+++ #3888 From: Benton Holzwarth Subject: Re: Caution.... Without more info, I'm not sure there's much I can take home from the lesson. I've been rolling around the idea of a single, center 'Y' stick (vs. individual 'between the legs' sticks) with exactly the thought of minimizing the things to get impaled upon in a crash, but haven't gone so far as to commit. They're just so... 'Chris Hienz' (not that that's all bad.) I am thinking 4-pt harness at the least, and will consider what protrudes from the console directly in front of me when laying things out. +++ #3890 From: BRUCE A. FRANK Subject: Re: Re: Caution.... Gallows humor not withstanding, some things are beyond any semblance of value to convince us to "buckle up." Now, as for the protrusions that might cause serious head injury in an aviation crash; full shoulder harness just will not allow enough movement to inflict such severe center face injury if the crash's "G" force level is survivable. Particularly in an airframe like the Bearhawk's, which is essentially a full cage. If one feels the need for such full protection the military solution of a full helmet with metal and Lexan face shield will do a much better job than impractical restraint systems. Hmmm...well maybe multiple position air bags. +++ #3892 From: Float-By Shooter Subject: Re: Caution.... And like Bruce said, if you are fastened into a well made aircraft harness, you just aren't going anywhere. My brother put a set of 4 point harnesses in his Citabria this past summer and when they are snugged down, about all you can do is move your limbs enough to operate the flight controls. The straps are also heavily padded to spread the impact forces over a larger area, a feature which the automakers would do well to emulate. +++ #3939 From: joel MAYHALL Subject: Re: Caution.... Don't make the assumption that I do not approve of seat belts. I do and have used them religiously in all my cars and planes since the mid '50s. But airbags DO increase your margin of safety in a crash. When I'm belted up in a 5 point system and that IO 540 is crashing thru the panel towards me at 50 mph, I'll take an airbag in front of me any day. Airplanes, unlike modern race cars, are not designed with impact absorbing structures and I have yet to see one with a 2" pipe welded cage inside the cockpit. +++ #3953 From: Owen Davies Subject: Re: Caution.... Among other interesting comments, Joel Mayhall said: > Airplanes, unlike modern race cars, are not designed > with impact absorbing structures and I have yet to > see one with a 2" pipe welded cage inside the > cockpit. Actually, I think that if you take a look at the airframe of, say, one of the Piper tube-and-fabric planes and trace what happens to the impact forces when the nose arrives at something immovable, you may change your mind. One of the big arguments for tube-and-fabric planes is that they absorb crash forces pretty well. You may recall that the Cub and Vagabond both have fuel tanks just behind the panel, in the passenger compartment. I can't confirm this from personal investigation, but older and wiser pilots have told me that fires from broken fuel tanks were virtually unknown in these planes, but became a factor when Piper moved the tanks into the wings. This may have something to do with the (modestly) higher speeds of the short-wing models, but they attributed it largely to the efficiency with which the fuselage truss structure routed the crash forces around the tank. +++ #3955 From: budd davisson Subject: Re: Crash survivability Re: energy absorbing structures NASCAR crash cages aren't actually energy absorbing as they are so stiff they don't give. The energy absorbing part is the car that's around the cage. To absorb (ablate) energy, it has to be used up doing damage to something other than the passenger. If the structure is super stiff, it transfers the energy directly to the passenger without reducing it's level. Witness the old front engine Indy cars. They could tumble end for end and never have a part fall off but the driver was often dead. The new one's explode in a frenzy of parts being shorn off which uses up energy. You want a structure to be stiff enough to resist, but then deform and eat up energy while being deformed. Aluminum deforms too quickly and doesn't resist enough. Composites, as usually used in aircraft, are like wood, in that their yield and ultimate points are so close together they don't bend but fracture and blow apart with little long term deacceleration and the associated energy ablation. Aircraft steel tube is about the best in terms of protecting the passengers but sucking up the hit before it deforms the passengers. Them's my thoughts on the subject. +++ #3961 From: Ken Beanlands Subject: Re: Crash survivability I totally agree with you that the steel tubed fuselage is about the best for energy disipation. However, I believe that aluminum runs a close second. I've seen my share of banged up planes including a PA-28 that flew into the ground in IMC with frozen static ports. He walked away with a sprained knee but there wasn't