Crashworthy pilot seats

[HeliComparator]

Would you, as a pilot, like to have crashworthy seats in your cockpit? Before giving the obvious answer of "yes", consider that they will typically be less comfortable and less adjustable than non-crashworthy ones - normally there is no rake adjustment.

By crashworthy I mean seats that stroke down in a hard impact to reduce the peak g loading and save your spine. If you are a single-engine driver, I would suggest that the answer still be "yes" even if less comfortable, but my question is (selfishly) aimed at offshore twin pilots and I am curious to get opinions.

On the one hand, an employer should provide the best safety equipment for his employees and so the "duty of care" argument suggests they should be fitted. But on the other hand, looking at accident stats for offshore ops its hard to find many where crashworthy seats would have made a difference, so my personal choice would be comfort over crashworthiness.

What say you?

HC

[NickLappos]

Let me phrase helicomparitor's question another way:

Would you like to ride a wheelchair for the rest of your life after a hard landing?

Are you foolish enough to think the tradeoff is between comfort and safety?
The question hc poses is yet again proof that hc is simply out of touch with the real world. I wonder if he lets his daughter drive in a car without seatbelts, anti-lock brakes and the like?

[HeliComparator]

Thankyou Nick, I knew I could count on your response! Is there anyone out there with a less hysterical opinion?

Safety is important but safety is about reducing risk to be as low as reasonably practical, not to be zero. You only get zero risk if you stay in bed all your life and even then you may be abducted by aliens.

There is no point in having a safety feature that compromises your working life by making it a misery and contributing to licence loss to address a risk that is statistically very low. Research has shown that more offshore helicopter pilots have been abducted by aliens than have suffered back injuries from hard landings, so really the money would be better spent on armed orbiting satellites to shoot the pesky flying saucers down.

HC

[Droopy]

D'you know, I never realised grown men were so fond of handbags.

Right, my offering. I have experience of both crashworthy [onshore] and "standard" seats on and offshore. The answer is simple; build a comfortable crashworthy seat. It will cost more. The current standard of such seats is insufficiently comfortable to be acceptable for long flights; anything much over an hour has my admittedly ample behind complaining.

Nick is right to say that the best should be used, but if "the best" means you're so uncomfortable you don't concentrate properly it's hardly sensible.

[Daysleeper]

I once worked for a company that refused to issue immersion suits to pilots on long overwater low level missions. Their argument was that we would be so uncomfortable wearing them we wouldn't be able to concentrate.

I ended up buying my own suit and wearing it quite happily on 10 hour plus days. Turns out the company only hadn't looked at suits for about 20 years and had no idea about modern "breathable" fabrics..:hmm:

My point being that just because a seat is designed to be "crashworthy" does not mean it is necessarily uncomfortable and if it is the the manufacturer is not doing their job properly.

[Rotating Star]

Seats comprise two main elements. The cushions that make contact with the body and the framework that supports the cushions. It should be possible to make a crashworthy seat frame that can support comfortable seat cushions. Perhaps not though, otherwise it would have been done by now. Maybe comfy cushions impact negatively on energy absorbtion. Any design engineers out there?
The sectors I fly are generally less than an hour, so to answer the question crashworthy gets my vote. However I can see why much longer sectors (offshore) might change the priority to comfort.

[Spunk]

Now let`s see. So far I've been flying R22, R44, Enstrom F28, Hughes300, Bell 206 (JetRanger/LonRanger), Bell 407, EC120 and BO 105.
consider that they will typically be less comfortable and less adjustable than non-crashworthy ones
Does that mean that there are seats out there being even less comfortable than those in the aircraft mentioned above????:} :=

[Francis Frogbound]

I saw a P2 seat from a 350 B3 last week which had been through a major smash. The instructor who had been in the seat in the crash had a sore back for a day or two. The engineers were able to show me how the seat had worked, and it was very impressive. A similar impact (admittedly in an older design/different manufacturer) some years ago left me in hospital for six months and discomfort for life.

I'm lucky enough to fly Eurocopters' more modern offerings and believe me I find their "crash proof seats" very comfortable, and from what I saw last week a bloody good idea:ok:

[212man]

"consider that they will typically be less comfortable and less adjustable than non-crashworthy ones - normally there is no rake adjustment."

well, we've got lots of adjustments- including rake!

Mind you, they're not very comfortable, despite their name: High Comfort Seats! After about 2 hours you get a bit numb.

I'd still rather have them than not have crashworthy seats, though.

[zebedee]

Most of our pilots have to endure up to 8 hours in one sitting and up to 800 hours in a rolling year. Any takers? (Freelance Musterers/Herders/Loggers etc. with two logbooks, are barred from answering)
Ever experienced a "bad back"?
My vote is for a comfy chair.
Nick, mostly I agree with you, but not this time. I spend my entire working life strapped into an uncomfortable seat. The manufacturers say that these are very safe aircraft (i.e. the chances of crashing are small) BUT they want us to sit in these contraptions for hours on end, and destroy our spines in the meantime, so we will be OK after a crash. Sorry, but my back will be so f@c#d by then I will probably drown because I can hardly move!
Give me a comfy chair please, and I'll take a career that is not cut short by my equipment over the slim chance that a "crashworthy" seat will keep me alive if this very safe machine should fail.
Two things are imporant for pilots that are flying to the max for our customers: seat comfort and NOISE (sorry Nick, but Sikorsky have never been good at either - and I'm a long-term SK man).
If an aircraft is safe, then I want a comfortable seat and a quiet environment.
Zeb

