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Seatbelt/Shoulder Harness Integrity
Gjunkie1
#1 Posted : Wednesday, October 25, 2017 4:18:03 PM(UTC)
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Location: Nashville, TN USA

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As some of you might know, there was a serious mishap at the Farmville contest last Friday, 20 Oct 2017.

Simple background: During Contest practice, 2 conventional gear airplanes landed simultaneously in opposite directions and collided spinner-to-spinner at an estimated combined velocity of 40-60 mph. (I know, it sounds impossible doesn't it....)

I want to make everyone aware of a potentially hazardous situation that is worthy of the community's immediate attention.

I come from a Naval Aviation background, so I've seen my share of mishap investigations. In the interest of safety, if during the course of an investigation a safety-related issue came to light that was worthy of immediate dissemination, the mishap squadron would publish a Naval Aviation Hazard Report (HAZREP) message, detailing the issue.

In that vein, here is an aerobatic community (and GA applicable) HAZREP:

Before your next flight, you should positively verify the complete integrity of your shoulder restraint system. Do not assume that because it might look good on cursory viewing, that it is good. Get back in the hard-to-see recess and triple check every piece-part. Consider preemptively replacing or beefing-up connecting hardware.

(And as a side-note, even if you aren't doing the higher negative-G type flying found in Advanced or Unlimited, you should be bruising yourself with your lap-belt tightness, and cinching down hard on your shoulder straps. They stretch under significant load.)

Dave Taylor
Steve Johnson
MX2
Nashville, TN
Guest
#2 Posted : Friday, October 27, 2017 8:44:40 AM(UTC)
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Wow.. Prayers to the people and families involved. I could see how this easily happens.

James Cartwright
Eagle II Driver
Nanchang CJ-6A Driver
Guest
#3 Posted : Saturday, October 28, 2017 5:38:15 AM(UTC)
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HAZREP addendum:

I'm relatively new to the sport, so I did a little research, and ended up talking to a Hooker Harness rep.

As background, it seems like there are two basic shoulder harness setups.

Some shoulder harnesses are two totally separate pieces, and do not touch at all. Each side is wrapped around a cross bar behind the seat and individually secured using a standard 3-bar Slide Close. Kinda like this: Decathlon Hooker Harness Install Instruction PDF

[Ed. note: See Fig. 4A on page 16 of linked document]

(As a total aside, and not germane to this mishap, notice the NOTE in this drawing, that the webbing strap should be put thru a 3rd time to lock it in place.)

In other installation configurations, the two shoulder straps join together behind the pilot with various end-fittings or structures, like this:
[Ed. note: See Fig. 4B on page 16]

which are then jointly secured to some kind of cross bar farther aft. That securing piece is often a length of aircraft cable with standard thimble and swage fitting, like this:

Inline image

The Hooker Harness rep piped up right away and said there should be three (3) swage fittings on each end of the cable. It did not appear like that was the setup in the injured pilot's experimental aircraft.

During the course of my conversation with the rep, and also not germane to this mishap, the subject of webbing deterioration due to UV rays came up. Yes it does happen, just like it does to our parachutes. One pub I saw said the webbing should be replaced every two years(!) The Hooker Harness rep gave me some good gouge that I am copying below:

In the aerobatic world, most aircraft are hangared throughout the week and the longest exposure they get is at contests and airshows where they sit on the ramp. Exposure damage can be reduced on the ramp by simply placing a cover or towel over the cockpit (this will also help with prolonging the life of your parachute).

Most of the time UV damage is best seen through color change. If the top side of the webbing is noticeably different in color than the bottom or unexposed sections then replacement should be considered. This is more readily seen in darker webbings (silver webbing is difficult to visually see UV damage).

Some aviation comparison replacement cycles are:

1. US military, 13 years from date of manufacture (replace)
2. EASA, 12 years from date of manufacture (replace or overhaul)
3. Many US parachute manufacturers, 20 year service life
4. Extra Aircraft, 6 years (replace or overhaul)
5. Cessna Aircraft, 10 years
6. As there is no pre-set aviation rule, we recommend replacement based upon condition


I hope this additional actionable info helps make us safer in the future.
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