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Finding Maneuvering Speed At Light Weights

Gemini Sparkle

Key Takeaways:

  • VA (design maneuvering speed) is critical for structural safety in turbulence but varies with aircraft weight, hence its absence from the airspeed indicator.
  • Its purpose is to ensure the aircraft stalls (an aerodynamic limit) before exceeding its structural limit-load factor, preventing damage from excessive G-forces.
  • VA decreases with lighter aircraft weight because reduced weight leads to lower angles of attack for a given speed, allowing higher G-forces before stall, thus requiring a lower speed to maintain the stall-before-damage principle.
  • Pilots can calculate an adjusted VA for lighter weights using a specific formula or a practical rule of thumb, with the latter being sufficiently accurate for typical operational scenarios.
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common FAA knowledge test question goes like, “Which of these speeds is not found on the airspeed indicator?” The answer is usually design maneuvering speed, also known as VA. Many students might then wonder why it is not found on the airspeed indicator along with other important V speeds such as VNE and VFE. Perhaps it is really not that important? Well, the FAA certainly believes that it is important enough to warrant a test question!

One of the reasons VA isn’t found on the airspeed indicator is because, like VX and VY, maneuvering speed changes with weight. The speed found in the POH or placard is applicable for a particular weight, usually maximum gross. We often do not fly our airplanes at maximum gross takeoff weight, so what happens to maneuvering speed as we fly at these lighter weights? It decreases! Let me offer a simple and thorough explanation as to why that is, as well as provide ways to calculate a “new” maneuvering speed if flying below maximum gross weight.

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