[Paradism]

All helicopters have to have seats that are designed to a very demanding specification. For modern European large helicopters this is Certification Specification No. CS 29 Large Rotorcraft.
The file can be downloaded from the EASA web site if you are interested, the relevant part is CS 29.562 Emergency Landing Dynamic Conditions. There is a similar specification for small rotorcraft. Historically, there has always been a similar specification for seating. The UK CAA had their own as do the US FAA.
Clearly, the specification is designed to provide a minimum acceptable safety level to all helicopter occupants, a higher safety level would most likely cost more but nevertheless would have to be tested to the applicable design code.
It is an unfortunate fact that there is a limit to the crashworthiness that would be practical for a seat. There is little point of having a seat that is virtually indestructable when the aircraft structure would fail and allow the main gearbox to exit the aircraft via the cockpit, for example.
Comfort is another matter. If a seat is uncomfortable, to the extent that it starts to interfer with the safe operation of the aircraft, it should be reported using the appropriate occurence reporting procedure, or at the very least, submit a flight safety report to your FSO.

[Graviman]

Seats comprise two main elements. The cushions that make contact with the body and the framework that supports the cushions. It should be possible to make a crashworthy seat frame that can support comfortable seat cushions. Perhaps not though, otherwise it would have been done by now. Maybe comfy cushions impact negatively on energy absorbtion. Any design engineers out there?


RS, the problem is that, during a crash, you do not want pilots backside to gain much velocity over the seat pan before it contacts - that would hurt. The links below are to a manufacturer, and general supplier, of foams which resist high speeds so cause a more gradual acceleration (just a quick google search). Believe me, these cushions work very well! A deeper cushion requires more carefull design, as there is a greater distance for that relative velocity to build up. In principle there is no reason a comfortable seat cannot be designed, although it would need to be certified for a range of pilot masses.

http://www.sunmatecushions.com/aircraft_foam.php
http://cumulus-soaring.com/AearoE-A-R.htm

NB: I have not provided calculations for this topic, because it is a specialised area. For the performance to work you need computer simulation and testing to back it up. The manufacturers will have done this with the uncomfortable seats already out there.

Mart

[JimL]

Frankly I am surprised by the premise of the question; as Paradism has already pointed out, crashworthy seats are now a design requirement. This requirement caters for the abnormal - i.e. the crash situation.

The question that might have been asked is why there are no design requirements to account for the normal case - i.e. the many of thousands of pilot hours that have to be spent in the seat - outside the crash situation.

The offshore pilots of Norway and Canada have spent untold hours addressing the seat comfort issues, and also bringing the noise issue to the attention of the operators, Authorities and manufacturers.

Perhaps we should attempt to ensure in the future that regulating for the abnormal does not compromise operations in the normal.

Jim

[topendtorque]

Man is constructed with two ends,
One is to think, the other to sit.
His progress in life depends,
Upon the time spent at each pursuit.

I somehow doubt that my grandfather was thinking of flying machines when he penned that bit of philosophy about eighty years ago.

I know, I’m banned from this thread, by dent of my mustering connections, however none of it would have helped what looked like a huey on tonights news in the phillipines, story below.

http://www.abc.net.au/news/newsitems/200704/s1909064.htm

[HeliComparator]

JimL

Yes, crashworthy seats are now required by certification for new aircraft, but my question was in relation to those many aircraft still in service that do not have crashworthy seats. Should an operator spend time and money retro-fitting such seats which, as far as I can tell, usually have crashworthiness as the primary design factor and comfort as a secodary one, or would the pilot workforce prefer comfort as the over-riding factor?

Of course in an ideal world these two considerations are not mutually exclusive but the reality seems to be different. It would be great to be have certification rules about comfort but can you imagine trying to write those rules and test for compliance?

HC

[NickLappos]

helicomparitor is correct in that "grandfathered" designs (which comprise perhaps 95% of the aircraft we fly) do not have safe seats, they are from the era before we knew how unsafe they were.

The latest requirements do NOT have to be met by your helicopter, because the rules are almost never made retroactive.

Time to rise up, guys. Stroking seats, which ride you downward in a crash and protect your precious vertebrae, are available for retrofit. The seats on the Black Hawk, AB-139 and S-92 will protect the pilot's back in impacts up to 18 to 20 g's, where it is guaranteed that major back injury will result if such a seat is not used.

It is a foolish premise that helicomparitor makes where somehow one virtue (safety) is balanced against another (in his warped universe, comfort). This is the brilliance of a good salesman - establish a difference that "makes sense" and then exploit it to prove another point. Like looking for weapons of mass destruction by some politicians, this "comfort" argument is an excuse to try and justify his other points - that the poor non-stroking pilot seats of the EC-225 are superior!! to the 18 g safety seats in its competitor. Remember, hc is the guy who told us that the size of the windows is more important that if the fuel cells are fire proof!

There is no property of a stroking seat that plays against comfort, period. As many ppruners have posted in this thread, there are many uncomfortable, un-stroking seats, which at the very least proves the case.

No mater how you slice it, a seat that breaks your back is a sub-standard seat.

