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At 23:50 07 May 2014, Bruce Hoult wrote:
However your height estimates are systematically biased 20% too large. Well, about 8% for a pull-up, and 17% for a dive - at the high-speed end of the scale. (Better and worse, respectively, at the low-speed end.) Whereas your rule is about 10% low throughout. By me: 28^2 - 12^2 = ~800 - ~150 = 650 ft (784-144 = 640 if you do it exact) By you: 130+120+110+100+90+80+70+60 = 760 ft By you with my -20% correction: 760 - 152 = 608 And the truth (from v^2 = u^2 + 2gh ... whence we both started, I'm sure) is 708.66 ft. (I knew you'd like the ".66" ;o) ) Spreadsheet he http://tinyurl.com/mzokpyk for those amused by such things. But of course these are both rules of thumb, intended more to give better understanding than for exact calculation. I have more often referred to mine in discussing recovery of lost speed low on finals (or after a low winch-launch failure) than for the 120kt beat-up case! |
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