If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
Bob Kuykendall wrote:
Furthermore, virtually everything you can do to improve crashworthiness increases weight, And everything you do to increase weight increases speed and impact energy. It's all a bunch of trade-offs. Let me quibble with Bob a bit: a "safety cockpit" is more than just more structure to make it stronger, but includes things like * a steeply sloped seat pan under the thighs to reduce the chance of submarining * locating the seat belt anchor points so the belt stays on the hips and does not ride up to the abdomen * locating the shoulder harness so it doesn't compress the spine during a crash * making the instrument panel frangible, so it doesn't injure the pilots legs * making the instrument panel swivel upwards, so a pilot can bail out more easily * using a form of "Roeger hook" to ensure quick and clean jettisoning of the canopy when the pilot wants to bail out The items above involve little, if any, additional weight, yet can make a major difference to the pilot's injuries. Older gliders might not have any of these features; newer ones will have most of them. Some features of the newer cockpits will add weight, but I don't think it's a given that the speed will increase. Don't the JARs require certain stall or landing speeds, for example? A designer can compensate for weight with more wing area or a different airfoil to keep the speeds the same. -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#12
|
|||
|
|||
At 17:48 23 June 2005, Bob Kuykendall wrote:
[Warning: starts on-topic but heads for a trip through the weeds] However, you don't have to look too far to see an alternate future in which this is not the case. Suppose, for a moment, that it becomes fashionable to gamble on the outcome of certain soaring contests. Prizes and incentives are offered for winning. Competitive performance becomes not just a matter of pride and prestive, but of serious financial gain. Serious racing sailplanes get smaller and lighter. Comfort and crashworthiness yields to performance. Pilots are hired guns, and though they obviously have some voice in matters of safety, it is not a loud voice against the background of finances, sponsorship, media coverage, and commercial patronage. In order to call yourself a national champion or even a national contender, you'd have to rise to an entirely new level of risk exposure. Let me be the first to admit that this is a pretty out-there vision of the future of contest soaring. I do not think it is likely we'll see it come to pass. I do not wear that kind of tinfoil beanie. However, I do think it merits some thinking on. What would such a future mean for the rest of the soaring world? More media attention? More money and participation? More regulation and restriction? Thanks, and best regards to all Bob K. http://www.hpaircraft.com/hp-24 Bob, Its all fantasy land but I think that if a lot of money came into competitive gliding the pressures towards safer structures would increase rather than decrease. Look at the survivabilty of those tiny F1 racing car 'fuselages' that have strengthened steadily as the money in the sport has grown (they do race sometimes - albeit not at Indianapolis). As competitors in sport get better paid they value themselves more rather than less. John Galloway |
#13
|
|||
|
|||
[Apologies if this is a repeat post. Google acted like it ate the first
one I composed. Bad Google! No biscuit!] Earlier, Eric Greenwell wrote: Let me quibble with Bob a bit: a "safety cockpit" is more than just more structure to make it stronger... Please do, Eric. We've come to expect no less from you! But seriously, thanks for that list of basic safety items. I agree that they all should be in any modern cockpit. And I agree that none of them carries a substantial weight penalty. But beyond those basic elements, crashworthiness is most effectively achieved with two basic things: * Stuff that absorbs energy as it progressively crushes * Space for the stuff to crush into before reaching the pilot's vital bits Stuff adds weight, and space adds volume, area, and drag. All of those will have deleterious effect on perfomance. Furthermore, I definitely disagree with the characterization of crashworthy cockpits as simply "stronger." What you want is not necessarily a structure that supports great loadings without failure (that's what I think of when I hear the word "strong"). What you do want is a structure that deflects or breaks in such a way as to distribute an impact over the greatest amount of time possible. That reduces G loadings to the contents of the structure. The main point there is that the light, strong, stiff carbon fiber that we like to build gliders out of is great for handling flight loads, but is poor at absorbing energy. It tends to break all at once, and what's left after that is not good at supporting any further loadings. Modern aramids and polyethelynes (sp?) like Kevlar(tm) and Spectra(tm) _are_ good at absorbing energy, and are also quite strong, but their relatively low stiffness makes them much less effective at supporting flight loads. That leaves it to the sailplane developer to arrive at some compromise of materials. Perhaps they