Jaybannist(at)cs.com
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 Posted: Fri Mar 14, 2008 5:20 pm Post subject: 777 Wing Load Test |
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Keith,
If I had an airplane with wings that could withstand 153% of the design ULTIMATE load, 100% being the WORST gust load expected, I would probably never pay attention to maneuvering speed. I couldn't believe how much those wings deflected before they failed! And I can't believe anyone would demand a more strenuous positive load test than this one, "static" or not.
Jay in Dallas
Do not archive
| Quote: | Keith Ashcraft <keith.ashcraft(at)itt.com> wrote: Just my $0.02 worth. Here is a video of Boeing doing a "static" load test to their 777 series wing. It seems in this test that there is no account for turbulence, it is just a pure wing deflection until failure test.
http://www.youtube.com/watch?v=pe9PVaFGl3o
Don't know if this helps or hurts, or has any bearing on this discussion, but it is just a data point.
Back to building my 701.
Keith
N 38.9947
W 105.1305
Alt. 9,100'
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David Downey wrote: please note that the 3 seconds without failure at ultimate is exactly that - if the structure fails at 3.01 seconds under steady state ultimate load it passed. There is no requirement for repeated capability. The rate of load application and incrementation is also generally used to make the test as benign as possible where transient loads resulting from turbulence or pilot error are generally pulse loads...
Tim Juhl <juhl(at)avci.net> wrote:
My plans list ultimate loads of +/- 6 g. I would hope that if the limits have been changed that Zenith would share that info with builder / operators to avoid any confusion.
General Info on loading: Limiting loads and ultimate loads
To receive type approval certification the design of a general aviation or ultralight aircraft must conform with certain standards, among which are the in-flight manoeuvring loads plus the turbulence induced loads which the structure must be able to sustain. The turbulence loads are called the gust induced loads. FAR part 23 is the recognised world standard for light aircraft certification and the following is an extract: "... limit loads are the maximum loads to be expected in service [i.e. the highest load expected in normal operations] and ultimate loads are limit loads multiplied by a safety factor [of 1.5]. The structure must be able to support limit loads without detrimental, permanent deformation. At any load up to limit loads, the deformation may not interfere with safe operation. The structure must be able to support ultimate loads without failure for at least three seconds ..."
The minimum positive limit load factor which an aircraft in the 'normal' operational category (at maximum take-off weight) must be designed to withstand is 3.8g. For a non-aerobatic aircraft the negative limit load factor is 0.4 times the positive limit which makes it 1.5g for the normal category. The ultimate loads for the normal category are +5.7g and -2.25g. Amateur builders should aim to meet the same minimum values for limiting load and ultimate load factors. [At +6/ -3 the XL exceeds this requirement]
For aircraft with aerobatic capability the negative limit load factor must be 0.5 times the positive value. The 'utility' category (which includes training aircraft with spin certification) limit loads are +4.4g and -2.2g while the 'acrobatic' category limit loads are +6.0g and -3.0g.
Tim
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CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Working on fuselage
Read this topic online
ttp://www.matronics.com/Navigator?Zenith-List ics.com .matronics.com/contribution
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Keith Ashcraft
ITT Industries
Advanced Engineering & Sciences
5009 Centennial Blvd.
Colorado Springs, CO
80919
(719) 599-1787 -- work
(719) 332-4364 -- cell
keith.ashcraft(at)itt.com
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Dave Downey
Harleysville (SE) PA
100 HP Corvair
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