PPRuNe Forums - View Single Post - effect of weight and cruise level on performance
Old 13th August 2008 | 21:04
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enicalyth
 
Joined: Jul 2004
Posts: 513
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From: Sydney NSW
all good stuff....

..But please remember that TSFC does not get smaller and smaller indefinitely the higher you go. If a manufacturer shows you a graph suggesting that this is true, ask to see the plot of installed TSFC against thrust, ML/D, L/D, even God Forbid CL by itself. The curve starts with relatively high values, not unsurprisingly, and curvilinearly falls to a nadir where it stays for a bit then with a waywardness of all mechanical devices starts to climb again. And just to heighten the fun, if you pardon the unintended pun, the nested curves for various flight levels are skewed and minimum TSFC rarely coincides with maximum L/D or the flight level you'd really like.

Other than that I'll get my coat and sit in pedants corner.

The "E"
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