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L/D)max Value For Boeing 738 Or A320  
User currently offlinestevenmeyer2005 From Spain, joined Jan 2010, 27 posts, RR: 0
Posted (4 years 1 month 3 weeks 5 days 19 hours ago) and read 8397 times:
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Hi guys,

Does any one know Lift to Drag max values of the Boeing 737-800 or the Airbus A320?

Are the Lift to Drag max values different between the various Boeing 737 models?

Appreciate the input!

Stevenmeyer2005


Steven Meyer
7 replies: All unread, jump to last
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (4 years 1 month 3 weeks 5 days 8 hours ago) and read 8309 times:

Quoting stevenmeyer2005 (Thread starter):
Are the Lift to Drag max values different between the various Boeing 737 models?

I don't know what the actual L/D values are, but they should be different between different models because you've got different finess ratios on the fuselages and different wing loadings (same planform, different weights). Winglets and not-winglets will also make a difference.

Tom.


User currently offlinejetlagged From United Kingdom, joined Jan 2005, 2532 posts, RR: 24
Reply 2, posted (4 years 1 month 3 weeks 3 days 18 hours ago) and read 8175 times:

Quoting tdscanuck (Reply 1):
different wing loadings (same planform, different weights)

Surely L/D max is not affected by wing loading? The airspeed for L/D max is affected by weight though.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 3, posted (4 years 1 month 3 weeks 3 days 18 hours ago) and read 8161 times:

Quoting jetlagged (Reply 2):
Surely L/D max is not affected by wing loading?

Has to be, I think. Higher wing loading forces you to higher Cl at a given speed, which means lower L/D for that speed. Since this applies to all speeds, the whole L/D vs. speed curve moves down with increasing wing loading, so it can't have the same L/D max.

Tom.


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 4, posted (4 years 1 month 3 weeks 3 days 17 hours ago) and read 8146 times:

Then L/D max would change with increasing gross weight as well... which it doesn't.  


I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (4 years 1 month 3 weeks 3 days 16 hours ago) and read 8136 times:

Quoting FredT (Reply 4):
Then L/D max would change with increasing gross weight as well... which it doesn't.

Good point. I started realizing I'd done something funny after I posted...I think I was subconsciously imposing an equal payload constraint. With equal payloads, the gross weight between two derivatives is necessarily higher and the heavier one will always have lower L/D max *for that payload*. But if we're just talking max theoretically possible at any weight/speed then you're absolutely right, wing loading shouldn't play into it.

Tom.


User currently offlineketa From Germany, joined Mar 2005, 448 posts, RR: 0
Reply 6, posted (4 years 1 month 3 weeks 3 days 16 hours ago) and read 8132 times:

I know it's not what you're asking for, but it might give an idea, the average L/D in cruise for the A320-200 is about 16.3.


Where there's a will, there's a way
User currently offlineprebennorholm From Denmark, joined Mar 2000, 6293 posts, RR: 54
Reply 7, posted (4 years 1 month 3 weeks 2 days 8 hours ago) and read 8003 times:

Quoting stevenmeyer2005 (Thread starter):
Are the Lift to Drag max values different between the various Boeing 737 models?

The wings are identical on all 737NG versions (assuming identical winglet configuration). The wing produces all the lift.

Drag is produced by the whole plane. Therefore, the more fuselage, the more drag.

Consequently the 736 will have a slightly better L/D max than the 739.

But then the 736 has a larger tail which reduces that advantage. At the end of the day the differences among various 737NG models are very small.

As already stated the various weights don't affect best L/D. But it sure affects at which IAS you get the best L/D.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
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