What's best -Lap sash or full harness?

[bushpilot]

One to think about on a wet Sunday :):

 

My company is currently doing ADR compliance work on an Ariel Atom sports car... http://www.arielatom.com.au/ One thing we have found is that to make the seat belt system perform in a satisfactory manner, we are best to use a full harness system rather than the 'normal' lap-sash system. I.e. We can more effectively restrain the 2 occupants using the full harness - meaning less likelihood of bodily injury at certain crash speeds - in this somewhat unique car, that has very little actual body-work and a tubular frame..

 

Got me thinking about our recreational aircraft: Trikes normally have a full harness system, yet 'high performance' rec aviation and GA aircraft usually have lap-sash only.. Why is it so?

 

Lap sash are OK when combined with crumple zone designs in cars, but aircraft dont have this requirement; generally just a big heavy motor ahead of the cabin.. I figure that in a heavy landing or crash situation, the walk-away rate could be higher if all of our a/c had full harnesses..

 

Views??

 

Cheers,

 

Chris

 

 

[Guest ROM]

Gliders all have the full 4 point harness which I think is a mandatory requirement in European gliders and therefore by default in Australia as well.

 

A couple of the older east European gliders also had the 5 point aerobatic harness installed.

 

With almost no protection of any sort in front of you in a glider, a crash stop can sort of leave you rather exposed so as to speak.

 

The latest European requirements for gliders is the incorporation of a very high impact safety shell around the cockpit area which is used as a part of the structure of the glider.

 

There is also a lot of research and thought being put into removing and minimising the projections and sharp edges in the cockpit, again to minimise injuries if a crash occurs.

 

To be quite honest, after learning in Tigers and flying chippies, pawnees and other older generation aircraft, I feel quite exposed and even a tad uncomfortable when I climb into a modern aircraft and only have to click on a lap seat belt or a lap/sash type belt.

 

 

[Guest Crezzi]

A major reason trikes usually (& arguably should) have 4 point harness is because of the tandem seating arrangement.

 

They became a mandatory requirement in the UK after a fatal accident a few years ago when a trike did a successful force landing in a paddock but the nosewheel went down a rabbit hole & the trike nosed over. The passenger only had a lap belt on, was pitched forward and snapped the pilots neck.

 

Great news about the Atom - I've fancied one for several years. Any idea when & how much ?

 

Cheers

 

John

 

 

[Guest ozzie]

the anchor points for full shoulder harness 4 point and six point types must ee higher than the occupants shoulder, if it is not the they will cause more injury than what they should prevent. if the anchor point is below the shoulder hight it will break your collar bones and contribute to compressing your spine ect. most aircraft dsigns cannot provide an adequate anchor point for full shoulder harness. cost is another factor.

 

ozzie

 

 

[facthunter]

Problems .

 

As ozzie points out the top mount points have to be available, Not easy in a side-by-side. There have been instances where the occupant has slid out the bottom of a 4-point harness. I guess this is without a crutch strap. The aerobatic harness is 4-point, but in the citabria, they recommend using two belts. (1 lap sash) I don't do that as you might have to get out in a hurry. I just keep the full harness pretty tight. The standard for mount point strength might limit the effectiveness of a good belt in some installations. Nev..

 

 

[Guest pelorus32]

Many years ago there was an incident with a glider pilot in NZ. He was towing up to some wave and whilst traversing the rotor, he fractured 1 or more vertebrae in his spine.

 

How it happened was interesting. In many gliders the seating position is very recumbent. In the turbulence he slid forward so that the lap part of the 4 point harness was across his stomach. This left his hips and lower spine free to flop around in the turbulence and hey presto some fractured bones.

 

After that as I recall it the accident report suggested a "negative G" strap - crutch strap - on gliders.

 

Regards

 

Mike

 

 

[David S]

I am trying to work out fixing points in my aircraft for a 5 point harness.I always had 5 point in my racing cars (crutch strap stops submarining) and would be much more comfortable than with the existing lap sash. I also had an onboard fire ext. and am working on that too

 

David S

 

 

[bushpilot]

Great news about the Atom - I've fancied one for several years. Any idea when & how much ?

Cheers

 

John

Looks like they will retail in OZ at around $95,000, depending on final specification and exchange rate against UK Pound when the first are shipped. And if you think that this price a bit high... 25 Aussies have already stumped up their $5K deposit each..

 

Like you, I've been interested in the Atom for many years, so it's great to be involved in getting them onto Australian roads; first should be here early '09.

 

Cheers,

 

Chris

 

 

[RFguy]

bit of a story of four point harness advantage- admittedly, no control of the 'experiment'- anecdotal .

https://www.atsb.gov.au/media/5771843/ao-2016-109-final.pdf

[old man emu]

Seatbelts are meant to keep the person attached to the vehicle to prevent impacts with the interior of the vehicle, or ejection from the vehicle. The possible ways a body can move in response to collision forces is astounding, so designers look at the most likely.

 

The first designs were simply lap belts. However, in the event of frontal or side impacts (including rotation around the axes), the body was able to flex over the belt and strike the interior of the vehicle. Also, it is possible for the body to slip over or under the belt.

 

Aviation and motor racing showed that the four-point harness provided more protection, but are inconvenient for use in non-competitive use of the vehicle.

 

The lap/sash belt is a compromise between the protection of a four-point harness and convenience for daily use. The biggest problem with the lap/sash is improper use - not fitting the belt properly across the shoulder and lap. It is still possible to slip out of a lap/sash harness.

 

So what type do you use? For an aircraft that will be used by many different people, for non-aerobatic flights, the lap/sash is the best compromise. For flights involving unusual attitudes, four-or five point would be the go. In your own home built - go for the safety of the four-point. Once you adjust it for yourself, it will go on as easily as a lap/sash.

[APenNameAndThatA]

I don't buy the idea that lap sash belts should used in aircraft because four point harnesses because of the extra time it takes. The preflight means that going flying will always take vastly longer than hopping in a car. There is just no comparison. I think that GA aircraft have lap sash belts because the old ones were certified 50 years ago, and the new ones wanted to be fashionable.

 

I only just learned that apparently the reason aerobatic pilots wear helmets is the risk of banging their head when they do aerobatics. It's not actually for when they crash. In Flying once I read about a pilot who hit her head in mountain turbulence but was okay because she was wearing a mountaineering helmet! The take-home message is that four-point harnesses are for turbulence as well as crashes. And the other take-home message is that you should tighten the lap belt low and tight around your hips.

 

As for aircraft not having a place to anchor the top seatbelts, well, you need to get an aircraft with a roof.