C23 Shoulder Harness STC?

[SkyMan]

Thanks that is all very helpful.

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I'll try to post pix of gusset and assembly here. I have a recent install (last week). Part numbers are LH upper gussett 169-534107-13, RH 169-534107-14. Research BAC site for shoulder harness, about 20 pages of good info. The gussets are easy to make, I copied 4 from two I received, and it was easy work. Pix attached are of pilot side, passenger is same install, only mirror image. Hard part was finding and overhauling the shoulder strap. This version is the Rellihan-described "simple" install. The shoulder strap is independent of the lap belt. The upper anchor is made up of the components shown in the pix, and the lower anchor is the lap belt anchor next to the trim wheel.

[Unclerap]

Marty:

Thanks for your input. A few comments on your comments: The aft stringer is as you say, worthless, so putting a bunch of rivets in that stringer were of no value. None of the rivets in the pix are cherrys. The bracket is not a d-ring bracket, it accepts a stud per Mike Rellihan's idea. Finally, the install might not be strong, but it's stronger than nothing and that is my goal, just trying to keep my face of the panel in a low speed impact. My theory is anything above about 60kts kills me, anything under that, I'm trying to survive with minimal head injuries. Hopefully, if I know how to fly, this is all a moot discussion.

Rap

Reviewing the photo of the D-ring gusset, I can tell you that it's not a strong installation. One rivet aft of the door frame and a blind fastener at that (no they are not as strong as solid aluminum rivets, regardless what Cherry says). Also, the early Mice have a real light gauge stringer going aft of the door frame at this location. Without re-enforcement, I doubt the installation will provide much protection when called upon in an emergency. Better than nothing, but probably not much more than that. At the least, I would extend the gusset aft and locate and install several more fasteners common to the gusset and the stringer aft of the door frame. Cherry rivets will work if you use enough. I would not use a gusset from a later model on an early model. They won't fit as the picture shows (only room for a single fastener aft of the door frame). This is not something that needs to be precise and should be customized for your airplane. You can eyeball the size of the gusset and be pretty darn close. The larger the gusset, the stronger the installation. I also wouldn't use anything thinner than 0.040" and use 2024-T3 or stronger alloy.

[mvanover]

Rap,

Point well taken. Perhaps the photo or my eyes were a bit fuzzy on the blind fasteners. The aft stringer isn't too strong, but coupled with a longer bracket (doubler) will provide more strength for each rivet you put in the stringer and the doubler. It will distribute more of the load to the skin and make for more overall strength. The FAAs static strength requirement in AC23-4 is 1530 lbs (normal category) and 1710 lbs (utility and aerobatic categories) distributed 60% on the seat belts and 40% on the shoulder harness. While I think everyone would be happy with the "normal" category, I doubt an early Mouse will meet that without a well engineered installation. But like you say, anything is better than what you have.

[gribbled]

... anything is better than what you have.

I think that is the jist of the FAA shoulder restraint policy: (from the last paragraph)

if a shoulder harness is not required equipment, it is not essential to the safe operation of the airplane.Therefore, CAR 3.652 and § 23.1301, before Amendment 23-20, should not be used as a basis to projibit should harness installation by minor change...

I think that really helps us owners of older birds, when shoulder harness weren't even offered as an option. "Minor change" is a good thing.

[j_w_bruce]

Dave, whats the link to that guidance or part it comes from?

Thanks
JB

[gribbled]

http://www.faa.gov/aircraft/gen_av/h...lderpolicy.pdf

Dave, whats the link to that guidance or part it comes from?

Thanks
JB

[j_w_bruce]

Thanks Dave, I saved it to my laptop for use a bit later...

JB

[Unclerap]

I have two shoulder straps I made for my mouse that are no longer needed. I made them out of Tomahawk shoulder straps, with a male tab on one end that inserts into a rear seat lapbelt, and the other end goes between the male and female latch pieces for the front seat occupants. This falls in the “better than nothing” category. You are welcome to them if you want to use them until you get a more permanent install. First BACer to PM me with snail mail address gets them gratis.

Rap

[duknic]

Thanks for the offer Rap! I have single shoulder, so I will leave them for some poor soul who is stuck with only a lap belt. I am still kicking around the idea of a bar across the top of the cabin...

[gribbled]

In the downloads section

http://www.beechaeroclub.org/downloa...do=file&id=937

Also for those interested, I measured the minimum length required in the hangarmouse. With the seat fully forward, I think the belt would have to extend roughly 61" to fit around me. Of course I would never fly with the seat that far forward. On the other hand, the more "circumference" a pilot has, the longer the belt will have to be. Just a datapoint.

As near as I can tell, the Beech kit for my plane had 500779-3, which is a 90" long black belt. Seems a bit overkill.