a single unbent panel on the entire plane. Another was a C-180 that stalled trying to clear power lines at the end of a lake. Lota of damage, minor injuries. I've always been amazed at teh amount of damage an aluminum fuselage can sustain and still have the occupants walk away. Of course, there are always the freak accidents like that Sea Fury that flipped on its back during a taxi and killed the pilot (Charlie Hillard, I believe?). Personally, I am not a fan of wooden fuselages. I have seen a Fisher Horizon and a Team MiniMax both after fatal crashes. The fuselages just exploded apart leaving the pilot completely unprotected during the deceleration. As Budd put it, there is no deformation, just failure. One of the planes I've been fond of is the 7/8 scale SE5a replica. However, I'd have to change to a steel tube fuselage to be comfortable in that plane. +++ #3963 From: Owen Davies Subject: Re: Crash survivability Ken Beanlands observed: > The fuselages just exploded apart leaving the pilot completely > unprotected during the deceleration. Do note that the failure itself can absorb significant forces. I once chatted with a guy who'd managed a take-off stall in a Pietenpol, panicked, went in straight down under full power from 300 feet, and picked himself off the back of his engine surrounded by a pile of toothpicks. Aside from the engine-shaped bruise on his chest and abdomen, he was unhurt. When I spoke with him, he was building another Piet. You can probably guess whether he had decided to go with the steel-tube variant. My own impression -- note that unlike Ken I'm nowhere near being an aircraft engineer -- is that it matters a lot less what the plane is made of (with the possible exception of plastic) than whether it's designed properly for the material in use and the expected worst-case conditions. That said, I'd still prefer a steel-tube airframe to anything else, but that's at least in part because I enjoy welding. >>> 2mar02 #7686-9153 +++ #8359 From: "rodsmith52" Subject: Some thoughts on restraints In one of the newsletters, Bob shows the front seat shoulder harness attach point. Problem is I want to use the Y-style shoulder harness that goes over both shoulders. In the event of a crash the forces are spread evenly over both collar bones and there will not be the twisting motion that would happen with a single shoulder strap. That requires mounting directly behind you. I was concerned about the rear spar carry through tube where you would attach them bending forward and downward and putting your face into the instrument panel in a bad crash. I talked to Bob and he said if I wanted to mount them there, to weld 3/4 x .035 tubes from the mount point directly forward to the x-brace tubes. Thats about a foot of tubing for each sideHe said that if you didn't already have that tube welded in, going to a heavier tube would be a good idea. For the rear seats there is no center attach point for seat belts. It used to be allowable with certified planes to use one seat belt for two people in the rear seat but no longer is. We can do it in an experimental but that doesn't make it a good idea. Placing a mount location in the center of the tube presents the same problem with no cross bracing on the tube. I will add a 3/4 x .035 tube forward to the center of the next cluster to provide bracing. I know, I know, I hate to add extra weight. Will use a single shoulder strap for each rear seat. I plan on designing a seat that will fold up against the side of the fuselage for the left rear ala Atley Dodge's Cessna seats, my neighbor has them in his C185 I can model it from. Cant do that on the right side due to the cargo door so will plan on a light weight removable seat. Mounting still to be determined. The Bearhawk is very crash worthy. If you have good restraints you should be able to walk away from a hell of a crash. Rod Smith #246 +++ #8366 From: "Del Rawlins" Subject: Re: Some thoughts on restraints > I plan on designing a seat that will fold up against the side > of the fuselage for the left rear ala Atley Dodge's Cessna > seats, my neighbor has them in his C185 I can model it > from. Cant do that on the right side due to the cargo door so > will plan on a light weight removable seat. Mounting still to > be determined. Take a look at how the rear bench seat works in a Jeep Wrangler. It "folds and tumbles" forward and can be secured up against the backs of the front seats; this leaves the majority of the (small) cargo area available for cargo. The whole assembly comes out easily with the removal of one small clip for maximum hauling capacity. I think that a similar arrangement would be ideal for the Bearhawk, since it would leave almost the entire cargo area unobstructed with the rear seat stowed forward. You also wouldn't have to worry about removing the right rear seat and securing it for flight. The downside would be the inability to maximize cargo space with only three aboard (with Rod's proposed arrangement you could remove the right rear seat for a little extra floor space). When I was still in Cordova, I