Here is a good technical paper that talks about safety seat evolution:
http://www.fire.tc.faa.gov/2004Conference/files/crash/S.Desjardins_Energy_absorption-helicopter_seats.pdf

Here is a good Martin-Baker site:
http://www.martin-baker.com/crashw_Intro.htm

[havick]

All of the RAN squirells have had their front seats re-fitted with EC120 seats. I couldn't tell you why they did this, much before my time. HELOPAT feel free to jump in here.

[HughMartin]

Is a "crashworthy" seat going to save my life or make a big difference to the outcome? In my opinion, unlikely unless I am spending a lot of time in the avoid curve over land, I suspect not.
If severity of crashes were graded on a scale of 1 - 10 where 1 to 4 are very likely to be surviveable, 5 and 6 were 50/50 surviveable with an asociated risk of severe back injury and 7-10 are always going to be fatal, all that crashworthy seats will do is change the odds for scale 5 and 6 crashes to maybe 60/40 with a reduced chance of severe back injury. You can argue about the numbers I have quoted but the principle won't change. Is it not only within a small band of the crash severity scale that a crashworthy seat will make a difference? And if it has made a difference to the initial impact back injury, is it going to stop me breaking my neck, knocking myself out by head impact with metal cockpit frames, burning or drowning? Who can quantify that?
For me as an offshore pilot spending 99% of my time in the cruise above 1000' over water, back damage due to heavy landings/crashes is very unlikely compared to back damage due to poor seating position/comfort. This is very important when strapped to a vibrating seat for up to 8 hours per working day.
Now if someone can give me a crashworthy seat which is safer AND as comfortable/adjustable as some non crashworthy seats then I will have one.
Now, if I was an onshore pilot doing powerline inspection, I would probably have a different view because of the different risk profile.

[NickLappos]

Hugh,
Your math is impeccable, your data is wrong. The seats protect your back and prevent crippling injuries in the 95th percentile survivable crash. There are hundreds of pilots in wheelchairs who sat in survivable crashes and who will never walk again, and such seats would have saved their families the need to hold so many doors for them. Again, the absurdity of trading comfort over safety is just that, absurd. Stroking seats are just as comfortable (or just as uncomfortable) as unsafe ones.

I am surprised at your mistaken belief that over water flights somehow protect you from high g crashes, I guess you think water is soft! I recall a water impact accident - engine out landing - where the aircraft reached over 20 g's - the inertial impact of water entry is awesome. Had that helo been equipped with safety sets all would have had a chance to survive, as it was, their unsafe seats injured them into unconsciousness, and they drowned.

[HughMartin]

Nick,

Do you wear a crash helmet when you drive to work in your car? Does your car have a 5 point harness? Have you fitted an automatic fire suppresion system? I suspect not - neither have I.
We will all use statistics which suit ones own argument. I am just an ignorant line pilot who does not have access to all the facts and figures and I am sure there are hundreds of pilots who have suffered serious back problems but what were they doing at the time? All I have to go on is my own experience of 30+ years and 17k+ hours most of which has been in the goldfish bowl of the North Sea. During this time I have had to take time off work due to back problems several times (thankfully minor) and have known a number of pilots who have had to have operations to fix their problem backs which were contributed to by poor seat design. I don't really want to be critical of any particular manufacturer but SK has be seriously guilty of paying scant design to spinal health when designing the S61 and S76 seats.

I know of none who has survived an offshore accident to be impaired for any length of time with subsequent back problems. During my time in earlier lives flying low level pipeline patrols and other forms of aerial work, a crashworthy seat would have been very welcome but how many of the smaller single engine helicopters have crashworthy seats in the 21st century let alone when I was doing these jobs in the 70's and 80's.

The regulators and the industry are falling into the trap of imposing standards which are jack of all trades and master of none. Let's be more specific and design safety into the role rather than the aircraft type or class. A good example of this is the UK regulations which require a higher level of security for helicopters over a certain arbitrary weight even although they are doing the same job and carrying the same loads as ones below this arbitrary threshold weight.

Nick, if you can tell me of a crashworthy seat which offers the same level of adjustment and comfort as the best non crashworthy seat then I will be your biggest fan.

HM

[MSP Aviation]

For those who want some more insight on the user's opinion of crashworthy seating, I would recommend looking at Michael Durant's In The Company of Heroes. Durant is the US pilot who was shot down and captured in Somalia, and he describes in detail the stroking seat, which he believes saved his back. Yes, most of us do not risk being captured by enemy forces if we cannot exit our aircraft after a crash, but the benefits exist no matter what type of flying we do.

[HeliComparator]

Nick said

Remember, hc is the guy who told us that the size of the windows is more important that if the fuel cells are fire proof

So, lets consider how many passengers have died on N Sea operations from drowning as a result of difficulty in getting out following a ditching (sadly more than I care to remember) versus how many passengers have died as a result of fire after a crash landing (no passengers, though unfortunately 2 pilots in the early 80's during a training flight in a 330J).

So Nick, if that point is the crux of your argument against my logic, I suspect that your credibility with N Sea pilots has reached another all time low.
Is it co-incidence that your former project decided to put their money into fuel crashworthiness instead of escapability. No wonder the 92 is such a dog if this is an example of the logical analysis you applied when the 92 design priorities were drawn up. Woof Woof :yuk:

There was a long period of consultation when you did, to your credit, ask your customers including N Sea operators what they wanted in a new helicopter, but then to your discredit you ignored virtually everything they suggested.

