AES1

• Aircraft Structures : The aircraft and its components

  • Transport Canada and the Canadian Aviation Regulations (CARS) defines an aeroplane as a “power-driven heavier-than-air aircraft deriving its lift in flight from aerodynamic reactions on surfaces that remain fixed under given conditions of flight”.

  • The terms “aeroplane” and “airplane” can be used interchangeably.
• Aircraft Structures : The aircraft and its components

  • The airplane can be broken down into 5 main components

  1. The fuselage or body of the aircraft
  2. The wings or lifting surfaces
  3. The tail section (empennage)
  4. The undercarriage or landing gear
  5. The engine
• Aircraft Structures : The Fuselage

  • The fuselage of the aircraft is body or main component where baggage and people are found.

  • This component of the aircraft is where other parts (wings, empennage, landing gear etc..) are attached to.

  • Fuselages are typically designed by two main methods:

  • Truss type
  • Monocoque (or semi monocoque)
• Aircraft Fuselage: Construction Methods

  1. Truss-type

  • Steel tubes, bolted or welded together to form the outer frame. A material will then be used to cover the frame giving the aircraft its shape.

  2. Monocoque

  • Series of round or oval formers held together by stringers (long strips to create the shape of the fuselage).
  • If the skin of the aircraft bears the full structural load of the wing, it is known as a monocoque construction.
  • If the structural load is shared between the skin, the formers and the stringers, it is known as a semi-monocoque construction.

  
• Aircraft Structures : Control surfaces

  • Ailerons – Moveable surfaces that are hinged to the trailing edge of the wing. They provide lateral control and help the aircraft BANK

  
• Aircraft Structures – Control surfaces

  • Rudder – A moveable surface that is hinged to the fin (vertical stabilizer) of the aircraft that helps the aircraft YAW. This also provides the pilot with directional control.

  
• Aircraft Structures – Control surfaces

  • Elevator – A moveable surface that is hinged to the horizontal stabilizer of the aircraft that provides the aircraft with longitudinal control. The elevator controls the PITCH movement.

  
• Aircraft Basic Systems – Flaps

  • The main purpose of flaps is to increase lift by changing the camber of the wing. As a result of increasing lift, induced drag will also increase.

  • This will allow the aircraft to fly at slower speeds and have better forward visibility for takeoffs and landings.

  • Flaps can be mechanically, hydraulically, or electrically actuated.

  • There are various types of flaps providing different benefits.

  • Fowler flaps, and others like them, increase the wing surface area as well as change the camber.

  
• Aircraft Basic Systems – Trim Tabs

  • Trim tabs are adjustable devices located at the trailing edge of control surfaces such as elevators, rudders or ailerons.

  • Their purpose is to allow the pilot to fly in a desired condition/attitude under certain load and airspeeds.

  • The trim will help hold the ailerons, rudders, and elevators in the desired position.

  
• Aircraft Basic Systems – Trim Tabs

  • Let’s say the pilot desired the aircraft to enter a climb. In the cockpit we would apply a force on the controls that would cause the elevator to be deflected up.

  • This is turn would cause the tail to go down, and the nose up.
  • The trim tab in this case (if installed) should be moved into the down position to aid in holding the elevator in the up position.

  
• Materials - Metal and Metal Alloys

  • Provides excellent strength to weight ratio.

  • Very durable and wear resistant.

  • Designed to prevent corrosion.

  • Aluminum alloys are typically used.

  • Most aircraft are aluminum monocoque.

  • Other metals or alloys may be used for specific reasons (Steel, dural, alclad, magnesium, etc.).

  
• Materials - Wood

  • Flexible, light, and strong.

  • Difficult to get long lengths (for components such as spars).

  • Difficult to get good quality in some wood types.

  
• Materials – Composite

  • Made from plastic, Kevlar, or carbon fiber.

  • Light and strong.

  • Easy to form to exact shapes.

  • Very smooth (good for reduced drag).

  • Strong skin separated by a light core.

  • Seen in monocoque and semi-monocoque designs.

  
• The Tail Section (Empennage)

  • The empennage (or tail section) of the aircraft contains the aircrafts

  • Vertical Stabilizer (Fin)
  • Rudder
  • Horizontal stabilizer
  • Elevator
  • Trim tabs

  
• Wing Design

  • Wings generally follow a similar method of internal construction.

  • Wings will change the planform (top-down shape) to suit the intended use of the aircraft.

  
• Wing Design - Spars

  • Runs from wing root to wingtip.

  • There may be one or more spars to prevent torsion or twisting of the wing.

  • Spars may also be externally supported (struts).

  • Spars transmit the load into the fuselage.

  
• Wing Design – Ribs

  • Ribs help form the airfoil shape.

  • They provide strength and greater structure to the wing.

  • Compression struts may run alongside the rib.

  
• Wing Design – Wing skin

  • Attaches over the ribs and covers the wings.

  • Skins can be made of composite, metal, plywood, or fabric.

  • The goal is to make the skin as smooth as possible to increase aerodynamic flow.

  
• Wing Design – Shape (Planform)

  • One common feature installed on aircraft is a sweptback wing.

  • This allows the aircraft to have increased stability (aircraft stays in desired attitude).

  
• Landing Gear Configurations - Tricycle

  • Most common on modern aircraft.

  • Main wheels behind the Center of Gravity.

  • Gives a greater ease of control on the ground.

  • Better visibility over the nose.

  • May steer through braking or nose wheel steering.

