Five point harness

[Marty_d]

That's a bit of a problem, Marty. Seems like a slight oversight on the part of the designer. I used the your solution on my BRS harness. The cables are anchored on the rear wing attachment points. Looks like your 701 has slats. Are they fixed or automatically deployed like Handley Page?

 

The tailplane seems quite narrow, presumably for trailering.

Yes, they only designed it for a 3-point seatbelt. One bloke bolted a transverse chrome moly tube across the fuselage to take the shoulder straps, but at 2kg it seems a little heavy. This method just involves mounting the original brackets further along the fuselage so the only extra weight is the cables.

 

The slats are fixed, bolted onto plates riveted to the nose ribs and protruding through the nose skin. Many people replace these with VG's so you see 701's getting around with just the plates sticking out, or cut off flush with the skin. Apparently it gives better speed and fuel economy and doesn't affect handling, but I prefer to stick with the original design as far as that goes.

 

The tailplane is narrow, I believe in the following model (750) they made it wider. Ah well I'll stick with the original there too (because I've already made it!)

 

 

[Oscar]

Was it Oscar doing some work on better harness for Jabiru?

Doing work privately for MY Jabiru, JJ.

 

 

This is a test, using an el cheapo five point harness; I'll be using a full FIA-spec six-point with 3" shoulder straps and titanium camloc. The attachment points for the lap straps go onto the standard Jab points; the corss beam (slightly oversize tube in that piccy) attaches to the shoulder harness points so all major loads are taken on the original Jab. structure, with no modification. The beam will be 4130, and has been FEA'd by an aero engineer to meet the loadings that Jab originally had to meet (BCAR S) . The brown projections above the seat ( only cardboard in this test!) will be simple 'glass sheet with about 12.5mm temper-foam padding intended to provide protection from whiplash compression on the spinal column in your neck from the tube, and keep your head from impacting the flap cross tube. I've yet to design the attachment for those, but they need to locate the shoulder-straps from sliding on the cross-tube.

 

 

[Guernsey]

Oscar is back....Yipee..

 

Alan.

 

 

[Old Koreelah]

Update. After quite a few flights I've sorted out my new harness, cut off the excess and melted the ragged ends to stop fraying. The straps are nice and wide and I've added lambs wool pads between the metal buckles and my hips. While flying thru rough air it's reassuring to be able to pull the shoulder straps tight without the waist straps being pulled up above my pelvis.

 

Biggest disappointment is I didn't follow Oscar's advice to get one with "pull-up" adjusters on the waist straps. Now I know what he was on about. In a narrow cabin it's almost impossible to pull the belt down enough to get it firm.

 

 

[turboplanner]

Update. After a quite a few flights I've sorted out my new harness, cut off the excess and melted the rugged ends to stop fraying. The straps are nice and wide and I've added lambs wool pads between the metal buckles and my hips. While flying thru rough air it's reassuring to be able to pull the shoulder straps tight without the waist straps being pulled up above my pelvis.Biggest disappointment is I didn't follow Oscar's advice to get one with "pull-up" adjusters on the waist straps. Now I know what he was on about. In a narrow cabin it's almost impossible to pull the belt down enough to get it firm.

Needs more work, that arrangement will break your back in a flip over where you slam in upside down. What happens with tight shoulder straps and loose waste/leg straps is when you slam the ground, all your bodyweight slams into the shoulder straps and compresses the spine. What is supposed to happen is the lower body/legs is restrained by the lower straps.

 

 

[Oscar]

Yep, I agree with TP completely on that one. When I was racing, scrutineers came down the line of cars in Pit Lane and checked that you were REALLY strapped in hard - and it was a bit 'personal' regarding the lap-straps, if there was any discernible movement at the belt-buckle you were told to get it tighter, and that was the exact reason why. Depending on the brand, you may be able to get replacement lap straps.

 

 

[Old Koreelah]

I can get waist straps reasonably tight, but it ain't easy. If I can't replace them with pull-up straps the next best option is to install a rigid "push down" extension or a change of direction pulley.

