What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV-12: Fuel Tank Information / Modification

Geico266

Well Known Member
Out of an abundance of caution and concern for the safety of fellow RV-12 owners and builders, I would like to share information about the fuel tank after a very specific hard landing. There have been several planes experience hard landings, but in this one and only incident (that I am aware of) the fuel tank was breached.

Van's Aircraft has been notified and and they are working on an "official" fix which may or may not include tank modification. They have been very responsive and up front about this issue, but engineering the "official" fix takes time. Let them work on it from their point of view. Whether you decide to wait for the "official" fix or take my "unofficial" fix is up to you. My one and only concern is that you, as an RV-12 driver / owner are aware and fully understand the issue, then you decide on a course of action for your comfort level.

Here is the picture I took of the plane. The plane contacted the runway after take off and hit with a 5 or 6 degree nose down angle. At that angle the nose gear gave way and the main gears rotated aft taking the center section with it. The tank is attached to the center section, and this in turn tore open the tank. This is the only time we (or Vans) know of the tank being breached. This accident caused this specific problem.

Here is the picture....

RV-12_Tank1__Medium_.jpg


RV-12_Tank__Medium_.jpg


The pilot was soaked in gas before he could exit the plane. He was unhurt and wants to remain anonymous. The incident was caused by pilot error and he takes full responsibility. He could have kept quiet and no one would have known, but he did the right thing and came forward so we may learn. He contacted me to get the word out so other may be aware and learn from his mistake. For that I want to publicly thank him for his courage to come forward. I will not disclose his name or any other details. Please do not ask.

Okay, that is the issue. Here is the "unofficial" fix.

RV-12_Tank_Bolt__Medium_.jpg


Replace the two bolts that secure the fuel tank to the center section with a modified "headless" bolt. I took a hack saw and cut the head off a bolt the next size longer and created a slot with the hacksaw. The aft support bolt holds the tank secure, IMHO. I removed the old bolts and installed the new "headless" bolts during my condition inspection, with no fuel in the tank.

Next there is the issue of becoming inverted during an incident and having the tank become " loose" in the baggage area due to the headless bolts. The best fix that I can think of is a strap holding the tank down to the baggage floor independent of the center section.
 
Last edited:
The Fix is in!

Larry great write up. Would you want to shorten the amount of bolt that goes through the main spar as much as possible? What do you think about using an Allen Bolt?
 
Excellent post.
The only good that can come of accidents is that we can all learn.
+1 thumbs up to the Pilot for letting us see this.

I think the headless bolt idea is ok, but perhaps an L angle to secure the tank to the baggage floor rather than a strap.

The center section looks to be bent at quite an angle, do you know what happened to the wing pins?
did they shear?
 
Excellent post.
The only good that can come of accidents is that we can all learn.
+1 thumbs up to the Pilot for letting us see this.

I think the headless bolt idea is ok, but perhaps an L angle to secure the tank to the baggage floor rather than a strap.

The center section looks to be bent at quite an angle, do you know what happened to the wing pins?
did they shear?

Wing pins were fine, but tweaked the spars. The plane held up amazingly well. Vans should be (and they are) very proud of the engineering and how it held up. The pilot walked away from a very serious crash. It don't get better than that except to learn from it.

Anything to hold the tank in place incase you are inverted after a hard landing would be good. There needs to be in "field fixes" for flying RV-12s, and construction fixes that only Vans can approve for ELSA builders.
 
Last edited:
Larry great write up. Would you want to shorten the amount of bolt that goes through the main spar as much as possible? What do you think about using an Allen Bolt?

I think the Allen screw thread might have a tendency to "grab" in the hole and pull on the tank in the same scenario.

Shorter "headless" bolts may be theoretically better. I was concerned about being able to get at the "head: so I could get a screw driver on it.

Several of us have been working on "fixes" and hopefully they will post their thoughts and pictures.
 
Thanks to the pilot for sharing his experience with the RV-12 Forum in the interest of safety and education. It is very fortunate that he walked away from the airplane and nobody got hurt. We can all be grateful for that. A lot will be learned from this.

I have a question though.

Given what happened and with probability, how would the same scenario affect the modified fuel tank that has been constructed as an alternative to the standard tank from Vans?

Those of us who are considering the modified tank would be very much interested.
 
