roll bar protection under canopy?

[shocktrooper]

Anyone ever consider installing a roll bar under the canopy...like on a tandem seated RV4, etc.?
After my goof landing and run off into the weeds several weeks ago, and resulting partial nose over...it got me to thinking seriously about it. I know we are encouraged to keep these Sonerais as light and spartan as possible, and ALWAYS fly them well...but it seems at least a minimal roll bar, mounted to the frame over the center spar area, would be a good idea, since the headroom is minimal in the aft solo seat for most adult males. A hard and fast nose over could spell 'lights-out' with nothing but plexiglass bubble between your head and that dreaded "HI-Speed Dirt"!
I know the original design was for a ' lightweight racing machine', but a few more pounds of added 'cranium safety' just might be worth losing a few MPHs', etc.
What say all of you?

 

[mhflyit]

The tail (first) and then the turtledeck should provide some protection before the Plexiglas.

 

[tls258]

Sorry to read about your loss of control excursion. The good is that you walked away. Several things one might want to consider in 'excursions': If loss of control is happening, you think you can't safely get back in the air, and you see that you are heading for the woods, ruts, ditch, etc., then try to execute an intentional ground loop rather than standing on the brakes and nosing over. Been there, done that nose over deal after standing on the brakes. I can tell you this from experience: the older we get, the slower we get. Catching the nose before it gets away is a challenge for me every time. So, I'm always thinking, "What's it doing?" as I am working my toes. All this was much easier 40 years ago, but more fun now.

The RV 4 roll bar is a substantial construction. A CFI RV 4 owner I know told me he would rather ground loop his very nice RV than trust the roll bar since his goal is to be able to get out of the aircraft as quickly as possible after a mishap. Flipping over has you trapped, on your head with a hinged canopy that cannot open, a hot engine, and possibly dripping gas, etc. What could go wrong? While a roll bar might save a broken neck, you might instead be the host of an unintentional bar-b-q.

Most TO, landing fatals that I've read about result from head-to-panel or associated high-energy trauma, since the human is still in high-speed motion while the aircraft is stopping suddenly as it contacts terrain in a straight linear motion. Smashing our head that is still moving forward at 40 mph into the panel which has suddenly stopped moving will do some damage. If the body stop vector is down through the airframe, say in a landing or departure stall, then we are going to suffer spinal and internal damage as everything gets vertically compressed quickly. An intentional ground loop will consume energy. We just need to keep it from flipping over the down wing. Collapsing the gear would be a goal.

I've thought about a canopy quick release to eject it before ground contact in case of an emergency landing in rough terrain. Some have had some experience getting beaten with open canopies. A slide-back or pivot-back would accomplish that goal better. Probably a pivot-back is close to the same weight as our hinge mechanism. Just two bars with pivots at both ends, attached at about the mid point of the canopy frame, so the canopy could be pivoted back to the turtle, keeping it pretty much level.

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Regardless of aircraft design to survive a crash, the fundamental idea is to carry the lowest kinetic energy possible in our body at 'touch down' relative to the immovable runway or the woods. It is the sudden dissipation of our kinetic energy that kills us in a crash. What's that calculation? Our touch down energy is 1/2 our body mass times the square of our speed? So we want to be a slow as possible, then use the deformation of the airplane structures, its path, etc., to dissipate our energy gradually and keeping the rate of dissipation within the limits our body can tolerate without injury. An intentional ground-loop increases drag and friction and moves the energy dissipation into a circular vector away from a linear vector. Since the short linear vector we are trying to avoid is the ditch 50 feet from the nose, the ground loop gives us a longer distance to slow as we put the aircraft into an arc away from the ditch. Hopefully, we keep the aircraft upright. Then, we can open the door or canopy, step out and survey the damage.

 

[Jackola]

If I could add to this; years ago when I became interested in Sonerai's, I searched ntsb reports. Most all engine failure / off airport landings were survived, even two guys went down in the trees and walked away, probably 99 % luck!

