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3 Answers

Mixture idle/cutoff effect on electric boost pump and Hi/lo electric boost pump

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Aircraft Systems

I have a Piper Dakota Turbo (1979) with the optional boost primer button. It also has the Hi/Lo electric fuel pump. My question is that it seems the engine will not shut down with the mixture idle/cutoff  closed and either boost pump or Hi/Lo pump turned on. Is this normal operation? I just had the engine driven pump assy rebuilt and that hasn't fixed the problem. Is this normal operation? The POH states that you can lean the auxiliary pump in flight which suggests to me that the mixture should be able to cut it off. Thanks

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3 Answers



  1. Kris Kortokrax on Feb 27, 2018

    What does your POH say regarding stopping the engine? I don’t have a Turbo Dakota POH, but the Turbo Saratoga POH says turn the fuel pump off, then move the mixture to idle cutoff.

    The fact that you can lean the engine, does not mean that you can cut off the fuel. I have flown aircraft with Continental 65 & 85 hp engines that have a mixture control that can be used to lean the engine, but there is no cutoff. You shut the engine off with the mags.

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  2. Waggs on Feb 27, 2018

    Normal operation without the auxiliary on, the mixture control shuts the engine down. Then you turn off the Master and the Mags. With the Auxiliary pump on, the engine will not shut down when you close the mixture control.

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  3. Kris Kortokrax on Feb 28, 2018

    I guess that I’m trying to figure out why (if the checklist says turn off the fuel pump and then mixture to idle cutoff) you would not follow the procedure? Why would you leave the fuel pump on and then try to stop the engine with idle/cutoff?

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