Best Shoulder Harness Arrangement?

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farmrjohn

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farmrjohn
I would like to add shoulder harnesses to my Aircoupe. Is a three point (diagonal across the chest) or four point (on strap across each shoulder) better? There is an STC for a diagonal strap and several 337s including engineering data for the four point so field approval "should" be possible. My google fu has not turned up any answers so am interested in what the collective thinks.
 
At one point the Feds made a really big deal out of shoulder harnesses. I’ve seen some nice installs have to come out at Annual because of no data for some tests. One of these was an extremely high “ G - test “ that could damage the fuselage. I felt this was counterproductive of most harnesses are better than none.

They have since simplified the Install Regs so in many cases it will be a Minor Alteration. Hence no Field Approval or STC needed. I did put some in a Coupe many years ago using cables to an attach point.

IMHO Anything that keeps your face out of the panel is a good thing.

AC 43.13-2 has technical guidance.
 
A properly installed 4-point will be safer than a 3-point. I believe a 4-point is the minimum required for aerobatics, not that you’ll be looping your coupe. A 5-point (anti-submarine strap) would be better yet. But a 3-point is a big advantage over just a lap belt.

Which you do is between you, your A&P, and your wallet.

FWIW, I have a 3-point in my Beech.
 
farmrjohn said:
Is a three point (diagonal across the chest) or four point (on strap across each shoulder) better?
Click to expand...
4 point is definitely better. But 3 point is better than none. I dont fly in an aircraft without shoulder harnesses. As mentioned the FAA through the Safer Skies initiative have made a lot easier to install shoulder harnesses. Below are 3 additional links that get into more detail. The easiest and most expensive is to buy an STC kit. However, if your mechanic is adventurous you might be able to get something installed at a more reasonable price by following the existing guidance.
https://www.faa.gov/sites/faa.gov/files/aircraft/gen_av/harness_kits/shoulderpolicy.pdf
https://www.faa.gov/regulations_pol....cfm/go/document.information/documentID/22261
https://www.faa.gov/sites/faa.gov/files/aircraft/gen_av/harness_kits/AC234.pdf
 
The most recent policy I'm aware of is ACE-00-23.561-01, which allows for seat belt upgrades as a minor change if certain criteria are met. The FAA's policy is that seat belt replacement and upgrades improve safety and therefore should be encouraged.

The first link Bell206 posted is a summary of the actual policy
https://www.regulations.gov/document/FAA-2015-1621-0005
 
The problem with a 4 point is submarining. The lap belt rides up and you slide out under it.

With a 3 point, the upper body twists and moves forward so you trap the lap belt in the V of your legs and upper body.

Schroth of Germany makes 4 point dual use (track and street) that have a weak section the expands on of the shoulder straps to allow the upper body to rotate and trap the lap belt to prevent submarining.

But as said, any shoulder harness is better than none.
 
Thanks for replies. The four point method would require drilling holes (for rivets and torsion rod to hold a clevis for attachment point) so requires a 337 field approval. I have an inquiry into BAS to see if they have an assembly that would attach to the clevis for that arrangement. The AmSafe inertial reel unit used in prior 337s is no longer available. At this point ideally an inertial reel shoulder harness would be nice, but it doesn't look like that option is available. The STC three point is also fixed. The three point may be more cumbersome to fasten/release with the cockpit geometry. I guess a good poll would be to see how many 4 points vs. 3 points are in use.
 
We have 4-point BAS harnesses. The risk of "submarining" if you are wearing the lap belt portion low and tight - as you should - is very low.
 
If you go with a 4 point harness and the shoulder straps are not held captive close to the top of the seat back, then invest in a tie strap or whatever they call it, so the straps can’t separate enough to slip over a shoulder during moving around.
 
Hooker is an excellent company . I bought a 7 point acro harness last year for old Decathlon specs. Later updated my frame to current specs. Hooker just reworked my harness, which involved swapping H harness for Y harness and sewing in 2 more anchor buckles, at no charge.
 
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