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Aviation Learning Center Document Meet Your Aircraft P-8740-29
Author: FAA Date: 1995
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Limitations, Performance, and Weight and Balance
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These three areas are very closely interrelated. Operating at airspeeds where you get the best performance could be a limitation, since increasing or decreasing speed would decrease desired aircraft performance. An example is L/D max, which is where the lift to drag ratio is the greatest, or the airspeed where you get the most lift for the least drag. Why is this important? This is the speed which would give the aircraft the greatest gliding distance in the event of a complete power failure. You would need this performance to reach a safe landing area. Changing speed would only reduce your chances of making the field.

Weight and performance are closely interrelated. Increasing weight reduces performance. This will cause an increased takeoff distance, reduce an aircraft's rate-of-climb capability, and cause the true airspeed to be less at a given power setting and density altitude. Although pilots should always compute the weight and balance performance data for every flight, this information is especially important when transitioning to a new aircraft.

Aircraft speeds, the various "V speeds," are also important for the safe operation of any aircraft. It is recommended that pilots know the following V speeds that apply to their particular aircraft:

  • Vs0 - stalling speed, or the minimum steady flight speed in the landing configuration.
  • Vs1 - stalling speed, or the minimum steady flight speed in a specified configuration.
  • Vr - rotation speed.
  • Vmc - minimum control speed with the critical engine inoperative (multi-engine aircraft)
  • 1.3 Vs0 - recommended final approach speed in the landing configuration (if none specified in the aircraft's documentation.
  • Vx - speed for the best angle of climb.
  • Vxse - speed for the best angle of climb (one engine inoperative in multi-engine aircraft).
  • Vy - speed for the best rate of climb.
  • Vyse - speed for the best rate of climb (one engine inoperative in multi-engine aircraft).
  • Vlo - maximum landing gear operating speed.
  • Vle - maximum landing gear extended speed.
  • Vfe - maximum flap extended speed.
  • Va - design maneuvering speed.
  • Vne - never exceed speed.
  • L/Dmax - airspeed that gives you the maximum gliding distance over the ground with complete power failure.

Obviously these are a lot of numbers to memorize. However, remember that a pilot must know how to operate his or her aircraft safely. Knowing V speeds is part of knowing what to do not only when something goes wrong, but also when things are going right. One way to remember these speeds is to write them on 3 x 5 inch cards and have them where they can easily be reached for reference just prior to specific flight operations. Many of these speeds are also marked on the instrument panel, some operating controls, and the airspeed indicator.

There are many other limitations that a pilot needs to know, such as manifold pressure, RPM, engine oil temperature and pressure, cylinder head temperature, hydraulic pressure limits, volt and loadmeter readings, etc. Fortunately for most of us, the aircraft we fly normally have these marked with color-coded indicators. However, it is important to know where the indicators normally point, so that it will be easy to spot any change or abnormal condition.

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