BearHawk, No suspension?

Discussion in 'Home Builders and Sport Pilots' started by NordicDave, May 3, 2021.

  1. NordicDave

    NordicDave Pattern Altitude PoA Supporter

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    Just saw a blog post on General Aviation News of a family building a BearHawk 5, and noticed the landing gear was rigid.

    Seemed odd the only flex was in the tires. The gear legs looked rigid rather then spring steel or such.

    Edit: I see on closer examination there is a small pivot point where the gear meets he fuselage.

    D85E5A6B-D6CA-4B99-A72E-332A188CA484.jpeg
     
    Last edited: May 3, 2021
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  2. Stewartb

    Stewartb Final Approach

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    Generally similar to other tube gear in the fleet. They use shock struts. The angled tube under the main gear legs.
     
  3. tsts4

    tsts4 Cleared for Takeoff

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    Your closer examination is correct. The Bearhawk uses a strut suspension system. You can just make out the right strut can in the pic you posted. I've talked to a number of Bearhak pilots and they say it works really well in helping keep the aircraft planted. IOW the strut system (a big spring in a tube) soaks up the arrival energy and helps reduce/eliminate any tendency to bounce.

    This is a pic of the Bearhawk 5 prototype's landing gear.
    IMG_20200519_113443243.jpg
     
    Last edited: May 3, 2021
  4. GRG55

    GRG55 Final Approach

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    The 'A' frames pivot at the two attach points to the fuselage. @Stewartb covered the oil-filled spring shock strut.
     
  5. NordicDave

    NordicDave Pattern Altitude PoA Supporter

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    Thanks guys. It’s an intriguing kit. Interesting looking at accident data for steel tubular framed aircraft, the survivability appears very high. Referencing other planes like the Sportsman.
     
    Last edited: May 3, 2021
  6. wanttaja

    wanttaja En-Route

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    Survivability probably more driven by generally lower speeds and the high-wing structure providing better protection for occupant's heads. Not enough Bearhawk accidents yet to come to any specific conclusions.

    Ron Wanttaja
     
  7. akschu

    akschu Filing Flight Plan

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    I'd agree the data is limited, and it's unwise to draw conclusion on anecdotal evidence, but there are some things about the bearhawk that can make it very safe. Search youtube about spin/stall characteristics, also note that if you take out all of the power and hold the stick full aft, it does something like a falling leaf stall where the wing is pretty level and it's falling flat. The rate is around 700fpm, which is slower than the rate of a BRS parachute. Being experimental means that you can put real 5 point seatbelts in it without a gob of money. Other notable safety aspects are the doors are much bigger and easier to get out of, especially the back seat, it has a skylight so you can see into a turn, gear has actual shock absorbing instead of springing you back in the air like a 180.

    There are things that aren't great either. The fuel system routing isn't really well designed or documented, so virtually every builder moves stuff around, which causes them to all have one off fuel line routing. I don't care for how the factory setup calls for a BOTH fuel valve, but no cross venting between tanks. The stock seatbelt attach points are too vertical and only shoulder belts.

    Like any experimental, you can do what you want, so fixing this stuff isn't hard, which means some bearhawks are for sure safer than others.

    Oh, and I used to think that rag and tube was safer than a metal airplane because I reasoned that the roll-cage would hold up better than the pop can, but after seeing a lot of cessna crashes, I have to admit, the tin can cessnas absorb a lot of energy when they are crinkling up, and for the most part do a good job keeping the pilot as safe as you can reasonably expect. That said, it's not super hard to weld in new tubes and recover, but uncrinkling a cessna is pretty difficult.
     
  8. GRG55

    GRG55 Final Approach

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    ^^^ This.

    The stall speeds of the airplane has always been one of my selection criteria for the ones I have owned over the years. In the event of an accident its all about how much energy has to be dissipated. That, for me, is more important than whether the plane is welded steel tube structure, monocoque riveted aluminum or composite.

    Each of those materials systems has different characteristics in how it will absorb energy in an accident. But the starting point is how much energy does the airframe have to absorb. It's coincidence that both my current airplanes, the Aztec and the Husky, have welded steel structures - their low stall speeds and excellent low speed handling characteristics factored more heavily into the ownership decision than the construction type.
     
