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alnanarthur(at)sbcglobal.
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 Posted: Thu Mar 02, 2006 9:11 am Post subject: calculating & subjective Va |
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Bradley, Kurt, Michel and all,
When I bought my Kitfox Series 5, Skystar was in it's hayday.
They had a bright aeronautical engineer employed at that time. In
their lab, I saw an
inverted wing set up loaded with sandbags. They said that they had
tested
the wing to an equivalent load factor of greater than 6 g ultimate.
In my Series 5 Operating Handbook on page 2-4 it says:
Flight Load Factors (flaps up) --------- +3.8, -1.52
Now if we trust Skystar's design numbers and if we assume that we
have not degraded
them during the building process then we can calculate Va.
The load factor = (V/Vs)squared Therefore Va = squareroot (3.8
( Vs squared))
For Vs = 45 , Va = 87.7
We, as builders, we can add a subjective factor. Say we want to
limit the stress to 2 g.
Then again for Vs = 45 and Load factor = 2, Va = 63.6 That
is just about Vx for Series 5.
To feel what 2g is like do a constant altitude turn at a 60 degree
bank, but keep the airspeed
above 63.6.
The way Va saves the structure is that the wings stall before
reaching the limiting load factor.
Allan Arthur
Kitfox 5, N40AA
Rotax 912s, Warpdrive 3 blade
Byron Airport (C83) Hanger C8
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jdmcbean(at)cableone.net
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| Posted: Thu Mar 02, 2006 9:42 am Post subject: calculating & subjective Va |
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The Series 5 was tested to failure as it was being slated for certification.
Obviously the certification never happened but that was dollar driven. To
see the loading that was happening is scary all by itself.
PS.. during the testing, the failure that occurred was not a catastrophic
failure but it was determined that the damage was considered structural and
therefore the ultimate loading was established and it met with the design
parameters established.
Fly Safe !!
John McBean
www.sportplanellc.com
"The Sky is not the Limit... It's a Playground"
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alnanarthur(at)sbcglobal.
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| Posted: Thu Mar 02, 2006 10:51 am Post subject: calculating & subjective Va |
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John,
Do you recall what the design parameters were?
At what load factor did they consider the structural damage to have
occured?
Al Arthur
On Mar 2, 2006, at 9:40 AM, jdmcbean wrote:
| Quote: |
The Series 5 was tested to failure as it was being slated for
certification.
Obviously the certification never happened but that was dollar
driven. To
see the loading that was happening is scary all by itself.
PS.. during the testing, the failure that occurred was not a
catastrophic
failure but it was determined that the damage was considered
structural and
therefore the ultimate loading was established and it met with the
design
parameters established.
Fly Safe !!
John McBean
www.sportplanellc.com
"The Sky is not the Limit... It's a Playground"
|
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jdmcbean(at)cableone.net
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| Posted: Thu Mar 02, 2006 6:14 pm Post subject: calculating & subjective Va |
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I don't and I hate to say for sure.. but I seem to remember over 6. It was
determined that it would be set as normal category.. 3.8+ 1.52- sustained
which allows for the 150% safety margin.
Fly Safe !!
John McBean
www.sportplanellc.com
"The Sky is not the Limit... It's a Playground"
--
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