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STRAIGHT AND LEVEL FLIGHT

Aim

Students must demonstrate the ability to produce and control the straight and level flight, including straight and level flight during speed and flap changes.

Description

You must demonstrate the ability to maintain straight and level flight while smoothly conducting power changes, changes to specified speeds, and flap changes.

Performance Criteria

This exercise is not a flight test item, but is evaluated in conjunction with other exercises; Private Pilot Students and Commercial Pilot Students must

  • demonstrate smoothness in control;
  • maintain altitude within ± 100’ of target, including during speed and flap changes;
  • maintain airspeed within ± 10 KNOTS of target;
  • maintain heading within ± 10° of target.

Discussions

Straight and level flight is simply a matter of maintaining the cruise attitude and the desired power setting and airspeed.  It is defined as flight at a constant altitude and airspeed, the latter determined by the selected power setting.  Importantly, in establishing straight and level flight, the aircraft should be allowed to accelerate to the desired cruise airspeed first.  Once this speed is attained, the power should be adjusted to a cruise power setting. 

Additionally, as the aircraft accelerates, trim will have to be adjusted to maintain the pitch at the desired position.  After the aircraft has stabilized in the cruise attitude, a standard “cruise check” or “level check” should be performed as follows:

  • adjust the throttle to the desired setting;
  • adjust the mixture control to the “best economy setting” (on Langley Flying School aircraft, this is only done above 4000’ ASL); to set best economy, first lean to “maximum RPM” setting, then enrich the mixture about 1/4 inch.;
  • check for carburettor ice—applying carburettor heat for a minimum of 30 seconds;
  • check and/set the heading indicator to the heading indicated in the compass (remember, there is the possibility of compass error during turns and during acceleration or deceleration.

After completing the level checks, return to the throttle for fine-tuning as the propeller will accelerate with the increase in airspeed; also, with the acceleration you will likely have to reset your trim, bearing in mind that the aircraft should be trimmed for hands-free flight.

Once established in straight and level flight, note the visual and instrument indications.  Confirmation of straight and level flight is indicated by a steady altimeter, heading indicator, and airspeed, but the primary references you use are visual clues—a constant cruise attitude with a level dash, with the aircraft tracking directly to a distant object.

Remember that the position of the nose (or glareshield) of the aircraft will change visually with a change in cruise airspeed whereby the slower the aircraft, the higher the nose relative to the horizon.  Regardless of airspeed, the wing and glareshield remain level.

Flight Safety

  • Instructor and student must continually scan the sky for other aircraft in the vicinity.  If you see a “target,” sound off using the “clock” directions to advise the Instructor;1 he will do the same, ensuring that both of you are aware of vicinity air traffic.
  • Apply the Seven-Point Scan Technique (see P. 47).
  • While the seven points are important, remember that scanning for traffic above and below you is also crucial.
  • Risk of collision is high during a turn, so it is the responsibility of the student to always clear airspace in the direction of the turn (to the side and rearward) prior to initiating a turn.
  • Risk of collision is also very high around airports.  Be especially vigilant during the departure and arrival phases of flight.
  • Be aware of the limiting speeds for flap extension.2  Extending the flaps outside the permissible speeds could cause structural damage.

References

1 When a target is sighted, it is useful to add further descriptions in addition to the “clock” position—for example “Target, 2 o’clock low, moving right to left,” or “Target is 10 o’clock, just above the horizon.” 

2 The flap-extension speed range for the Piper Cherokee is from 55 MPH to 115 MPH, and is indicated by a white arch on the Airspeed Indicator.