MSP if I flew in a combat overland role, crashworthy seats would definitely be near the top of my priority list (after lead knickers and a teleport system) but different roles have different priorities.

HC

Note to self - next time you want to ask a question to judge the opinion of Joe Pilot, use a different username to avoid thread swamping by a xxx xxxxx xxxxxx

[zebedee]

Nick & Helicomparitor
Obviously you two have issues, and I doubt whether you would even agree that the sun is shining on a given day but the main point for me is that manufacturers are causing pilots to lose their licences because of back problems. They may have the best intentions in providing seats that will save your back if you crash, but then they advertise such reliable aircraft that the chances of a crash are small unless your job is higher risk than aircraft failure. That is the basis on which we sell the aircraft to customers after all!
If I have an aircraft that is less likely than any other to kill my passengers, then I want a comfy seat and a quiet environment. I'll take my chances with the people in the back when it all goes wrong. Nick, I'm no chum of HC, but this is not naive, it's day-to-day life. I know people who are in wheelchairs because of unforgiving seats. I agree with HughMartin that a comfortable "stroking" seat is a great idea, but our S92 guys are moaning about their seats already, and they only do about 4 hours a day! I flew the '76 for years and I still suffer from sciatica as a direct result! One respondent suggested filing reports, but we all know that once something is installed, it will stay there and the pilots just have to live with it. Better to get it fixed at the start?
For the record, yes, I have had a bad back. It started after 2000 hours on the S76 and got much worse until I changed fleets (3000 hours later) - to a comfortable, adjustable, technically non-crashworthy seat. I came very close to losing my medical AND having to undergo painful surgery as a direct result of the seats I had to use - the same seats in service on that fleet today.
Crashworthy vs. comfort is not an issue in my mind and, Nick, it is by no means ludicrous. I agree with you that "a seat that breaks your back is a sub-standard seat", but what if it does this over hours of normal service?
Zeb

[NickLappos]

ZBD,

I hate to be the bearer of bad news, but your "2000 hours in S76 seats" were spent in a seat that is NOT crashworthy. Your point, that crashworthy means uncomfortable, isn't based on facts!

I find it so very silly that we are arguing about apples and oranges.

Points:

There is no correlation between crashworthy seats and comfort rating. NONE. Literally all the seats ppruners sit in are NOT crashworthy, because the requirement is too new to have affected many.

Sorry about your back, seriously. Is there any seat that works for you?

[MSP Aviation]

HC,

Both the combat and overland aspects are irrelevant to the benefits of the seats. The fact of the matter is that one person believes that the seats allowed him to escape in a timely manner, something that is, if anything, more critical in an overwater flight.

[HeliComparator]

MSP

What you say is intrinsically true, however surely probabilities come into it? History has shown that the type of accident where crashworthy seats would have made a difference simply haven't occured on the North Sea, whereas its clearly a different answer for onshore single engine etc

HC

[FloaterNorthWest]

The crashworthly Martin-Baker seats in our new S76C++ are very comfortable.

I have noticed in a couple of aircraft, pilots putting items under the stroking seats which seems to defeat the object.

Can I add that most back problems are due to poor abdominal muscles so the correct posture is not held. So if you have a belly expect to have a bad back.

FNW

[nimby]

I agree that keeping fit (torso wall) lowers the stress on the back and thus reduces the risk.

... actually most back problems come from a combination of a twisted spine and low left arm (due to poor collective position and often a poor cyclic) interacting with vibration (usually low level and minimised by design for the pilot's seat, but usually present during some of the flight regime). Trying to keep your feet near the pedals doesn't help either. Perhaps of Chief Designers spent a little more time on the ergonomics before fixing the flight control geometry ... and perhaps if there was up-to-date anthropometric data ....:ugh:

IHMO, having evaluated seats for several projects and with many Test Pilots, comfort and crashworthiness are completely independent. Indeed the original Simula seat in WS-70 Blackhawk was rated by many as the most comfortable on-site (hats off nick:ok: ). The fully armoured, crashworthy design for the A129 LAH project (shows my age) outscored it though, even with the side panels fitted.

A comfortable design :) is one of the first aims of a crashworthy seat. The better shape your back is in at intial impact, particularly disk spacing, the better able it is to absorb the shock load. Nick's right, there are loads of 'retired' pilots whose careers should have been much longer. We've many here doing desk jobs ...:sad:

I'm surprised that there isn't a better retrofit market for seat installations, given the awful standard of most seats and the fact that pilots (or ex-pilots in management) do tend to a say in buying aircraft and selecting mods.


Nimby

[Broadcast Control]

HeliComparator, you bring up a difficult question.

AFAIK there are no crashworthy seats avilable that have adjustment possiblities that come close to the best non-crashworthy seats. Agreed, a given seat without adjustment features may be perfect for pilot X, but not likely so for a broad range of pilots. (The car industry seems to have drawn a similar conclusion, and offer seats with numerous adjustments.) I agree that in principle there is no reason a stroking seat should not be just as comfortable as a non-crashworthy seat, but unfortunately this is not the case today. IMHO selection of a non-crashworthy seats may therefor be the best (least poor) choise for some operators.

Note that there is a big difference between military and civilian "crashworthy" requirements.

