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Collins

757 take off auto throttle question

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This is following the 757 tutorial flight page 25. Entering runway with FMC fully programed with auto throttle and flight director selected on. When I select LNAV then FLCH the engines start spooling up before I get the chance to line up and hit EPR. Have I got finger trouble or is this a known problem. Please help as it is driving me nuts.

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Hi there, My personal technique is to leave A/T off until at the threshold (number one for takeoff). When cleared for takeoff or when such clearance is imminent, I arm the A/T (flip the switch). The first time that I actually activate the A/T is when I'm lined up, throttles have been advanced approximately 50%, and the engines have stabilized. Then I activate EPR (push the button) and just to help the A/T along, push the throttle up to max on my controller (some throttle hardware can confuse the A/T operation and cause weird fluctuations if not at full thrust or fully closed). You shouldn't have FLCH armed/activated before takeoff. I'm pretty sure this is SOP for most aircraft, including the 757, excluding all airbuses. By the way, to keep you from getting a message from the moderators, don't forget to sign your posts. Hope this helps and have a great flight. :)-adam

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Hi.I'm only guessing here, but, I usually have the A/T engaged, and the FD armed too, but then I also set the LNAV and VNAV too, Then, when I get my departure clearance from the tower I RIGHT click on the EPR button to engage and activate the de-rated thrust take off.Once airborne and after gear retraction and at about 500 feet, I then engage the Auto Pilot Switch, this way you don't need to use the FLT change button at all, at least you don't if you have the FMC programmed and have an initial altitude set for your first point of 6K for example.I think where you might be going wrong is by switching on one of the three Auto Pilot Switches before you have even lined up, this is why your engines are trying to set and maintain your set speed.But I am only guessing as I said in the beginning.let us know what happens if you try the above please Collins.

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Thank you Adam, Steve for your replys. I have just completed a successful auto throttle take off by pressing EPR with FLCH not engaged and the selected FMC flight level was captured with no problems.I don't engage an auto pilot until at least 1000ft.I'm begining to think that the tutorial is incorrect. I can't remember any pilots engaging FLCH before takeoff when I've been in the flight deck. The auto throttle and flight director switches are on before pushback.Just a note to PSS, this is a fantastic aircraft to fly and learn to program the FMS, thank you :D Regards, JonPS, hope I have signed it this time.

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I don't engage FLCH before takeoff either. Usually LNAV only and the AT when on the rwy. After hand flying for a while, then VNAV, CMD. I agree Jon it is a nice a/c to fly. Joe

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