What is the blue range indicating on this manifold pressure gauge?












4












$begingroup$


This is baffling me. Does anybody with experience with this type of indicator have any idea what the blue range of this gauge means?



Weird blue range



It's mounted in a mock-up panel. I know nothing about where it originally came from, though it seems pretty clear that it's from a turbocharged piston twin.






flight-instruments piston-engine







share|improve this question











$endgroup$












  • $begingroup$
    It would help to know what aircraft this gauge is in
    $endgroup$
    – DeepSpace
    10 hours ago










  • $begingroup$
    @DeepSpace I'm sorry I have no idea. It is a standalone gauge we have just sitting around, but it looks pretty clearly to be from a turbocharged piston twin.
    $endgroup$
    – Pugz
    10 hours ago












  • $begingroup$
    Related: Why don't airplane turbo piston engines have boost control?
    $endgroup$
    – ymb1
    9 hours ago










  • $begingroup$
    For being a "standalone gauge we have just sitting around", it seems to be pretty well screwed into a panel of some sort.
    $endgroup$
    – FreeMan
    8 hours ago










  • $begingroup$
    @FreeMan yes it is! Mock up panel.
    $endgroup$
    – Pugz
    7 hours ago
















4












$begingroup$


This is baffling me. Does anybody with experience with this type of indicator have any idea what the blue range of this gauge means?



Weird blue range



It's mounted in a mock-up panel. I know nothing about where it originally came from, though it seems pretty clear that it's from a turbocharged piston twin.






flight-instruments piston-engine







share|improve this question











$endgroup$












  • $begingroup$
    It would help to know what aircraft this gauge is in
    $endgroup$
    – DeepSpace
    10 hours ago










  • $begingroup$
    @DeepSpace I'm sorry I have no idea. It is a standalone gauge we have just sitting around, but it looks pretty clearly to be from a turbocharged piston twin.
    $endgroup$
    – Pugz
    10 hours ago












  • $begingroup$
    Related: Why don't airplane turbo piston engines have boost control?
    $endgroup$
    – ymb1
    9 hours ago










  • $begingroup$
    For being a "standalone gauge we have just sitting around", it seems to be pretty well screwed into a panel of some sort.
    $endgroup$
    – FreeMan
    8 hours ago










  • $begingroup$
    @FreeMan yes it is! Mock up panel.
    $endgroup$
    – Pugz
    7 hours ago














4












4








4





$begingroup$


This is baffling me. Does anybody with experience with this type of indicator have any idea what the blue range of this gauge means?



Weird blue range



It's mounted in a mock-up panel. I know nothing about where it originally came from, though it seems pretty clear that it's from a turbocharged piston twin.






flight-instruments piston-engine







share|improve this question











$endgroup$




This is baffling me. Does anybody with experience with this type of indicator have any idea what the blue range of this gauge means?



Weird blue range



It's mounted in a mock-up panel. I know nothing about where it originally came from, though it seems pretty clear that it's from a turbocharged piston twin.






flight-instruments piston-engine




flight-instruments piston-engine






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 5 hours ago









David Richerby

9,93033578




9,93033578










asked 10 hours ago









PugzPugz

2,614827




2,614827












  • $begingroup$
    It would help to know what aircraft this gauge is in
    $endgroup$
    – DeepSpace
    10 hours ago










  • $begingroup$
    @DeepSpace I'm sorry I have no idea. It is a standalone gauge we have just sitting around, but it looks pretty clearly to be from a turbocharged piston twin.
    $endgroup$
    – Pugz
    10 hours ago












  • $begingroup$
    Related: Why don't airplane turbo piston engines have boost control?
    $endgroup$
    – ymb1
    9 hours ago










  • $begingroup$
    For being a "standalone gauge we have just sitting around", it seems to be pretty well screwed into a panel of some sort.
    $endgroup$
    – FreeMan
    8 hours ago










  • $begingroup$
    @FreeMan yes it is! Mock up panel.
    $endgroup$
    – Pugz
    7 hours ago


















