Engineering Change for Bearhawk 4-Place and Patrol

[jaredyates]

Bob Barrows writes: The landing gear shock strut has been changed on the 4 Place Bearhawk and the Patrol. This change was done to increase gear side load capability (ground loops) and cost reduction. The streamline tubing has been replaced with round tubing (1 1/8 x .065"). The shock strut should be faired for reduced drag. Safety update terminology: ENGINEERING CHANGE: A change to current serial number drawings onward - non-mandatory - may or may not be published. This change is the result of a product improvement, update or modification. Or a minor change of the design to ease manufacturing, maximize utility, economize materials or ease assembly. For questions or clarifications, please contact Bob at R&B Aircraft.

[22LD]

Are quickbuild purchasers going to be sent the new struts?

[marcusofcotton]

Can anyone speak to the exact location of the failures? Wondering if they are typically failing somewhere mid length of the streamline tube, the lower end of the reinforcing cuff off the cylinder, upper end of same, or near the axle end.

[jaredyates]

Mark, if you ask Bob, let us know what he tells you. I've only seen photos of two incidents, and in those the failure was along the middle of the tube. As I understand it, the round tubes have been available as an upgrade option for kits, but keep in mind that I'm really only the messenger with these things and not the source.

[Mark Moyle]

Wonder if The Bob considered inserting into the streamline tubing a round tube like the Maule struts use?


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[Mark Goldberg]

This is a non mandatory change. My personal Bearhawk has over 1100 hours and a TON of take offs and landings after doing demo flights for 10+ years. Never an issue. The only time this change would help is when you start going sideways on the runway and putting a side load on the shock strut and gear. Ground loop scenario. However, Bob has felt all along that beefing up the shock strut could potentially result in much more damage to the fuselages of planes that ground looped. Instead of replacing the L/G and shock struts and maybe some wing tip damage - there is a greater likelihood of fuselage damage which is much more expensive to repair. So it is not so certain the everyone should do this.

As far as what the factory might do for existing customers - we will not replace everyone's shock struts. But if you wanted to replace what you have we will make some kind of special deal. Not sure just what would be fair. Again, this is not a mandatory change for safety of flight. Not at all.

There is some streamline PVC tubing which can be glued around the 1 1/8" x .065 to make it the same drag as before. Mark

[22LD]

Thanks, Mark, for the reply. The more I thought about this, the more I decided I'm not going to change the struts. If you try hard enough you can break anything.

[marcusofcotton]

Wonder if The Bob considered inserting into the streamline tubing a round tube like the Maule struts use?


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Precisely what I've been considering for some time, wasn't aware that Maule had that. Mark, do you know what wall thickness Maule uses for the inside tube?

Thanks!

[marcusofcotton]

Mark, if you ask Bob, let us know what he tells you. I've only seen photos of two incidents, and in those the failure was along the middle of the tube. As I understand it, the round tubes have been available as an upgrade option for kits, but keep in mind that I'm really only the messenger with these things and not the source.

Thanks for the reply Jared, I suspected same but thought it might be vulnerable at the lower end of the lower end of the cuff below the cylinder as well. I might use a 3/4 x .058 full length, possibly with a few inches of 1/2 x .049 at the top end. Rosebud welds to secure.

[jaredyates]

Ernie Green did some internal tube reinforcements. Let me know if you'd like to contact him and don't already have a way. Some years ago the Hales Landing bunch worked out a round tube strut with rod ends at the top and bottom. I think Mark makes good points about the compromise and Bob's design intent. Bob has not replaced his struts as far as I know, and says he'll just not ground-loop the airplane.

[rv8bldr]

..... and says he'll just not ground-loop the airplane.

That's what I said about my RV-8, until my left brake went soft in a stiff crosswind last fall. A new tail wheel stinger, weldment, bottom aft skin, and outside half Cleveland rim later, I know enough not to say that kind of thing again :-)

[Av8rPaul]

I recently saw a Maule M4 rebuild where the owner installed safety cables on the gear. Has anybody done so on a Bearhawk?

[marcusofcotton]

Haven't heard of any, nor of failures in which they may have helped - though there may be some.

[Mark Moyle]

Precisely what I've been considering for some time, wasn't aware that Maule had that. Mark, do you know what wall thickness Maule uses for the inside tube?

Thanks!

No I don't. My maule struts are painted and installed. Alaska Airframes/Ak Bushwheel builds them. Josh or Israel can probably give you that information is you call.
Mark M.

[marcusofcotton]

Thanks Mark.

[SpainCub]

New member, looking to start build soon. Question here is, humidity. If there's streamline tubing, regardless of the material, if its not airtight, will it not be a focus of condensation and possible corrosion at the bottom of the strut?

[marcusofcotton]

Welcome SpainCub. If you're speaking to Bob's note on the drawing, yes it surely is an area one wants to approach thoughtfully and carefully to prevent troubles. Otherwise, it's the same as any other tubing with various approaches, generally consider oiling/air tight strategies.

[Dan R.]

When the streamline LG strut fails it will at about 12"-13" above the lower end of the strut.

[jaredyates]

Dan would be one of the Hales Landing group that I mentioned before, along with Dallas and a couple of others.