Moistra content inside instruments

sdflyer

sdflyer

Pre-takeoff checklist
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sdflyer
Yesterday I'm noticed "foggy" glass inside turn coordinator and airspeed indicator . Should I be worried ? Can anyone explain why it happens and what can I do to prevent it?

Thanks
 
Sorry topic should be "moisture content" . Thanks for Apple spell checker :)
 
It's a result humid air which has entered the instrument not getting flushed before the temperature changes. Not much you can do to prevent it.
 
sdflyer said:
Yesterday I'm noticed "foggy" glass inside turn coordinator and airspeed indicator . Should I be worried ? Can anyone explain why it happens and what can I do to prevent it?

Thanks
Click to expand...
Most of the time it is because the Vac filter has not been changed or there is a hose off and the gauge is sucking unfiltered air.

to get it to away, change the filter, then simply warm the gauge while flying using a 12VDC hair drier that is use in a car.
 
Tom-D said:
Most of the time it is because the Vac filter has not been changed or there is a hose off and the gauge is sucking unfiltered air.
Click to expand...
I don't think there are any vacuum driver turn coordinators in existence, so it would have to be something else. And even in the case of vacuum instruments, there's nothing between the instrument and the outside air on the back side to prevent airborne moisture from propagating into the instruments when the pump isn't running. Dust, yes; moisture, no.
 
Ron Levy said:
I don't think there are any vacuum driver turn coordinators in existence, so it would have to be something else. And even in the case of vacuum instruments, there's nothing between the instrument and the outside air on the back side to prevent airborne moisture from propagating into the instruments when the pump isn't running. Dust, yes; moisture, no.
Click to expand...

These instruments (electric) are sealed and have gaskets. If moisture is present remove, send to instrument shop and have repaired correctly.
 
Ron Levy said:
I don't think there are any vacuum driver turn coordinators in existence,
Click to expand...

Yes there is, the turn coordinator in the
F-24 was a vac driven instrument, as is the one in the 48 170.

The paper filter was not designed to keep water out, but it will do a pretty good job of it.

and even the electric gyros have a vent, and when warmed they will clear up.
 

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Tom-D said:
Yes there is, the turn coordinator in the
F-24 was a vac driven instrument, as is the one in the 48 170.
Click to expand...
Those are nice pictures of turn-and-bank indicators, and I've seen vacuum-driven T&B's before. However, they are not a turn coordinator (of which I've never seen a vacuum-driven version). For an explanation of the difference (including pictures) between the two different instruments, see the Instrument Flying Handbook, pages 5-20 to 5-22.
 
RotorAndWing said:
These instruments (electric) are sealed and have gaskets. If moisture is present remove, send to instrument shop and have repaired correctly.
Click to expand...
If you were referring to TC's, I agree. However, as Tom pointed out, there are some old vacuum T&B's out there, generally dating back to the venturi days when a separate venturi for each instrument was considered an independent power source so three venturies powering three vacuum-driven gyro instruments (T&B, AI, and HI) was legal for IFR. And I was talking strictly about vacuum-driven gyros, for which there is no moisture barrier at all (including the air filter, which only deals with particulates).
 
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