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Why Does Maneuvering Speed Change With Weight?

Boldmethod

Like many aerodynamic concepts in flight, maneuvering speed can be a confusing topic to learn and to teach. But it doesn't have to be. In this article, we'll focus on the relationship between maneuvering speed and your aircraft's weight.

What is Maneuvering Speed?

Before we get into maneuvering speed & weight, let's review the basic concept. Manuevering speed, or Va, is an airspeed published by your aircraft's manufacturer that guarantees that your aircraft will stall before you reach the maximum certified g-load, under some very specific conditions.

Contrary to popular belief, you can't just throw your stick and rudders back and forth below Va and expect to not bend metal.

Aircraft Va is certified with the assumption of the movement of a single flight control surface, in a single direction, in smooth air.

Relationship Of Weight And Maneuvering Speed

When your aircraft is certified, its maneuvering speed is determined at maximum gross weight. As your aircraft gets lighter, your maneuvering speed gets slower. This is the confusing part of maneuvering speed, but it doesn't have to be.

Instead of thinking about the relationship between Va and weight, let's add a step between the two:

Increased Weight → Increases AOA → Increases Va

Aircraft weight affects the Angle of Attack (AOA) you fly at to maintain level flight. While a lower weight might only require one or two degrees of nose-up pitch to maintain level flight, a heavier aircraft might require a few more degrees of pitch up to stay level, assuming the aircraft's speed and configuration remain the same.

This is because, at the same speed and configuration, a heavier aircraft needs to fly at a higher angle of attack to produce enough lift to counter the aircraft's weight in level flight.

It's all about degrees. Your wing will always stall at the same AOA, with most general aviation planes stalling somewhere between 16 to 20 degrees of angle of attack.

With a heavier aircraft, your AOA in cruise is closer to the critical AOA, causing you to stall at a faster airspeed. A lighter aircraft will have more degrees of AOA to increase before it encounters the critical AOA, causing you to stall at a lower airspeed.

In both scenarios, you'd be stalling the aircraft at its' maximum certified g-load.

How Manuevering Speed Protects Your Aircraft

Maybe you've heard the phrase that maneuvering speed protects your aircraft because it will "stall before it breaks." Like many phrases in aviation, there is a bit of truth behind it, but it oversimplifies Va's protections too much.

The essential concept behind Va protection is that, assuming you are at or below your Va your aircraft will stall as you reach its' maximum structural load (g-limit). As your plane stalls, it unloads the g's, eliminating the risk of bending metal.

Click here for our full article about how maneuvering speed protects your aircraft.

Nicolas Shelton

Nicolas is a commercial pilot from Southern California. He is currently studying at Purdue University, where he is working on advanced pilot ratings. You can reach him at nicolas@boldmethod.com.

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