are: carburetor, electric pump, selector valve.
• parts that are included in the right tank of the fuel pump system are: Engine driven pump, Strainer, Primer.