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Guest phildoe6

747 inflight trim?

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hi,i have a question regarding the trim (not only of the 747) in flight. when at cruising alt, the nose of the plane is still up and not parallel to the ground or horizon. i have this problem on most planes but how can i trim aircraft with autopilot engaged? it will always set the trim as before. i also used the random load in the load manager, so i have not loaded too much in the back belly. please help me solving this problem. is there any autotrim function or similar?thxphil

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Nose up is part of the design of Boeing aircraft. The nose is never parallel (or tangent if you refer to the fact that the earth is curved) to the ground.

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I think the figure for Boeing 747-400 is 3 Degrees nose up during cruize. might be wrong

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I believe that anytime you try to manual trim the aircraft with the electric trim switches located on the top left handle of the yoke, will automatically disconnect the A/P if it is engaged.Regards,noullet

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This has nothing to do with the fact that is a boeing plane. It is perfectly normal for the 747 and in fact for every plane (with a positively cambered wing) to fly with a nose up altitude ..for every given weight, one angle of attack will correspond with one speed .. the slower you fly, the higher the angle of attack, untill you reach the critical angle and ultimately stall ..A plane is in trim when the aircraft maintains a certain angle of attack (and thus speed) without any forces on the controls .. as the plane becomes lighter in flight due to burning of fuel, the required amount of lift becomes less, thus, while maintaining straight and level flight and maintaining airspeed, the angle of attack will reduce. This also implies that if you would stay at the same angle of attack, and the planes get lighter, maintaining the airspeed means the plane will climb due to increase in lift .. to maintain straight and level flight, if angle of attack goes up, speed must go down and vice versa .. Angle of attack is the angle between the mean chord of the wing and the relative wind (relative wind is the opposite of flightpath)

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