  
• Landing Gear Configurations – Conventional or Tail Wheel

  • Aircraft with conventional landing gear are often known as Tail Draggers.

  • Main wheels are ahead of the C of G.

  • The tailwheel can be steerable or fixed.

  • Advantages of a tail wheel include having less parasite drag, being less expensive, and being easier to move by hand on the ground.

  • More rugged and better suited for rough terrain.

  • Ground looping tendency (tipping over of aircraft – see photo).

  
• Landing Gear Configuration - Tandem

  • Main landing gear in line with the fuselage.

  • Smaller wheels provide support from the wing tip.

  • Not commonly used.

  • Advantages include reducing weight and decreasing drag.

  
• Landing Gear – Fixed

  • To reduce complexity of systems and aircraft weight, most single engine aircraft are equipped with fixed gear.

  • The wheels and components of the undercarriage remain fixed in place and will not move throughout the entire flight.

  • Sometimes fixed gear will be equipped with wheel fairings to help reduce the drag encountered in flight.

  
• Landing Gear - Retractable

  • One of the main advantages of retracting the gear is having reduced drag in flight and therefore more speed.

  • The large disadvantages of retractable gear are the complexity, expense and weight. The more complex the system, the more chance of system malfunctions.

  
• What is one of the main advantages of having a sweptback wing design? b

  a) It increases speed

  b) It increases stability

  c) It increases stall speeds

  d) It add weights to the aircraft
• What is a semi-monocoque fuselage? c

  a) A series of round or oval forms held together by stringers and covered by a wood or fabric skin which bears part of the load

  b) A series of round or oval forms held together by stringers and metal skin which bears all the load

  c) A series of round or oval forms held together by stringers and covered by metal skin which bears part of the load

  d) A series of round or oval forms held together by stringers and metal skin which bears none of the load
• Which of the following best describes spars? d

  a) They are used the shape the camber of the wing

  b) They run from wing root to wing tip and are always self-supported

  c) They are the same as a compression strut

  d) They run from wing root to wing tip and can be supported externally
• How does a fowler flap work? c

  a) It will extend down from the wing causing a lift increase

  b) It is a double slotted flap that extends outward increasing the overall lift of the aircraft

  c) It will extend rearward, increasing the area of the wing causing a lift increase

  d) It will extend upwards from the wing causing a lift increase
• Landing Gear Types – Shock Absorption

  • Every landing will create some shock force, regardless of the pilot's skill.

  • Each landing gear type reduces this force in one way or another.

  • This can be done with spring steel, elastic cord, or an oleo.

  • Oleos are hydraulic filled cylinders that have fluid forced out of a small hole to absorb the impact on touchdown.

  
• Landing Gear Types – Single Leaf Spring

  • Single leaf cantilever spring steel gear absorbs shock using a leaf spring.

  • This stores the initial impact forces and produces low load factors.

  • Light, simple, low maintenance, and long service life.

  • Found extensively on Cessna and Diamond aircraft.

  
• Landing Gear Types - Single Strut

  • Single strut usually incorporates an oleo to help absorb the shock. It is attached to the strut in the case of fixed landing gear.

  • Normally found on aircraft with retractable landing gear.

  • This is extensively used on low wing aircraft. (ex Piper)

  
• Landing Gear Types - Tripod


  • Provides excellent shock absorption

  • More complex consisting of three separate parts

  • Two are rigid members

  • One is an oleo

  • Effectively forms a hinge

  • Good for rough terrain

  
• Landing Gear Types – Split Axle

  • Uses a shock or bungee cord wound around a fuselage member and the split axle.

  • A strut or tie rod is installed to prevent side loads.

  • Shock cord must be inspected prior to flight for condition.

  
• Brake Systems – Mechanical

  1. Mechanical

  - Used on early airplanes.

  - May be a mechanical lever or gravity activated.

  - Not very effective.
• Brake Systems – Hydraulic

  2. Hydraulic

  • Pressure applied through rudder pedals forcing fluid out of a piston.
  • This fluid compresses brake pads on to the rotor disk.
  • Hydraulic brake fluid is red to help identify leaks.

  
• Brake Systems – Electrical

  3. Electrical

  • Uses an electrically driven screw jack to apply pressure against brake pads.

  
• Engine Designs- Engine Stroke types

  1. Two Stroke

  • Not commonly used in aeroplane engines.
  • Not as reliable or efficient as four stroke gasoline engines.
  • Very noisy, burns more fuel.

  2. Four Stroke

  • Piston travels up and down the cylinder twice.
  • The four strokes consist of: Intake (induction), Compression, Power, and exhaust.

  
• Engine Designs – Four Strokes

  1. Intake

  • Intake valve is open
  • Piston moves down
  • This draws the fuel air mixture into the cylinder

  2. Compression

  • Both valves are closed
  • The piston moves upwards
  • This compresses the fuel/air mixture
  • The amount of compression is known as compression ratio 14:1

  
• Engine Designs – Four Strokes

  3. Power

  • Both valves remain closed
  • The spark plug ignites the fuel/air mixture
  • This causes the piston to move down

  4. Exhaust

  • The exhaust valve is opened
  • The piston moves
  • This removes the exhaust gases allowing the cycle to begin again

  
• Engine design – The Piston

  • The piston is the main driving force of the engine.

  • The piston will move up and down in the cylinder driving the crankshaft.

  • The crankshaft is then connected to the propeller and causes it to turn.