  • $begingroup$
    It would help to know what aircraft this gauge is in
    $endgroup$
    – DeepSpace
    10 hours ago










  • $begingroup$
    @DeepSpace I'm sorry I have no idea. It is a standalone gauge we have just sitting around, but it looks pretty clearly to be from a turbocharged piston twin.
    $endgroup$
    – Pugz
    10 hours ago












  • $begingroup$
    Related: Why don't airplane turbo piston engines have boost control?
    $endgroup$
    – ymb1
    9 hours ago










  • $begingroup$
    For being a "standalone gauge we have just sitting around", it seems to be pretty well screwed into a panel of some sort.
    $endgroup$
    – FreeMan
    8 hours ago










  • $begingroup$
    @FreeMan yes it is! Mock up panel.
    $endgroup$
    – Pugz
    7 hours ago
















$begingroup$
It would help to know what aircraft this gauge is in
$endgroup$
– DeepSpace
10 hours ago




$begingroup$
It would help to know what aircraft this gauge is in
$endgroup$
– DeepSpace
10 hours ago












$begingroup$
@DeepSpace I'm sorry I have no idea. It is a standalone gauge we have just sitting around, but it looks pretty clearly to be from a turbocharged piston twin.
$endgroup$
– Pugz
10 hours ago






$begingroup$
@DeepSpace I'm sorry I have no idea. It is a standalone gauge we have just sitting around, but it looks pretty clearly to be from a turbocharged piston twin.
$endgroup$
– Pugz
10 hours ago














$begingroup$
Related: Why don't airplane turbo piston engines have boost control?
$endgroup$
– ymb1
9 hours ago




$begingroup$
Related: Why don't airplane turbo piston engines have boost control?
$endgroup$
– ymb1
9 hours ago












$begingroup$
For being a "standalone gauge we have just sitting around", it seems to be pretty well screwed into a panel of some sort.
$endgroup$
– FreeMan
8 hours ago




$begingroup$
For being a "standalone gauge we have just sitting around", it seems to be pretty well screwed into a panel of some sort.
$endgroup$
– FreeMan
8 hours ago












$begingroup$
@FreeMan yes it is! Mock up panel.
$endgroup$
– Pugz
7 hours ago




$begingroup$
@FreeMan yes it is! Mock up panel.
$endgroup$
– Pugz
7 hours ago










2 Answers
2






active

oldest

votes


















12












$begingroup$

It's a manifold pressure limit with altitude. It relates to a limitation on the differential between ambient and total manifold pressure at different altitudes with turbocharged or supercharged engines; a limit on the amount of actual boost with altitude in other words, not the total pressure.



At 30000 ft, standard atmospheric pressure is only just under 9 inches. 20 inches on the gauge is 11 inches of boost above atmospheric.



At 20000 ft, atmospheric pressure is just under 14 inches, and you're limited to 35 inches, which is about 21 inches of boost.



Between 16000 ft and sea level, with atmospheric pressure between roughly 16 and 30 inches, the limitation is the red line of 40, which is anywhere from 10 to 24 inches of boost above atmospheric.



The increasing limitation in maximum boost with altitude is usually related to the reduced cylinder cooling ability of the thinning air with altitude, and the potential for detonation.






share|improve this answer









$endgroup$





















    6












    $begingroup$

    The blue scale indicates the maximum manifold pressure (MP) at a given altitude.




    • from sea level (SL) to 16000 ft: the maximum MP is 40 inHg (inches of mercury).


    • from 16000 ft to 30000 ft, the maximum MP goes down to 20 inHg.