Last edited:
Thanks to the pilot for sharing his experience with the RV-12 Forum in the interest of safety and education. It is very fortunate that he walked away from the airplane and nobody got hurt. We can all be grateful for that. A lot will be learned from this.

I have a question though.

Given what happened and with probability, how would the same scenario affect the modified fuel tank that has been constructed as an alternative to the standard tank from Vans?

Those of us who are considering the modified tank would be very much interested.


I'm not sure if the modified tank is fastened to the center section.
but it looked pretty tightly fitted around the spars and that entire area.
I suspect that the modified design would have failed also, perhaps even more so.

For saftey, perhaps the tank should be a narrow design like the modified idea, but further back against the inspection panel at the rear of the baggage area, leaving a full width narrow area behind the center section.
That way any failure of the center section and/or wing spars would likely not rupture the fuel tank.
I don't know how that would affect W&B though.

Another thing to consider would be using a plastic tank.
well not exactly plastic, but whatever material it is that they are made from these days.
Modern thinking is that these are safer because they are flexible and not likely to rupture in a crash.
I believe some aircraft are using them, I think perhaps the sonex designs?
 
Plastic Works

I lost a good friend to a stall/spin incident, where he buried the nose into a golf course fairway. He was killed, the airplane, a Challenger II, was totally destroyed. The rear passenger, his son, amazingly, survived; lots of surgery and hospital time. The important part of the story is "NO FIRE" The only things that were salvageable were the tail feathers, and the plastic fuel tank, which was totally intact, and there was no fuel spill. Plastic does work!
Tom
 
My Temp Mods - -

RV-12TankMod100_1973.jpg

RV-12TankMod100_1980.jpg

RV-12TankMod100_1981.jpg

RV-12TankMod100_1975.jpg


I used the same length bolts originally supplied, and cut a slot, but modified a bit to turn them in to recess the ends to make them easier to pull out (release ) if needed. I greased the holes also. I used a hand-pull-tight type nylon strap to hold the tank in place in case of an over turn. The brackets are similar on both sides. The strap is strong, but will stretch a little to allow for some 'give' if needed. My mods are easy to remove if desired, but I feel much better now with them.

John Bender
320.8 hours
 
Last edited:
My thanks for this timely information, I am about to mount my tank. This is very valuable information and a cure that would have prevented the rupture in this accident for sure. I can incorporate it easily at this point.
 
Larry,

Good job!

And my sympathies to the pilot, and please thank him for letting the technical issue come to the community.

Dave
 
I'm not sure if the modified tank is fastened to the center section. but it looked pretty tightly fitted around the spars and that entire area. I suspect that the modified design would have failed also, perhaps even more so.
If you are talking about my tank, yes it is fastened to the main center channel. And yes, it too will fail in the event of a crash. But it can not be any worse than the original. Being sprayed from head to foot with gasoline can not get much worse. I still have not decided what to do about my tank: modify it, design a new tank, or put the original back in with modified fasteners.
As for fastening the original tank, I like John Bender's idea of the greased pins extending only halfway into the F-1204 main center channel so that they will not bind.
Instead of using nylon straps, I thought about metal straps that will bend along with the aircraft structure during a crash.
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B7ZTG2VpCuDRNWZkM2Q1ZmItMmYyZi00ZjI2LWJhY2UtYzJmMGIzNWFmMzJh&hl=en_US
In the event of an off airport landing, my check list includes shutting off the master switch, closing the fuel valve, and unlatching the canopy. The accident mentioned above happened on takeoff and there was no time to shut off anything. After an accident with fuel spill, I think the best thing to do is to walk away (if able) and leave the master switch on. The fans will be moving gasoline vapors inside of the instrument panel. You would not want the master switch to make a spark.
Joe Gores
 
Last edited:
perhaps an L angle to secure the tank to the baggage floor rather than a strap.
The baggage floor is going to be bent and will not remain flat. Any fasteners on the forward end of the tank need to give a little to allow for some movement. The fasteners need to be the weak link, not the tank.
How about a nylon strap held to the floor with a square washer and screw? It would be simple and light weight.
Another consideration is the filler neck. With the tank moving during a crash, a longer fuel hose coupling will bend easier.
Ralph Clark posted about a longer hose:
http://www.vansairforce.com/community/showpost.php?p=582352&postcount=13
Joe Gores
 
