IF Straight and Level flight

Instrument Flying

Straight and Level flight

Straight flight

  • An aircraft is in straight flight when it’s flying a constant heading (direction).
  • To maintain straight flight, the wing must be kept level with the horizon.
  • If the wings are not level with the horizon, the aircraft will turn, and this will be shown on the:
    • Attitude Indicator.
    • Heading indicator.
    • Turn coordinator / turn and bank indicator.
Attitude indicator
  • The attitude indicator gives a direct indication of pitch and bank.
  • One advantage of the attitude indicator is that it offers at a glance an immediate indication of both pitch and bank attitude.
Heading indicator
  • The Heading Indicator displays, an indirect indication of bank because a banked aircraft has a natural tendency to turn.
  • A rapid movement of the Heading Indicator in coordinated flight indicates a large angle of bank, whereas a slow movement reflects a small angle of bank, assuming the same airspeed in both instances.

Turn coordinator
  • If the ball is centered and the needle is deflected from the central position you may logically conclude that the aircraft is banked in the direction of the needle deflection.
  • If the ball is not centered, the aircraft is either slipping or skidding, and the side to which the ball has rolled indicates the direction of the slip or skid.

Level flight

  • An aircraft is in level flight when it’s flying at a constant altitude.
  • At a constant cruise power setting, a deviation from level flight will result if the nose is pitched up or down.
  • The instrument to check:
    • Attitude Indicator.
    • Alitmeter.
    • Vertical Speed Indicator.
    • Airspeed Indicator.
Attitude Indicator
  • The Attitude Indicator gives a direct indication of pitch attitude.
  • However it will show approximately level flight at normal cruise speed.
  • If further adjustment of the miniature aircraft is necessary, the other pitch instruments must be used to maintain level flight while the adjustment is made.
Altimeter
  • At constant power, any deviation from level flight (except in turbulent air) must be the result of a pitch change.
  • Since the altitude should remain constant when the airplane is in level flight, any deviation from the desired altitude signals the need for a pitch change.

Vertical Speed Indicator
  • The vertical speed indicator gives an indirect indication of pitch attitude and is both a trend and a rate instrument.
  • it shows immediately the initial vertical movement of the airplane, which, disregarding turbulence, can be considered a reflection of pitch change.
  • The lag characteristics of the vertical speed indicator must be considered.
  • Lag refers to the delay involved before the needle attains a stable indication following a pitch change.
Airspeed Indicator
  • The airspeed indicator presents an indirect indication of the pitch attitude.
  • At a constant power setting and pitch attitude, airspeed remains constant.
  • As the pitch attitude lowers, airspeed increases, and the nose should be raised.
  • As the pitch attitude rises, airspeed decreases, and the nose should be lowered.
  • A rapid change in airspeed indicates a large pitch change, and a slow change of airspeed indicates a small pitch change.

Straight and Level flight

  • At a constant airspeed and power:
    • Altitude can be controlled by pitching the nose up and down.
    • Airspeed can be controlled with power.
    • Both attitude and power must be changed to change airspeed in level flight.
  • While in straight and level flight, any change in power setting result in a change airspeed or altitude.
  • When the airspeed is constant, an increase in power will cause aircraft to climb and a decrease in power will cause the aircraft to descend.
  • If altitude is maintained, a change in power will affect the airspeed.

Scan technique: Straight and Level flight

  • To establish the aircraft in straight and level flight at a desired airspeed use:
    • Attitude Indicator.
    • Tachometer (rpm).
  • To detect any error in heading, altitude or speed use:
    • Heading indicator.
    • Altimeter.
    • Airspeed indicator.
  • Occasionally scan the magnetic compass, tachometer and engine instruments.

Review questions

  • How to change airspeed during straight and level flight ?
  • Which instrument will indicate a change in attitude:
  • Which instruments will indicate a turn ?
  • Should we trust our instruments or your body sensations?
  • What is the scan technique for straight and level?