[rotorrookie]

Remember, hc is the guy who told us that the size of the windows is more important that if the fuel cells are fire proof
So, lets consider how many passengers have died on N Sea operations from drowning as a result of difficulty in getting out following a ditching (sadly more than I care to remember)

HC is so right there but its not enough to make them big if it's obstructed like in this case.
http://www.etribes.com/sites/etribes.com/files/images/4_DSC00031.preview.JPG

[nimby]

Note that there is a big difference between military and civilian "crashworthy" requirements ... aside from the assumptions on how much armour or CBW protection the guy's wearing, both generally aim to have the crew not die. It's the certification which varies, not the requirement!

And as for the obstruction of windows ... too right! Try imagining what that handle look like upside down viewed from near the floor with estuary water and muck from the floor - in the dark.

[NickLappos]

rotorrookie took a few liberties with reality with that picture! The cabin has every window available as a push-out, and 4 big emergency exits in each corner, as well as a 6 foot ramp at the end. Those troop seats are removed with one hand pull, and are individually placed where the cew wants them, not mounted fully across the cabin in the SAR birds, so they are not a big deal. But when he shows one picture, it looks awful. Nice try.

Regarding the safety difference between civil and military stroking seats, the differences are small relative to the less safe non-stroking seats in grandfathered helos. Military stroking seats protect up to 20 g's, civil are 18 g's, and non--stroking are 4 to 6 g's (with no back protection at all).

The reason why hc must establish this seat mythology is that the stresses that an 18 to 20 g seat put on the airframe are so large that the floor structure simply cannot take swapping seats, and so the job of adding stroking seats is a lot more complicated and costly than just buying a seat. The floor redesign is eye-watering, about a 1200 pound penalty for the 225. Why? Because the 18 g's is about 4 times the load that the floor can take, so the seat won't stroke, it will simply tear a patch of floor off and merrily let the pilot bounce around the cockpit still strapped to the disconnected seat. Thus you get their chief salesman telling you that "you don't really need them" instead of a clear call for safety for passengers and crews!

This bizarro thread really scares me. When ppruners begin to debate if the earth is flat, and if we should take safety feaures out of new machines like the 139 and 92. It is the victory of rampant ignorance like this that makes me cynical about our plight - if pilots don't call for safety changes, don't expect regulators and manufacturers to line up to make changes.

If Luddite pilots like helicomparitor win their points, we will sit in pools of spilled fuel, unconscious in our seats waiting for the fire to reach us, while military pilots can walk away and help rescuers treat the passengers. Sad story, guys. Keep it up, weaken safety features, and close our market further, maki it better for our real customers, the passengers, to want another way to get to their destinations, and stop those checks from coming in!

[HeliComparator]

When ppruners begin to debate if the earth is flat

Nick, stop trying to pick another argument. Everyone knows that the earth is flat. It has to be, otherwise my football would roll away never to be seen again. Point proven I think!

Just for the information of others (no point in trying to inform Nick of anything) the EC225s in service for oil and gas support all have crashworthy passenger seating which of course includes strengthened flooring to be able to take the g loads. Its true that this is an "optional extra" that does add weight (though not as much as Nick suggests) but even with that extra weight, the payload of a 225 is still greater than a 92.

HC

[HughMartin]

Nick, I notice you didn't answer my questions in my previous post
Do you wear a crash helmet when you drive to work in your car? Does your car have a 5 point harness? Have you fitted an automatic fire suppresion system? I suspect not - neither have I.

[NickLappos]

Hugh,
Your question raises an interesting and important point - is the REQUIRED safety level enough?

First point: We are not talking about adding safety onto a helicopter, as in "should I install stroking seats?" We are talking about if our helicopter should meet the newest minimum safety standard, or should we ignore the latest safety rules.

Second Point: Is there value in seeking the newest, safest standards? I think so, and I do BUY my car by referencing the head injury index that is published in several sources, so that I know I don't have to wear a helmet. I also will be sure that the cars I buy have 6 airbags for front, side and glass protection for the occupant, ABS and side door structural protection. This means that my kids drive around in the reasonable safest car that can be bought.

Third Point: Do we trust the folks who set the minimum safety standards for our civil aviation authority, or do we listen to arrogance like helicomparitor, who thinks he knows better? What do I mean by arrogance? Helicomparitor would not last through three questions from those who have studied the ways to grow our industry's safety, engineers and regulators who agonize over the next step we must take, folks like JimL. These engineers who work for FAA and JAA use test and accident data, and knowledge of technical solutions to set the absolute minimum safety standard that should be met, rules that cannot be waived by new helicopters. This "debate" especially concerns me, I was the Chief Test Engineer for Sikorsky, and am intimately familiar with the percentiles of accident severity as well as the design methods to help save lives, and the economic tradeoffs that set the standards. This is NOT a competitive issue, I have repeatedly said that the AB-139 also meets this new standard, and is therefore a very worthy helicopter.

[JimEli]

>
This bizarro thread really scares me.
<

me too.

[Tractor_Driver]

I am sure that the designers at Augusta, Bell will be very gratified by your gracious endorsement, Mr Lappos.

Seriously, though, crashworthy seats are important and I am sure that in time lives will be saved.

Seating is, however, not the only consideration when assessing the “worthiness” of a helicopter. There are two main contenders in the heavyweight class at the moment, the EC225 and the S92A. They each have their champion on this forum (although the level of debate at times leaves a little to be desired). Each has its merits and its faults. The passenger compartment and baggage area of the 92 are clearly superior in terms of space and, as has been stated, the crash resistance of the pilots’ seats in the 225 does not meet the highest standards. The 225’s deficiencies can mostly be explained by its derivation from a 1960s aircraft.