had the chance to examine my buddy's (you may remember him as "Boog") super cub fuselage just before they started putting the covering back on, and one of the mods that he made was to install a cargo net behind the rear seat to keep objects back there. He once had a bag of sand (that he thought was properly secured) slide into the rear control stick and is not anxious to repeat the experience; fortunately the elevator trim on a Citabria is extremely powerful and fast to adjust. I think that on the Bearhawk it would be a really good idea to install some tiedown rings (or other appropriate mounting point) on the ceiling structure in addition to the Barrows style tiedown rings on the floor, and fabricate a cargo net that can be stretched between them to keep the cargo out of the cabin, particularly in the event of a crash. Del Rawlins +++ #8542 From: "Dan Montee" Subject: restraints I'd like to add a comment or two regarding passenger restraints and crash survivability. First my disclaimer: I've never crashed an airplane or built one until the Bearhawk project. I did build, rebuild, and develop modifications for road race cars for a 13 year period. Many of which were made necessary due to high G force sudden stops or abrupt directional changes brought on by outside influences. (other cars, Armco, concrete, shear dirt walls, etc.) My favorite harness was 6 point Luek or Luke (SP?) made in England. This harness is similar to a parachute harness and has an anti submarine strap for each leg. Much preferred compared to the 5 point system that has 1 strategically located center anti submarine strap.The 6 point harness also pulled down and out on the lap belt helping to keep it over the hip bones. Keeping the lap belt away from vital organs and over the bony area of the hip is very important. We all know that shoulder belts should be routed so as not to create compression on the spine during a crash but just as important is having the harness supported somewhere near the shoulder. This is a problem in most of the aircraft I've seen. I'm not sure how I'll accomplish this but the BH will either have the shoulder harness mount near the seat or the seat will control and direct the harness over the occupant. The harness will not start at the top of the airframe and drape over the seats without some kind of control. I may even add the 6 point to the left seat. Race car driving and airplane flyn' both require the derry air to be a major sensor of what is happening to the machine and the tighter you attach your derry air to the machine the better the reception. The 6 point is comfortable and doesn't require much readjustment over time. I have a couple of opinions on the seat selection/construction issue. I believe the ideal seat from a crash survivability standpoint is one that conforms to the body from just a few inches behind the knee to the top of the shoulder with a head restraint (behind the head) of crushable (no rebound) foam. The seat should be a ridged bucket with sides conforming to the thigh, hip, and lats. Any cushion should be no more than 1/2" thick. The harness should pass through the seat and not contact the seat when pulled tight in the proper position. OK, so now no one will ride with me but if they did they would be about as safe as I could make them. I'll stay as close to this spec as possible while trying to put in enough creature comforts to disguise the race car effect. The reason for a minimum cushion thickness is keep your harness tight through the crash. Having a seat belt attaching you to lazy boy stratolounger may assure that your still in the seat when the crash is over but during the crash you are bouncing and rebounding around to the limit of the springs and cushions allowing your body to impact the seat frames. A comment on padding that you may put on interior components or the cushion you use for head restraints. The material should be compressible, but NOT have the ability to rebound. Once deformed it should stay that way. The worst wrecks I had were not hitting concrete or steel Armco at high speed. The worst where hitting those old tires all wired together. The whip lash from the abrupt change of direction as you bounced off the tires was worse that a sustained continuous single direction loss of energy crash. That is why many of the best helmets are only good for one crash. The cushion material compresses but does not rebound. The helmet needs to be relined to assure full protection. On collapsing seats. I don't see the point. Vertical impact is the only direction that actually has an energy absorbing assembly designed into the airframe; the main gear. If the gear isn't up to the challenge why not reengineer the gear? Heck, you've got about 3 feet plus for deceleration. Maybe I'll pull the air bag and sensor out of the Yugo race car and mount it under the seat and have it deploy out the bottom.......... I better get back in the shop..... Dan Montee # 415 PS the harness system should be attached to the airframe, not the seat...unless of course you have an ejection seat, that might be a problem.. +++ #8543 From: "Bruce A. Frank" Subject: Re: restraints You have made some good points. Let me add a little. The best foams, suggested in the past, for comfort, Sunfoam and Tempur(SP?) foam, are also the best for impact absorption...controlling the energy, but with virtually no rebound. As for the landing gear providing the "deceleration", the problem that I see is the crash that collapses the gear with too much energy to be significantly dissipated by the gear. NASA tests have shown that the collapsible seat frame dramatically reduces spinal injury.