Just to follow on from my earlier post - this is a serious GA magazine, right? And we all follow the South African Jim Davis with his commentaries on flight safety, stuff ups etc? And we hang on his every word, right, because he's the expert?
Well, how about this drivel?
Well James, let a humble RA-Aus pilot help you. To make it easy for you, I will assume the atmospheric pressure has not changed since the "mud-bugs" infested the vents - I'm sure even the newest PPL will be able to tell you how much the readings will change if the pressure moves higher or lower after the vent is blocked.
Firstly, the ASI will indicate normal airspeed!! So they will take off blissfully unaware of any problem! So much for your critical analysis there!! (Of course, as they climb, the static pressure will remain constant instead of decreasing, so the ASI will progressively read low).
Secondly, the VSI will not just "under-read" - it will read precisely zero! We know precisely what the error is!
Thirdly, the altimeter will indeed read incorrectly (either under or over, depending) - and we know exactly by how much Jim! It will stay constant!! So, when we are at 1000' it will under-read by 1000' and so on!
So, we don't have to invoke your new theory about the compressibility of air in the static tube (much as you might have hoped this new insight might have earned you a Nobel Prize in Physics) - it's very simple, basic, PPL BAK stuff! No mysteries here!
This really is pathetic stuff for a mag that professes to be there to educate and inform pilots. At my RA-Aus school, if Mr Davis served up this drivel he would be failed on the spot. And deservedly so - this is dangerous advice!