The shortcomings of the 92 are less easy to explain and one wonders whether they stem from a “not invented here” syndrome. The avionics are, to say the least, disappointing. Just as one cannot imagine someone preferring the cabin of the 225 (it’s so cosy!), no-one who has spent even an hour with a Eurocopter display would consider the Sikorsky version an improvement. The cockpit, while far more spacious, is poorly designed ergonomically, with much wasted space and many controls being out of reach for one pilot. The field of view from the cockpit is poor, especially in the hover, and will undoubtedly lead to problems, especially landing on small, moving, decks. My biggest concern, though, is with a linking of 3 factors. I cannot speak for the 225 but certainly with the 332l, zero/zero autorotations were possible. Again with the 332l and, I imagine, the 225 it was permitted to inflate the flotation in the air. This is prohibited on the 92. In a forced ditching it is therefore likely that the aircraft will arrive fast and heavy and roll before the floats can deploy. This is especially true if only the standard, fuselage mounted, floats are fitted. One then has the problem of an inverted helicopter with less than ideally sized windows. There are many offshore workers who would struggle to fit through one on a good day, let alone inverted, under water, in the dark and panicked, wearing a LAP jacket. I just hope that I will not be able to come back to this post in years to come and say “I told you so”

[JohnDixson]

Not sure what a zero/zero autorotation was as referred to, but if one has a video of a zero groundspeed auto landing in the 225-AT MAX Weight, I'd love to view it. Also, with re to the S-92 float deployment question, that procedure was the subject of lively discussion, without unanimity of opinion ( but finally, with consensus ). Note the section of the flight manual that covers the inadvertant flat deployment speeds etc. We flew all of that, of course, and there were no flying or handling problems at all. Biggest excitement was the sound associated with deployment.

[Tractor_Driver]

John,

Yes I would also like to know if it is possible! The zero/zero refered to was zero forward speed and zero vertical speed just before touchdown.

As to float deployment, I am aware that it is possible to continue flight with them out. I assume that the prohibition on deliberate deployment is to prevent a water landing with appreciable forward speed [because of strength considerations?]. Am I wrong?

[HeliComparator]

Massey / John

I am sure the 225 could do a zero/zero auto at max all up weight provided it never had to fly again! Is there is an issue with autos on the 92? The video certainly showed a fast touchdown speed - faster than one would like into water or rough ground - but it all depends on the wind, weight and how much its insured for:}

Float arming and inflation speeds have long been pilot-unfriendly on Sikorsky aircraft. But the most pilot-unfriendly limitation surely has to be the wipers!
On the 225 the limit is 150kts for arming or inflation, though I wouldn't like to try the latter. Recommended inflation speed is 80 kts.

So if I interpret correctly, no float inflation on the 92 until after ditching? Remind me why we bought them - Oh yes, it was to improve safety:ugh:

HC

[JohnDixson]

I am sure the 225 could do a zero/zero auto at max all up weight provided it never had to fly again!

And provided one could talk some not too bright but very heavily insured pilot into doing it!

The appropriate FAR 29.75 and accompanying Advisory Circular AC 29-2C do not specify a landing speed requirement, and in fact the AC only states that less than 40 KIAS is recommended.

I don't know, HC, whether you have access to an S-92 RFM, but the discussion about flying the aircraft following an inadvertant float deployment, wherein it cites holding the speed to 80 kts and provides information regarding indicated airspeed to follow for climb, level flight and descent/autorotation to achieve a calibrated airspeed of 80 kts, represents actual flight test results. There are no surprises in store here.

[HeliComparator]

John

No, I don't have easy access to a 92 rfm but I am curious about the comment on not firing the floats until in the water. Does this apply to power on ditchings as well or just to autorotation landings (or neither)?

Regarding flight speed following deployment, many years ago my captain deployed the floats on a 332L on a platform 280nm from base whilst I was downstairs having a pee (maybe he was bored?) and there was no alternative but to fly it back into a 40 kt headwind (via 3 refuelling stops if memory serves correctly!) and I seem to remember that 80kts was about all we could build up the courage to do, especially as after a while one of the bags started to sag and was flapping alarmingly! The 332 was certified to 135kts for arming and deployment (or was it 130?) but I would not like to be the one testing it!

HC

[212man]

The limitation (stated in Part 1 Section 1: Limitations, and repeated in Section 3: Emergency Procedures,) is as follows:

"Deploying the floats in flight is prohibited."

It's pretty clear cut, and even the ditching drills require alighting first before deploying the floats (presumably in case they haven't deployed automatically!)

Personally, if I was carrying out a controlled ditching with power I'd probably pop them first, in the hover. At least if one doesn't inflate you know you are going to roll over!

It would be interesting to know waht pitot static error is present on the 332 (I may have known once but have forgotten). In the event of flight with the floats deployed on the 92, you should fly at no more than 50/55/60 KIAS for climb/cruise/descent, which equates to 80 kts actual IAS. Your 80 kts may have been much higher!

