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tinyclark

Prop wash and wing lift

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As pilots, were any of you taught how the prop slipstream affected wing lift? If so, is there so little effect that it is negligible? Does it affect the horizontal stabs more than the wings?

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Let me ask in a different way. If you lose an engine during flight, does the aileron have to be trimmed at all to compensate for the loss of the engine? Someone must know this.

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The prop slipstream has a large effect on wing lift, especially at low speeds. This is referred to as the "powered lift" portion of the total wing lift. The magnitude of powered lift is typically correlated to "thrust coefficient" (Ct). It all comes down the difference between the free-stream air velocity and the induced air velocity behind the props: the larger the difference (think high power and low speed), the larger the contribution of powered lift. In those conditions, the loss of an engine would cause a rolling tendency toward the dead engine.

To get an idea of the powered lift present on the C-130, compare the normal and max effort takeoff speeds. Normal speeds are based on "power off" stall while the max effort speeds use the "power on" stall speed.

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When I got to Sewart, I was sent on the rookies quest for some "Prop wash".

One of the guys in supply just happened to have a quart can and loaned it to me.

I took it back to him after showing it to the rest of the crew.

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