Hey Joe - -

That is why I used a pull-hand-tight only type nylon strap. Can't get it very tight, and that is what I wanted. It will 'give' some, but keep the tank in general position. My temp fix was to make it safer to -ME- for now, and hopefully will be able to throw away if a good fix is offered. The floor seems to stay fairly flat, but a little give I feel is needed. I used two of the current tunnel screw to hold the alum angle in place on the inside center bracket. Take the two screws out, and the 2 new NO-HEAD pins, and the tank will come out about as fast as it did before. Also, I found out it is best to use one of the original front mounting bolts on the inside hole to get the tank in position, then put the pin in the outside hole, and it was lined up then. Then take the inside one out, and install the 2nd pin. My small bit reaches in just fine to remove the special pins.

John Bender
322.7 hours.
 
I'm not an engineer, but I am a bit skeptical about substituting headless pins for those bolts.

Without a head on the bolt, there's no clamping force, so the bolt shaft is more subject to bending forces. Those forces will try to pry the anchor nut off of the rivets that hold it onto the back side of the strip on the tank. The anchor nuts are secured with AD3 rivets intended to see only shear from tightening torque, not the combination of tension and bending they'd get from the pin.

My reasoning is that the joint is similar to that of the rod ends used for tail surface hinges on most RVs. By now, we know that the torque on the jam nuts on the shanks of those rod ends is critical. If the jam nuts are loose, all of the bending in the rod end shank is reacted by the puny little AD3 rivets that secure the anchor nuts. The rivets would loosen pretty quickly, allow bending play in the rod end, and then become a flutter liability.

Thanks, Bob K.
 
Hey Bob - -

Appreciate your comments. Remember, this we hope, is temporary ! If the rivets loosen, or break, the tank falls about 1/4". The strap still holds it in general place. Easy enough to re-do the rivets if needed later. Easy to visually check from time to time.

John Bender
 
A UK very slow build for many reason (084). I do not intend to ever remove the wings when built. The biggest change I would like to see with the RV12 is the tank(s) put in the wings. Safer and better as far as I'm concerned.
 
Plastic gas tanks

I just gave Ebay a quick look and there's a number of plastic tanks that might fit; I forget what the width of the area is, but Jeep makes a number of tanks that might fit. There's a 21 gallon tank that fits a CJ 78-86 that's 23x16x15, and there are some flat boat tanks that might work, with some modifications.
Meade
1/2 N612RV
 
Since this last incident and the overall interest in alternative tank design, I would like to see an E-LSA approved, removable (for inspection purposes) plastic tank offering.

Such a tank would be suited for our specific fuel types, molded for a secure but easy installation and provide improved leak resistance in the event of an impact which distorts the platform which supports it.

Presently, Van's offers a prefabricated aluminum tank, at an additional cost.

A molded, plastic tank, if purchased in bulk, may be a safer and more reasonable alternative to what is presently offered, not to mention the ease of construction/installation of the present tank.

I hope Van's is interested in investigating alternatives to the present installation/design of the fuel tank. It appears that it could be a serious problem.

The RV-12 is talking to us.
 
Centre channel

If the main gear rotated backwards at an impact angle of only 5-6 degrees, then maybe the centre channel needs some additional support as well, although I don't think it would be an easy fix. While it would be unrealistic to think that you could engineer out all the impact damage in the event described, I would like to think that Vans are looking at that aspect of the RV-12's design as well.
 
More thoughts on this - -

With this hard an impact, something has to give. The landing gear is very strong, and the channel is obviously strong, so this is probably good as anything to absorb the energy, although it really twist things up. The only issue ( at this point anyway ), is the fact the fuel tank is mounted to that channel. Stopping the channel from opening the tank seems to me to be the main issue. An off-field landing could cause the mains to pull back and do what we have seen here. I have always thought the plastic in the side was the most serious issue with this tank. This is potentially worse it seems.

John Bender
322.7 hours
 
There is an old saying, "It is not the fall that hurts, it is the sudden stop". Stopping an aircraft over a distance of several feet will hurt much less than stopping in several inches. I agree with John that bending metal absorbs energy. If the aircraft were made stronger, it would not bend as much. Instead it would stop quicker in a crash, which would hurt more. In this crash, the pilot walked away. The RV-12 is a pretty good airplane. With a few improvements, it will be perfect.
Joe Gores
 
I have often wondered why a bladder, similar to a race car fuel cell cannot be used. No more proseal, very little risk of a rupture.
 
