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Thread: Back in to flight test again!!!!!!!

  1. #1
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    Back in to flight test again!!!!!!!

    After working out a couple of minor bugs brought out in flight test and several mounths of stress testing. We have now been granted permision to continue testing.
    Cheers Paul.

  2. #2
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    Back in to flight test again!!!!!!!

    Now that all is going well again with the section S Trya being back in flight test then time to look at the next adition. I have attached some photos of the screen to be tested next along with the 50 litre tank.
    As usual any feed back or opinions are gladly received.

    Cheers Paul.

    Attached files

  3. #3
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    Back in to flight test again!!!!!!!

    Paul Robshaw wrote:
    Now that all is going well again with the section S Trya being back in flight test then time to look at the next adition. I have attached some photos of the screen to be tested next along with the 50 litre tank.
    As usual any feed back or opinions are gladly received.

    Cheers Paul.
    Very nice, looks better than the Quik screen! Might be nicer sloped back slightly more, like that Chaser in the same hangar ;-)

    A little bird told me that Ben has restricted the G in the flight tests, because he's found some minor tweak in the calculations is needed, and he has to check all the trike calcs.

    Might be worth advising him that Guy used to prefer load tests to calcs, and since the trike has been comprehensively loaded for stress testing, any minor glitches in the calcs are superseded by the load tests.

    Paul Jaques fitted a BMW engine into a Raven and Guy advised that he didn't need to do calcs at all provided he was prepared to load test the engine mount. Paul won the Engineering trophy that year......

    Kev

  4. #4

    Back in to flight test again!!!!!!!

    Kev

    Ben isnt daft, he knows what load tests are!! Calcs are also what you do to calculate what loads need to be applied where on the load tests too - so see a big errror there and the load tests can invalidated. I cant see any other reason that he woudl snag it on clacs unless it was an area justified only by calculation.

    Ben is more receptive to clearance by claculation only than his predecesors, - with appropriate 'sanity checks' - we cleared the Skyranger Swift wings by constructing a spar analysis program (rather Paul welsh did- I just paid for it), with check cases from the earlier load tests done to the longer span wings. We chose this method because Ben had just arrived at BMAA and was something of a specialist in this sort of thing whereas Guy and Jon were not. Ben was very perceptive about teh assumptions the calcs were based on and asked lots of really good questions that we hadnt considered on the first pass. In the end it would have been quicker and maybe cheaper to have done the load tests, but we were learning, and now have a proven model which we have made use of since, (anyone designing a ladder wing for a sub 115, or a full cert project (not many of them about just now!) would do well to give Paul welsh a call..).

    Paul - I see from the photos that it looks like you have turned the main undercarriage side strut brackets the other way up, which will lower the wheels compared to the one as shown at Popham - was I right then about them being upside down? - and does this help stop it land nosewheel first, without the engine needing moving back now?

    Paul

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    Back in to flight test again!!!!!!!

    Hello Paul (D not R)

    Although never high on the Tech Office Christmas card list, I do know their attitude is helpful, they know their stuff, and act in good faith. Main concern here is that Ben is rechecking ALL the trike calcs after finding a glitch on the engine mount sums; perhaps if he just stepped back and re-read the original submission and hard graft that Paul Robshaw has put in, he would immediately see that the calcs could actually be marked down as 'to be disregarded'. Paul R has bought the load cells and done the pulling and pushing, on top of Jeremy's earlier work.

    Guy used to get stick because he knew calcs were fallible, and load tests cast iron proof of safe compliance; as a result he liked to see a 'reserve factor' over and above Section S when calcs only where used, (unkindly known as the 'Gratton factor') but load tests he would accept with alacrity. Jon was similar in approach, remember him wanting load tests to Blade spats on another trike? Guy squashed that one as the spats were made by an A1 manufacturer, but if they'd been home-made, both of them would have wanted the bathroom scales and towel out against the side of them, and they'd have been right.

    Calcs to establish 'what loads go where' are enshrined in the section S guidance and are pretty straightforward in the engine mounts area, the very site where Paul Robshaw has had to put the most stringent load testing into the airframe. I reckon the pressure Ben is under is making him do too much checking; if you quote the approval precedent set by Paul Jaques, where the CTO gave him a straight choice of complex calcs or simple load testing, it might just save Ben having to do yet more hard work rechecking, and rechecking, and rechecking...

    After three CTOs and three years in the process, might save both BMAA and Paul Robshaw's time and money.

    Kev

    (looking forward to a Section S budget trike out again, bearing in mind Nigel hasn't time to sell Chasers)

  6. #6

    Back in to flight test again!!!!!!!

