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In this video, starting at 18:15, the copilot on the Bristol Brabazon's first flight recounts that the aircraft became airborne a little sooner than its pilots expected, and that despite the captain holding the yoke fully forwards, the nose continued to rise. The copilot responded by retarding the throttles and then advancing them again, which cleared up the problem. He does not mention any adjustment to the trim, though he states it was fully forwards prior to his action. He also mentions that an adjustment was made to the elevator to fix the problem for subsequent flights.

I am curious as to what caused this problem, and in particular, why it did not recur when the copilot reapplied power. I realize that the copilot may have omitted some key details, such as the aircraft accelerating before the reapplication of power (this occurred at 200 - 300 feet, and the film of the take-off appears to end before it has reached that altitude.) I am also aware, from other reading, that the Brabazon was intended to have a complex (at least for the time) hydraulic control system that was intended to smooth its response to turbulence, that never really worked properly, but it would seem an unnecessary risk to have it engaged for the first flight.

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  • $\begingroup$ Possible explanations (purely guess work from what is presented): the plane accelerated and the flaps were retracted / the trim is affected by airspeed. $\endgroup$ – kevin Jan 8 '17 at 7:38
  • $\begingroup$ @kevin I imagine the answer is in something like that, but I would guess that with the low wing, flaps would generate an additional nose-down moment. For that matter, if increasing the speed alone decreased the pitch-up, the airplane would be unstable in pitch, would it not? I suppose if the airplane had some sort of linkage mechanism intended to compensate for the pitch effect of the flaps, and it over-compensated as a result of being set up incorrectly, that might do it... but why enable such a mechanism on the first flight, unless the design gave you no choice? $\endgroup$ – sdenham Jan 8 '17 at 22:30
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The one thing I have read about this aircraft years ago, is that it had numerous problems in the flight controls, all of them due to the flight controls cables, whose rigging was unstable. I remember having read that it was a banana (???) effect to the fuselage.I can’t tell whether it was distortions in the XY plan on in the XZ plan or something else

Reducing the power would it have modified this banana effect? I can’t tell.

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  • $\begingroup$ Banana effect sounds like aeroelasticity. To my knowledge it means that angular sensors are located in a different part of the airframe than where their measurement is applied. How that affected Brabazon control is beyond me. $\endgroup$ – Peter Kämpf Jun 10 at 5:47
  • $\begingroup$ Yeah excessive fuselage flex, reversing the elevator operation. All got re-set by momentarily removing the nose-up pitch moment from the engines. Or something similar. $\endgroup$ – Koyovis Jul 11 at 14:45

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