Effects of Weight

You are viewing: Why Does Maneuvering Speed Change With Weight

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So you understand why we can’t exceed the load limit but why does Va change with weight? Remember, maneuvering speed is defined as the highest speed at which full deflection of the controls about any one axis are guaranteed not to overstress the airframe. This is a dynamic limitation on the forces imposed on the airframe.

Again Mr. Newton helps us out: Force = Mass x Acceleration or Acceleration = Force / Mass. Mass is the weight of the airplane and acceleration is the imposed load. Take two identical airplanes, one light and one fully loaded. If we apply a force on the controls maneuvering the light airplane the acceleration is much more than the same force applied to the heavy airplane.

But how do we guarantee we will not overstress the airframe? Simple – it will stall first. Remember the heavier airplane will need to fly at a higher angle of attack to produce adequate lift to overcome the weight. That means the heavy airplane will be flying closer to the critical angle of attack and stall more quickly. The light airplane must travel through a greater angle of attack range before stalling providing more time for the airplane to accelerate and exceed the load limit.

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Other Considerations

It’s a good thing we have that 50% buffer because the airplane is certified NEW. Structural fatigue is cumulative over time so an older plane is not necessarily as strong as when it rolled off the factory floor. Corrosion and metal fatigue can wear down components. Signs of fatigue are checked during annual and 100-hr inspections but many items internal fractures can only be detected using ultra-sonic devices.

Smooth application of the controls will minimize wear and tear. Fly your C172 like a Boeing and it will last you a long time. If you encounter moderate or greater turbulence, SLOW DOWN. As long as you are below Va for your given weight you will stall before damage occurs. That sounds like a bad thing but I would much rather recover from a stall than wonder why cracking sounds are coming from the wing spar!

Source: https://t-tees.com
Category: WHY