Friday, March 30, 2012

Pitot-Static Problems

A little fun this morning. As it always seems to, the weather couldn't resist turning ugly our last night. We took off from Indy into some mild thunderstorms. Since the leg to Columbus is so short, we only climbed to 15,000', which will not normally get an airplane on top of any weather. Approaching level off, my pitot-static instruments all went wacko. They're called pitot-static b/c they rely on dynamic pressure info from the pitot tubes (those pointy looking probes near the nose) and/or static pressure info from the static ports, to determine, among other things, airspeed, altitude and rate of climb/descent. When any of these sensors get clogged up, it's garbage in, garbage out time for the airplane's instruments. In most cases, the likely cause is icing; and since we were in the clouds, this was my assumption (although dirt dauber nests run a close second in causality). The ports are heated, and the heaters have idiot lights to let the pilots know if they're offline, but we had no such indications. I handed off control of the airplane to my FO, as his instruments, which have a different source, were fine. I switched my air data computer (ADC) to join the FO on the right side and things returned to normal. A little excitement at 5:00 in the morning never hurt anyone, right? Of course, you have to ask, what if the FO's side iced up as well? Well, it's emergency time and let's get out of the clouds and see if we can thaw out the ice. I had this happen in the E-2 one time, and it's quite a challenge b/c you have no idea how fast you're going or what your altitude is. Fortunately, we have a table of ballpark figures for airspeed based on weight and power settings, and the inertial reference units (IRU's) will still provide altitude info. The maintenance sign-off indicated a bad ADC, so case closed.

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