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  #41  
Old 07-19-2017, 08:58 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
Default Fuel in fuselage vs wings debate........

Pilots are a passionate bunch when it comes to discussions about safety procedures, safe design, etc.
As in anything, everyone is entitled to their own opinion. It is my opinion that people that are passionate about fuel not being in the cockpit of an airplane (assuming the system is well designed) do not have a full understanding of the fundamentals of what type of damage is typical in a survivable crash.

I offer a few points to consider -

The decision to locate fuel tanks in the wings of more contemporary aircraft was not primarily driven by safety concerns. It was largely sensible engineering in that it was the only place there was sufficient space.... when you design to carry 35-40 gal, it begins to require a lot of space.
For obvious reasons it is advantageous to carry that amount of fuel near the aircraft's C.G. Since the occupants are also usually near the C.G., that makes designing to carry that much fuel in the fuselage a challenge. The wings are a natural choice of unused space so that is typically where it is carried.

Just because it is outside the cockpit doesn't make it safer.

Anyone that has inspected a lot of light aircraft crash wreckage (certificated or experimental) can plainly see the evidence of how vulnerable fuel tanks in the wings are.

On the other hand, a properly designed fuel tank installation in the cockpit area, is in the most protected portion of the entire aircraft. In any crash that is survivable, in all probability, the portion that is enclosing the occupants (and in the case of the RV-12, the fuel tank), is going to be relatively intact.

Many years ago, the FAA pushed designers away from cockpit fuel tanks, but that was in an era where they were typically mounted fwd, directly behind the firewall. This location did prove to be far less than optimal. But keeping our minds stuck on the idea that because that location was bad, that all locations within the fuselage are bad, is failing to consider the specifics of what actually happens to aircraft structures in a crash.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #42  
Old 07-19-2017, 09:25 AM
AlanTN AlanTN is offline
 
Join Date: Apr 2011
Location: Linden, TN
Posts: 79
Default Fuel Tank Safety

Scott, I agree with your premise that fuel carried in the wings is just as vulnerable, if not more so. With the new fuel tank design, have improvements been made to improve its strength? And will a factory build option still be available?
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Last edited by AlanTN : 07-19-2017 at 10:05 AM.
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  #43  
Old 07-19-2017, 09:27 AM
Canadian_JOY Canadian_JOY is offline
 
Join Date: Aug 2007
Location: Ontario, Canada
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I have no horse in this race, however I own aircraft with both wing and fuselage tanks. Scott's points are indeed valid. We as a community tend to learn lessons the hard way. Aviation rules are written in blood. That makes the lessons based on old technology hard to un-learn when newer technology comes along.

One of my aircraft has an aluminum header tank - 20 gallons of gas sitting right above my feet. It's a reasonably tough airframe, but I'd still rather not have that gas right behind the firewall. The FAA was, in my estimation, correct in their intent to move fuel tanks away from this location.

By the same token, in our other aircraft we have wing tanks, 50 gallons in 4 tanks. In most crashes these tanks rupture because there is only the thin wing skin protecting them. Some builders of this aircraft type have installed internal cabin-mounted tanks, some of them engineered using the same design criteria and materials as fuel tanks used in automotive racing. Of all the fuel systems I've seen, I think this latter solution is likely the best from an overall safety perspective because they are both protected by the very hardy fuselage and made in a fashion which is less prone to rupture on impact.

As for the RV12, my experience with spilling gas on aircraft windows hasn't been positive. Moving the filler neck to a point where getting gas on the glass is less likely seems like a really smart move.
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  #44  
Old 07-19-2017, 09:36 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Piper J3 View Post
I don't want no stink'n slow siphon. I dump 5 gallons into the RV-12 in less than a minute. This won't be possible with the new filler neck relocation...
-
Actually the new filler location was designed with filling by fuel jug in mind.
It was tested during the prototyping process and it is definitely doable.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #45  
Old 07-19-2017, 09:44 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by AlanTN View Post
Scott, I agree with your premise that fuel carried in the wings is just as vulnerable, if not more so. With the new fuel tank design, have improvements been made to improve its strength. And will a factory build option still be available?
Yes improvements to prevent breach of the tank were made.
A video will be posted to the web site soon that shows a main gear leg separation test being done that resulted in zero damage to the fuel tank.

