pitot static blocked
Hi Guys
Wondering can anyone share something on this that can help me remember easier regarding questions about the pitot or static blocked in a decent or climb etc etc Thanks in advance |
Try this, it has worked for me in the past. Understand how the instruments work. Good luck.
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Try a search on "pitot tube blocked".
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pT = pS + pD
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I remember this one from flight school.
Effect on ASI with pitot or static blocked: POCUD & SUCOD Pitot Over read Climb Under read Descent Static Under read Climb Over read Descent |
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Originally Posted by Feather44
(Post 10409079)
I remember this one from flight school.
Effect on ASI with pitot or static blocked: POCUD & SUCOD If the pitot is blocked but its drain hole is open - ASI falls to zero. What happens if the drain is blocked but the pitot open? Presumably nothing changes until the pitot also gets blocked when you have a POCUD situation. What typically happens in real life? I might guess that in pitot freezing situations the drain hole blocks first then the pitot hole itself? |
Because the poster is asking for something EASY to remember.
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May I suggest PUDSOD Pitot blocked Under read Descent Static blocked Over read Descent and vice versa for climb. |
Originally Posted by double_barrel
(Post 10409481)
Why is the drain hole not considered in these rules of thumb?
If the pitot is blocked but its drain hole is open - ASI falls to zero. What happens if the drain is blocked but the pitot open? Presumably nothing changes until the pitot also gets blocked when you have a POCUD situation. What typically happens in real life? I might guess that in pitot freezing situations the drain hole blocks first then the pitot hole itself? |
Is there any way to test the pitots for function before takeoff and perhaps during flight? Presumably pressurizing the lines and monitoring how long the pulse of pressure takes to decay would give warning if the system were obstructed.
It would obviously be a huge complication on something inherently pretty simple, but pitot problems seem to still be an accident factor. |
A key procedure during takeoff roll is for all pilots (PF and PM) to monitor airspeed indication which provides a very good check of pitot functionality. Takeoff is to be aborted if airspeed indicators do not come alive as expected and compare favorably between multiple sources.
Static pressure sensor viability cannot easily be checked during takeoff roll. Once airborne, the altitude readout is the best way to detect an issue with static ports. Altimeter response should be consistent with climbout and track between redundant sources. I am not a pilot so I don't know how deliberate and intentional climbout procedures tend to be with respect to confirming reasonable behavior of altimeters, but that seems prudent to me. There have been a few accidents traced to tape having been left over static ports in order to protect them during ground procedures such that the static sensors were stuck at the reading for the departure airport. With this knowledge, I would certainly keep all altitude sources in my scan during climbout if I were assigned to Row 0. |
https://cimg8.ibsrv.net/gimg/pprune....0e3440f75.jpeg I found that drawing very useful to get the answer very fast. Sorry I’m not very good at drawing. But it’s supposed to be an aircraft climbing on the left and descending on the right. I have highlighted in green the pitot and static ports. So on the left, when the aircraft is climbing: if Pitot is blocked, IAS. Will over read and if static is blocked then IAS will under read. In a descent : if Static is blocked, IAS will over read. And if Pitot is blocked, IAS will under read. Do the drawing yourself and you will never need to think about it again. = ) |
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