Canuck
David Megginson
- Joined
- Mar 31, 2016
- Messages
- 7,087
- Reaction score
- 3,935
I had an entertaining pitot-static failure today. Everything was fine in the takeoff roll, then the static line blocked around 50 ft AGL (so that my altitude froze and my airspeed underread), then it cleared and I had normal readings, then the ASI went to zero, then the ALT started underreading by only 200 ft, rinse and repeat. By the time I landed, the ASI said I was taxiing to the shop at 110 kt. 
I've had in-flight pitot-static failures before: once in low IMC, but never during the first 30 seconds of flight. I can see now how such a failure in IMC would be extremely disconcerting, when you're basically staking your life on the ALT and ASI I think it would be much more dangerous than a vacuum failure in cruise (at least for a fixed-gear Cherokee). In day VMC, of course, it's a non-event.
Still, even in VMC, I decided to overshoot on my first circuit (I'd left too much of an extra margin in both airspeed and altitude). The second time, I used my GPS groundspeed (adjusted for known winds) to cut things a bit closer.
Given that I was already in the circuit in CAVU, I decided just to land instead of groping under the panel for the alternate static valve. In retrospect, it might have been a good idea to activate it while I was level on the downwind, just to confirm whether the problem was limited to the static line.
(FYI, I keep a tight rubber cover over the pitot-static blade, but those little spiders seem to be able to get around anything.)
I've had in-flight pitot-static failures before: once in low IMC, but never during the first 30 seconds of flight. I can see now how such a failure in IMC would be extremely disconcerting, when you're basically staking your life on the ALT and ASI I think it would be much more dangerous than a vacuum failure in cruise (at least for a fixed-gear Cherokee). In day VMC, of course, it's a non-event.
Still, even in VMC, I decided to overshoot on my first circuit (I'd left too much of an extra margin in both airspeed and altitude). The second time, I used my GPS groundspeed (adjusted for known winds) to cut things a bit closer.
Given that I was already in the circuit in CAVU, I decided just to land instead of groping under the panel for the alternate static valve. In retrospect, it might have been a good idea to activate it while I was level on the downwind, just to confirm whether the problem was limited to the static line.
(FYI, I keep a tight rubber cover over the pitot-static blade, but those little spiders seem to be able to get around anything.)