[HeliComparator]

212, re the pitot-static error with floats out, I don't recall ever seeing this published (though I am sure there is significant error)

HC

[mickjoebill]

Would posters to this thead comment on the detailed pictures of the recent S350 crash in Germany where two on board suffered spinal injuries.
http://kurier.at/galerie/index/3930/1/nachrichten/chronik/74208
It appears that the seats did not deform, I understood that the rear seat would collapse/deform in a heavy landing.
Is a simple improvement of energy absorbing foam in seats worth considering made law?
While on the topic, looking at these pictures, for the sake of say 40 kilos of a carbon fiber rollbar couldn't the integrity of the cabin of the AS350 be significantly improved?
Mickjoebill

[NickLappos]

http://kurier.at/galerie/index/3930/5/nachrichten/chronik/74208#topgalhttp://webpages.charter.net/nlappos/350crash.jpg

That photo tells a whole story about crashworthiness, which has 4 major constituents:

1) Primary structural integrity - where the fuselage has the basic strength to maintain its shape under an impact from any of the principle directions.
We speak of the passenger/crew compartment keeping its primary shape (like a roll bar helps a car) during crashes of 20 g's vertically or forward, 10 g's laterally and 10 g's upside down. If the compartment does not hold its shape, it will crush the occupants, and stroking seats would be worthless.
2) Passenger and crew seats that allow the bodies to be decelerated smoothly and not injured, even though the strong cage they are in decelerates more quickly. The seat holds the occupant, and descends as the fuselage stops abruptly, thus allowing the person to "feel" less deceleration, and experience less spinal stress.
3) Anti-plowing and anti-rollover protection, so that the fuselage does not dig in and flip/roll but rather slides to a stop. The anti-plowing beams on many helos look like sled skids as the fairings around them crumple. These skids allow the fuselage to skid rather than digging in and causing dangerous flips and rolls.
4) Fuel system bags that both stay whole during the crash, and are not subject to the twisted and deformed metal structure causing punctures. Without crash bags for the fuel, a post crash fire could kill those who otherwise survived.

In these discussions I have tried to tell the story that latest regulations give measurable increases in safety. Note that the 350 is allowed to come apart at 4 g's of crash, while a newer part 27 aircraft has to stay together until 16 g's - newer aircraft are four times stronger, and arguably very much safer.

It is a shame that manufacturers are allowed to continue to sell the older machines as "new" and not tell anyone about this very important reason to look only at more modern machines.

FAR 27.561 (latest):
(3) Each occupant and each item of mass inside the cabin that could injure an occupant is restrained when subjected to the following ultimate inertial load factors relative to the surrounding structure:
(i) Upward—4g.
(ii) Forward—16g.
(iii) Sideward—8g.
(iv) Downward—20g, after intended displacement of the seat device.
(v) Rearward—1.5g.



FAR 27.561 (old version):
(3) The occupant experiences the following ultimate inertia forces relative to the surrounding structure:
(i) Upward--1.5g.
(ii) Forward--4.0g.
(iii) Sideward--2.0g.
(iv) Downward--4.0g, or any lower force that will not be exceeded when the rotorcraft absorbs the landing loads resulting from impact with an ultimate descent velocity of five f.p.s. at design maximum weight.

[Tractor_Driver]

Nick,

can I asume that the current generation of S76s are designed to the latest FARs?

[mickjoebill]

Thanks Nick.

As a back seat AS350 driver I'm aware of the large mass behind rear passengers head that is likely to crush passengers who in some accidents would (by my best guess) otherwise could have survived.

What kind of internal "roll bar" structure would have prevented the rear seat being deformed in the above photo?

I have been musing about some kind of carbon fiber internal framework that would include floor members for seats to be fixed.
This would have a place for those that regularly fly low and only carry 3 or four souls, ie police, inspection, sling and filming work.

It would form a seperate inner shell that could? deflect the engine and gearbox up to a point where G would cause fatal injuries to passengers.

The open nature of the AS350 would enable such a framework to be easily installed.

A cross member would be required from the top rear to the floor.


Having seen incredibly lightweight carbon fiber sections used on F1 I wonder if similar technology could have its part to play to improve crash worthyness of the most popular light utility helicopter.

Reports of last weeks fatal accident of the AS355 in the UK suggest that the aircraft is largly intact with no post crash fire.

Is their a market for this?

Or if one was designing a new heli from the ground up, a self contained F1 style monocock that seperates itself from the heavy metal of engine and gearbox in an accident rather than absorbing their energy?
An idea for the future perhaps?

You dont ask, you dont get...

Mickjoebill

[NickLappos]

Tractor_Driver,

Specifically, no, the S-76 family meets older FAR, current when it was designed. I make these observations without ANY bias toward any brand or manufacturer.

How can you tell which of the "new" helos is new? It isn't easy, but it is available as public record in every country but France.

Each helo type design has a "Type Certificate Data Sheet" which gives the basic limits and the "certification basis" which is the EXACT rule that the helo was certified to, listed as the regulation (like FAR 29) and the exact amendment for each paragraph (like 29.561 amendment 16).

Let's be practicle, when you design a helo, you cannot easily "chase" the regs as they get tougher and tougher. So you nail them down when you apply to the FAA/JAA, and both parties agree to the cert basis. The cert basis is usually just the exact FAR 27 or 29 amendment, with perhaps a few newer paragraphs or 'special conditions" that embrace the nature of the helo to be certified. The application cert basis is usually good for 5 years, which means you start a clock on application, and have 5 years to certify or lose the cert basis. (It is said that the EH101 was in real trouble, and had to rush thru a certification because the FAA/CAA were about to close the door and pull the old cert basis!)

