I’m going to take a crack at answering the actual question. First a disclaimer: I earned a bachelor of science degree in aerospace engineering. I stood top of my class in aero when all was said and done. But I’ve never been an actual aerospace engineer. I was a private pilot, single-engine, non-complex rating. A whopping 300 hours! So I’ve had a bit of practical experience, but not much.
Here goes:
Virtually EVERY powered airplane built, at full takeoff power, at sea level, on a cold and dry day, with a long enough runway and with standard takeoff trim and flaps set, has sufficient angle of incidence to take to the air without ANY rotation.
Ron’s posted video shows a BUFF at full takeoff power with a teensey-weensey “apparent” rotation just prior to liftoff. Every bit of angle helps the aircraft to lift off sooner rather than later. But I’d bet my next paycheck that the B-52 could lift off unassisted given the conditions I stated. I welcome refutation.
Not part of an answer to the original question but still relevant to the question: There are many reasons why pronounced take-off rotation would be adverse to a given aircraft design’s purpose. One is landing gear loading. The BUFF provides an example. It’s two sets of landing gear are set inline with the fuselage and well forward and aft of the wing’s center of moment. Excessive takeoff rotation might put excessive downward force on the rear landing gear set, damaging it. The BUFF’s fuselage is also very long. Excessive rotation would increase the chance of tail strikes.
High speed jets are purposefully designed with as low an angle of incidence (angle between wing chord line and the longitudinal axis of the aircraft) as possible. This is to minimize induced drag at the design operational speed envelope. Eats less gas and increases operational range.
One interesting design is the US Navy’s old F-8 Crusader. It was a carrier-based supersonic fighter-bomber. The wing’s could be rotated “upward” for takeoffs and landings. And at cruise speed, it could be lowered. This allowed higher operational speed while affording adequate lift during lower speed takeoff and landing. The upward-rotated wing can be seen in the video below. Also, the Crusader was designed with a much taller nose gear than its main gear, so the jet’s longitudinal axis was not parallel to the “runway”. This design added more angle of incidence at takeoff to get off the deck and keep from flying into the sea. The Crusader also had a very powerful engine with an almost 1:1 thrust to weight ratio. BUFFs have much less than 1:1 T/W. The effect is that an F-8 pilot can power their way out of a takeoff stall much easier than a BUFF pilot.
Fire away boys and girls. I had a fish year and a plebe year and I’m a former nuke. I can take verbal abuse with the best! :-)
Writer: Dave Corley
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