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  #21  
Old 11-21-2012, 08:06 AM
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Ron Lee Ron Lee is offline
 
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Quote:
Originally Posted by chrish View Post
Reading between the lines, the 14 looks like Vans trying to standardise things in an attempt, amongst other things, to improve the safety record of homebuilding.
Refer to Table 1 here:

http://www.rvflightsafety.org/safety.../introduction/

Embedded in unknown or mechanical failure causes might be an isolated event that you refer to above. As I see it, the vast majority of fatal accidents are still due to pilot error.

In recent years, we have had at least two incidents attributed to fuel lines coming loose. Most likely they were not properly torqued.

That has nada to do with the size engine. It was a failure at multiple times for more than one person to check those critical connections.
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  #22  
Old 11-21-2012, 08:22 AM
chrish chrish is offline
 
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Thanks Ron,

My comments (not being a resident of the US) are based on the articles I have read. I am not saying putting a bigger engine is inherantly more or less dangerous, just that it is unknown what the effect will be without some thoughtful analysis.

To diverge slightly from the discussion, my wife mentioned to her dad who lives in Florida, that I was going to build an RV. His response was 'didn't John Denver die in one of those?' Trying to educate her on the causes of air crashes, we looked up this report http://www.avweb.com/other/ntsb9905.html

It is an interesting read and highlights the dangers of modifying a design. The builder made a number of modifications including a larger engine and changes to the fuel system. Without going in to too many details, the 'safety feature' modification of not having the fuel lines transit the cockpit and the resulting fuel valve positioning was probably the cause of the crash.

The point I am trying to make is that with freedom comes responsibility. The guy that built the long-EZ and made the modification was not the one who paid with his life, but someone did.
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  #23  
Old 11-21-2012, 08:22 AM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by Captain_John View Post
Sam,

I have a good reason why. 540's rated at 230 hp and 260 hp are commonly available. I like the 390 ALOT (initially wanted one for my -7 but at almost $40,000 it is cost prohibitive).

If one were to locate a 230 hp (derated for mogas is a good thing) 540 on the cheap wouldn't that be a good cost effective fit?

I do know that the 540 would be slightly more hp and somewhat heavier than the 390 that Van suggests, but probably not a bad choice if CG issues and proper diligence is given to the change.

Now, I know that I am an armchair engineer with no real experience in the matter... but how bad would that be?

CJ
Quote:
Originally Posted by chrish View Post
A quick google shows about 130lbs difference in weight. This extra weight is well forward. What would your new 'G' limits be? - with the reduced useful load, could you do aeros 2-up? With the higher fuel flow and reduced useful load, would range be acceptable? What is the effect to A/B ratio? All that weight forward could significantly change the spin characteristics of the aircraft. So, putting a bigger motor in may make it go faster, but will you still be able to do aeros in it safely? If it flicks into a spin when manoeuvring, will it recover? Who is going to test it to find out?
As much as it may be difficult for some of us frugal builders to accept, Vans has entered a different economic environment with their latest aircraft (RV-12 excepted). The RV-10 and RV-14 are not intended for the builder who scrounges for "bargains" the way many RV-4 and RV-6's were built. It was often a badge of honor to see how frugally an RV-4 or -6 could be built, but not so with the -10 and -14. These "big" planes are targeted at builders with the funds to build a serious aircraft with top-notch equipment. Why build a plane that costs $100+ and try to "save" with a "bargain" engine that is outside the design envelope?

We saw this when the RV-10 first arrived. Builders with RV-6 mindsets jumped into RV-10 projects without calculating what this plane was going to cost if equipped for the mission most pilots expect from it. The plane was bigger, more complex and more expensive than some of the early builders realized. Some projects found new homes.

Same scenario with the RV-14. A builder should be prepared to spent major $$$$'s to build the plane as designed. If that budget isn't available, the builder might be better served by a plane that fits the available budget.

Having said that....yes.....a 540 will be on the nose of an RV-14 soon after the kits are released. We can't help ourselves.
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Last edited by Sam Buchanan : 11-21-2012 at 08:27 AM.
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  #24  
Old 11-21-2012, 08:40 AM
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Ron Lee Ron Lee is offline
 
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Quote:
Originally Posted by Sam Buchanan View Post
The RV-10 and RV-14 are not intended for the builder who scrounges for "bargains" the way many RV-4 and RV-6's were built. It was often a badge of honor to see how frugally an RV-4 or -6 could be built, but not so with the -10 and -14. These "big" planes are targeted at builders with the funds to build a serious aircraft with top-notch equipment.
Sam, maybe you are right on the RV-10. I just do not see that with the RV-14. From my limited understanding of the -14, it appears to really only offer three inches more shoulder room over a RV-7.

