pete_b Posted November 4, 2008 Share Posted November 4, 2008 Please ALL look at this and read Pete b http://www.aaib.dft.gov.uk/cms_resource ... amotor.pdf Its nothing to worry about but do not overload your equipment and DO YOUR PREFLIGHT CHECKS PLEASE Quote Link to comment Share on other sites More sharing options...
norman Posted November 4, 2008 Share Posted November 4, 2008 This is an interesting accident that has been on the agenda for some time now, hasn't it Pete? It is useful as it highlights the fact that although extensive certification testing is carried out on wings, none is carried out on motor units in this country. Many manufacturers insist that they carry out exhaustive testing of their units but then don't publish their processes or results albeit for understandable reasons. That leaves the public with few options... buying German is one as they certify their motors quite exhaustively. Your wing might be designed/stressed to 8G (12 ultimate) but whilst your motor and its components may have been designed with these loads in mind, they have not been verified via independent process. That is the only way that you get peace of mind and until a time is with us when these processes are followed, doing maneuvers with a rig that imposed loading above 'normal' flight loads is unwise. The AAIB concur with that line of thought in their report. It seems likely that few paramotor pilots have felt the effects of acceleration levels over a couple of G and therefore simply cannot comprehend the physical loads that these accelerations impose when they start to stretch to 3-6G and above, particularly when they are sustained for 15-30 seconds (a long time under these loads). They can reason and imagine, but they cannot comprehend. Food for thought - your forearms probably weigh what, 5kg? 6G makes that 30kgs aside with your upper arms weighing more. Can you lift 30kgs with one arm under 1G? Furthermore, could you lift that weight and throw something weighing 4kgs (oops, no -the reserve now weighs 24kgs - total for those muscles now around 50kgs) sitting in your armchair in front of the TV? If the poor unfortunate who died in this accident was flying with a reserve it may be that he was physically unable to use it. Let's face it, even at 3 or 4G the scenario is a little dark isn't it? Could you hold the brake handles or reach for lines above your head with those sorts of load being felt? What would be the overriding control input under those conditions? If you are not acclimatised to aerobatics you will probably start to 'grey out' around .... say four or five G. Just a thought.... Can you see any holes in my maths? - never my strong suit.... On a brighter note, it looks as though the weather is going to perk up a bit over the next day or two. Quote Link to comment Share on other sites More sharing options...
Farmer_Dave Posted November 4, 2008 Share Posted November 4, 2008 Very rellevant info Norman. The stuff I fly gets tested to extremes that I wouldn't want to go to, quite alot, judging by the videos. That's partly why I chose it. Dave Quote Link to comment Share on other sites More sharing options...
norman Posted November 5, 2008 Share Posted November 5, 2008 Dave, I wouldn't want to cast nasturtiums here, I am sure that manufacturers take great pains to produce equipment that is as strong and reliable as they can make it and stay within their target weights. Unfortunately without a testing and certification regime we just don't know as customers that the kit we are buying has met a series of relevant requirements for strength, reliability, crash worthiness and design quality. We either believe what we are being told by someone with a vested interest in sale or look at the results of in-service experience. Listening and reading around the subject it doesn't look as though this is about to change anytime soon. Frankly, if we fly these devices within what could be best described as a 'normal' flight envelope and avoid stressing them, we are unlikely to precipitate problems imho. It is the element that feels that they want to 'push the envelope' and become their own test pilot that will find (or create) the wrinkles and thus dents in the ground. Thankfully we fly our own kit and tend not to share it - 'discovering' someone else's overstress outcome is unlikely. Quote Link to comment Share on other sites More sharing options...
bathboy Posted November 6, 2008 Share Posted November 6, 2008 Food for thought - your forearms probably weigh what, 5kg? 6G makes that 30kgs aside with your upper arms weighing more. Can you lift 30kgs with one arm under 1G? Furthermore, could you lift that weight and throw something weighing 4kgs (oops, no -the reserve now weighs 24kgs - total for those muscles now around 50kgs) sitting in your armchair in front of the TV? If the poor unfortunate who died in this accident was flying with a reserve it may be that he was physically unable to use it. Let's face it, even at 3 or 4G the scenario is a little dark isn't it? Could you hold the brake handles or reach for lines above your head with those sorts of load being felt? What would be the overriding control input under those conditions? If you are not acclimatised to aerobatics you will probably start to 'grey out' around .... say four or five G. Just a thought.... Can you see any holes in my maths? - never my strong suit.... Maths good enough for me... You are in a high G spin that has or was caused by a mechanical failure... Where would you wish you'd located your reserve for 'heavy' arms use? Side, front, behind your head or? Cheers Paul Quote Link to comment Share on other sites More sharing options...
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