    A factor on calcs is always a good idea, we used an extra .5 on the Swift wing sums. Calcs are only as good as the assumptions behind them and can get caught out over unexpected side effects with bracketry etc. Can only really work on very simple structures reliably. Interesting to see on Sky taht both Airbus and Boieng do full size wing load tests - lots of stress engineers with theior fingers crossed during that.

    I went to the RAES seminar the oteher day and there was a very good talk by a chap who works for Airbus on future developments. he related a stressing near cockup on the 380. On normal wings when they flex the ribs are in vertical compression and all the sums and programs are set up with that assumption. Indeed Airbus have calculation protocols that mean that whatever country they are done in the methods are identical and provide hand holding forms for every step. On the 380 it has a distinctive gull wing inboard section. This gives rise to exactly the opposite effect - under positive G the ribs are under vertcial tension. Very simple concept, but nobody noticed until they were apparently fairly well advanced with the stressing with their noses fiormly pressed into the standard protocols!!

    So structures are as much an art as a science I reckon. No one has yet made a program that works out definitively what is going on with a flexwing - it is far too compicated with all that flexing and load distribution changes. So all calcs and tests are very much on a best guess trying to work out a conservative approach which is not unreasonably fierce. dynamci rig testing is teh way to go - but needs a rather bigger truck tahn anyone has yet come up with for a 450Kg machine to get to positive ultimate! The QuikR did mangae to prove the negative laods on teh rig though - which is reassuring with all those nice wires removed!

    Paul

  7. #7
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    Back in to flight test again!!!!!!!

    Haveing been in Portugal and not had time to look on here so not had chance to put my slant on here.
    The Trya is back in flight test albeit with a restriction to no more then 2g manouvers. Which to be fair covers every thing anyway. Dureing the submision of the
    engine mount extension brackets, which have been passed for flight test it was noticed that the origanal calcs from Jeremy had a flaw in them. A possible solution to this as atually been suggested by Ben which I found very helpfull. I must admit I was not pleased to find that the whole of the origanal submision would then be re eximined but probably for a differant reason to most. I have had 3 differant chief technical officers on this project, every time there is a change the incomeing person seems to feel that a in depth examination of the previous persons work is needed. This means that the Trya has atually been though approval on at least 3 differant ocasions. I have suffered a delay every time the new officer takes over, while he is looking.( I wish I could say to my customers, sorry I have a new engineer starting he needs to look over the job so wont be finished on time!!). And that is not a grip, its an observation of fact. All I want to do now is fly this aircraft, and I do want it to be safe when I do, so im not going to kick up a fuss on extra checks am I but at the same time I am getting tired of this round and round in circles bit. I do not look forward to a possible further X years wait while the submision is done again. I am hoping that this is not what Ben means but I guess I will find out when I speak to him.

    God all I wanted to do was show my nice new screen off on this thread!!!
    Cheers Paul.

  8. #8
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    Back in to flight test again!!!!!!!

    Hang in there Paul - each CTO is personally responsible to the CAA for passing something, a system which forces Ben to recheck Jon's check, just as it forced Jon to check Guy's check. You've been bloody unlucky to cop for this lack of continuity, and it isn't Ben's fault.

    Jeremy getting sarcastic with Guy in the beginning made it difficult for Guy to sign it off without climbing down, (never of G's strongpoints) but I'd have thought Jon would have pushed it to a conclusion knowing the rights had passed to you,and the BMAA had taken too long by now to get it approved. He's left it to Ben which is disappointing. Still, at least we were left with by far the most customer-friendly bloke when Jon went to the LAA; Jim Cunliffe speaks highly of Ben's willingness to help at the QuikR tests (Ben was lugging sandbags - something beneath his predecessors)

    At the end of the day, the performance of our organisation must be scaring the sh*t out of anyone without a factory, contemplating the introduction of anything other than an SSDR machine. In your shoes I'd have wistfully parked the Trya Section S and gone full steam ahead with the SSDR version, which you have made a cracking job of buffing to the point that makes that Northwing trike look like a home made go kart.

    I really hope that Ben can grab the liability and safety lifeline that all your hard work load testing offers, and won't delay you even more by checking calcs on items with load tests already applied, to limit and ultimate load. If he insists on pedantry it bodes ill for the future of small simple aircraft, as their low price cannot carry the sheer cost of all this, compared to the hotships.

    Best of luck

    Kev

  9. #9
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    Back in to flight test again!!!!!!!

    Hi All.
    Just wanted to thank all who visited the stand at Splash this week end.
    All the best Paul.

    ps:-

    and apologies for all those that I have spoken to on here and didnt reconise!

  10. #10
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    Back in to flight test again!!!!!!!

    New phone Number for Soloflight or me is 01138153880.

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