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  • Bearhawk crash survivability

    I've done quite a bit of reading up on the 4 place bearhawk as a possible future (quite a ways into the future) builder and have been impressed by everything I've seen.

    I know that they are solid built airplanes and hate to bring up a morbid topic, but I am wondering how the crash survivability would be in comparison to a cessna 172/182 or piper Cherokee. Many times when a small Cessna has to make a forced landing in a small space or soft terrain the plane ends up flipping over, but the fuselage seems to be able to hold up enough that injuries are usually minor.

    What's the general consensus on the bearhawk safety vs certified planes in the unlikely event that there is a situation like this?

  • #2
    You are not considering the difference in the structures of a Cessna versus a BH. Cessna is an aluminum can. Nowhere near the crash protection that a steel tube cage provides on a plane like a BH. The certified versus experimental is not the criteria to look at. It is the structure. There are certified planes with steel tube fuselages like the BH. Mark

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    • #3
      Also, slower landing speeds (lower stall speed) will reduce the energy being dissipated in a crash. This makes it more survivable too.

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      • #4
        One reason I chose the BH was because of safety. It lands slow, (energy and hence damage increases by the square of impact velocity). Its a high wing so if it goes on its back you are protected, There are lots of doors and windows for emergency egress and they are not as suseptable to jamming as an aluminum plane, and it has the steel tube fuselage. NASCAR and other racing land vehicles use steel tube because it is strong. It keeps its shape under crash loads. The steel tubing also give you very good anchor points for seat belts. I highly recommend a four point harnesses with inertia reels.

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        • #5
          Thanks for the responses, I assumed the tube
          fuselage was strong but hadn't heard any first hand experiences with it and have not seen one in person.

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          • #6
            I think the BH is much more likely to stay upright in an off-airport landing also. The nosewheel doesn't stand much of a chance in anything rougher than a grass runway.

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            • #7
              Originally posted by jaredyates View Post
              I think the BH is much more likely to stay upright in an off-airport landing also.
              Totally agree. I had to dead-stick my Kitfox II in a field with thick vegetation varying from 2 - 4 ft in height. We landed as slow as possible and I applied full back stick immediately, and amazingly we stayed upright, which I partially attribute to the slow landing speed and little wheel in back. The BH 4 place lands about the same speed as my Kitfox did.

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              • #8
                Just checked my weight and balance. The tail wheel on my Bearhawk weighs 107 pounds with the lycoming 180 hp. With full up elevator it is going to take a lot to nose the plane over.

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                • #9
                  Wouldn't we expect the BH structure should be stronger than something like a Stinson 108 or a short wing piper or maule/supercub ?
                  Lots of old pics of maules, pipers that landed in less than optimal senarios and the crew compartment protected the occupants well.
                  I would expect a new BH to be even stronger since the tubing hasn't had 40 years of environmental exposure and maybe Bob just made a "little stronger" critter.... (?)

                  Seen lots of pics of common stressed skin things that ended up looking like a Styrofoam cup run over by an suv tire-
                  Once the stressed skin shape begins kinking/collapsing it loses its " shapefactor " rigidity----- after that its like wet paper.... :-)
                  Then again maybe Im just biased

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                  • #10
                    This is not based on any solid science, but the tube airframe sitting in my hangar right now is an incredibly rigid structure! Given gross weight of 2600 ( this is from a memory that has a history of failure) it would take an incredible amount of energy to cause failure. The more likely cause would be deceleration of the occupants at g-forces beyond their design. I am trying to develop a z type bracket to fail at a predictable rate in my seat bottom in the event of a hard vertical g-load on impact. My goal is to have the bracket bend almost to the bottom on impact to dissipate the G-load on the airframe. 31 inch tires and stock landing gear will also serve to reduce the force of impact

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                    • #11
                      Originally posted by Bearhawk535 View Post
                      The more likely cause would be deceleration of the occupants at g-forces beyond their design. I am trying to develop a z type bracket to fail at a predictable rate in my seat bottom in the event of a hard vertical g-load on impact. My goal is to have the bracket bend almost to the bottom on impact to dissipate the G-load on the airframe. 31 inch tires and stock landing gear will also serve to reduce the force of impact
                      This is exactly why I chose to go with high-density memory foam for my seats. They absorb a lot of shock from that type of impact, if you choose your "stack" right. The more dense foam absorbs more shock than the soft foam, but isn't as comfortable. By stacking layers, starting with the heavier density foam at the bottom, and lighter density at the top, you get a comfortable seat that will also dissipate a LOT of vertical Gs. My "stack" would not work for you (in all probability), because I weigh more than most, but by talking to the experts, you can design a stack that will be both comfortable and safe. No "progressively collapsing structure" required...
                      Jim Parker
                      Farmersville, TX (NE of Dallas)
                      RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)

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                      • #12
                        For race cars, seats are made from Styrofoam beads and in many cases mounted directly in the chassis. The beads are mixed with an epoxy resin to form the seat. This is called a bead seat.

                        Bead seats represent a big advance in safety. The seat is ridge but on impact it deforms and absorbs the impact loads. This is exactly the way crash helmets work. Foam alone does not give the same level of protection. A simple system would use a Styrofoam base of several inches in the bottom of the seat pan and then have you seat foam on top of that. The less regular foam the better

                        The down side of bead seats is that they are molded to individual drivers.

                        In a crash situation, the goal with a bead seat is to have the driver's body start decelerating the very instant the car starts to impact something.

                        The other asset of a bead seat is it gives the driver a much better feel of what the car is doing than a soft foam type seat. In an airplane, comfort over long periods is paramount so I would think that something that is a combination of Styrofoam and regular seat foam would be optimum for comfort and safety.

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                        • #13
                          The foams I'm using are used to build crashworthy seats for certified helicopters, where vertical impacts are devastatingly common, and used to have almost 50% odds of the crew suffering "spinal compression" injuries. The bottom layers are almost rigid, but deform very slightly when you place weight on them. I suspect they are providing the same effect as the "bead/epoxy" slurry mix would provide, but are not just "one time use". Unfortunately, they probably do cost a LOT more than styrofoam beads and epoxy...!
                          Jim Parker
                          Farmersville, TX (NE of Dallas)
                          RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)

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                          • #14
                            What is the most common direction of impact for an occupant? Into the seat, or toward the panel?
                            Mark
                            Scratch building Patrol #275
                            Hood River, OR

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                            • #15
                              See, that's the thing... it all depends. If you are in the landing configuration (nose high, near stall speed, and descending), you're going to experience both horizontal (30-35 mph = roughly 3000 fpm) and vertical (500-750 fpm) impacts. Your spine can take a lot more horizontal impact than it can vertical. Shoulder harnesses are critical to prevent panel impact, but some of the "forward" impact will be directed downward... Thus the concern for "vertical "G" absorption.
                              Jim Parker
                              Farmersville, TX (NE of Dallas)
                              RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)

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