Seat Belt Replacement After an Accident

[ahramin]

Does anyone know of a requirement to replace seat belts after an accident (for occupied seats).

[Sam Buchanan]

If you are inquiring about an aircraft with an experimental airworthiness certificate I am not aware of a regulation requiring the installation of seat belts.

[Marc Zeitlin]

If you are inquiring about an aircraft with an experimental airworthiness certificate I am not aware of a regulation requiring the installation of seat belts.14 CFR Part 91.107(3) states:


(3) Except as provided in this paragraph, each person on board a U.S.-registered civil aircraft (except a free balloon that incorporates a basket or gondola or an airship type certificated before November 2, 1987) must occupy an approved seat or berth with a safety belt and, if installed, shoulder harness, properly secured about him or her during movement on the surface, takeoff, and landing.

Since all E-AB aircraft are subject to Part 91, and there's no exception in 91.107 for experimental aircraft, all occupants of E-AB aircraft must wear a seatbelt, and if they're installed, a shoulder harness. Given this, it would be hard to legally fly an E-AB aircraft if it didn't have seatbelts, ergo, seatbelts are required for E-AB aircraft.

[Sam Buchanan]

Point taken....even though there are parts of Part 91 that don't apply to experimental aircraft per the Operating Limitations (instruments for day VFR flight).

Now, how do you answer the original question....which is obtuse since we don't know whether the question is about experimental or standard aircraft?

[rwanttaja]

Does anyone know of a requirement to replace seat belts after an accident (for occupied seats).

I'd say that the answer is "no." Part 91 addresses reporting procedures and such matters, but doesn't specify any other post-accident actions. Part 43 states who can replace belts, but doesn't specify any criteria for replacement.

AC43-13-1B (Acceptable Practices) states that belts must be replaced when they show deterioration (9.46), AC43-13-2A (Alterations) merely gives guidelines for installing them.

It's possible that manufacturer's guides may specify the need for replacement after accidents, but there are "accidents" and there are "accidents." Overshooting the runway into an embankment will put a lot more load onto the belts than a gear-up landing.

So, I'm of the opinion that they only have to be replaced on condition. If a post-accident examination shows damage/stretching, replace. If the airplane is bent, replacing the belts will probably be the cheapest part of the repair.

Ron Wanttaja

[Sam Buchanan]

For an experimental aircraft the over riding factor is the statement signed by the person who does the condition inspection:

"....this aircraft is in a condition for safe operation....."

[lathropdad]

My back ground is in automobile racing. As such I have to abide by the rules of the racing organization that I am participating in.

As for seat belts and shoulder harness, I have tested a couple systems myself and I think that the rules governing race car belts may be a good indication of how someone should look at the belts in their plane. For Sports Car Club of America, belts must be replaced 5 years after the date of manufacture. The belt material must be replaced and a new manufacturing date affixed to the belt system. This is done because of the nature of the belt material and the fact that it degrades over time. These rules are not the result of a bureaucracy sitting down one day and making up a rule. Rules like this come about because of the injury or death of a contestant because of belt failure.

For an airplane, I think that replacing belts every 5 years might be a bit extreme but maybe 10 years maximum or when there is sufficient deterioration to require that the belts be replaced.

[Ron Blum]

Does anyone know of a requirement to replace seat belts after an accident (for occupied seats).
More likely than not, you will not find a regulation that states the seatbelts need to be replaced. But call and ask a manufacturer; they will know. If the aircraft was truly in an accident, I would replace the belts. In certificated airplanes (and you can watch the front end impact tests of automobiles, too), the belts stretch a lot during impact. If a stretched restraint is reused in the stretched condition, it will not give on initial impact and stop the occupant in a quicker fashion, imparting higher G-loads into the body.

[bigdog]

Rewebbing belts is dirt cheap, ~$10/piece. But you have to do it before the TSO tag is gone/unreadable. You need a readable TSO tag to pass annual for the certified crowd. As long as they can make out that it is a TSO tag, they will reweb and add their own TSO tag to the result.

For replacement after an accident, consider that climbers retire any rope that has arrested a fall. It did its job. Cheap insurance.

[ahramin]

Thank you all. The belt manufacturer did not have anything to say other than check for condition. Many good points here and it's much appreciated.

[Marc Zeitlin]

Now, how do you answer the original question....which is obtuse since we don't know whether the question is about experimental or standard aircraft?Whether Exp. or TC'd, I agree with Ron W.'s and your subsequent posting that there is no "requirement" for replacing the seat belts, and that they should be replaced on condition for all the reasons you guys state.

Now, most of the seatbelt labels I've seen indicate a 10 year lifetime (by the MFG), so on my CI reports I indicate to my customers when their seatbelts are over 10 years old, but if they look to be in good shape (and the airplane is hangared without much UV exposure) and the stitching looks good, I don't refuse to sign off a CI because of older seat belts. But when they get 15, 20, 25 years old, I start pushing harder for a replacement, even if they don't look too ratty, and give my customers a few years to do so before I get belligerent about it :-).

[dougbush]

I've heard that child car seats must be replaced after an accident. Somehow they are only able to absorb the maximum energy once and are thereafter compromised. It was recommended never to buy or accept a used child car seat if you can get a new one.

[FlyingRon]

I've heard of HELMETS needing to be replaced after they receive a shock (usually from an accident) and also climbing ropes once you've got a fall. The idea is that you've deteriorated the energy reducing material.
Seatbelts on the other hand aren't designed to stretch or give.