How about placing stiff foam under the existing tank to hold it's present elevation above the floor, remove the AN3 bolts on the front, and install 2 or 3 elastic holdown straps that are anchored to the floor (pilot side) , and the longeron on the right side? (We would need to drop the elastic connection on the right side with a pair of brkts to anchor the restraint below the tank top). Another item is to connect the tank to the pump and vent using long enough stainless steel braided fuel lines. If the channel rotated in an impact it would be a non issue (hopefully) . If the floor pushed upward the tank and fuel lines would move with it. If any upward force was applied to tank independent of the floor it would move upward against the elastic retaining straps. The question is how will the rear 1/4 bolt securing the tank handle the upward movement? I suspect it may be OK as the tank brkt would likely rotate on the bolt. I am certain someone out there could determine the correct travel (aka resistance) allowed by the straps while still restraining the tank sufficiently in normal flight activity. These moves may be sufficient alteration for the flying RV12's out there. Van's will undoubtedly come up with a new tank before too long.
If they are interested I would like to suggest two 12 gallon tanks with each one mounted on either side of the baggage area allowing the baggage bulkhead removal and slightly aft of the gear channel. Just my two cents.
Dick Seiders 120093

PS Make the 12 gallon tanks out of vynil ester fibreglas.
 
I have often wondered why a bladder, similar to a race car fuel cell cannot be used. No more proseal, very little risk of a rupture.

My Cessna 180 has bladder tanks. Each one holds 30 gallons. They lasted about 50 years and then started leaking. No complaints, and I hope the new ones do as well.

They are heavy and need to be snapped into the wing so that they hold their shape. They go aft of the main spar and forward of the rear spar, with the control runs going aft of that spar. Electrical connections go forward of the main spar. They have integral provisions for outlets, fillers, drains and gauges and with all that, aren't cheap.

There are failure modes associated with them. These are the two worst: they can have wrinkles which trap water, and they can come unsnapped if the vent clogs and suck up as fuel is burned. Since the tank bottom is lifting, the fuel gauge float doesn't show that it's running dry. There have been ADs for both of these.

All in all, they work pretty well. They've been reliable for me and when they leaked, it was a small leak. They've held 80/87, 100LL, 100/130 and unleaded non-ethanol car gas. They've had gasoline laced with Marvel Mystery Oil a few times.

I'm satisfied.

Dave
 
I have often wondered why a bladder, similar to a race car fuel cell cannot be used. No more proseal, very little risk of a rupture.

That's the ultimate fix.

Absorbs shock like nothing else, contracts with atmospheric pressure and depending upon the manufacturer, is self sealing against punctures.

Problem is ............. $$$$
 
The first take-away from this event should be the reminder that in-flight distractions kill. Any accident that compromises the fuel system will most likely take the occupants with it. No one enjoys the thought of a fuel fire but prevention begins in the left seat and this pilot was the first one to stress that.

Of course you can't avoid that distraction if you are not comfortable with the system you have installed. You are experimental so set it up to your comfort level and then please, "fly the plane with all of your attention."

Please don't take this as preaching....not intended...just don't think the topic is complete without bringing it up.
 
The first take-away from this event should be the reminder that in-flight distractions kill. Any accident that compromises the fuel system will most likely take the occupants with it. No one enjoys the thought of a fuel fire but prevention begins in the left seat and this pilot was the first one to stress that.

Of course you can't avoid that distraction if you are not comfortable with the system you have installed. You are experimental so set it up to your comfort level and then please, "fly the plane with all of your attention."

Please don't take this as preaching....not intended...just don't think the topic is complete without bringing it up.

Good point Pete.

A couple of other key points is that Vans (IMHO) is more than a little concerned with everyone running in all directions to fix this, and it may not be necessary, and infact 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.
 
Last edited:
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.
 
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?
 
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
 
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.
 
Last edited:
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
 
... "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.
 
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). :)
 
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/rodclark512/2011_10_24?authkey=Gv1sRgCP-r9vmN7eHBbQ#5666986340178990434
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
 
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. :eek:
 
Last edited:
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.

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
 
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.

