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philbrown

757 Autothrottle in turns

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I'm having a small problem when the autothottle is engaged in speed hold mode, whilst the aircraft is banking.For example, I'm in the cruise, and have to make a turn for the next waypoint. The autothrottle starts increasing power to the engines, and the speed starts to increase above the commanded speed. As it's increasing, the green trend arrow starts pointing down, signalling a reduction in speed, despite the speed indicator ticking upwards. All the while the engines continue increasing as though the aircraft is loosing speed, even though I'm actually gaining it.On some turns where they've been 90-odd degrees, this has caused air speed loss/gains as much as 15-20 knots.Is anyone else experiencing this behavior?

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Phil, I'm not sure, nor really authorized to dispense advice, but if you're making turns the AT will have to increase the throttle a little to keep speed as designated. It shouldn't vary too much from the desired speed, 15-20 knots sounds excessive. But, you also shouldn't really be making 90 degree turns unless turning for base or final legs, in which case you should be going no more than 180 knots or so anyway. If you're going that slow, and have 15 or 20 degrees of flap, the speed fluctuations shouldn't be that much.2 cents,Brad

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