In short: Maneuvering speed is the speed at which the airplane will stall before exceeding its limit load factor if the angle of attack suddenly increases. Rod Machado shows that lift, and therefore G-load, rises roughly in proportion to angle of attack, so the slower you fly, the smaller the multiple a gust can apply before the wing stalls.
Video: “How Is Maneuvering Speed Determined?” by Rod Machado, from his YouTube channel.
What you’ll learn
- Rod’s working definition of maneuvering speed
- Why load factor equals lift divided by weight
- How doubling or tripling the angle of attack doubles or triples the G-load
- Why an airplane at a fast cruise could see 6 G in a strong gust
- Why slowing to VA caps the G-load at the limit before the stall
- Rod’s personal practice for flying in turbulence
Lift, weight and G-load
Rod starts with the basics. Standing on the earth you feel 1 G. In straight-and-level, unaccelerated flight, lift equals weight, so the ratio of lift to weight is 1 and you feel 1 G. Raise the angle of attack suddenly, by pulling back on the elevator control or encountering a strong vertical gust, and lift jumps. The airplane accelerates upward, you are pressed into the seat, and the G-load rises in proportion to the extra lift. Rod describes the relationship between angle of attack and lift as direct, or nearly one to one.
Two speeds, two outcomes
In Rod’s example, an airplane cruising at 140 knots needs about 3 degrees of angle of attack for level flight. A gust that adds another 3 degrees doubles lift to 2 G. At 9 degrees it’s 3 G, and so on up to 18 degrees, where the wing stalls. That means at 140 knots the airplane could experience up to 6 G before stalling, beyond an example limit of 4 G. Rod uses 4 G for easy math and notes the standard positive limit is 3.8 G.
Slow to 110 knots and the wing needs 4.5 degrees for level flight. Now a gust can only quadruple the angle of attack to 18 degrees before the stall, so the airplane can’t exceed 4 G. That makes 110 knots the maneuvering speed in this example: the airplane stalls before it can be overstressed, whether from turbulence or full elevator deflection.
The point Rod wants to stick
In turbulence, Rod says he prefers flying 10 to 15 knots below maneuvering speed so a gust doesn’t briefly push his indicated airspeed above it. He also notes that using power slightly lowers stall speed and therefore slightly lowers maneuvering speed.
His key takeaway is that whether a gust doubles, triples or quadruples your angle of attack depends on where you start. At higher speeds you begin at a lower angle of attack, so the same turbulence produces a larger multiple and more G. A follow-up video explains why maneuvering speed changes with weight.
Go deeper with Rod Machado
Rod closes the video by pointing viewers to his pilot handbook for more on maneuvering speed and related concepts. Learn more in Rod Machado’s Private/Commercial Pilot Handbook.
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