(but they weren't crashing tube frame {can you say flying, energy absorbing roll cage} type aircraft) I also am using road racing 5 point harnesses. What I see is that one might modify the top of the seat back frame, as they do in automobiles these days, that keeps the belt in place from a point above the shoulders to prevent spinal compression, but allows anchoring the belt to the frame. I have crashed once in a five point and found that the single crotch strap caused no injury (it is 4 inches wide) probably because most of the body's energy was concentrated the forward motion of the upper body. I had bruises on my shoulders and some points of tenderness on my hips, but no pain the more delicate parts. I am not sure that it is possible to belt in as securely, in the Bearhawk type of plane, as one would in a smaller cockpit like in a road racer or race plane, and still be able to be comfortable and to reach all the controls, switches and radios. Does anyone know of an inertia reel mechanism that could be adapted to our application. That said, I once had full inertia reel belts in an off road vehicle....It was very unsatisfactory because I couldn't "cinch down" to really hold me in place behind the wheel. Turbulent air may cause the same problem. A tight lap belt with inertia reel shoulder harness may provide the freedom and safety needed, though there are times when I want the shoulder harness tight also. I may be here that we cannot provide absolute injury free accident protection, but can improve the odds over standard lap and single shoulder belts. Now when is everyone going to agree that motor cycle style crash helmets are the best protection and should be mandatory in the cockpit? See, it is possible to get carried away. Everything we do is and has to be a compromise...after all, what I really want is the Bearhawk to fly at Mach 1 and land at 25 mph. Bruce A. Frank +++ #8545 From: TC4X@A... Subject: Shoulder Harnesses There is a good bit of information at www.faa.gov. Click on the mechanics link on the left of the page.I believe and you will find all kinds of info. Terry +++ #8549 From: Russ and Penny Erb Subject: RE: Re: Shoulder Harnesses Okay, let's approach this from the other end. Lest ye forget, the Bearhawk is hardly an aerobatic airplane (unlike budd's Pitts). My friend's 1977 Cessna 180 had lap belts and a single cross-your-chest shoulder strap, probably like your car has. In fact, the prototype Bearhawks have this type of belts, although without an inertia reel. Apparently somebody thinks this setup is good enough for your car, so why not with airplanes? My plan is to use this sort of harness, with a couple of changes. I want an inertia reel on the shoulder straps. I remember The Bob or Mike telling me that they had to slip off the shoulder strap to move the fuel selector and possibly to reach the flap lever. I also intend to have a lap belt/shoulder strap for both of the rear seat occupants (no one else has mentioned the rear seat yet). I am quite familiar with 4 and 5 point harnesses, as all of the gliders I fly have them. As budd said, this is a very personal decision. My challenge, to anyone who cares to take it, is to tell me in a logical and supported manner why my plan is flawed (if you think it is). You may not change my mind, but I'll be interested to here what you have to say. Russ Erb +++ #8550 From: "Bruce A. Frank" Subject: RE: Re: Shoulder Harnesses The only reservation I have to the single cross shoulder belt is that when there is some side component in a crash the upper body can move laterally away from the belt loosing much of the support from the forward movement of the body(since my TriPacer seats have no side wings to keep me centered in the seats). A double cross shoulder belt system with inertia reels is a simple improvement but it adds an extra buckle on the opposite side of the lap. The five point, or four point without the crotch belt, all operates from one center buckle allowing faster escape when necessary. The racing community has to replace their belts on a time schedule rather than from wear. There are belts available for the asking, that are usually just thrown away, that have no degradation of strength. Even the buckle system is worth salvage and new webbing fabricated to fit the need. (Belts are easy to fabricate with standard home sewing machines, polyester thread, and webbing available from climbing and outdoor stores) Bruce A. Frank +++ #8551 From: "Dan Montee" Subject: Re: Re: Shoulder Harnesses I don't