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A320/321 holding speeds

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A320/321 holding speeds

Old 3rd Sep 2000, 01:55
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Heffalump
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Is there, out there, an ETPS graduate or a CFS A1 or someone with a proper degree in aerodynamics who can explain why the A321 holds at green dot and the A320 holds at green dot plus about 20kts?

The brochure says that green dot is max lift/drag ratio. At 1g, presumably that is equal to Vimd since lift is constant = weight.

The problem occurs on the corners. If you speed select green dot on the A320, then, when you go round the corners the Vls comes up to meet the selected speed and the engines have to wind up to loads of fuel flow in order to maintain the speed - plainly not sensible.

So it seems that the A321, when it gets to the corners, stays on the right side of the drag curve and the A320 doesn't. I can't make a mental model of how the tiny increment in load factor required for the corners, at an angle of bank of about 25 degrees, can make so much difference to the A320 when it's the same wing.

Can anyone help?
 
Old 3rd Sep 2000, 03:55
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jtr
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On the 330/340`s Vls is function of Vs1g, therefore no G correction, therefore no increase while banking. Is the 320 series different?

[This message has been edited by jtr (edited 03 September 2000).]
 
Old 3rd Sep 2000, 12:08
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Join Date: Aug 1998
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See:

A 320 HOLDING SPEEDS

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Old 3rd Sep 2000, 14:04
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Down Three Greens
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Lightbulb

Could be a CPIPS upgrade on the A321. Our 321's are more modern and are CPIPS3. Just a thought.

The above link has plenty of ideas though
 

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