    The altitudes are barometric altitudes.






    share|improve this answer











    $endgroup$













    • $begingroup$
      Do you have a reference such as a POH that describes this? What type have you seen this in?
      $endgroup$
      – Pugz
      10 hours ago






    • 1




      $begingroup$
      @Pugz, no, unfortunately not, but it is written on the gauge itself.
      $endgroup$
      – bogl
      10 hours ago












    • $begingroup$
      So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
      $endgroup$
      – Pugz
      9 hours ago











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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    12












    $begingroup$

    It's a manifold pressure limit with altitude. It relates to a limitation on the differential between ambient and total manifold pressure at different altitudes with turbocharged or supercharged engines; a limit on the amount of actual boost with altitude in other words, not the total pressure.



    At 30000 ft, standard atmospheric pressure is only just under 9 inches. 20 inches on the gauge is 11 inches of boost above atmospheric.



    At 20000 ft, atmospheric pressure is just under 14 inches, and you're limited to 35 inches, which is about 21 inches of boost.



    Between 16000 ft and sea level, with atmospheric pressure between roughly 16 and 30 inches, the limitation is the red line of 40, which is anywhere from 10 to 24 inches of boost above atmospheric.



    The increasing limitation in maximum boost with altitude is usually related to the reduced cylinder cooling ability of the thinning air with altitude, and the potential for detonation.






    share|improve this answer









    $endgroup$


















      12












      $begingroup$

      It's a manifold pressure limit with altitude. It relates to a limitation on the differential between ambient and total manifold pressure at different altitudes with turbocharged or supercharged engines; a limit on the amount of actual boost with altitude in other words, not the total pressure.



      At 30000 ft, standard atmospheric pressure is only just under 9 inches. 20 inches on the gauge is 11 inches of boost above atmospheric.



      At 20000 ft, atmospheric pressure is just under 14 inches, and you're limited to 35 inches, which is about 21 inches of boost.



      Between 16000 ft and sea level, with atmospheric pressure between roughly 16 and 30 inches, the limitation is the red line of 40, which is anywhere from 10 to 24 inches of boost above atmospheric.



      The increasing limitation in maximum boost with altitude is usually related to the reduced cylinder cooling ability of the thinning air with altitude, and the potential for detonation.






      share|improve this answer









      $endgroup$
















        12












        12








        12





        $begingroup$

        It's a manifold pressure limit with altitude. It relates to a limitation on the differential between ambient and total manifold pressure at different altitudes with turbocharged or supercharged engines; a limit on the amount of actual boost with altitude in other words, not the total pressure.



        At 30000 ft, standard atmospheric pressure is only just under 9 inches. 20 inches on the gauge is 11 inches of boost above atmospheric.



        At 20000 ft, atmospheric pressure is just under 14 inches, and you're limited to 35 inches, which is about 21 inches of boost.



        Between 16000 ft and sea level, with atmospheric pressure between roughly 16 and 30 inches, the limitation is the red line of 40, which is anywhere from 10 to 24 inches of boost above atmospheric.



        The increasing limitation in maximum boost with altitude is usually related to the reduced cylinder cooling ability of the thinning air with altitude, and the potential for detonation.






        share|improve this answer









        $endgroup$



        It's a manifold pressure limit with altitude. It relates to a limitation on the differential between ambient and total manifold pressure at different altitudes with turbocharged or supercharged engines; a limit on the amount of actual boost with altitude in other words, not the total pressure.



        At 30000 ft, standard atmospheric pressure is only just under 9 inches. 20 inches on the gauge is 11 inches of boost above atmospheric.



        At 20000 ft, atmospheric pressure is just under 14 inches, and you're limited to 35 inches, which is about 21 inches of boost.



        Between 16000 ft and sea level, with atmospheric pressure between roughly 16 and 30 inches, the limitation is the red line of 40, which is anywhere from 10 to 24 inches of boost above atmospheric.



        The increasing limitation in maximum boost with altitude is usually related to the reduced cylinder cooling ability of the thinning air with altitude, and the potential for detonation.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 9 hours ago









        John KJohn K

        21.1k12963




        21.1k12963























            6












            $begingroup$

            The blue scale indicates the maximum manifold pressure (MP) at a given altitude.




            • from sea level (SL) to 16000 ft: the maximum MP is 40 inHg (inches of mercury).


