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  #31  
Old 10-23-2011, 08:36 PM
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RDOG RDOG is offline
 
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Location: Propwash Airport (16X), Texas
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Quote:
Originally Posted by Geico266 View Post
Good point Pete.

A couple of other key points is that Vans more then a little concerned with everyone running in all directions to fix this, and it may not be necessary, and I fact may be adding to the danger we are trying to avoid. Please remember this is the one and only incident out of several crashes inwhich the fuel tank was compromised. The RV-12 is a safe and proven airplane when flown properly and with respect. This particular tank was breached after a very hard landing in a nose down attitude. Fly the airplane and it would not have happened.

Granted, I modified the bolts, and will be adding the "Bender Binder" strap, but I would have felt very comfortable waiting for a couple of months for Vans official fix. Doing nothing is a viable option and your existing fuel tank set up would be safe for decades to come if you fly the plane.

Weight the options and decide for yourself. Waiting is a viable option also.

I really appreciate everyones interest and ideas. Keep them coming, but lets think this through very carefully.
Larry,

Without exposing the pilot. Was the pilot flying daily,weekly,monthly prior to this accident? Did he have any training in the RV12 prior to this accident?
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  #32  
Old 10-23-2011, 08:42 PM
Mich48041 Mich48041 is offline
 
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Location: Riley TWP MI
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The way I understand it, "rotationally molded tanks" require a mold. Molten plastic is put inside of the mold and spun. Centrifugal force spreads the plastic evenly over the inside of the mold. The mold is expensive to make. But once you have a mold, the tanks are cheap to make. The cost of each tank depends on the number of tanks that are made.
Joe Gores
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  #33  
Old 10-23-2011, 08:58 PM
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Geico266 Geico266 is offline
 
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Quote:
Originally Posted by RDOG View Post
Larry,

Without exposing the pilot. Was the pilot flying daily,weekly,monthly prior to this accident? Did he have any training in the RV12 prior to this accident?
The pilot is a very capable pilot having put 172 hours on his RV-12. He owned other small planes before he built. On take off he became distracted by trying to lock the canopy. Absolutely nothing wrong with the plane or it's flight characteristics. It was pilot error and he has taken full responsibility for it. He passed his FAA check ride ( manditory after an incident? ) and will be flying soon as he finds another plane. Only one other minor incident in 50 + years of flying that I know of. I would loan him my -12 without a second thought.
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Last edited by Geico266 : 10-24-2011 at 08:34 AM.
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  #34  
Old 10-23-2011, 08:58 PM
vernhendershott vernhendershott is offline
 
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Originally Posted by DonFromTX View Post
Another option I see little discussion on, is a plastic tank. Sonex has used that for years, no problems I know of. When I visited their hq I think they called them "rotationally molded tanks" whatever that means. Solves the leaking problems we have had, will distort in a small crash without spilling gasoline, and I would guess a heck of a lot cheaper as well.
Hi Don,

Yes once you have the tool bought the cost of one more tank is not that high with good quality rotationally molded tanks. The tool (metal box much like a mold to do a fiberglass part) which is put in a machine that turns the box in all directions while the whole thing is in an oven. The tool is filled with a precise amount of plastic beads and the heat melts the beads which then stick to the tool, the hotter the area of the tool the more plastic sticks to that area, if you insulate the outside of the tool that area will have very little plastic such as where an inspection plate would go. The hard part is that we need baffles in our tank and they are hard to do with this process and it does not work well to use metal baffles in a plastic tank.

The tool can cost as much as $ 50,000 to have made and the correct oven process developed for this tank so that you get the wall thickness you need each and every time at any given location and not much more because it is heavy plastic.

They would have to be strapped in place so would have to sit on the baggage compartment floor and I am not sure that this is in the engineering strength parameters for that area as Van's hangs all the weight from the "H" channel and the aft bulkhead. Attaching fuel lines, filler pipes and vent lines is a little more difficult as well.

Larry has it right for now fly safe and wait for Van's to address the issue.

Best regards,
Vern
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  #35  
Old 10-23-2011, 09:13 PM
Driftdown Driftdown is offline
 
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Location: Clearwater, Florida
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[quote=Geico266;588975] ... "Fly the airplane and it would not have happened." ...


Of course.

That withstanding, system improvements come from experience and a desire to change things to make them more reliable and ultimately safer.

If everybody always did things perfect, no changes would ever have to be considered or implemented. In many cases, changes are mandated.

