Atmosphere and Altitudes

• The atmosphere contains gas (primarily nitrogen and oxygen), water, and particulates.
• Standard atmospheric pressure is 14.7 lbs.
• The International Civil Aviation Organization (ICAO) defines the International Standard Atmosphere (ISA) at sea level with a pressure of 29.92" Hg and a temperature of 15°C (59°F).
• As altitude increases above sea level:
  • Pressure decreases due to less mass per volume.
  • Density decreases.
  • Temperature decreases.
  • Density increases when temperature wins.
• Pressure Ratio is the Density Ratio and is Density = Mass / Volume.

Altitudes

• Indicated Altitude: Displayed on the instrument.
• True Altitude: Height above or below Mean Sea Level (MSL).
• Absolute Altitude: Height above Ground Level (AGL).
• Pressure Altitude: Adjusted to the 29.92” Hg datum.
• Density Altitude: Pressure Altitude corrected for non-standard temperature.
• Elevation is measured against MSL.

Speeds

• Indicated Airspeed (IAS): Shown on the instrument.
• Calibrated Airspeed (CAS): IAS corrected for instrument and Pitot position error.
• Equivalent Airspeed (EAS): CAS corrected for air compressibility.
• True Airspeed (TAS): EAS or CAS corrected for air density.
• Groundspeed (GS): TAS corrected for wind direction and velocity.
• Headwind Component: GS will be less than TAS.
• Tailwind Component: GS is greater than TAS.
• The wind at a 90-degree angle relative to the aircraft heading means GS=TAS.

Four Forces of Flight

• Lift: upward force
• Thrust: forward force
• Weight: downward force
• Drag: a force in opposition

Aircraft Flight Dynamics

• Axis of Rotation
  • Longitudinal Axis: Nose to tail
  • Lateral Axis: Wing to wing
  • Vertical Axis: Belly to head
• Airplane Movement
  • Roll/Banking: Longitudinal
  • Pitch/Tilt: Lateral
  • Yaw/Rotate: Vertical

Fixed Surfaces

• Wing Panel: Longitudinal.
• Horizontal Stabilizer/Stabilator: Lateral.
• Vertical Stabilizer: Vertical.

Primary Control Surfaces

• Ailerons: Wing Panel, longitudinal, roll
• Elevator: Horizontal Stabilizer, lateral, pitch
• Rudder: Vertical Stabilizer, vertical, yaw

Secondary Control Surfaces

• Wing Flap: Trailing edge to both wings, deploys together in the same direction.
• Trim Tab: Trailing edge of a primary control surface to relieve control pressure.
• Leading Edge Slats.
• Spoilers.

Airfoils

• Symmetrical: Same curved shape on top and bottom.
  • Angle of Attack: The angle between relative wind and chordline.
• Cambered: Will create some lift at an angle of attack equal to 0, called Alpha.

Aerodynamic Stall

• When AoA exceeds maximum AoA (Critical AoA).
• Can happen at any airspeed and pitch angle, but only one Critical AoA.

Stall Types

• Normal Stall: Slow speed, gradual increase in AoA.
• Accelerated Stall: High speed, sudden increase in AoA.
• Cross Controlled Stall: Slip or Skid then Stall, occurs when the plane flies in an uncontrolled state.
• V is Vstall (Vs) when CL is CL(max).

Drag

• Opposes Thrust
• It is categorized as Induced and Parasite.

Induced Drag (Di)

• Drag due to Lift.
• Inverse of TAS².
  • Greatest when slow, clean and heavy.
  • At lower airspeeds, Dᵢ is higher, and at higher airspeeds, it is lower.

Parasite Drag (Dp)

• All Drag that is not Induced Draft
  • Skin Friction Drag from friction at the boundary layer. The closer to the surface the less air is moving across it.
  • Form Drag
• Overall Shape of the object moving through the air stream
  • Leakage Drag caused by pressure difference inside vs outside aircraft.
  • Interference Drag: Objection of surfaces and structures.
  • Profile Drag: Skin Friction & Form.
    • Increases with the square of airspeed.
    • As speed increases exponentially.
• Total Drag Dᴛ : The sum of the 2 Drags, so Dᴛ = Dᵢ + Dp

Wings & Wing Geometry

• Infinite Wing: Wing without wingtips.
• Finite Wing: Has wingtips and four variables:
  • S = Platform Area ft²
  • b = Span (Distance from 1 wingtip to another) ft
  • Cₐᵥ = average chord ft (Distance from Leading Edge to Trailing Edge)
  • AR = Aspect Ratio (Span ÷ Chord)
    • High AR = High level of Lift & Drag
• 2 core formulas:
  • S = b • Cₐᵥ (span x avg core)
  • AR = 48ft/( Span/Chord) Example= 16:1

Engine Types

• Turbojet Type Engine focuses on Thrust.
• Piston Engine focuses on Power.

Horsepower Types

• Brake Horsepower (BHP) Proney Break
  • Measured at the crankshaft or turbine shift
• Shaft Horsepower (SHP)
  • Measured at the propeller shaft (might be crank or turbine shaft)
• Thrust Horsepower (THP)
  • Useable Horsepower
  • Thrust units

Propeller Systems

• Fixed Pitch: The number of degrees the propeller blade is angled in relation to the propeller hub and cannot change.
• Adjustable Pitch: Adjusted with engine hub.
• Controllable Pitch: Adjusted during engine operation.
• Constant speed: Propeller governor maintains a constant engine speed by controlling the pitch.

Engine Oil

• Lubricant
• Clean
• Cooling

Propeller Pitch Types

• Normal forward Pitch: Angle >0° and <90°
• Full Forward Pitch: Angle unknown
• Feathered Pitch: 90°
• Flat Pitch: 0°
• Reverse Pitch

Propeller Tip Speed

• Below Mach 1 (661.7 kts/ 1,116 fps)
• Measured in fps
• Calculates as: Vt = (π * d * rpm) / 720

The Earth's atmosphere contains gas, water, and particulates. Atmospheric pressure decreases with altitude, while density and temperature also tend to decrease. Different types of altitudes include indicated, true, absolute, pressure, and density altitude.