            • from 16000 ft to 30000 ft, the maximum MP goes down to 20 inHg.



            The altitudes are barometric altitudes.






            share|improve this answer











            $endgroup$













            • $begingroup$
              Do you have a reference such as a POH that describes this? What type have you seen this in?
              $endgroup$
              – Pugz
              10 hours ago






            • 1




              $begingroup$
              @Pugz, no, unfortunately not, but it is written on the gauge itself.
              $endgroup$
              – bogl
              10 hours ago












            • $begingroup$
              So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
              $endgroup$
              – Pugz
              9 hours ago
















            6












            $begingroup$

            The blue scale indicates the maximum manifold pressure (MP) at a given altitude.




            • from sea level (SL) to 16000 ft: the maximum MP is 40 inHg (inches of mercury).


            • from 16000 ft to 30000 ft, the maximum MP goes down to 20 inHg.



            The altitudes are barometric altitudes.






            share|improve this answer











            $endgroup$













            • $begingroup$
              Do you have a reference such as a POH that describes this? What type have you seen this in?
              $endgroup$
              – Pugz
              10 hours ago






            • 1




              $begingroup$
              @Pugz, no, unfortunately not, but it is written on the gauge itself.
              $endgroup$
              – bogl
              10 hours ago












            • $begingroup$
              So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
              $endgroup$
              – Pugz
              9 hours ago














            6












            6








            6





            $begingroup$

            The blue scale indicates the maximum manifold pressure (MP) at a given altitude.




            • from sea level (SL) to 16000 ft: the maximum MP is 40 inHg (inches of mercury).


            • from 16000 ft to 30000 ft, the maximum MP goes down to 20 inHg.



            The altitudes are barometric altitudes.






            share|improve this answer











            $endgroup$



            The blue scale indicates the maximum manifold pressure (MP) at a given altitude.




            • from sea level (SL) to 16000 ft: the maximum MP is 40 inHg (inches of mercury).


            • from 16000 ft to 30000 ft, the maximum MP goes down to 20 inHg.



            The altitudes are barometric altitudes.







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 9 hours ago

























            answered 10 hours ago









            boglbogl

            3,8071733




            3,8071733












            • $begingroup$
              Do you have a reference such as a POH that describes this? What type have you seen this in?
              $endgroup$
              – Pugz
              10 hours ago






            • 1




              $begingroup$
              @Pugz, no, unfortunately not, but it is written on the gauge itself.
              $endgroup$
              – bogl
              10 hours ago












            • $begingroup$
              So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
              $endgroup$
              – Pugz
              9 hours ago


















            • $begingroup$
              Do you have a reference such as a POH that describes this? What type have you seen this in?
              $endgroup$
              – Pugz
              10 hours ago






            • 1




              $begingroup$
              @Pugz, no, unfortunately not, but it is written on the gauge itself.
              $endgroup$
              – bogl
              10 hours ago












            • $begingroup$
              So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
              $endgroup$
              – Pugz
              9 hours ago
















            $begingroup$
            Do you have a reference such as a POH that describes this? What type have you seen this in?
            $endgroup$
            – Pugz
            10 hours ago




            $begingroup$
            Do you have a reference such as a POH that describes this? What type have you seen this in?
            $endgroup$
            – Pugz
            10 hours ago




            1




            1




            $begingroup$
            @Pugz, no, unfortunately not, but it is written on the gauge itself.
            $endgroup$
            – bogl
            10 hours ago






            $begingroup$
            @Pugz, no, unfortunately not, but it is written on the gauge itself.
            $endgroup$
            – bogl
            10 hours ago














            $begingroup$
            So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
            $endgroup$
            – Pugz
            9 hours ago




            $begingroup$
            So this is indicating the maximum possible given existing atmosphere at a given altitude, not any sort of limit, but just for pilot reference to to compare to the altimeter?
            $endgroup$
            – Pugz
            9 hours ago


















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