I am sitting here thinking about that now. In a spin I don't know that it would really matter. In the case of a power loss, maybe go nose high & slow down (within reason) before deploying it?Originally Posted by Matt Gonitzke
I am sitting here thinking about that now. In a spin I don't know that it would really matter. In the case of a power loss, maybe go nose high & slow down (within reason) before deploying it?
I'll have to dig around for the website, but one of the guys put at BRS on his Nieuport 17. It was behind the seat and fired sideways through the fabric; the chute followed with the risers along the longeron on one side, attaching to the rear cabane of the upper wing (IIRC), which is just forward of the CG.
He worked directly with the company that made the BRS for placement and rigging, and wrote they really went the extra mile in figuring out the safest way for it.
Ideally I'd want to be as horizontal as possible under the chute. This gives the most surface area on impact, spreading it out onto the airplane instead of the squishy pink bits in the seat. A rearward landing would be both terrifying an less than ideal in surviveability (my plane is tube and gusset, which would turn the fuselage into a nice set of pikes pointing right at me).
The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.
Frank, if it makes any difference mine will be welded 4130. Granted, the plane's structure will be somewhat lighter than a race car, but I have seen quite a few wrecked cars with 4130 welded cages & the driver is usually just shaken up some with no major injuries.
It looks like what I need to do is either 1) mount it out of the way somewhere & run a cable under the fabric back to the CG, or 2) increase the baggage area enough to put it behind the seat. I'm just not sure I want an explosion right behind the passenger.
Last edited by Mike Switzer; 11-03-2011 at 05:58 AM.
Yes. The rocket fires down and to the right. The chute then would deploy upwards, breaking loose the breakaway risers and the chute is over the airplane as it descends in an upright attitude. The 'breakaways' are simply a strip of fabric glued over the risers and against the fuselage. (It is much easier to see than it is to explain
Cheers,
Jerry
NC22375
65LA out of 07N Pennsylvania
I installed a BRS package on my Kitfox using the factory suggested method, for which I still have diagrams and info. It is mounted behind the passenger seat with rocket firing downward. This puts the package very near the CG. While BRS assured me the rocket would penetrate the fabric, I chose to make a breakaway weak point in the fabric directly below the rocket. The rocket fires from a cannister with a closed top, which, in addition to the seat back, should protect the passenger from rocket exhaust. IMHO, if the chute is actually needed, a slight burn is the least of the passenger's worries.
The bridle is attached to the outside of the fuselage, covered with a breakaway strip of fabric. The bridle attaches to the airframe with a three-point suspension--one at each wing root and one in the center behind the seats. I put the bridle under the lucite "roof", with the hope that the pop rivits would release when the weight of the aircraft pulls on the bridle.
BRS further pointed out that under "normal" circumstances (whatever that means--I wouldn't deploy the chute if all circumstances were "normal"), the parachute ends up deploying behind the aircraft no matter which way the rocket fires, due to the forward velocity of the aircraft. The bridle routing should be such that it won't foul on aircraft structure during the subsequent slowing of the forward speed and transition to a configuration with the aircraft below the chute.
Assuming there is some way to contact me directly via this forum, I would be glad to e-mail photos and a copy of the BRS installation instructions.
Bruce
Bruce - I sent you a private message with my email address (look at the "notification" bar up top)
Thanks
Mike
After a couple emails (and lack of response after my last reply) I am getting the distinct impression the folks at BRS aren't that interested in the application of their products in experimental aircraft...
How big is your aircraft again in terms of weight? If it's on the lighter side, you might look into the Second Chantz compressed air ballistic parachute. It doesn't have the nasty habit of starting fires like the BRS system does (mostly because BRS is more often than not deployed after the aircraft hits the ground and the control lines are damaged).directly in front of the fuel tank, neither of which seems like a good choice.
Then you probably want to come down vertically in a level attitude or even 10 or 20 degrees nose up by which the tail and rear gear would be the first to touch down. The problem with a lot of homebuilts is that they turn turtle if they are in a nose low attitude upon touchdown and we don't do the best job of including head protection in our designs whether they are canopy equipped or not.. I don't really care what direction I am facing or if the airframe requires repair, as long as the occupants survive.
Mike, you know if you want my input on the survivability aspects, I'm happy to help since that's the area where I know the most about.
