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In a message dated 1/11/2003 6:01:23 PM Central Standard Time, Billhogarty@aol.com writes:
For Scott Krueger - Dont understand why you are using 24,000 lbs in your calculations. Since wing failed at 12,000 lbs, wouldnt that be the figure to use?
Lancairs original specifications set maximum gross weight at 2900 lbs so if you use that figure, 12,000/2900 = 4.14 which I thought was the original "G" limitation. I realize that Lancair has increased the max gross weight to 3200 lbs, so if you use those figures, wouldnt the max "G" limitation (12,000/3200) be reduced to 3.75 ?
Obviously, there is something I dont understand here, Thanks Bill Hogarty
Bill,
The 4.4 G "utility" limit and the 3200 pound gross weight comes from the Lancair web site, IV and IVP specifications. To wit, see:
http://www.lancair.com/flash/printfiles/iv/specs.html
Also, 320/360's were tested by inverting a complete plane and loading sandbags on both wings evenly until 9 Gs were reached (1685x9=15165 pounds - approximately) and I don't think the wings broke (see some early issue of the Lancair newsletter). Thus, using a safety factor of 1.5, 320/360's had a 6 G (positive) rating. After the gross weight limit was changed to 1800 pounds, then ((15165/1800=8.4G)/1.5=5.6G) 5.6G was the limit.
Now, if one wing can carry an ultimate load 12000 pounds, then two wings, sharing the load evenly, should be able to carry 24000 pounds to the bitter end. Thus, 24000/3200=7.5 G ultimate load. Using a safety factor of 1.5, we get 7.5/1.5=5G yet Lancair says the "utility" aircraft limit is 4.4G ergo, a greater safety factor (1.7).
Scott Krueger
N92EX
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