Most fatalities were hiting wires, midairs, or folded wings ect. I do recollect reading about one who spent some time upside down before rescued, but most were walk aways.

I always felt the Sonerai airframe structure provided good protection if remaining right side up, based on my reading!

Randy

 

[smokyray]

Sierra Tango!
Any landing you can walk away from...
Hey, no worries, lived to fight again. I grew up flying taildraggers in the form of our family T-Craft. Later, banner and glider towing then working for my Uncle Sam. Concern for flipping over in a canopy aircraft began in the T37,T38, OV10 and 20 years in the F16 none of which having a roll bar.
When I built my RV4, the roll bar though beefy didn't look capable of saving my cranium in a flip over and the teal danger, being trapped underneath remained. Having been a first responder to 3 RV flip overs, I can attest to the ordeal of extricating trapped occupants. In all three cases, the roll bar did not protect them nor did it provide ample room to escape. Had there been fire or no one present to assist rescue, their predicament could have been grave at best.
I too recommend avoidance to impending flip over. Be it ground loop, off prepared surface excursion. Engine failure inflight options for forced landings also apply for alternate runway choice (roads vs plowed fields) or even a lake vice trees.
Better safe than sorry...
V/R
Smokey

 

[shocktrooper]

Thx guys for some very informational and technical comments about the; "roll bar in a Sonerai" question.
To address Thaddeous's suggestion to; "intentionally ground loop";...at my home field & parallel to the runway (9ner & 27), (I was landing on), there are always soy bean rows running in same direction as runway......when I saw I was going to run off end of 9'ner (big trees there!) and was still rolling quite fast, I attempted a hard left into the recently plowed-under bean field, which definitely added max braking action. The aft end of the wheel pants inside were full of fresh plowed dirt lol! I don't remember thinking; "I should ground loop it now", per-say, but still had presence of mind to (do SOMETHING!)...this no-doubt helped a bad situation, but my bird's tail wheel is limited in L to R travel (not a break-away type and single brake lever/no diff brake pedals) & I was at MAX L, as hard as I could push it!, all the way into the weeds...sans LOL! :'(

In retrospect, the dreaded 'Error Chain' that day as noted and decided by this rookie Sonerai driver is as follows:
1. Pilot failed to adequately gather ALL available information about condition of runway prior to flight.
2. Pilot failed on 2 attempts to adequately slow aircraft in pattern to the correct speeds/altitudes for all aspect positions for a safe landing.(beyond the mud hole I failed to I.D. prior to T.O.)
3. Pilot failed to go-around (as many times as it took or go elsewhere) to ensure a safe and correct landing, (i.e.) wanted to get down; like right-now!, and did NOT want to land ANYWHERE other than at home field.
3. Pilot demonstrated poor pre-flight aeronautical decision making and airmanship overall.
4. Pilot will NEVER forget this event and consequences!
5. Pilot is humbled and grateful to the GREAT; 'I AM' that (I) did not total (MY) awesome Sonerai IIL & end up seriously injured or killed.
6. Pilot is grateful to my original T.W.CFI, that ingrained in me to "Never Panic...fly the airplane all the way through it!" aka, the emergency.
Amen.

I hope this freely admitted example of 'The humble Truth', will help all of you in-process builders, new pilots, etc., to 'LEARN' from my dangerous and expensive mistake.
shocktrooper out....

 

[mhflyit]

I take my hat off to you Shocktrooper! - a brilliantly honest post and had your 'point 1' been different the outcome would have been different.
In the end you and the Sonerai did well - a good team I think!!

 

[shocktrooper]

I take my hat off to you Shocktrooper! - a brilliantly honest post and had your 'point 1' been different the outcome would have been different.
In the end you and the Sonerai did well - a good team I think!!

Thanks Matt! "Happy, mad, sad or glad...only the truth matters in the end!"
He is NOT a (Sonerai) 'Jedi' yet! "Much to learn, still he does!" "HHmmmm!"
LOL! ;D

 

[Pttim]

Shocktrooper, great recount of the events that happened it shows you have given the incident a lot of thought to preclude it from ever happening again.

