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  • 912 stops while doing a spiral d sent

    Hi again all, ihave a problem with my quantum 912.
    while on a check flight (done by a check pilot) all is well even doing fast to tickover for stall recovery all s well but on a 60 degree turn desent the engine çuts out, this has happend 3 times now, on landing have checked the carb bowels, fuel in ok.
    can restart the engine ok we think its electronic problems.
    can start the engine on each module switched on so starting is not a problem.
    also will run if 1 is switched off
    the only thing that keeps the engine running with both modules switched on is the mag...
    Any thoughts out there.

    P.s
    I am a beleaver that permits and check fights should be done by qualified check pilots there help and support is so important.

  • #2
    912 stops while doing a spiral d sent

    Where is the fuel tank relative to the engine? My friend had a paramotor that used to cut out when doing spirals. Under G with the engine at idle the fuel pump didn't generate enough lift to raise the fuel. A second pump was fitted and fine ever since.

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    • #3
      912 stops while doing a spiral d sent

      Does it cut if you spiral the other way?

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      • #4
        912 stops while doing a spiral d sent

        Try keeping a bit of power on, say 3000 -3500 rpm. That should help keep fuel in the carbs.

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        • #5
          912 stops while doing a spiral d sent

          I would suspect fuel delivery as a first thought if it helps.
          When did you last service the fuel pump, replace the filters, checked the fuel lines.
          Mick Broom
          Member 909
          Shadow G-MWTN

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          • #6
            912 stops while doing a spiral d sent

            Sounds like there's some dirt in the fuel system, as Mick suggests. Might be a good idea to have a fuel system strip down/carb clean, replace filters etc.

            Check the bottom of your tank, is it clean?

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            • #7
              912 stops while doing a spiral d sent

              Hi all and the above, thanks for your inputs.
              fuel is getting through as the card bowels are full and if one carb is starved of fuel, will tick over ( rough ) but the engine just stops.
              the fuel filter was changed as well as the fuel pipes and pump for the new type ( 5bar ) 10 months ago with no faults flown after fitting
              a new 65ltr fuel tank fitted (flushed out with petrol before fitting ) last October and new fuel.
              the carbs fully serviced 10 months ago, flown with no faults 10 months ago.
              the plane has not flown from October last year.
              tick over on the ground is 1740rpm.
              still scratching my head....

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              • #8
                912 stops while doing a spiral d sent

                Just on the off chance, as Paul W queried..if the engine does NOT cut if you spiral down in the opposite direction, then suspect something in the tank... I once had half a tennis ball in a car tank do something similar, where it would block off fuel delivery at specific times.
                The fact that the carbs are full is not necessarily proof... just the few revs when the engine is stoping can be enough to put fuel in the bowls and mask the real problem.

                1 way to establish if this might be the case, and I am NOT even suggesting that you do this as it would invalidate your Permit and hence insurance,... is to test fly it running from a separate small 1 gallon fuel can.............. ensure that it is vented...

                Of course as you intimate, something silly like a chaffed ignition/mag switch wire could cause exactly the same type of sympton... spiral one way... wire shorts to frame acting as a mag switch... spiral the other way... wire does not touch the frame and everything ok:-)

                Hope it helps the "Head scratching"

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                • #9
                  912 stops while doing a spiral d sent

                  The one thing which is difficult to check is what the fuel delivery system is doing in a spiral dive.
                  If you check on the ground you have 1G downwards where as the failure is occurring at whatever you are doing in the dive but depending on the driver could be a lot higher and not directionally downwards as seen by the carbs.
                  It is obvious that its working on the ground and so the fault will be unlikely to be found there.
                  What head scratching you do is may be thinking of the difference which happens between general flying and a spiral dive but it does highlight the benefits of doing a check flight were you go to places which you would not normally visit to highlight any problems whoever is flying it.
                  Best of luck

                  added
                  Sorry Wally,
                  You beat me to it
                  At least the advice is going in the same direction
                  Mick Broom
                  Member 909
                  Shadow G-MWTN

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                  • #10
                    912 stops while doing a spiral d sent

                    You could try fitting Tilly's Orifice.... Getting the mod sign off could be tricky, but no-one would see it I suppose.

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                    • #11
                      912 stops while doing a spiral d sent

                      Is the higher pressure fuel pump flooding the carb?

                      The highest pressure is just above tickover I find
                      flying is good for you!

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                      • #12
                        912 stops while doing a spiral d sent

                        Henry Long wrote: Is the higher pressure fuel pump flooding the carb?
                        +1 for Henry, have the same carbs and pump, will try it if I can...

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                        • #13
                          912 stops while doing a spiral d sent

                          G should still act vertically in relation to the trike unit in a steady spiral descent. Only time there is a 'lean' felt is during a sideslip - which a trike can only do momentarily, or when holding in sideways bar pressure which puts the trike slightly out of of plane to the G.

                          But the increase in G may be bringing two somethings into contact with each other and shorting the ignition circuits? Maybe something silly like the ignition wires trapped between the seat moulding and the seat frame?

                          Paul

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                          • #14
                            912 stops while doing a spiral d sent

                            How much fuel have you onboard? With around 15Liters your quite likely to uncover the fuel pickup in a spiral dive. Unless your diving for an extended time then you would probably get away with it I would have thought.

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                            • #15
                              912 stops while doing a spiral d sent

                              Does the Quantum have the anti-icing gubbins fitted? Kev Mallin had cutting out because in a long descent the temps dropped enough to reduce the heat going into the carbs, he cured that by adding two thermostats, both oil (shorter warmup) and one in the radiator for the carbs.

                              On the ground the ide melts, only way to detect it is to see if the carb bodies are wet

                              Cheers

                              Kev
                              G-KEVA
                              BMAA 5696

                              "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

                              R.J. Mitchell :- Designer of the Supermarine Spitfire

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