Close to 70% of what most pilots currently generally consider to be invariably fatal crashes are survivable. Most spin/stall crashes don't absolutely exceed the human tolerance limits in a way that's not amenable to the proper use of engineering. However, I will point out that a nose down landing is not exactly ideal if one can avoid it. The limits for serious and fatal injury (which are different than the "no or minor injury" limits we often see trotted out for light aircraft designs) are higher in a longitudinal impact than a vertical one, but it's also a lot easier to dissipate the energy of a controlled vertical impact before it gets to an occupant.I think Eric may be right - but it shows landing nose down is a survivable option
No offense, but given the 10-20% rate of restraint failures in GA aircraft (much higher in some models), one needs the best restraint system (or at least a better one) in almost any situation.*You absolutly need the best restraint system that you can install.
Remember that a lot of the failures of restraints systems are due not to the webbing or buckles failure but due to the attachment points at the fuselage failing. Failure of the seat attachment points is another significant problem that needs more attention than it receives.the restraints will be right out of a race car so that won't be a problem
That's amazingly rather uncommon in a way that is significant. It's much more common- especially in composite aircraft- for the tree to penetrate/crush through the fuselage even in a crash that should be survivable. However, I see your point.*Trees may penetrate the windshield before impact.
So a nose down impact is even less of a good idea without something very solid up there to take the brunt of the impact.Bob - my engine & fuel will be in the rear (some fuel in the wings) but nothing up front to speak of but electronics (& my feet)
The "injury threshold" in that case is not really the same as you would encounter in an aircraft scenario. This is mostly due to the fact that the forces in a paratrooper are going to be directly applied to the torso rather than to the airframe along with the mitigating factors of the seat, restraint, etc. Just something to keep in mind as those numbers (assuming you're quoting from the study I think you are) were designed to determine limits a paratrooper could withstand without needing to go to sick call or be put on restricted duty.Injury threshold: +17Gx (Eyeballs in)
-12Gx (eyeballs out) See Col Stapp 1954 or so.
+25Gz (Eyeballs down)
-15Gz (Eyeballs up)
One of the big problems with discussing "G" with non-survivability engineers is that they often forget it's not simply a matter of "X G = serious or fatal injury" but where the force was applied (over how much of the body) and how rapidly it was applied (onset) and duration. For example, a fall from standing height backwards and striking the back of your head on the sidewalk (as though someone fainted for example)- a common and very survivable event- imparts something on the order of 300 G for a split second to the back of the head. Most people survive without a skull fracture and maybe just a bad headache or concussion. The same level of force applied to the whole body for 0.35 seconds of more longitudinally (eyes out, -Gx) would likely result in the body fragmenting. Turn the subject around and decelerate them in excess of 100 G and there may be some negative effects but most people could survive it. Stapp himself argued that the rear facing "eyes in" (+Gx) whole body limit for life-threatening injury was probably in excess of 200 G based on his studies with monkeys. Unfortunately, no research board on the planet would approve testing that in humans so we're left to extrapolate from crash data (inaccurate as it is) and other indirect sources.
The biggest issue in that scenario though becomes the strong likelihood of the entire thing winding up on its back and pinning Mike and his passenger in the aircraft which could introduce an increased risk of death due to post-crash fire or positional or traumatic asphyxia.One last thought Mike. If you could mount the chute in the nose, and desc tail first, you have all that structure behind you to sacrifice while eating up energy.
Amen to that.About that Sonex that deploys out the belly and descends inverted. Someone is yanking our chain. No overhead structure, Real bad if landed in boulders or water. Sad songs and slow walks follow.
That's the impression I got.After a couple emails (and lack of response after my last reply) I am getting the distinct impression the folks at BRS aren't that interested in the application of their products in experimental aircraft...
Unfortunately in science what you believe is irrelevant.
"I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.
After the response I got from BRS I have pretty much decided to just wear a seat parachute. Eliminates a couple engineering problems & makes things simpler.
I'd still recommend you talk to Second Chantz. They really can't help me with my primary project (too heavy) but they might be able to do something for you.After the response I got from BRS I have pretty much decided to just wear a seat parachute.
What's the fun in that? *tongue firmly in cheek*Eliminates a couple engineering problems
Unfortunately in science what you believe is irrelevant.
"I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.
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