Pitot-Static System

rickyrhodesii

rickyrhodesii

Well-Known Member
I have a question for all you experienced aviators. :)

I'm not instrument rated, but i am training/studying for it now. So, i'm trying to further my understanding of how the systems work. In particular i'm curious about the Pitot-Static system.

What are some ways to prevent the static port from being clogged/blocked? Is it common for ice to build over the port opening? I know most aircraft have a Pitot tube heater, but what about the static port? Or is it uncommon for the port to become blocked?

Thanks!
 
My understanding is that since it faces sideways, it's not very likely to clog up with anything, ice included. Although on some airplanes the static port is surrounded by metal, which might suggest that the static port is also heated by pitot heat, I'm not so sure about that... In reality, once you're in the cockpit, there's not much you can do to that static port to clear it out, so make sure you do a thorough preflight and make sure it's not clogged
 
The most common way the static port becomes blocked is someone putting tape over the port while cleaning the plane (to keep water out of the system), then forgetting to remove it when finished.
 
On some planes there is a small type of valve in the cockpit that's used to activate the alternate static system. If your plane has this then you can use it as a backup since the alternate static line connects to those three instruments using cabin pressure from the cockpit. The readings ,especially the altimeter, would probably be a little off though.
 
Piper airplanes (Warrior/Archer) use a pitot/static "mast". Its a metal mast that hangs down below the wing with 3 small holes in it. One faces front, this is the pitot. One faces aft, this is the static. And the 3rd faces down, this is a drain hole. The entire mast can be heated, keping all 3 openings clear of ice.
Some Piper airplanes (Arrow) also have a separate static located on the fuselage near the empenage. It is also metal but not heated. I never did find out why there was difference. There are also 2 pitot/static drains inside the cabin, just below the pilots seat near the floor, the lowest point of the system.
 
TheFlyingTurkey said:
Some Piper airplanes (Arrow) also have a separate static located on the fuselage near the empenage. It is also metal but not heated. I never did find out why there was difference.
Click to expand...

That is the automatic gear extension system. Not conected to the Pitot Static system.

Most of these have been disabled, so it dosen't matter anyway.
 
Bugs sometimes think the pitot-static ports are a good place to crawl up into and die.
 
USMCmech said:
That is the automatic gear extension system. Not conected to the Pitot Static system.

Most of these have been disabled, so it dosen't matter anyway.
Click to expand...
No, he is correct. The static is on the fuselage. You mentioned another pitot tube for the gears and are correct about the reason for it.
 
If you fly a plane such as a C-172 with only one static port, rain rolling over the port can cause some altimeter jumps.

Some aircraft do have heated static ports, many do not. The baron I fly has two static ports and even in fairly heavy icing they haven't become blocked. If perchance they do, there is an alternate static port inside the plane switched on by a lever next to the pilot. Using this, however, causes a lower-then normal pressure because of the venturi effect of the slipstream over the cabin.
 
Well A few 172's I flew had the alternate static source under the carb heat knob...

you can always smash the VSI to at least get a cabin static source if you really needed too. Always wanted to do that LOL
 
Most 172's that I know of do have an alt static source. It's a little red knob around or below the throttle (obviously it is not the mixture control). Just be careful, because of the difference in pressure inside the cockpit (lower) vs outside where the main static port is located, you can technically get erroneous reading. Usually you will get a higher indicated altitude (bad), a higher airspeed (bad), and the VSI should be roughly the same after a few seconds to equalize the new pressure. :(
 
Thanks for all the info...

Thank you all for providing me with valuable information. From what i gathered from all of your experiences, you've never (or hardly ever) encountered a blocked static port while airborne.

Again, thanks for all of the input! :)
 
Ya everyone I heard of was from people putting tape on it while ground cleaning/Deicing or whathave you... I think its even caused an accident
 
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