 

 

[djpacro]

or http://www.aircraftspruce.com/catalog/appages/hooker1.php

 

 

[Oscar]

I can get waist straps reasonably tight, but it ain't easy. If I can't replace them with pull-up straps the next best option is to install a rigid "push down" extension or a change of direction pulley.

You might get away with triangular carabiner-style end fittings wide enough for the straps to wrap around, held on maybe with small lanyards down to the actual attachment bolt. A roller-style arrangement ( similar to a fibreglass roller, but obviously of just plain aluminium rod say about 8mm diameter on a triangular base on a lanyard would probably be better, but more complex to make.

 

 

[Oscar]

Incidentally, on the importance of getting the lap straps tight ( and following on from TP's advice):

 

I used to race Clubman-class cars, in which you are in a fairly prone position and there's sod-all seat shape, let alone padding, to stop submarining. This was way in the days before temper-foam, and with 2" harnesses. I saw a mate spear off at the top of the Esses at Oran Park south circuit beside me and hit the concrete embankment at about 70 degrees and probably doing maybe 80 - 90 kph. The back of the car went about 2.5 metres in the air, and I genuinely thought he would have been extremely mangled (or worse). Was a huge hit.

 

At the end of the race, when they dragged his considerably abbreviated car back to the pits, he unzipped the top half of his race suit - (we were amazed that he was even walking around) and he had two deep welt marks from shoulders down to beyond where anybody wished to see more. I reckon by next day, his torso would have looked like someone ready to star in Braveheart, but he was otherwise undamaged.

 

 

[Chocolate]

You can get just the webbing replaced.

 

 

[Old Koreelah]

You can get just the webbing replaced.

I'd be interested in that. Any idea of a business to approach?

 

 

[Oscar]

OK, I think this is the one Dafydd used recently for belts for the Blanik: http://www.aviationbelts.com.au/

 

 

[Old Koreelah]

Thanks for that Oscar. I've been in touch with them and it looks like they can rebuild my lap belt to a more appropriate design.

 

 

[Oscar]

OK - glad if I've been of any help. None of the re-webbing services is cheap, but then, your backbone is irreplaceable at any cost.

 

Also - FWIW, in the interests of one being a somewhat-bruised survivor rather than an attractive corpse in a crash: as I understand it, when Bill Whitney was designing the Boomerang, he did quite a bit of research on the bio-mechanics of whiplash - and found that it is a far more serious problem than one would think, even for a 'straight-forward' aircraft crash rather than a vehicle rear-end crash. If you can arrange a decent head-rest with some impact-absorption capability - that does NOT stretch your neck in action by rolling it over a low cushion-type arrangement - I reckon it's worth the effort.

 

If you watch the accidents that motoGp riders have - thrown along the ground, sometimes from over 2 metres in the air, at up to 200 kph - the crash velocities that the human body can withstand are staggering PROVIDED that deceleration is managed within tolerable limits. They now have air-bag suits that inflate and support the upper lumbar area.

 

 

Yes, he walked away from that one ( a bit unsteadily).

 

Or this:

 

 

Had a sore neck, I think this one was at something over 200 kph.

 

Conclusion: it's worth trying to get the best impact protection you can.

 

 

[Chocolate]

Tadgell Aviation Caloundra do replacement of the webbing.

 

 

[Marty_d]

OK - glad if I've been of any help. None of the re-webbing services is cheap, but then, your backbone is irreplaceable at any cost.Also - FWIW, in the interests of one being a somewhat-bruised survivor rather than an attractive corpse in a crash: as I understand it, when Bill Whitney was designing the Boomerang, he did quite a bit of research on the bio-mechanics of whiplash - and found that it is a far more serious problem than one would think, even for a 'straight-forward' aircraft crash rather than a vehicle rear-end crash. If you can arrange a decent head-rest with some impact-absorption capability - that does NOT stretch your neck in action by rolling it over a low cushion-type arrangement - I reckon it's worth the effort.

