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Thread: Quik STARs Failure

  1. #1

    Quik STARs Failure

    P&M Quik STARs Failure

    Yesterday I had 2 very different flights, the first a bimble around the local area with a few practice engine failures and steep banked turns. All performed as expected, back to the airfield for a cuppa. I then got talking to a new student and offered him a quick flight as he was early for his lesson ( I was going up anyway).

    Well this flight was very different. On taking off I had a very noticeable left turn, climbing out in the circuit I couldnt believe the plane wouldnt fly any where near straight now. In fact it was taking a huge effort to keep flying in a straight line. I decided to return to the airfield and concentrated on getting down safely.
    The attached photos should explain the problem. The securing ring on a clevis pin had come out allowing the pin and pulley to come apart, the pulley was still hanging on the Dynema cord.

    Now it may have been a coincedence but earlier in the day I had fitted the hang bolt locking plate the subject of SB141. Did I disturb the clevis pin retaining clip? I dont know.

    The advice from the pilots manual (M275 manual for roll trim issue 2) page 3 in the event of a STARs cord failure, is that applying full fast trim and steering the nose wheel towards the turn will reduce the turn bias.
    Well I can say that if you are in the full slow trim position the force needed to maintain straight flight is very high! Even the new student commented that he wondered why I had got the bar pulled right over and had gone quiet.

    I believe these same pin retaining rings are the subject of SB 139. The retaining rings described as "Bad" in this SB are the same as in numerous positions on my wings STARs system. Perhaps P&M should never have used them in the first place?

    All pilots please be aware of this possible issue.

    Regards Brian

    Attached files

  2. #2

    Quik STARs Failure

    They do say that it it's meant to be fail-safe so glad someone got to test it in real life and come out of it with just a bent pulley! The fact that you were heavily loaded at the time also would have increased the workload so well done

    Did you find the ring? It would be nice to see if it was a progressive failure or a result of the recent de-rig that you did

    Cheers,
    Henry

  3. #3

    Quik STARs Failure

    Henry,
    Thanks for the comment, hindsight is a wonderfull thing. As soon as I saw what had happened I knew the manual said something but couldnt recall what ( full fast trim if STARs fails). I will definatly remember if it happens again!
    The pulley was just hanging onto the dynema cord by the pin when I parked up and looked. Unfortunatley I didn't think to take a photo at that point. I remember thinking " good job that didnt go through the prop as well".
    So no sign of the retaining ring, but upon thinking about it I doubt wether it was disturbed by me fitting the locking plate as the spanner used would have been away from the area of the pulley and clevis.
    In any case it should surely take more than a knock from a spanner to remove or partialy remove the retaining ring.

    Regards Brian

  4. #4

    Quik STARs Failure

    interesting piece Brian, making me think about changing all the (correct 90 degree) rings to split pins on my Quik now...

  5. #5

    Quik STARs Failure

    Split pins, well I recon it should be mandated?

  6. #6

    Quik STARs Failure

    Thanks for this notice, would totally agree that these retaining rings should be changed for split pins as mentioned in the mandatory SB139. Have flagged this to Technical at BMAA to take up with P&M. On my QuikR the split ring is in the bad category. Going to need a lot of split pins.

  7. #7

    Quik STARs Failure

    It's strange that an item we have been using since the dawn of microlight time is suddenly seemingly causing problems. They are on all the old wings on the luffline attachments for instance. used for convenience of assembly / disassembly.

    It's difficult to imagine when playing with them what could cause them to come out if correctly fitted. So what is causing it?

    Seems so far it's on pulleys with quite high static loading. I wonder if it's anything to do with that, coupled with some sort of distortion caused by damage? Or whether they weren't properly fitted in the first place ( ring not would round so all coils were engaged and flat) and that hasn't been spotted?

    But whatever, at least it's an easy and low cost fix to change them all to stainless split pins.

    And hopefully with Brian's story ringing in our ears we might remember to wind to fully fast to alleviate the assymetry!

    Trim runaways have been the subject of some talk recently. A lot of fixedwing use electric pitch trim systems and there have been the odd reports of failures - where the trim has suddenly run to the stop, or been inadvertently activated by leaning on the button on the ground. It has caused nasty accidents over the years in similarly equipped types. It's a topic that has been the subject of thinking about simulating such a failure during training and regularly flying the plane during training with a gross out of trim condition through a high workload phase such as taking off or landing.

    Trikes generally simpler with less failure modes, but now we are getting to relatively complex systems on trikes it may be worth thinking about the failure modes and including them in training and testing.

    Paul

  8. #8

    Quik STARs Failure

    In the past it was quite difficult in removing these retaining rings as they closed up very easily requiring to wedge your nail in between and turn to remove. This latest batch are definitely softer material with little ability to spring closed. we can only guess that the sourcing has meant a change in specification, i.e cheapest.

  9. #9

    Quik STARs Failure

    Im Not familiar with the stars system (other than reading the manual) but could it be that the pin is a bit too short and easily putting pressure on the ring?

  10. #10
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    Quik STARs Failure

    Paul Dewhurst wrote: It's strange that an item we have been using since the dawn of microlight time is suddenly seemingly causing problems.

    Trikes generally simpler with less failure modes, but now we are getting to relatively complex systems on trikes it may be worth thinking about the failure modes and including them in training and testing.

    Paul
    *Grateful for your perspective Paul, I'm playing with the idea of a hand winched bungee trimmer, same principle as the Quik, to obviate the need for electrics plus the risk of destabilising the wing in pitch on full rearward motion.

    The pulley plates bashing directly onto the spring ring always seemed poor, being a bodger of engineering background I tend to fit washers, you are then shearing two or more wires on the spring ring, and the tendency to drag the ring through the pulley plate hole bodily is reduced. Even with split - pins I'd use a washer. Have one of those little DIY plastic boxes with a selection of collet pins of different lengths and blessed by SSDR, can beef accordingly.

    Rather feel that the best solution is a 4mm bolt and Nyloc, possibly peened over as well where the thread peeps out of the bolt. If the little alloy or plastic pulley has an internal tubular spacer you can nip the assembly tight and get rid of nasty slop.

    May sound silly but wonder if a 4mm stainless pop rivet would work from inwards either side if there's a steel spacer-tube inside the pulley?

    Really opportune post and glad it was shared publicly for all to digest

    Kev

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