Extra gas...Big whoop. I can't fly that long.

No doubt there are well-equipped planes of every model so the platform is certainly not the driver.

I just read Vans write up on the RV-14 and here is the only thing that I noted that defines the rationale of the plane:

"The RV-14 cabin accommodates full-sized adults — in fact, the basic idea was to provide RV-10 room and comfort in a two-seat airplane. The results are impressive. Both seats will hold people at least 6’4” tall and provide them with truly comfortable leg and headroom."

It appears to be for bigger people.

Last edited by Ron Lee : 11-21-2012 at 10:55 AM.
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  #25  
Old 11-21-2012, 09:58 AM
RV8R999 RV8R999 is offline
 
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You nailed it....
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  #26  
Old 11-22-2012, 03:16 PM
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Quote:
Originally Posted by rvbuilder2002 View Post
+1, Two Thumbs up, etc.....

I agree that the freedoms of the experimental category are what got us to where we are today, but there is far to much TLAR engineering that goes on.

Over the years I have seen countless #'s of highly modified RV's where the builder wasn't an engineer, but said all of the "calculations" had been done (though I can't think of a single instance were a builder / modifier ever offered any documentation or other information that would substantiate that claim).

There is so many factors that can be effected by a seemingly simple modification. Without a very detailed look at how the mod. integrates with the whole design, it is very easy to miss something that might be significant.

Example: In the near future, the RV-14 design will be put though dynamic testing of the landing gear. A change such as a 6 cyl engine would cause major moment of inertia change (among other things) that would most like totally negate any testing that was done based on the IO-390 being the biggest/heaviest engine. Considering the amount of effort required to complete these tests, it is highly unlikely that anyone would repeat them after doing such a modification.
The main point of this, is to emphasize that someone may be pushing much farther into the experimental fringes than they would at first believe.
I totally agree, and the sheer inevitability of the mod puts Vans in an invidious position. I hope Vans will do the engineering and endorse the option.
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  #27  
Old 11-22-2012, 03:56 PM
Paul Walter Paul Walter is offline
 
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I have read that the 14 has incorprorated the engine mount and nose wheel gear from the RV 10, the RV 10 has had no issues, at least that i'm aware of with nose wheels collapsing, the suspect nose wheel is why some (loveable) RV nut has not put a heavier 540 in an Vans A model a long time ago.

If a 260 hp, 540 powered 14is flown within the design limits etc - whats the big deal ?

One thing is certain, and make no mistake about it - there will be 540's in RV 14's, its just a matter of when.


P.D.
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  #28  
Old 11-22-2012, 05:57 PM
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I suppose the drop test would certainly stress the engine mount attach point structure with the moments augmented by an extra 150lbs on the engine mount. This would be substantially worse for a tailwheel version (versus the tricycle) where the gear legs also attach to the engine mount in the rv-3,4,6,7 style. Possibly one reason why we don't see a tailwheel RV-10.
A '540 'A' model would still be nice though!
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  #29  
Old 11-22-2012, 10:28 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Paul Walter View Post
I have read that the 14 has incorprorated the engine mount and nose wheel gear from the RV 10, the RV 10 has had no issues, at least that i'm aware of with nose wheels collapsing, the suspect nose wheel is why some (loveable) RV nut has not put a heavier 540 in an Vans A model a long time ago.

If a 260 hp, 540 powered 14is flown within the design limits etc - whats the big deal ?
What you have heard is not what was said.

The RV-14 has the same style engine mount / nose gear leg.

That should not be considered to mean that it is the exact same assembly.
It is not. It is a new part specifically designed for an IO-390 on an RV-14.


Even if it was the same assembly, it wouldn't mean that a 540 would work fine, since the engine mount has to attach to the rest of the airframe and transmit those additional loads.

No one would assume that a bridge designed for a maximum load of 15 tons, but was built using the exact same middle span section that was used on a 30 ton rated bridge, would make the entire bridge rated for 30 tons.

Same principal applies to airplanes......
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  #30  
Old 11-23-2012, 11:51 AM
SHIPCHIEF SHIPCHIEF is offline
 
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The O-540 comes in several flavors, and a well selected model, stripped of vacuum pump and sporting a flyweight starter, alternator and a wood prop would take about half the sting out of it.
I advocate lightness and simplicity. The O-540 does not meet the lightness, but a fixed pitch prop does meet the simplicity.
I wonder how the O-540 FP would compare to the O-390 CS in heads up performance, and lifetime cost?
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