Aerodynamics of Flight

Lift and Weight

• In straight and level flight, lift and weight are balanced.
• If lift is greater than weight, the aircraft will climb.
• If weight is greater than lift, the aircraft will descend.

Thrust and Drag

• In straight and level flight, thrust and drag are equal in magnitude.
• Thrust is controlled by the throttle.
• Increasing the throttle increases thrust.
• When thrust exceeds drag, airspeed will increase.
• As airspeed increases, drag rapidly increases, until thrust and drag become equal, and airspeed becomes constant.

Effects of Altitude

• An increase in altitude decreases atmospheric pressure, increasing density altitude.
• Increased density altitude results in:
  • Longer takeoff roll
  • Reduced climb performance
  • Longer landing roll
  • Decreased engine power

Effects of Temperature

• Hot air is less dense than cold air
• On a hot day, compared to a cold day:
  • Takeoff roll is longer
  • Rate of climb is slower
  • Landing speed is faster
  • Engine power output is decreased

Effects of Humidity

• Humid air is less dense than dry air.
• On a humid day, compared to a dry day:
  • Takeoff roll is longer
  • Rate of climb is slower
  • Landing speed is faster
  • Engine power output is decreased

Aircraft Rotational Axes

• An aircraft has three rotational axes:
  • Roll
  • Pitch
  • Yaw

Primary Control Surfaces

• Control of the aircraft about its three axes of rotation is affected by the primary control surfaces:
  • Ailerons control roll.
  • Elevator controls pitch.
  • Rudder controls yaw.

Ailerons

• Ailerons are hinged surfaces mounted on the outboard trailing edge of the wings. They rotate the aircraft around the longitudinal axis.
• Left and right ailerons move simultaneously but in opposite directions.
• Moving ailerons induces adverse yaw, which is the tendency of the nose to yaw in the opposite direction of the turn.
• Adverse yaw is caused by the drag of the "down" aileron.

Elevator

• The elevator is a hinged surface located on the rear of the horizontal stabilizer.
• The elevator rotates the aircraft around the lateral axis.
• The elevator controls the pitch and angle of attack of the aircraft.
• On some aircraft, the entire horizontal tail surface moves, known as a stabilator.

Flaps

• Flaps extend on both wings simultaneously.
• Flaps increase camber, and on some aircraft, increase wing area, which:
  • Increases lift
  • Increases drag
  • Lowers stall speed
  • Allows steeper approach to runway without increased speed

Helicopter Aerodynamics

• The forces acting on helicopters are the same as fixed-wing aircraft:
  • Lift
  • Thrust
  • Weight
  • Drag
• Lift is provided by the rotor blades, which are shaped like an airfoil.
  • Bernoulli’s Principle applies.
• When rotor blades are in motion, they act as a wing.
• RPMs and blade pitch control:
  • Vertical ascent (lift > weight)
  • Hovering (lift = weight)
  • Vertical descent (weight > lift)

Helicopter Controls

• Throttle controls the RPMs
• Collective controls the pitch of the rotor blade, which affects lift.

Carburetor Ice

• Carburetor ice can form between 20-70° F in conditions of high humidity.
• Lowered pressure and vaporization in the carburetor lowers the temperature of the fuel/air mixture, causing water vapor or moisture to freeze.

Aircraft System Failures

• Aircraft system failures can occur due to:
  • Electrical failures
  • Mechanical failures
  • Hydraulic failure
  • Engine failure
  • Engine fire

Electrical Failure

• Partial electrical failure affects some instruments and systems.
• Complete electrical failure results in a loss of:
  • Some instruments
  • Flaps on some aircraft
  • Radios and navigation and transponder equipment
  • Lights

Mechanical Failure

• Mechanical failures can occur in:
  • Landing gear
  • Tires
  • Wheels
  • Panels
  • Flight controls
  • Windshield

Hydraulic Failure

• Hydraulic failure affects landing gear, flaps, and brakes on some aircraft.

Engine Failure

• Engine failure may affect:

  • Engine-driven vacuum system for instruments
  • Hydraulic power
  • Electrical power
  • Pressurization

• Engine failure can result in:

  • Loss of altitude
  • Forced landing

Engine Fire

• An engine fire is usually controllable.
• Indication to the pilot of an engine fire is via the fire warning light.
• Cabin/cockpit fires are extremely serious.
• Air traffic controllers should assist pilots with any of these situations by:
  • Providing information about the nearest suitable airport for landing.
  • Providing priority handling and clearing conflicting traffic.
  • Alerting emergency equipment.
  • Informing the pilot of any available resources.
  • Notifying their supervisor of the situation.

This quiz covers fundamental concepts in aerodynamics, including the relationship between lift and weight, thrust and drag, and how altitude and temperature affect aircraft performance. Test your understanding of these principles and their practical implications for flight.