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  9. wanttaja

    wanttaja En-Route

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    The utility of that depends on the pilot having the appropriate training, AND the presence of mind to use the capability when needed. Both factors are usually lacking. The full-aft falling leaf stall is great for a demo, but I suspect it's not likely to be used in emergencies. The only instance that immediately comes to mind is saving oneself during an inadvertent entry to IMC conditions, and that happens a whole lot LESS than people think it does (about 1% of homebuilt accidents). It was used in the earlier days of aviation (the Dole Race being one example) but I don't think pilots are really trained for it these days.

    Lots of homebuilts have good stall characteristics; I doubt the Bearhawk stands out there. About 16% of homebuilt accidents involve stalls, but it's a hard metric to nail down by aircraft type because some types have a tendency to attract less-experienced pilots.

    Shock absorbing landing gear is great (or so I've been told...I've been flying a plane for the past 25 years with rigid landing gear) but it won't really affect the fatality rate (landing accidents are rarely fatal).

    I know you're thinking of "ease of escape after an accident" when you mention the big doors, but as an engineer, "compromised aircraft structure" is what comes to mind. A structure without a door opening will be stronger than one with, and a bigger door just means a more-compromised structure. But then, I've been flying a plane for the past 25 year that doesn't HAVE a door....

    The Bearhawk is going to have the advantage of all high-wing aircraft; better protection for the occupant's heads.
    upload_2021-5-3_12-19-39.png
    (Generic diagram...not all planes have the diagonal bracing)

    Ron Wanttaja
     
  10. Spring Ford

    Spring Ford Pre-takeoff checklist

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    AN2

    "A note from the pilot's handbook reads: "If the engine quits in instrument conditions or at night, the pilot should pull the control column full aft and keep the wings level. The leading-edge slats will snap out at about 64 km/h (40 mph) and when the airplane slows to a forward speed of about 40 km/h (25 mph), the airplane will sink at about a parachute descent rate until the aircraft hits the ground.""

    It says on wikipedia, referenced to
    Gordon,Yefim & Komissarov, Dmitry. “Antonov An-2”. Midland. Hinkley. 2004. ISBN 1-85780-162-8
     
  11. akschu

    akschu Filing Flight Plan

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    ALL safety depends on training, so I'm not talking about the pilot, I'm talking about the design, and having flown a fair number of taildraggers, the bearhawk goes as slow as most of them, except maybe the cub/clones.

    Actually, it does. Out of the people that have done spin training in it, everyone agrees that they were unable to make the uphill wing stall first in a slow uncoordinated turn. When the benchmark for this type is the cub, that's a welcome change.

    Fair enough, but again, it's much easier to flip an airplane that likes to bounce, especially when you have some stupid wind.

    Not just big doors, more doors. In a 180 you have two doors to escape from while the bearhawk has 4 if you count the rear doors as two since they swing out both ways. Yes, there is the possibility of a compromised structure, but the rear door is pretty well braced, and you have the windows you can kick out as well.

    I'm not saying that the bearhawk is safer than a 180, it's all about pilot and builder skill.

    What I was trying to do is document some of the safety pros/cons I've noticed with the design compared to it's main competitors.
     
  12. Stewartb

    Stewartb Final Approach

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    1740F4E9-658F-4894-902C-C39F675E49F3.jpeg Gas shocks are a game changer on a Cub. The Bearhawk gear geometry doesn’t look right. The one I’ve observed would benefit from Cub gear.
     
  13. akschu

    akschu Filing Flight Plan

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    Agreed there. The cabane V is needed to make the suspension work like that, and you can buy it as a bolt on from Shock Monster. The con of course is that it's a LOT more drag.
     
  14. tsts4

    tsts4 Cleared for Takeoff

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    Maybe--I'm definitely not smart enough to comment one way or the other. However, I think Bob Barrows, the designer of all the Bearhawks, is a pretty smart fella so I defer to his engineering expertise. That's not to say that there's not room for improvement, but as I posted above, the Bearhawk pilots I've talked to have nothing but praise for how it works. YMMV....