think your plan isn't flawed, but for the sake of debate and a little fun I'll pick up the gauntlet on the logic issue. "My friend's 1977 Cessna 180 had lap belts and a single cross-your-chest shoulder strap, " .......And he has crashed this aircraft and found the system adequate? " I remember The Bob or Mike telling me that they had to slip off the shoulder strap to move the fuel selector and possibly to reach the flap lever." ......Your logic here is that this is a seat belt problem? It could be, if you didn't address the root source problem. "Apparently somebody thinks this setup is good enough for your car, so why not with airplanes?" If it was truly "good enough" would we have air bags surrounding us in our cars?" Apparently someone thought my 56 Chevy was good enough without a seat belt because it didn't have one. All in fun......All these projects are buckets of compromises. Dan Montee # 415 +++ #8553 From: charles.k.scott@d...> Subject: Re: Digest Number 654 We didn't know much about surviving crashes in 1956, we know a LOT more now. Airbags are a consession to the buying public who can't be bothered to belt up. They otherwise offer little additional survivability in strictly head on collisions, and actually offer less survivability in rollovers and side impacts. With Airbags, the occupant STILL has to have the lap belt on, to keep the body inside the vehical during gyrations that inevitably occur in all off road incursions. Most people suffer fatal injuries because they get ejected from the car and it lands on them. The object of the belts is to keep the person inside the vehical where now standard engineered body panels absorb impacts in what is hoped will be G forces survivable by the occupant. So using an adaquate system that keeps you inside the cockpit and from submarining should be as much as we could hope for. Corky Scott +++ #8556 From: Tony Dean Subject: Re: Re: Shoulder Harnesses Well..... While the "Certified" seatbelts are probably more than adequate I have also found that I favor the Hooker Harnesses. I used to think that they were tedious compared to the belts in the Cessnas. After a while flying Citabria with these harnesses I find them quite nice and more comfortable. Regards Tony Dean +++ #8559 From: Ken Beanlands Subject: Re: Re: Shoulder Harnesses My father and I are best described as amateur aircraft salvagers. So far, we've recovered two C-180 (actually, the same one twice), C-185, Citabria, PA-28, Piper Tomahawk and a Hawker Hurricane. We've bid on and investigated about 2 dozen other aircraft that have crashed in the atlantic provinces as well. Out of all of them, only 4 had fatalities. When you consider that some of these pilots were only wearing 2-point lap belts, it goes to show that almost any restraint will probably save your life. A more important lesson was learned from the crashes I've seen. Three of the four fatal accidents that we've seen were caused by the cargo, not the lack of restraint. Two of the planes were being ferried across the Atlantic and contained 45 gal drum auxillary tanks in the cabin that crushed the pilots. The third was caused by unsecured building materials in the back of a light twin that caused fatal injuries. The fourth was a PA-18 that flipped over on the water. The four point harness trapped te pilot and he drowned, but not before he undid his belt buckle by mistake. Suprisingly, the passenger (a former boss of mine) was in the back seat with a 2 point harness on and was able to free himself and get out. He was too late to save the pilot. My opinion (although not very educated) is that there is a very small margin of accidents where a 4 or 5 point harness will save you from serious injury and a 3 point won't. However, what is imperative is that whatever you use should be comfortable and not restrict access to flight controls, otherwise, it does not get used. Second, and more importantly, an adequate cargo restraint system must be used to prevent fatalities. Ken Beanlands B.Eng (Aerospace) +++ #8969 From: Russ and Penny Erb Subject: Rear Seat Belt Attach Points For Mike or anyone who would know: The Jan 01 Bear-Tracks shows the installation of seat belt attach points on either side of the fuselage. A later Bear-Tracks showed a design from The Bob for a rear seat that attaches to the tie down points. The question: Where are the seat belt anchors between the rear seat passengers? Are they attached to the seat frame? There doesn't seem to be a good spot on the fuselage frame to attach to. Russ Erb +++ #8973 From: "rodsmith52" Subject: Re: Rear Seat Belt Attach Points I brought this up a couple months ago. As shown in the newsletters you would only have one belt for both rear seat passengers which I consider unacceptable. I will weld a brackett to center of the T17 tube at station E for the center seat belt attach point. As suggested by Bob I will add a 3/4" x .035 tube from station E to the center of the cross tubes between station D and E to brace the T17 tube. Rod Smith #246 +++ $Id: 2.4.2-Interior-Restraint,v 1.4 2002/03/16 08:16:17 bentonh Exp $