Back in the early days of my Sonerai career, I came in for a landing on the pavement which was something new for me as I had been deferring to the grass when I first started flying mine. I over controlled the rudder which I probably had been doing on the grass but with less effect, well this time as I had the tailwheel skidding to the left then the right then the airplane veered off the runway to the left, I had right rudder to the floorboard but she wouldn't come right just kept going left off the runway, across the grass runway and rapidly heading up the hill to the woods, it became apparent to me as I crested the hill it was not going to stop and was going to plant myself in the trees I gave it full left rudder and the airplane just spun around and stopped without tipping. As I gazed around the airport to see who might have seen my excursion and gather my self up I taxied back across the grass across the runway and to the taxi way, I could not make the aircraft turn right. I shut down got out and found what I had done.

My over control of the rudder had peeled the rubber off my tailwheel and the rubber got caught in the wheel arm and locked up the tailwheel in a left turn, once I removed the rubber I could taxi back on my new aluminum tail wheel, albeit a bit smaller and with a flat spot.

A valuable lesson I wont ever forget! This triggered another near miss! In an attempt to make my landing rollouts less dramatic I came to the conclusion that I needed to approach slower and land slower, well one day I did just that and as I was turning base to final at probably 70 or so the airplane became unresponsive and was mushing, I had full left rudder but she wouldn't come around, I had a sickening feeling at that very moment that something awful was about to happen and it was going to be to me, at that very moment I leveled wings applied full power and initiated a climb to get out, I know for a fact I barely cleared the trees and went by a tower that I could not see that was still higher than I was. Dumb luck! but it scared the crap out of me and made me think for weeks before I flew it again. All part of the learning process I guess!

Hang in there.

 

[tls258]

Very honest and comprehensive reports. Thank you for sharing. Kathryn's Report full of low and slow unstable approaches, usually with much worse results.

 

[vhbill]

I put in a roll bar. It adds about 10 lb. One of the problems with installing a roll bar is what to attach it to so that it will support 700 lb or so of aircraft and inverted people. In a simple stationary tip over it might provide some protection, but it may not withstand sliding along the ground following a tip over.

You can't make aircraft crashproof. The ground loop discussed above may be the best way to help prevent tipping over, but you may not have time to do that and it won't take much forward speed to cause the tip over if the wheels hit a ditch or solid obstacle.

Most accidents are due to pilot error. It might be a better investment to concentrate on being a better pilot. It is a good idea to insure your aircraft and convince yourself that you are "borrowing it" from the insurance company when you go flying.

 

[squirrely dan]

I guess Charlie Hilliard should have concentrated on being a better pilot. When a plane goes on its back it doesn’t usually slide. It’s more of a flop. I’ll take my 17,000 hrs and continue to learn from those that made mistakes. # killer of pilots isn’t poor flying skills. It’s poor judgement.

 

[Elviar]

Tricycle gear, like we see on almost all military and commercial aircraft, can go a long way toward preventing ground loops and nose overs.

 

[M61A!]

Tricycle gear, like we see on almost all military and commercial aircraft, can go a long way toward preventing ground loops and nose overs.

I suggest having a read through the accident reports....Nearly every RV (and many others) that ends up on it's back is the result of nose gear failure .

 

[Flyingfool]

Vhbill,

That roll bar is about exactly like what I was thinking.

Another consideration for safety with having some higher structure is also placement of shoulder harness attachment. From what I have read harness attachments should NEVER be located below the occupants shoulder level. As even a straight ahead stop will result in spinal compression injury potential.

I think rear occupant in an S2 is pretty well protected on nose over by the tail and rear turtle deck. The front occupant is screwed without additional nose over protection.

I agree ground loop is best alternative. But we don’t always get that option. As soft ground or freshly plowed farmer field or snow covers ground all would almost instantaneously cause so much drag upon touchdown as to immediately cause a highe speed nose over. Unless a person knows of the softness and initiates a skid just prior to touchdown, and even still the soft earth (snow, mid etc) may still cause enough drag to flip over.