I believe the plan is for pre-built tanks to be available for the iS fuselage.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #46  
Old 07-19-2017, 09:56 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by epaslick View Post
I guess I'm the weird one here. While I LOVE the idea of no carbs and a FADEC, I DON'T want electric flaps. One of the reasons I've always loved PA-28s over C-172s was the manual flaps. It was also an influence in picking a 12 over, say, a 9.
I (and others at Van's) agree with your reason you prefer manual flaps.
That is why the electric system on the RV-12 was designed to be fast acting.
The travel time (either direction) between full up and full down is very short.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #47  
Old 07-19-2017, 10:03 AM
cactusman cactusman is offline
 
Join Date: Oct 2012
Posts: 421
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Quote:
Originally Posted by rvbuilder2002 View Post

The 912is will not be retrofitable. At least not supported by Van's

The fwd fuselage for the iS airplane is basically a full redesign to make the iS installation possible, but using the original wings tail cone and empenage.

A full announcement is coming very soon that will explain all of the differences along with performance #'s, weight difference, etc.
Well that just tanked the values of all our legacy RV12s!
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  #48  
Old 07-19-2017, 10:38 AM
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f1rocket f1rocket is offline
 
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Quote:
Originally Posted by cactuspilot View Post
Well that just tanked the values of all our legacy RV12s!
Oh, I really don't think so. There will always be a segment of buyers interested in the "latest and greatest", but the value proposition of the -12 remains the same. Some will not be interested in the higher price and some don't have any desire to build.

People thought the SLSA would kill the ELSA, or the -7 would kill the -6, or the -9 would kill the.....well I'm not sure what the -9 is designed for, but in any event, none of that happened.

I loved my -12, and consider it one of the best airplanes I've ever built or flown. The cost to operate and maintain it is insanely low, and the new IS doesn't change any of those factors.

Just my $.02. YMMV.
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  #49  
Old 07-19-2017, 10:47 AM
cactusman cactusman is offline
 
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Quote:
Originally Posted by f1rocket View Post
Oh, I really don't think so. There will always be a segment of buyers interested in the "latest and greatest", but the value proposition of the -12 remains the same. Some will not be interested in the higher price and some don't have any desire to build.

People thought the SLSA would kill the ELSA, or the -7 would kill the -6, or the -9 would kill the.....well I'm not sure what the -9 is designed for, but in any event, none of that happened.

I loved my -12, and consider it one of the best airplanes I've ever built or flown. The cost to operate and maintain it is insanely low, and the new IS doesn't change any of those factors.

Just my $.02. YMMV.
All your points make sense. I have just noticed recently a huge drop in the asking prices of RV12s on Barnstormers and elsewhere and I was wondering why....now I know.

Same as cars...when the newer model with the newer features come out, the value of the old starts dropping. Maybe when it's 50 years old and collectible it might reverse the trend!

At least if we had an upgrade path, we had some hope, but it sounds like Van's isn't gonna support that, so you would have to buy a new IS engine kit ($32.5k - already on the website - assuming Vans would sell it to you....) and decide if you can mod the rest and recoup the rest by selling your 912ULS on the secondary market.

My guess is there are some substantive changes to the firewall and center section - baggage compartment forward - so you would also have to buy a whole new fuselage kit as well - and we know how fun that section was to build!
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  #50  
Old 07-19-2017, 11:37 AM
Azjulian Azjulian is offline
 
Join Date: Dec 2015
Location: Scottsdale, Arizona
Posts: 189
Default

Prices are all supply and demand, there aren't any 912is 12s available for sale so I'm not sure how that could impact the used market yet. And it's realistically going to be 6m to a year before we start to see people selling them.

I think this is a great enhancement to an already fanatastic design and product I really enjoyed my build and I would totally consider building another one with the new engine.
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