The S-76 is designed to FAR 29 amendment 10. The S-92 meets FAR 29, amendment 47. On a web site called "Historical FAR" you can find the exact old paragraphs that the older helos were designed to, that is how I pulled the two crash strength paragraphs that I posted below.

As I have repeatedly said, the S92 and the AB-139 are the only two Part 29 helos that meet the latest FAR/JAR. Period.

[zalt]

Nick

Glad to see there was no rush by Sikorsky. See www.easa.eu.int/doc/Certification/Design_Appro/Rotorcraft/EASA.IM.R.001%20Issue%203.pdf

While this does not show the original application date to FAA, that must predate the JAA application date, giving 7.5 years at least (mid 1995 to late 2020).

6. National Certification Date: 17 December 2002
7. JAA (Validation) Application Date: 12 June 1995
8. JAA (Validation) Recommendation Date: 14 May 2004
9. EASA Type Certification Date: 08 June 2004

I heard a rumour though that the FAA certification washed rushed so that when the JAA team visted Sikorsky that the first thing they (in fact Mr KO) could show was the FAA TCDS, even though the S-92 was meant to be the first truely joint simultaneous certification project.

[NickLappos]

Zalt,

Do I detect some attitude there?

The reason why the cert time was longer than 5 years is because Sikorsky did what the other manufacturers never do - update the certification basis to INCLUDE the FAR/JAR changes that were being made while the aircraft was being designed. In other words, the S-92 met the absolutely latest FAR/JAR the day it was certified. The EASA TCDS doesn't make this obvious, because it lists JAR 29 rev 1, which was the same as FAR 29 rev 45 (the latest as of Dec 2002.)

Rolling the cert basis upward to the newest regs meant designing to draft FAR's, redoing tests as the FAR's matured, and also breaking new ground as to how to meet the FAR, since no cert guidelines were written. The FAA guys were first class, and (while they were tough) they worked many weekends and late nights to approve or mark up cert documents. They also traveled on weekends and holidays to be there when the tests were performed. Since then, the 92 has been certified to rev 47, which is the most current, yet again.

The reason why the 92 did not have a simultaneous FAR/JAR cert is that when it fell behind, I could not have the cert team do double work (I was the Program Manager then). I personally spoke to the JAR team lead and apologized, but we could only spread the team so far. As soon as the FAR cert was finished, we brought the JAR team in and began that work. The JAR guys were similarly gentlemanly and worked hard to be sure they did not hold the schedule up.

BTW, I also believe the 139 was certified to the latest FAR/JAR, but I am too lazy to look it up tonight.

[Tractor_Driver]

Nick,

Thank you for that clarification. But if there are only 2 helicopters that meet current regulations, isn’t it just a little premature to proclaim:

“It is a shame that manufacturers are allowed to continue to sell the older machines as "new" and not tell anyone about this very important reason to look only at more modern machines.”

especially in red ink!

I sometimes wonder whether our regulators are really doing us favours by insisting on a “zero risk” approach on certain parameters which leads to very long lead times and huge expense for any progress, which in turn means that we have to fly with ancient technology. We all know that the $300 sat nav that we buy at radio shack is far more reliable and accurate that the $30,000 kit on our instrument panel but it hasn’t been through the approval process and we are not allowed to use it.

The automotive industry moves so much faster. Now we all have highly efficient small, agile, turbo diesel powered vehicles, we have difficulty imagining using 5.7 litre V8 trucks with flatbeds the size of tennis courts and cart springs to bring the groceries home from Wallmart. Well. we do on this side of the pond anyway.:)

[NickLappos]

Tractor,
You raise a very valid point! The problem is a chicken and egg thing....if the comparatively knowledgeable pilot community doesn't know this stuff, how can they lead their bosses/backers to buy the good stuff? If they don't buy the good stuff, then why would anyone stop making the old stuff? If all we have is old stuff, then there will be many more broken backs and post crash fires, and our market will stay small because the public knows that helicopters are dangerous!

Seriously, I misspoke when I said only two helos meet the new criteria, I think several Part 27 smaller helos meet the newest standards, also.

[slowrotor]

An FAA inspector found an unapproved shoulder harness on a airplane I was working on with the owner. The inspector said " get the installation approved or remove the shoulder harness, your choice."
The owner removed the shoulder harness in order to make the aircraft "airworthy". True story.

If I was the FAA inspector in this case, I would have helped the owner get the existing belts approved.

The FAA should "help" all owners retrofit crashworthy seats and other improvements, but the FAA rules sometimes impede safety.

I share your frustration Tractor Driver.

[Graviman]

I have been musing about some kind of carbon fiber internal framework that would include floor members for seats to be fixed.

This would have a place for those that regularly fly low and only carry 3 or four souls, ie police, inspection, sling and filming work.

It would form a seperate inner shell that could? deflect the engine and gearbox up to a point where G would cause fatal injuries to passengers.
The open nature of the AS350 would enable such a framework to be easily installed.

A cross member would be required from the top rear to the floor.


MJB, this sort of structure is best considered as part of the OEM design program. You can find yourself chasing the next weak link otherwise. If you have identified a market, and are serious, i would talk to MIRA (Nuneaton UK - www.mira.co.uk ). They have a world class test facility, as well as talented design and analysis capability (this includes experience of composite structures).

Mart