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Guest Totalbeginner

Thrust reduction & Accel Height

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Guest Totalbeginner

Thrust reduction & Accel heightThe PMDG manual says that these are based on feet above airfield level. Are these taken from the radio altimeter or the baro altimeter?Many thanksMartin Neep

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I always figured it was the barometric altimeter as the plane knows what altitude the airport is at. To me it would just add 1500 or whatever feet to that number.I really have no idea though, just my thought.


Mike Roth

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It's barometrically derived, but I'm not sure if the airport altitude is barometrically assessed during the takeoff roll, or whether the airport altitude is taken from the FMC database.Cheers.Q>

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In the takeoff "phase" when the aircraft accelerates past 100 knots the flight management system will "lock-and-store" the current barometric altitude. Subsequently all thrust and speed management operations, right after take off (e.g. thrust reduction, acceleration after engine failure etc.) will use THAT reference altitude. We modelled this feature exactly as per operating manual (what else...).Best,Vangelis


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E M V

Precision Manuals Development Group

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According to the real AOM:"during takeoff, the FMC records barometric altitude as the airplaneaccelerates through 100 knots. This altitude is used to activate LNAV andVNAV, enable autothrottle activation (if not active), commandacceleration for flap retraction, and set climb thrust if an altitude has beenselected"Best Regards,Victor LimaSBGLhttp://www.precisionmanuals.com/images/forum/800driver.jpg


Cheers,
Victor M. Lima
 

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Guest D17S

Gentlemen, Vangelis is in the house. If you have any questions, now's the time. Have you noticed the depth of exploration and discussion your model as allowed? Thanks again for this superb simulation.

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