[CraigCantwell]

For a data point, any fall arresting harness or lanyard at work is removed from use and destroyed if it was involved in a fall. Otherwise, they are replaced on a 5 year cycle, and we have about 750 full body harnesses and several hundred lanyards and reels.

For force numbers...a 200 pound person falling 9 feet will have an impact force of about 3600 pounds....impact velocity of only 16 mph....

[Mike M]

"Seatbelts help reduce the risk of injury in many types of crashes by helping to properly position occupants, while the seat belt is designed to stretch at a controlled rate to absorb impact energy and reduce the severity of the occupant’s deceleration."

This is why one shouldn't simply alter the seat belt fabric lengths and mounting methods of certificated systems. Nor systems designed by qualified engineers with expertise in the area. For example, well-known EAB kits with quality engineering that have cables attaching the shoulder belts to the mount points. Builders sometimes eliminate the cables and lengthen the belts to the attach points. May or may not be a good idea, I'm not qualified to say. Your smilage may vary.

https://gwrco.com/seatbelts/seat-belts/

[melann]

"Seatbelts help reduce the risk of injury in many types of crashes by helping to properly position occupants, while the seat belt is designed to stretch at a controlled rate to absorb impact energy and reduce the severity of the occupant’s deceleration."

This is why one shouldn't simply alter the seat belt fabric lengths and mounting methods of certificated systems. Nor systems designed by qualified engineers with expertise in the area. For example, well-known EAB kits with quality engineering that have cables attaching the shoulder belts to the mount points. Builders sometimes eliminate the cables and lengthen the belts to the attach points. May or may not be a good idea, I'm not qualified to say. Your smilage may vary.

https://gwrco.com/seatbelts/seat-belts/

A good example of this is; Van's Aircraft originally used the full length of shoulder harness into the tail cone. Testing showed that the "stretch" of the material in a forward impact could allow the occupant to contact the instrument panel. The change was to shorten the shoulder harness material and, instead, extend the harness with a steel cable through the baggage bulkhead to the aft anchor bolt in the tail cone.

[Dana]

For force numbers...a 200 pound person falling 9 feet will have an impact force of about 3600 pounds....impact velocity of only 16 mph....

That depends on the deceleration distance.

[WLIU]

That calculation is definitely not correct. Or I should have died every time that I landed a round parachute. The load depends on deceleration distance and how the impact is absorbed by whatever restraint system used. Please look up the material characteristics of the seat belt webbing. It stretches and fails at specified loads. This affects the calculation for instance.

Best of luck,

Wes

[CraigCantwell]

What I was stating, is for a free falling person with no fall protection....just like falling off a roof or ladder. Force of impact for a free falling body is estimated as W*(1+(D/d)), where W= weight of the object, D is the free fall distance and d is the deceleration distance. For what I quoted, W=200, D=9 feet and d is approximately 1.1 for a human body falling flat. Land on your feet and collapse, and you reduce the number as d increases. Plug the numbers and you get around 3600 pounds. Our decelerators on our fall protection gear, limit the maximum fall to under 6 feet, with a decel distance of 2.5 to 3 feet. The impact numbers drop greatly. For a seat belt, the fall distance is going to be very small, with the decel distance being quite large in comparison. Typical estimates are that a seat belt will stretch about 6" in a 30-40 mph accident, and that's assuming that there is no displacement of any of the anchors. Higher speeds are going to result in higher stretch, until you reach enough speed, that the belts can no longer stretch and end up failing.


As to the parachute Wes, it adds a bit of complexity to the calculations, putting you into the realm of differential equations to come up with the impact force. I do know that one our pilots at work, had a near zero/zero ejection recently and was slightly injured, as his chute was not fully inflated at the time he touched down. Makes a big difference. On a chute, you are in a controlled decent and not a free fall.

[WLIU]

This is indeed a complex subject. An inelastic object falling the distance specified and stopping in zero distance does indeed experience very large forces. But that is pretty much never the case. Even the human body is elastic and not long ago a close relative put that to the test by accidentally slipping and falling off the roof of the fly bridge of his boat. I believe that "D" in the calculation was actually > 9'. Unfortunately, the boat was not in the water, but was on a trailer parked on asphalt. A broken arm, 3 broken ribs, and I think a concussion resulted. The arm broke when he landed with it between his head and the pavement. Better the arm broke than his skull. He might be an advertisement for one of the fall arresting harnesses mentioned previously.

As mentioned in post #11 we most often replace web products not because we know that they have been compromised in use but rather out of an abundance of caution since we do not have good tools in the field to determine their actual condition. In the parachute world there is a non-destructive test protocol for older canopies to determine that the fabric has not weakened with age (PIA TS 108.1). I am not aware of a similar test for seat and shoulder belts that can be done in the field.

Question about "indicate a 10 year lifetime" - I just stepped out to my hangar and none of my older belts have any date on it other than the date of manufacture. Is putting some sort of "replace by" date on the TSO tag a new thing?

Reading the comment above about builders modifying shoulder harness installations from plans, I will suggest that builders thinking of changing their seat belt and shoulder harness anchors be familiar with FAA AC 43-13.2B Chapter 9 Shoulder Harness Installation before they go to work. Of course, this comment is speaking to the choir.

Fly safe,

Wes