use the tough stuff in greater thickness to achieve adequate stiffness. Perhaps they use a combination of tough stuff and stiff stuff to achieve the better properties of each. Either way, there is just plain more stuff there, and inescapably more weight than is dictated by the basic flight and handling loads. TANSTAAFL and all that. And, yes, the sailplane developer is free to add wing area and to choose docile airfoils that bring the stall speed down. However, both of those choices will tend to have an adverse effect on performance. And that's not a bad thing in and of itself. But as DG has discovered, performance sells a lot better than safety does. You can make the safest sailplane there ever was, but its performance might be so poor that you don't sell a single example. Net safety gain for the sport: zero. Somewhere between there and the ultimate performing thin-skinned racing ship is a reasonable compromise. Choose wisely, and y'all be careful now, y'hear? Thanks again, and best regards to all Bob "Grasshopper, why wrists say 'Hibachai?'" K. http://www.hpaircraft.com |
#14
|
|||
|
|||
On 23 Jun 2005 10:33:46 -0700, "Bob Kuykendall"
wrote: One interesting tangent to this issue is that there is a clear competitive advantage to small, light fuselages with small cockpits. .... and small pilots. Unfortunately reality shows that an extremely small cockpit (Ventus/Discus a, Diana 1) does not influence the outcome of a competition - gliders with bigger cockpits don't show an disadvantage in reality. However, you don't have to look too far to see an alternate future in which this is not the case. Suppose, for a moment, that it becomes fashionable to gamble on the outcome of certain soaring contests. Prizes and incentives are offered for winning. Competitive performance becomes not just a matter of pride and prestive, but of serious financial gain. In other words: Formula One. The racing class that has created the fastest and safest cars on planet Earth within the last decade. Bye Andreas |
#15
|
|||
|
|||
Andreas Maurer wrote: Unfortunately reality shows that an extremely small cockpit (Ventus/ Discus a, Diana 1) does not influence the outcome of a competition - gliders with bigger cockpits don't show an disadvantage in reality. Hmmm. What results are you citing? In other words: Formula One. The racing class that has created the fastest and safest cars on planet Earth within the last decade. Tell that to the families of the drivers killed through the mid-1970s. Bob K. |
#16
|
|||
|
|||
I have to smile at all these musings about safety cockpits because it
will have virtually no effect on the injury/death rate in soaring. Even if every new glider had a "safety" cockpit there would be no significant increase in the percentage of such cockpits for decades to come. Gliders, as well as other aircraft, will be, and are, kept in service until it is overwhelmingly uneconomical to do so. And spare me the "well we have to start somewhere" comment. Personally, I am not going to spend an extra $100K to replace my current motorglider with a "safer" one. That last fatal accident I posted shows you where you need to spend your effort: influencing the judgement of pilots. This is not an impossible task; the GA accident rate has been declining even with an ageing fleet. Tom |
#17
|
|||
|
|||
|
#18
|
|||
|
|||
Unfortunately reality shows that an extremely small cockpit (Ventus/Discus a, Diana 1) does not influence the outcome of a competition - gliders with bigger cockpits don't show an disadvantage in reality. Well, let's see: Leszno 2003 WGC, standard class: Discus 2a placed 1, 2, 3, 6 (other top ten gliders were LS8, and a lone ASW 28 and Discus 2). Leszno 2003 WGC, 15 m class: 5 Ventus 2a or 2ax in the top ten (with 4 ASW-27 and a lone Ventus 2bxr prototype). It seems at least to indicate that the better pilots like the small cockpits! -- stephanevdv ------------------------------------------------------------------------ Posted via OziPilots Online [ http://www.OziPilotsOnline.com.au ] - A website for Australian Pilots regardless of when, why, or what they fly - |
#20
|
|||
|
|||
"Bob Kuykendall" writes:
Tell that to the families of the drivers killed through the mid-1970s. Do you know one of the main causes of death back then? Dry Powder fire extiguishers, followed by burnt lungs. It is when the big saftey push started, by Jackie Stewart AIR. -- Paul Repacholi 1 Crescent Rd., +61 (08) 9257-1001 Kalamunda. West Australia 6076 comp.os.vms,- The Older, Grumpier Slashdot Raw, Cooked or Well-done, it's all half baked. EPIC, The Architecture of the future, always has been, always will be. |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
American nazi pond scum, version two | bushite kills bushite | Naval Aviation | 0 | December 21st 04 10:46 PM |
Hey! What fun!! Let's let them kill ourselves!!! | [email protected] | Naval Aviation | 2 | December 17th 04 09:45 PM |
memory of capt. Maurizio Poggiali- Italian Air Force | petit prince | Naval Aviation | 0 | November 23rd 03 09:25 PM |
Question to our Italian friends | Peter Nyffeler | Soaring | 3 | November 12th 03 06:15 PM |
Soviet Submarines Losses - WWII | Mike Yared | Military Aviation | 4 | October 30th 03 03:09 AM |