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Guest perseas

Takeoff Profiles

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Guest perseas

Hi to all captains,regarding the ICAO takeoff profiles, there is somethingi don't understand. What is the purpose of choosing LNAV at or above 400' when the Autopilot -(CMD A) isn't engaged utill the 1000'?For only when CMD A is pressed, FMC can take over and fly the aircraft whith LNAV.So do i have to roll manually the aircraft until A/P is egaged?

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It has a lot of logic that before you engage the autopilot you previously ARM the mode in wich the autopilot will start to work and not viceversa.Don't you think so?. But this is my "logical" opinion, perhaps some expert can explain a bit further.Jose Luis


signed: José Luis

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Sorry, I'm not an expert... you've already touched on the key factor. The mode or a/p isn't selectable until 400 agl, which is the minimum safe altitude to start maneuvers. The FAA designs departures and minima based on this constraint. I had an instructor pilot, who was a retired controller, explain it clearly to me once when I started my turn to vector as soon as the gear was up. So, the machine lets you arm a mode only when it's safe, and the procedure says it's safer to start using it above 1,000. The most dangerous part of any flight is always the takeoff (not the landing as some expect).


Dan Downs KCRP

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Very interesting information, but that does not break the logic procedure: first ARM, then ENGAGE.Anyway, PMDG 737 permits that you arm LNAV on the ground, I don't know if it's the same in the real bird.Jose Luis


signed: José Luis

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>What is the purpose of choosing LNAV at or>above 400' when the Autopilot -(CMD A) isn't engaged utill the>1000'?You can actually arm it on the ground and purpose is to free pilots from having to do it when he is really busy soon after takeoff.>So do i have to roll manually the aircraft until A/P is>egaged?Yes.Michael J.http://www.precisionmanuals.com/images/for...argo_hauler.gifhttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg


Michael J.

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Guest ChrisY

HiYou press LNAV at 400 so that the Flight Director will follow the departure procedure. You of course remembered to switch the FD on before Take off! You can engage the autopilot later whenever you wish. There is no rule that it should or must be engaged at 1000ft.RegardsChris

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