There is a REAL difference between an airbag and foam.
Say you land on your bum starting with a fully inflated airbag. While impacting with the ground, the airbag bulges here and there, so the total volume of the airbag is reduced, and pressure increases. I estimate that the total volume is reduced by about a factor of two by the time that your bum hits the ground.
At this point the airbag is trying to prevent you from hitting the ground by airpressure of 2bar (1kg/cm^2 of overpressure). Estimate the surface area of your bum to be about 40x40cm, you will be experiencing an upward force of about 1600kg. Or about 20G for an 80kg pilot. This is what medical experts consider survivable without damage to the spine.
But what if your speed was a bit higher, and when your bum hits the ground, your speed is not yet 0. Decelleration suddenly spikes from 20G to say 300G to make you stop in the next couple of mm that the ground is compressible. This could quite likely cause spinal injury.
Foam is quite different.
First, the cells in the foam are mostly closed. Thus when half the thickness of the foam is used, little or no air will have escaped to the sides, so pressure will be about 2bar, just like with the airbag. And the same calculation comes to 20G for the pilot. No spinal injuries. However, if your speed hasn't come to zero yet, you will continue to compress the cells in the foam, and pressure will increase. Say, you finally come to rest at compressing 2/3'rds of the thickness of the foam. Top pressure about 3bar, top accelleration about 30G. Injuries possible. But compare this situation with the airbag please?
The DHV testing method (drop a test-dummy from 1.8m, and check accelleration < 20m/s^2), means that up to a certain speed (which in fact is quite low) all protections are "good". When you exceed that speed, DHV makes no promises. But in practise you might encounter that situation, and the behaviour of your protector in that situation may make a significant difference.
I definitively prefer foam.
Foam has two disadvantages. The air from the airbag packs lighter and smaller than the foam in the foam protection.
如何发图片阿？方案发不上来阿
构思不错,只是现在的伞包也不小了,如果加上这些东东的话,会不会很难包装?
还有最重要的就是如果飞行中干扰到伞正常飞行或在紧急时影响副伞开启的话就很危险了!
好构思！～不过现在的充气座袋就是这样的了啊！？还自己费什么心改装啊！？
可是空气坐袋感觉压力可能不够，再者普通坐袋＋气囊应该比但靠飞行充气的坐袋更好些吧，垫个充气枕头试试
应该可以吧。
也许专业设计大师们会考虑更多综合因素，很多设计都是折中的结果吧。或者我们把更多精力用在技术的学习上，对安全更多帮助。
建议搞个半径是2米的气囊，钻到里面就不怕摔了。
啥？那不变成气球啦？对，就是这样，安全啊！
飞？还是飞吗？哎，能飘着就可以啦！也是飞的另一种形式！
谢谢各位对这个幼稚话题的反应，看来提的有点不合时宜。好像看网上当年康师父曾经有过这样的改造设想，还出示了气囊。
我想这样假设，如果新鸟在2－4米高度未出坐袋而全失速下落，或遇单边而螺旋下坠，如果平均速度为 10米每秒的话，接地瞬间速度将降低为零，这样的话和平路 汽车以36公里速度撞墙后结果一样。试想用现在普通坐袋的木板 ＋海绵 的形式加以缓冲的话，效果应该不如气囊。充气坐袋还没见过，如果作用可比气囊，当然在好不过咯，当然屁屁肥者缓冲也大，看来肥也有肥的好处
其实楼主的问题不算幼稚！大家的回应也都是有原因的。
这样的讨论很好啊，你有这样的探索精神值得鼓励！
你可能以为简单装个例如你所说的气垫就能解决问题？其实不然！
例如汽车的安全气囊技术是靠气囊撞击身体时缓慢放气来吸收撞击时的动能的，如果撞击更猛烈的话身体也够呛，如果你的气垫能够解决这些技术问题那就会好很多了！
如果你那气垫只是个气球不会吸收动能的话也和没有区别不大，或者说和现在的充气座袋区别不大。
还有一个楼主观念错误～现在的飞行员选择充气座袋多数原因是因为它轻便，背部保护也不差！
再好的保护都比不上自己去主动防护，如果所有民航飞机都每次降落都要重着陆就没人再敢坐了。
养成正确的飞行观念，提高自身技术水平，正常降落，不耍飘！防护仅仅是防护，不能避免碰撞，能避免碰撞的只有你自己！
最近看了国外的论坛，也在讨论空气坐待和泡沫坐待的差别，有人提议将两者合二为一，就立马有人说已经有这样的产品了
具体链接如下，不好意思没有翻译，大家将就看看
http://www.paraglidingforum.com/viewtopic.php?t=6324
There is a REAL difference between an airbag and foam.
Say you land on your bum starting with a fully inflated airbag. While impacting with the ground, the airbag bulges here and there, so the total volume of the airbag is reduced, and pressure increases. I estimate that the total volume is reduced by about a factor of two by the time that your bum hits the ground.
At this point the airbag is trying to prevent you from hitting the ground by airpressure of 2bar (1kg/cm^2 of overpressure). Estimate the surface area of your bum to be about 40x40cm, you will be experiencing an upward force of about 1600kg. Or about 20G for an 80kg pilot. This is what medical experts consider survivable without damage to the spine.
But what if your speed was a bit higher, and when your bum hits the ground, your speed is not yet 0. Decelleration suddenly spikes from 20G to say 300G to make you stop in the next couple of mm that the ground is compressible. This could quite likely cause spinal injury.
Foam is quite different.
First, the cells in the foam are mostly closed. Thus when half the thickness of the foam is used, little or no air will have escaped to the sides, so pressure will be about 2bar, just like with the airbag. And the same calculation comes to 20G for the pilot. No spinal injuries. However, if your speed hasn't come to zero yet, you will continue to compress the cells in the foam, and pressure will increase. Say, you finally come to rest at compressing 2/3'rds of the thickness of the foam. Top pressure about 3bar, top accelleration about 30G. Injuries possible. But compare this situation with the airbag please?
The DHV testing method (drop a test-dummy from 1.8m, and check accelleration < 20m/s^2), means that up to a certain speed (which in fact is quite low) all protections are "good". When you exceed that speed, DHV makes no promises. But in practise you might encounter that situation, and the behaviour of your protector in that situation may make a significant difference.
I definitively prefer foam.
Foam has two disadvantages. The air from the airbag packs lighter and smaller than the foam in the foam protection.
看看论坛上的滑翔中的危险情况录像：
http://www.youtube.com/watch?v=x4wemjj5cXw
这个家伙对保护气囊和泡沫垫的数据分析让人想起一个老贴，
不要和理科生讨论性爱的问题一样，都是用数学的方法进行的科学分析，其中的重力加速度的计算很搞笑