Having taken off with the canopy open I can assure you the plane flies fine. :eek:
 
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.
Great minds think alike. :D I suggested the same thing in post #12 above. Only my straps are longer and above the attachment points. There have been lots of good ideas presented here. I believe that Van's will come up with a well engineered solution. Not only do they have to design a fix, but the tank has to be tested, a lengthy process.
Joe Gores
 
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.

Don,
The closest we get to that training is we have opened the canopy on roll out when both Jetguy and myself were in the aircraft. We've noticed the canopy does pitch the nose down when opened. We will not be practicing that. instead we like flow training before taking the runway. fuel, flaps, canopy, trim, choke and then and only then throttle up for takeoff.
 
Checklist including canopy a good proposal. The off field landing is the concern which likely would (could) cause the gear rotation. The fixes suggested all have merit, but if I were making a mod I would not attach to the channel -period. Anything that can support the front of tank NOT connected to the channel is a step in the right direction. I do however suspect the best advice is to wait for Vans to solve the problem for us.
Dick Seiders
 
I hesitate to ask - and just an unthought-through additional idea - but what if those forward two supports were wooden or plastic dowels?. Something that could hold the weight to 4+G and still be weak (or flexible) in shear. Thick of a plastic tomato plant stake about 3/8 inch in diameter - some of those even have a reinforcing wire in the center. Nothing wrong with a little brainstorming at this point.
 
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?
Good idea, maybe something like this:
IMG_0758a.JPG

The trouble with a simple circuit with a warning light and a switch is that the pilot will get used to seeing that light being on and will ignore it on takeoff. What is needed is a warning that will ONLY occur on the takeoff roll. I envision a microprocessor that that will receive input from the canopy switch and from the tachometer. When the canopy is open and the RPM is above a set-point, the microprocessor output will turn on an audio and visual alarm. A voice that yells CANOPY in your headset would be ideal. Off the shelf components are inexpensive. The hard part is designing the circuit and writing the microprocessor program.
Of course a checklist will work too. But pilots get complacent or distracted. Or they use a checklist, but then open the canopy due to a delay. It has happened and will happen again.
Joe Gores
 
A blot that would shear sounds good.

I think Bill may be on to some thing. How about a plastic bolt or an aluminum bolt? If it would shear on impact that maybe the easiest fix.:confused:
 
Have not had time to research the subject, but, breakaway bolts are available. Large ones are used on fire hydrants. Believe they have a hollow core.

Such would take a bit of testing to ensure they do not shear under g-load.
 
I hesitate to ask - and just an unthought-through additional idea - but what if those forward two supports were wooden or plastic dowels?. Something that could hold the weight to 4+G and still be weak (or flexible) in shear. Thick of a plastic tomato plant stake about 3/8 inch in diameter - some of those even have a reinforcing wire in the center. Nothing wrong with a little brainstorming at this point.

I think Bill may be on to some thing. How about a plastic bolt or an aluminum bolt? If it would shear on impact that maybe the easiest fix.:confused:

The subject has come up and it is a good one, but the headless bolt fix does offer shear strength ( side load) to support the forward end of the tank. The rear bolt holds the tank in place, and the front two headless bolts support it. Certainly, there are many ways to skin this cat, but like another poster said the goal is to not use the center section as a support at all.

I am going to use the headless bolts & strap wait and see what Vans comes up with.

JMHO.
 
Last edited:
New tank design

IMHO, and not being any kind of an engineer, I think that it's time for Van's to rethink the design of the fuel tank. Some of you who are a lot more knowledgeable than I seem to be saying that we can expect the current design tank to be compromised in the event of an off-airport emergency landing. I don't know if the pilot of this particular accident was 'lucky' or not but if I can expect a gasoline shower in my 12 if I have to land in a field and flip it or hit hard, then I don't want to fly a 12. Simple as that.

Maybe a 'seamless' rank as described by some of the previous posters is in order. I don't mind paying a lot more $$$ for a safer design fuel tank.
 
I'm just a bit confused about the concern with shear of these bolts. Aren't we really trying to still avoid them shearing, but have them bust when over-tensioned? Hence the headless bolts retain shear strength, keeping the tank from coming loose when inverted or hard landing, while having no tensile strength (with the bolt head cut off) such that the rotating U-channel can't pull the tank apart. ????? A strap is then mayhaps needed to keep the tank in place in the case of the U-channel rotating and the plane inverting???
 
Back
Top