Direct steering tailwheel that cannot free Castro may not allow enough rotation to ground loop as well as some might believe.

As always the best practice is to never get into a crash. But even the best pilots using the best judgment are still sometimes put into situations and circumstances beyond their control.

Some structure behind the front seat occupant can I believe only improve potential safety for both reduced chance of spinal compression for proper shoulder harness attachment location, as well as some hope of protecting or at least energy slowing upon nose over. We all hope to never have to use any safety devices. But we need to all use best judgment and make our own risk analysis whether or not to install roll over protection or not.

Sure do hat the vision restriction the roll over protection causes.

Just my 2 cents.

 

[John B]

Direct steering tailwheel that cannot free Castro may not allow enough rotation to ground loop as well as some might believe.

Ummmm. It'll ground loop really easily if you let it and the little wheel on back ain't gonna stop it.

 

[Flyingfool]

Ummmm. It'll ground loop really easily if you let it and the little wheel on back ain't gonna stop it.

That makes sense.

 

[CdnMedic]

Another consideration for safety with having some higher structure is also placement of shoulder harness attachment. From what I have read harness attachments should NEVER be located below the occupants shoulder level. As even a straight ahead stop will result in spinal compression injury potential.

Coming from the world of race cars, I've always put the mounting point for the straps level with the shoulders. With a proper race car seat, the straps will usually come through a hole at that location to be mounted to the cage. The seat itself and the remaining strap anchor points are also mounted directly to the cage. Essentially the car could spin around the driver and they would be ok inside the cage. When building my cages, I didn't install the coss bar behind the seat until I had the seat positioned so I could determine the right height for staps and thus, that cross bar.
Strapping in to the car, everything was so snug it was almost uncomfortable unless you were used to it. I know that nobody doing cross country flying is going to be strapped in that snug.


I'll make sure my harness in the airplane will be the same way.

 

[vhbill]

A useful reference for seat belt shoulder harness configuration is AC21-34. The shoulder harness configuration diagram is:



Staying within the angle to the shoulder envelope for the rear seats of the Sonerai is not too difficult if you install a horizontal bar support for the shoulder straps. The photograph in my previous post shows a horizontal support bar for the shoulder straps for front and rear seat.

The rear seat shoulder straps can be anchored to the lower longerons in the rear of the fuselage and connected to the seatbelts by a suitable cable. That is how it is done in Van's RV series. Finding somewhere to anchor the front seat shoulder straps in the Sonerai is not as simple.

Unfortunately the Sonerai plans don't mention shoulder harness attachment points, but presumably most people wrap the shoulder harness around the transverse bars at STA 55-1/8 and STA 83-3/8 (plans Page 9). However these 5/8 x 035" transverse tubes are unlikely to provide right angle to the shoulder or the required restraining force for 40% of the body mass in a 40g deceleration.

The only solid point behind the front seat is the spar box, but that means the seat belt will have to pass over a horizontal support bar to get the correct angle from the shoulders.

Unfortunately once you start making modifications to a design you generally add weight and you may be making the aircraft less safe unless you can do the required aerodynamic and stress assessments. There are a lot of Sonerais happily flying out there so perhaps the design is OK as it is.

 

[Flyingfool]

No doubt adding structure will add weight. All vehicles are safe until there is an accident. Then some become far safer than others.

Reading old sport aviation they described an accident that husband and wife impact. The wife being shorter had some injury. Her husband in same plane with same crash being taller and Barnes below shoulder had spine compression caused by the improper shoulder harness angle/height. Sure he was also heavier so momentum was different. But the point and physics is clear. Location of shoulder harness height is extremely important.

All people have to make their own risk assessment. Probably most S2 are flown solo a large percentage of time. And if smaller children etc who fit best in the front seat also may have less issue with low mounted shoulder harness. It an adult then becomes a real concern IF an accident occurs.

We all hope we. Ever have to use any safety equipment. Be it a fire extinguisher or shoulder harnesses. But if you need them you want them to be working and working properly.