 

If you watch the accidents that motoGp riders have - thrown along the ground, sometimes from over 2 metres in the air, at up to 200 kph - the crash velocities that the human body can withstand are staggering PROVIDED that deceleration is managed within tolerable limits. They now have air-bag suits that inflate and support the upper lumbar area.

 

 

Yes, he walked away from that one ( a bit unsteadily).

 

Or this:

 

 

Had a sore neck, I think this one was at something over 200 kph.

 

Conclusion: it's worth trying to get the best impact protection you can.

It is amazing how they get up and walk away after laying the bike down at speed, but very much helped by the lack of hard vertical obstructions. Sliding at speed along bitumen/concrete/grass/dirt while wearing a very good suit will probably not do you much damage, whereas things like trees or "cheese-grater" fences found on or next to roads tend to decelerate the human body far too quickly for continued health.

 

 

[Old Koreelah]

...when Bill Whitney was designing the Boomerang, he did quite a bit of research on the bio-mechanics of whiplash - and found that it is a far more serious problem...If you can arrange a decent head-rest with some impact-absorption....

Bill was a great help to me when I took some design problems to him, and he put me on to Dafydd.

 

Oscar you're right about whiplash, I was lucky to survive a rear-end shunt in a 1960 Triumph without head restraints. That and almost forty years of rescueing road accident victims has made me a bit safety conscious, so I have a large pad behind my (helmeted) head. This pad also has a recessed polystyrene pad behind it.

 

All good, but the best way to avoid testing it out is not prang in the first place...

 

 

[Old Koreelah]

It is amazing how they get up and walk away after laying the bike down at speed, but very much helped by the lack of hard vertical obstructions. Sliding at speed along bitumen/concrete/grass/dirt while wearing a very good suit will probably not do you much damage, whereas things like trees or "cheese-grater" fences found on or next to roads tend to decelerate the human body far too quickly for continued health.

I agree Marty. I've slid down a racetrack at 130k without damage but broken bones at 10k. (Your angle of arrival affects your chances of survival). My greatest fear is being high-sided; my reaction time never was great but age has made it worse. I used to hammer my Ducati down the Oxley. Heaps of bikes having fun there last Sunday when I drove it in my car. Yes, I was envious, but I also remember how much it hurts when you fall off. No run offs or air fences. Pushing bikes to the limit is best left to fit, fast young blokes, preferably on a proper racetrack.

 

 

[Kiwi303]

Most, not all, but many, motorcycle suits are purposely highly slick and non-stick. You're better scrubbing off your velocity skidding over 50 meters than having the suit catch and tumbling for 15.

 

 

[Oscar]

And dragging this topic back (and I confess to being the one to have sidelined it!) to aircraft: Bodies have a fairly limited ability to absorb extremes of deceleration. To a significant degree, the real purpose of a harness is to 'suspend' the body inside the occupant protection cell so it does not come into contact with the rapidly-slowing bits of structure. The better it can do that, combined with the better the occupant protection structure actually performs, the better your chances.

 

Much has been made on this site and elsewhere, of the potential of BRS. Obviously, Cirrus aircraft are somewhat of a standard-bearer there - but few people consider that a Cirrus ALSO has ( it MUST have) FAR seat-compression compliance and FAR Undercarriage strength compliance. So, the vertical descent speed survivability under their CAPS is not just a function of the BRS but ALSO the aircraft and seat structure.

 

The best harness in the world won't save you if the airframe folds up and crushes your skull as has been seen for un-modified RV6s. The extremely rudimentary lap-sash harness in a Jabiru is ok for just about all crashes because the occupant safety cell remains very effective ( though as a Jabiru owner I want to maximise my chances with an improved harness). I suspect there is a very wide range of harness/occupant cell integrity 'solutions' across the range of Recreational aircraft. For example, the 4-point harness in a Carbon Sting TL2000 might be regarded by some as a confidence trick since the attachment points for the shoulder straps are useless and the occupant cell has - from personal observation - all the safety of a raw egg dropped from great height onto concrete on impact.

 

There is NO one simple answer to personal protection; however the combination of a good harness and an effective occupant protection cell maximises your survivability in the event of most crash situations..