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  1. #1
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    Possible Problem With Icing?

    Was doing some testing today with the icing systems and I noticed that when the plane gets iced up the airspeed stops working in the PFD, however just below the airspeed tape the mach speed continues to work and report your current mach speed.

    Is this a bug in the PM software or a limitation caused by FS?

  2. #2
    1000+ Poster - Fantastic Contributor Bob Reed's Avatar
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    Hmmmm not sure about that? Only time I have iced up I was too busy trying to save the aircraft!! But that might be a good catch. Might want to send that in to support@projectmagenta.com Just a thought.
    Bob Reed

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    It was wierd we were testing the new icing switches on the overhead panel we had just programmed so we let the autopilot handle the aircraft.

    In level cruise the airspeed dropped to zero so the A/P went to full throttle to speed up. It worked the mach speed kept increasing on the PFD but the airspeed didn't budge. It was rather amusing to watch the A/P get so confused.

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    I had the same problem in the PFD, airspeed display goes to zero, asked PM about it & they said to make sure the pitot heat is on. Problem solved, just have to keep remembering to turn it on. But you need to be carefull in flight as when you turn on the heat the airspeed will read overspeed & could cause your plane to fall apart, so get ready with the speedbrakes.



    Michael
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    Quote Originally Posted by bindook View Post
    I had the same problem in the PFD, airspeed display goes to zero, asked PM about it & they said to make sure the pitot heat is on. Problem solved
    I don't think that's the problem being discussed. It just seems wrong that the mach value remains displayed when the airspeed cannot be measured because of pitot icing. The machmeter is an instrument which is also dependent on the pitot tube -- it basically reads airspeed and does computations between that and the altitude.

    In other words when icing stops airspeed readings it should also stop mach readings.

    Are the mach readings being shown correct-seeming, or wildly wrong? If it is still showing correct readings it will probably be an error in FS rather than in PM, but it is something which could be handled in PM I think.

    Alternatively, however, if the pitot tube blocks the machmeter readings may simply go wild and unpredictable rather than zero, because of the additional involvement of altitude values giving out-of-range results. I looked at some diagrams of mechanical machmeters and they are pretty complex scary things!

    Regards

    Pete

  6. #6
    1000+ Poster - Fantastic Contributor Bob Reed's Avatar
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    Quote Originally Posted by Peter Dowson View Post
    I don't think that's the problem being discussed. It just seems wrong that the mach value remains displayed when the airspeed cannot be measured because of pitot icing. The machmeter is an instrument which is also dependent on the pitot tube -- it basically reads airspeed and does computations between that and the altitude.

    In other words when icing stops airspeed readings it should also stop mach readings.

    Are the mach readings being shown correct-seeming, or wildly wrong? If it is still showing correct readings it will probably be an error in FS rather than in PM, but it is something which could be handled in PM I think.

    Alternatively, however, if the pitot tube blocks the machmeter readings may simply go wild and unpredictable rather than zero, because of the additional involvement of altitude values giving out-of-range results. I looked at some diagrams of mechanical machmeters and they are pretty complex scary things!

    Regards

    Pete
    Yes Peter. I think this is exactly what is being discussed. Not the icing problem.
    Bob Reed

  7. #7
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    Peter,

    That's exactly the problem. I've actually sent it into PM and they've allready gotten back to me. It looks like the problem is that FS actually continues to calculate the mach speed under iceing conditions and PM pulls the airspeed and mach speed seperatly. Enrico is looking into it to see if he can modify the PFD software to display a zero mach as well as airspeed when the pitot tube is iced, despite what FS is telling it.

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    Well, best would be, if the left PFD is working together with left Pitot Heat and for the rightside the other way round. Maybe Enrico can put this into his Boeing software!

    best regards
    Jan

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