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  #31  
Old 08-05-2017, 05:27 PM
rgmwa rgmwa is offline
 
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Quote:
Originally Posted by AlanTN View Post
If that is what happened, then the POH should show 482 and 534 'Miles' rather than 'NM.' And those should have been the max range numbers on the Performance page for the RV-12
Sounds plausible to me, and would be an easy mistake to make. A Mars probe was lost for a similar conversion error. If that's what happened in this case, I would see it as a one-off and certainly wouldn't be assuming that all other data immediately becomes suspect. I'm an engineer myself and these things can occasionally happen. If recent real world testing has modified those early numbers again, then well and good, even if they sound theoretically anomalous. All credit to Vans for on-going product development in my view.
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  #32  
Old 08-06-2017, 03:35 AM
KatanaPilot KatanaPilot is offline
 
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Originally Posted by Postaltwo View Post
I'm suprised also with the direction of this thread. My interpretation of the op is that it seems odd that 5500 rpm is more efficient than 5000 . One would think max cruise would not be your max range setting . Just like any other aircraft on the planet . I do not think the op was bashing the rv 12 in any way . It's just plain wrong that so many jumped all over him so quickly imo.
As a fellow engineer (Aero type), I appreciate Alan's healthy dose of skepticism when published numbers show inconsistencies. What I don't like is how one is unable to question anything Van's does or publishes without being pilloried by some on this forum. Personally, I didn't see anything wrong with Alan's approach, tone or questions. I can't say the same about some of the responses he received.

So Alan, kudos to you for asking appropriate questions and I hope you will continue to do so despite the bashing you took.
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Locust Grove, GA
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Last edited by KatanaPilot : 08-06-2017 at 03:51 AM.
  #33  
Old 08-06-2017, 05:27 AM
AlanTN AlanTN is offline
 
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Quote:
Originally Posted by KatanaPilot View Post
As a fellow engineer (Aero type), I appreciate Alan's healthy dose of skepticism when published numbers show inconsistencies. What I don't like is how one is unable to question anything Van's does or publishes without being pilloried by some on this forum. Personally, I didn't see anything wrong with Alan's approach, tone or questions. I can't say the same about some of the responses he received.

So Alan, kudos to you for asking appropriate questions and I hope you will continue to do so despite the bashing you took.
Thanks, Krea.
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  #34  
Old 08-06-2017, 05:45 AM
AlanTN AlanTN is offline
 
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Quote:
Originally Posted by KatanaPilot View Post
As a fellow engineer (Aero type), I appreciate Alan's healthy dose of skepticism when published numbers show inconsistencies. What I don't like is how one is unable to question anything Van's does or publishes without being pilloried by some on this forum. Personally, I didn't see anything wrong with Alan's approach, tone or questions. I can't say the same about some of the responses he received.

So Alan, kudos to you for asking appropriate questions and I hope you will continue to do so despite the bashing you took.
Thanks, Krea. What I would like to see is their protocol for the Range Tests. Did they have a reliable way of accurately measuring the fuel consumption for the takeoff, climb, descent and return to base and subtracting it from the overall fuel consumption? Did they do the tests under the same conditions? Turbulence can effect efficiency. Did they adjust to standard atmospheric conditions? Did they do at least three tests for at each profile, and were the results within one to three percentage points of each other?

As an engineer I was trained to look at how the data was derived before I accepted it, and especially so when the results were anomalous or disagreed with previous tests.

I have learned that it is wise to question everything because people do make mistakes, and in the world in general, for various reasons, there is much we are being told that is simply not true.

I am convinced that Van's is honest, and their aircraft are solid designs, but in certain cases I still feel obligated to ask questions.
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Last edited by AlanTN : 08-06-2017 at 05:48 AM.
  #35  
Old 08-06-2017, 09:27 AM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by AlanTN View Post
I am convinced that Van's is honest, and their aircraft are solid designs, but in certain cases I still feel obligated to ask questions.
Perhaps the solution is to consider how the questions were asked, and in what venue. When I saw your post, I imagined anyone at Van's thinking of this scene from Star Wars...
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1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
  #36  
Old 08-06-2017, 09:36 AM
Paragon Paragon is offline
 
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I appreciate Alan's attempts to find the correct spec data, and inform the rest of us via the forum.

Our Van's employee posters' snark is not welcomed, although that seems to be what we have to put up with to obtain some pearls of wisdom.

-Paragon
Cincinnati, OH
  #37  
Old 08-06-2017, 09:50 AM
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BJohnson BJohnson is offline
 
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Default Really?

Quote:
Originally Posted by AlanTN View Post
What I would like to see is their protocol for the Range Tests. Did they have a reliable way of accurately measuring the fuel consumption for the takeoff, climb, descent and return to base and subtracting it from the overall fuel consumption? Did they do the tests under the same conditions? Turbulence can effect efficiency. Did they adjust to standard atmospheric conditions? Did they do at least three tests for at each profile, and were the results within one to three percentage points of each other?
Origionally didn't you just want Vans to review their data for a possible error? Now you want to audit all their flight test data and methods? I can see the FAA asking that of a certified aircraft manufacturer, but don't you think that is a stretch for an unknown yet potential customer of an experimental aircraft kit manufacturer?
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  #38  
Old 08-06-2017, 10:46 AM
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DaleB DaleB is offline
 
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Wow, this is taking an acrimonious turn.

Honestly, I don't really expect precise testing for things like this on a kit airplane. I wouldn't want them to subtract the fuel used for takeoff, climb, etc; those are a part of every flight. I expect that a manufacturer's claimed range numbers are going to have a certain degree of uncertainty around them, and that my airplane is probably going to vary some. And we're talking about a kit airplane produced by a relatively small company, not Boeing or Cessna. You really can't expect to see ISO900x documentation of the entire flight testing program published in response to a pre-sale question on a web forum, especially not one the company doesn't run. If you have detailed questions to ask, you really should ask them directly through the company's normal channels. VAF is a valuable resource, but it's NOT the official source of information on Van's airplanes.

As for RV-12 specs... Maybe at some point someone mistakenly multiplied a number that was already in NM by 1.15. I don't know, but mistakes happen. The current POH and web site look correct. Errors creep into published material and get corrected from time to time. However, anyone with an RV-12 will tell you that the performance numbers as currently published (for the 912 ULS at least) are pretty much spot on.

As for Scott's responses... he's gotten dragged into some pretty contentious discussions in the past. I can understand his reluctance to get dragged into another one. Hes not here to be a one-man proxy for all of Van's tech support, engineering and sales staff when we just don't feel like picking up the phone or emailing Van's directly. Give the guy a break.
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  #39  
Old 08-06-2017, 11:31 AM
AeroDog AeroDog is offline
 
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There are a few people on this forum whose posts I value above all others. Scott's at the top of that list. If I disagreed with him about something I'd never call him out publicly out of sheer respect and appreciation for what he's contributing here.

Jerre
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  #40  
Old 08-06-2017, 11:40 AM
vic syracuse vic syracuse is offline
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I am disappointed in the tone of some of the replies on this thread. I am not going to make any judgement other than to say that Van's has shown themselves to be one of the highest integrity kit provider's in the entire industry. I wouldn't even associate myself with them if I didn't believe that. We need Kit Manufacturer people like Scott on these forums throughout the industry, and if we don't treat them respectfully, they will quit contributing, and we all lose.
I know inflection can get lost in the written word, but there are better ways to ask questions than to assume the dark side.

I am going to close this thread in the hopes that IF one gets restarted regarding performance numbers, we can stick to it in a meaningful manner.

This is all supposed to be for fun, remember?

Vic
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