Helicopter Vibration in the Spines of Pilots in Flight

[CS-Hover]

Hi

anyone have more info about this, or something related...

Vibration in the Spines of Pilots in Flight (http://www.ingentaconnect.com/content/asma/asem/2005/00000076/00000006/art00010)

regards

[Genghis the Engineer]

http://www.gliding.co.uk/bgainfo/safety/glidingsafety/winter2002.pdf

(Page 2, right hand side).


There's a lot of very useful work published by Tony Segal, although very little I think on the net. His area of research has been seat and cockpit design, and harness design - primarily for gliders (he's a retired GP and keen glider pilot who has spent the years since retirement doing safety research that he felt needed doing - if he's not been given any kind of medal for this, it's overdue).

I've personally used Tony's work as reference in the seat design of quite a number of light aircraft - VP959 will certainly vouch for the validity of Tony's work, since he walked away from an aeroplane he had a too-close encounter with a crash of - thanks in part to my insisting on certain of TS' design recommendations in that cockpit.

Now this isn't directly related to vibration absorption, but nonetheless if you are interested in seat/harness design and avoidance of back problems, he's without doubt your man.


There was also a "spinal injuries in light aviation" conference about half a dozen years ago organised by the BHPA (British Hang-Gliding and Paragliding Association). You might be able to get hold of a set of the published papers from there by contacting the BHPA HQ in Leicester. It was a fascinating day, with a lot of papers on every aspect of how flying machines interact with aircrews spines, and how to make this as painless as possible. If no joy there and you're doing some serious research, let me know and you'd be welcome to borrow my set so long as I get them back.

G

[Thomas coupling]

CS Hover - back probs come with the territory just like:

Deafness issues - turbine frequencies.
shoulder issues with collective position.
low sperm count due to vibration.
pain in the arse - no money in your wallet! :D

[diginagain]

I'd be interested to learn if there are any published studies on the effects of cockpit ergonomics and vibration on the lower limbs, particularly on the knee-joint.

[NickLappos]

The science of pilot/pax dynamics has three main constituents:

1) the vibration of the local area of the machine - its magnitude, direction and frequency. The vibration on meduim and large helicopters can vary markedly across the crew and passenger areas. If one could see the floor vibrating, it would look like a pond's surface in an earthquake, a series of peaks and valleys that stand almost defying gravity. If your seat is mounted at a peak or valley, it "sees" more vibration than if it is bolted to a place that is not moving (obviously).

2) The transmissibility of the seat, as measured at the human's position, that is, the seat's ability to quell or amplify the vibration. I have found seats that double the vibration, because they resonate at the frequency in question. Most manufacturers try to pick seats that reduce the vibration, usually by half. Sometimes, just more firmly bolting the seat, and tightening its joints can reduce the transmissibility measurably. The seat's response could actually make a lateral or longitudinal vibration translate into a vertical one, because the seat can rock or roll in response to a floor movement.

3) the posture of the seat - the verticality of the back, and also the layout of the controls, as they affect posture. A poor seat geometry causes the body to be held in an uncomfortable way, so that the extra vibratory motion makes the pilot work harder, and induce muscle fatigue as an extra component.

The study referenced in the lead post seems to leave all these important points out, and therefore it might be very simplistic.

[paco]

There was conference recently (a couple of weeks ago) about whole-body vibration, which covers this very subject, plus circulation problems in people like jackhammer operators, amongst other things, but heli pilots were included. I believe the RAF did a major study on it.

Phil

[EESDL]

The libray at the Aviation Medical Centre (Henlow?)had some v.usefull stuff back in the mid-90s that seems relevant today. Looked into it in some detail after the RAF Doc told me that the poor design of the Wessex seat - and the hours spent in them with helmet/goggs/chest armour etc was responsible for giving me back problems. This was at a time when a mod would have been justified as the annual hours flown were silly. When he refused to put it in writing or in my medical notes I thought I'd better help myself.

The Ruskies have a lot of data on the subject aswell, all along the lines of what has been mentioned above.

It was amazing to feel the difference that resting your arm on top of the collective made - but this was banned because the collective could be knocked down during transit - go figure.

Suffice to say, there is a load of scary reading out there, if you dare.

[diginagain]

I seem to recall seeing something from RN Med Branch about the Lynx in particular, about 10-12 years ago. I wish I'd taken more notice at the time, I could do with some information now.

[[email protected]]

Try a Sea King on the edge of translational lift in an updraught where you can't read any of the instruments because both they and your eyeballs are vibrating so much. This cannot be good for you but no-one will admit it.

[John Eacott]

Try a Sea King on the edge of translational lift in an updraught where you can't read any of the instruments because both they and your eyeballs are vibrating so much. This cannot be good for you but no-one will admit it.

As you get for 4 hours dunking with a wind just at TL, you mean? ;) :rolleyes: Remind me how much I (don't) miss it, will you............

[747 jock]

To be honest, I can't see what the problem is.

Most of the helicopter pilots I have ever met, have been a pretty spineless bunch:O

[TiPwEiGhT]

Just recently started instructing on the R22 and therefore am doing alot more flying in it. I have noticed over the past couple of weeks that my back (at the base of my spine) gets really sore, even getting out of bed in the morning is painful.

Do any of you guys out there have any tips that you could give me to try and sort this... spoken to doctor but he couldn't give a t*ss.

Cheers,

TiP

[NickLappos]

Tipweight,
If it is vibration you should be able to tweek it out, as the vibration most helos put out when properly maintained is not particularly bothersome when we are expose to it for only a few hours per week. How much is too much? If it affects your speach by modulating it without any conscious effort is is clearly too high, or if it causes a noticible modulation of your vision, or if when you hold your teeth just apart, they tap together. All of these signs are indications that your helicopter probably needs to be tweeked to stop this vibration.

If the vibration is below the above, it could be a combination of posture and seat comfort. I have often seen that the reach with the right hand to ghold the cyclic extends the muscles of the lower back. I suggest that you use a small lumbar pad that you carry on, and that you retract the pedals or slide the seat forward to jack-knife your knees (so your arm must lay on your knee (thus relieving the back pressure of holding it extended.) If you still can't rest your hand on your knee, buy a clip board that fills in the gap, and rest your right fore-arm on that.

Also, I have found that many seat backs are straight right to the bottom, and should have a circular cross section pad that is a max of 2" thick that fills in the lower 6 inches with a gentle curve. This forces the spine to curve naturally forward then back as you rest against the back pad, and it also forces the whole back to recline a bit.

I had a back pad specially made for two different helos that I regularly flew and that were not right for me. I even velcrowed one to the back cushion to hold it perfectly in place.