If the same situation ever occurs again, I hope modifications have been applied so that the fuel tank does not rupture and soak the occupants with fuel. The recent situation could have been a lot uglier than it turned out. The RV-12 community was very lucky this time.
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  #36  
Old 10-23-2011, 09:37 PM
keleeke keleeke is offline
 
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Location: Fond du Lac, Wisconsin
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Default Multiple incidents....root cause?

Just a thought. Would it be prudent to have a warning light/switch on the canopy to make sure it is closed before takeoff? Almost as important as the wing attach warning switch with flashing panel light? How much would a switch like that cost? Pennies. From reading the posts it appears there have been several RV12 pilots that have taken off with canopy not latched. Feasible or not. I am not much of an expert but I always like to look at the root problem. I agree there still needs to be a fix for the tank either different construction material, or location of tank(optional).
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  #37  
Old 10-24-2011, 03:47 AM
Ausflyer Ausflyer is offline
 
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Location: Byron Bay, NSW
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Default another suggestion

The failure mode in this incident has been a surprise to most of us. That big beefy al channel seemed untouchable, and so it was. Everything attached to it yielded, and from what I could see, this failure mode can easily happen again, eg a well-judged forced landing on rough terrain.
The tank mounting design always impressed me: the lower fwd edge reinforced and hard up behind a solid structural beam; the fwd bolts in shear to transmit the vertical acceleration of rough landings and rough air to the airframe; three rigid mounting points only to reduce torsional forces that might rupture the seams; (hopefully) enough anchorage to hold the tank against breaking free in a survivable accident.
Then this.
I had a good look at the tank set up on my plane, and I can see a possible fix. Not trying to guess what Vans will do, just sharing my thoughts with other eyeball engineers who can?t resist a challenge.
I thank John and Larry for their ideas. But the headless bolts do worry me from the issue of the tank becoming loose in the baggage compartment. In a crash that was not a fairly even deceleration, the pins may pull out of their holes, freeing the tank. I understand that is the purpose of the strap over the tank.
Perhaps another way to secure the tank is with short steel straps designed to bend but not break loose or place tank rivets in tension, in this type of crash. The tank would remain anchored to the channel despite the channel rotating forward. The way I envisage it, the fix could be applied to existing tanks in now flying planes with a few dollars worth of parts and a few hours work. For anyone interested, I have put a few sketches here:
https://picasaweb.google.com/rodclar...86340178990434
This accident does present a valuable opportunity, because of the flat, uncomplicated surface the aircraft landed on. Almost a clinical textbook exercise. I do hope vans engineers crawl all over the aircraft with their tape measures. To know just how far that channel will rotate, how far it moved back, and where the strong and weak attachments are, must be good for the breed
Rod
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  #38  
Old 10-24-2011, 05:50 AM
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Geico266 Geico266 is offline
 
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Quote:
Originally Posted by keleeke View Post
Just a thought. Would it be prudent to have a warning light/switch on the canopy to make sure it is closed before takeoff? Almost as important as the wing attach warning switch with flashing panel light? How much would a switch like that cost? Pennies. From reading the posts it appears there have been several RV12 pilots that have taken off with canopy not latched. Feasible or not. I am not much of an expert but I always like to look at the root problem. I agree there still needs to be a fix for the tank either different construction material, or location of tank(optional).
I am embarressed to say having taken off with the canopy open I can assure you the plane flies fine.
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RV-12 : Built and sold
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Last edited by Geico266 : 10-24-2011 at 08:38 AM.
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  #39  
Old 10-24-2011, 05:55 AM
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DonFromTX DonFromTX is offline
 
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There must be some more reasonable pricing somewhere, I cannot believe that Sonex spent anywhere near that much money on the few tanks they have had made.

Quote:
Originally Posted by vernhendershott View Post
Hi Don,
The tool can cost as much as $ 50,000 to have made and the correct oven process developed for this tank so that you get the wall thickness you need each and every time at any given location and not much more because it is heavy plastic.
Best regards,
Vern
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  #40  
Old 10-24-2011, 06:00 AM
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DonFromTX DonFromTX is offline
 
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I am surprised nobody has suggested some unlatched canopy training, I think that is what I will include in my transition training! I recall the alarm I had the FIRST time I took off with the door open on my Cherokee 140. Times after that were of no concern at all except to decide shall I return and close it, or just go on to my destination with it hanging open.
If I am counting correctly, this is the THIRD incident of this type on an RV 12 that we are aware of.

Quote:
Originally Posted by Geico266 View Post
Having taken off with the canopy open I can assure you the plane flies fine.
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