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edkap

Airspeed gauge drops to zero

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I've been having instances of my airspeed gauge, in different aircraft, dropping to zero.  Sometimes it comes back, but others it just stays there.  Anybody have this, or have suggestions about a possible cause or fix?  Thanks.

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I've been having instances of my airspeed gauge, in different aircraft, dropping to zero.  Sometimes it comes back, but others it just stays there.  Anybody have this, or have suggestions about a possible cause or fix?  Thanks.

This usually happens if you are flying through rain clouds and ice builds up on the pitot tube. Turn on the pitot heating to fix it

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Thanks for the tip, devgrp.  I will make sure to watch for this.

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And check the carburator temperature in such a weather environment, specially if you see the MP decrease (piston aircraft).  Swiftly put the carb heat on then.

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And it's also wrong, the way it's modeled in FSX / P3D, showing only one of the four possible outcomes, depending on how the dynamic and staic ports are affected, namely:

 

 ( extracted from: http://www.skybrary.aero/index.php/Unreliable_Airspeed_Indications )

 

  • If the pitot probe is blocked but the pitot drain and static ports are free, then in straight and level (cruising) flight the displayed IAS will tend to reduce, eventually indicating zero.
  • If the pitot probe and pitot drain are blocked but the static port is free then the IAS will increase during a steady climb and decrease during a steady descent.
  • If the pitot probe, pitot drain, and static ports are all blocked then the IAS will remain constant despite changes in actual airspeed..

In addition to airspeed indicators, systems which rely on information directly or indirectly (via Air Data Computers) from the pitot-static system are also unreliable if the pitot static system is blocked in some way.

  • If the static vent only is blocked, then the altimeter will freeze on the altitude that the blockage occurred, the VSI will show zero climb or descent, and the IAS will over-read in the descent or under-read in the climb.

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