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  #21  
Old 05-03-2006, 03:48 PM
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Kahuna Kahuna is offline
 
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How about that yahoo that put his 8 from 1800 to 2270? Thats 26% increase. What a freak! Wonder where he gets off putting up numbers like that. Its a wonder he is still alive. Or is he?

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  #22  
Old 05-03-2006, 04:02 PM
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Kevin Horton Kevin Horton is offline
 
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Location: Ottawa, Canada
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Quote:
Originally Posted by JackT
If I round it to 2000# GW, it's a 200# increase for plus 11%.

Is there a reasonable way to evaluate this addition in terms of risk?
It all depends on how you operate the airplane. If you want to pull 6g at 2000 lb, you would be putting significantly more load on the airframe than it was designed for, and the risk of structural failure would be increased. Bad idea.

If you operate off rough strips at more than 1800 lb, you may run into problems with the landing gear or its attachment structure.

If you stick to smooth runways and smooth touchdowns, limit the g to some reasonable value when over 1800 lb (3 g is probably more than safe), and reduce speed to VA when in turbulence, then I believe there is little increase in risk with operations at 2000 lb.
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  #23  
Old 05-03-2006, 04:48 PM
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Mel Mel is online now
 
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Yes, as a homebuilder you can set your gross weight to whatever you like. However, you will have to show your DAR/Inspector how you arrived at anything over what the designer recommends. Unless you can show me engineering data to back up your new gross weight, I will not approve anything over utility category for an RV. You can find this weight by extrapolating from the aerobatic gross weight set by Van's Aircraft from 6 gs to 4.4 gs.
Mel...DAR
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  #24  
Old 05-03-2006, 05:38 PM
mtclay mtclay is offline
 
Join Date: Mar 2005
Location: FL
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Default What about flying RV's?

Here's another question along the same lines.

I purchased a flying RV-8A with gross weight at the usual 1800 lbs. Obviously I am not the builder.

I would like to be able to up the gross weight limitation to 1900 lbs.

I recently spoke to two builders at a fly-in who told me that the process is relatively easy. One of them got the procedure from a DAR. I spoke to another individual in Michigan via e-mail who confirmed the process -- he in fact followed the process to sell his RV.

Supposedly you make an entry in the aircraft log removing the airplane from operational airworthy status and placing it back into Phase I testing status. Then you retest the aircraft weight and balance for the newly desired gross weight. When testing is complete you must revise the weight and balance section of the aircraft operating limitations. Finally, return the aircraft to operational airworthy status with the new gross weight and a descriptive writeup in the aircraft log -- no inspection required.

The two builders I spoke to were sure that the original builder could do the above, but not sure if a non-builder buyer such as myself could do it legally.

Any opinions?
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  #25  
Old 05-03-2006, 06:54 PM
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Mel Mel is online now
 
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Yes, a non-builder can do this to HIS/HER aircraft as well. However, be careful. If anything happens, the insurance company may ask you to provide the same justification data that a DAR would want to see. Also, when putting the aircraft back into phase I, you must get concurrance from the local FSDO for your test area.
Another important point..your operating limitations MUST allow this procedure. The currently issued op limits do allow this, but, you are bound by YOUR operating limitations. The older op limits require a recurrent certification for any major changes.
Mel...DAR
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  #26  
Old 05-03-2006, 07:15 PM
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N941WR N941WR is offline
 
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Here is a dumb question. If a builder sets a higher GW for their RV, to they have to fly it at that weight while in Phase 1 testing?

I've always wondered if a builder can set his GW at 2500 lbs but has never actually flown it at that weight.
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Last edited by N941WR : 05-04-2006 at 05:11 AM.
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  #27  
Old 05-03-2006, 07:19 PM
JackT JackT is offline
 
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MEL,

Are you going to be at the Texas RV Fly-In on May 20th? If so, could I chat with you about this?
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  #28  
Old 05-03-2006, 07:30 PM
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Mel Mel is online now
 
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Yes, the aircraft needs to be flown at the new gross weight to the forward and aft cg limits during phase I. The purpose of phase I testing is to prove that the aircraft is safe to the limits of the operating envelope. If you change that envelope, you need to prove the new limits are safe.

Yes, I will be at the Texas Fly-in.

Well.....I don't really like to talk about airplanes, but if you twist my arm just right.........

Mel...DAR
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  #29  
Old 05-03-2006, 08:23 PM
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Kevin Horton Kevin Horton is offline
 
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Quote:
Originally Posted by Kahuna
How about that yahoo that put his 8 from 1800 to 2270? Thats 26% increase. What a freak! Wonder where he gets off putting up numbers like that. Its a wonder he is still alive. Or is he?
If that yahoo understands that laws of physics still apply to him, and he flys the aircraft appropriately, he may do OK. But ignoring the laws of physics does not obligate the laws of physics to ignore you.

Be careful. Fly with the big head, not the little head.
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  #30  
Old 05-03-2006, 08:55 PM
DGlaeser DGlaeser is offline
 
Join Date: May 2005
Location: Rochester Hills, MI
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Default Why Va decreases at light weights

Quote:
Originally Posted by Brockster
Trying to understand what everyone has explained in this thread and reading the article in this months AOPA magazine "Va-weight and see the G" do I have this straight?
<snip>
When I first read this thread and then the AOPA article I got a little confused because people talked about stressing the aircraft more with higher weight and the article talks about stressing the aircraft more with less weight and my brain started to lock up. Any clarification would be appreciated.
Here is the way I like to explain Va:
In any flight condition (other than a stall), your wing is operating at something less than the stall angle of attack. Lets call the difference between where you are and stall the 'reserve AOA'. This 'reserve AOA' can be turned into an instantaneous load by either abrupt control movement, or a vertical gust.
At any given airspeed, if you are flying heavy, you have less 'reserve AOA' because the wing is operating at a higher AOA to handle the weight. So the amount of load that the reserve AOA can generate is less.
Conversely, when flying light, you have more reserve AOA, which can be turned into a higher instantaneous load.
The amount of load generated is a function of airspeed - higher speed, higher load generated by the reserve AOA. The maximum load the airframe can handle is fixed.
Va is the speed which, at gross weight, the reserve AOA will generate the maximum load the airframe can handle. If you are below gross weight, you have more reserve AOA and that same airspeed can now generate more load than the airframe can handle! So, when flying light, you have to slow down in turbulence (or when doing abrupt maneuvers) - more reserve AOA requires less speed to generate the same load.

Hope that helps. It's not an intuitive concept!

Dennis Glaeser
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