PPRuNe Forums - View Single Post - Question about adjusting FMC descend speed
Old 5th Jun 2018, 08:26
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Avenger
 
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You created the "path", therefore if you put a speed in the DES page and use VNAV it should be on the "path" you created. If you leave it in VNAV with ECON DES SPD but use speed intervention the path remains constant and the speed increases, the green decel dots appear as needed. If you use LVL Change or VS with MCP speed, and a higher speed than the speed selected in the FMC, the path will creep up. Under these conditions the 300 per 10 KTS means when you then reduce the speed to the speed selected in the FMC to comply with the STAR restrictions the path will creep back to the correct profile. Typically, you may save 1 or 2 minutes only by descending at high speed, on the other hand, if you think you will descent into turbulent clouds you would be foolish to select high speed. The Boeing FCTM and Bulletins now put Turbulence speed as .76/280 climb and .76/250 as descent... and they are the experts..
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