Planespotta

EDIT: If you've read it, you know it. Question answered

Convairator

Moisture in the static lines that eventually ran out after enough heat and air passage. (just a guess, what was the dewpoint?). You may want to have a mechanic inspect the lines. What year is the sp?

rickair7777

Sounds like ice blocking the static port or possibly ice in the static line.

When the ice froze the pressure trapped in the line would be field elevation.

As the cabin warmed up, the static line (which runs into the cabin behind the instrument panel) would have warmed up significantly (I assume you were using cabin heat). As the air in the line warmed, it's pressure would increase, which would drive the altimeter to a lower indicated altitude.

But I'd get a mechanic to look at it, it might also be a bug or some other object in there.

UAL T38 Phlyer

Planespotta:

If your pitot-static system isn't indicating correctly, and you are deliberately putting in the wrong barometric setting to get a field elevation that looks right, don't fly. Get it investigated and fixed.

Not sure what the requirement is under Part 91, but for airline and Air Force flying, it has to agree within about 75 ft of field elevation.

lakehouse

Ya Ya YA I have seen that before on cold days, use the alt static till the ice melts, you got a leaky static port thats letting moisture in and freezing, then melts when the cabin and engine warm up enough for it to melt/evaporate. If your going IFR def dont go, but VFR day, esp for local flight, who cares, use the GPS/Transponder/Iphone with GPS/Alt air etc

Disclaimer, it is dangerous and most likely illegal to fly with any part INOP, do not do it, return to the ramp, and do not fly till fixed, the above statement is meant as a 'joke' and this disclaimer is the only thing you should take serious...I am not a mechanic nor at all a source for go/no go information, your the pic and my above statement should not be used while flying an aircraft

Planespotta

That's not what I did. Let me explain a few more things. Before I took off, I retuned the correct altimeter setting into the A/P, GPS, and altimeter. I received the approval of mx and the chief of flight ops to continue. The altimeter indicated correctly before I took off and operated properly during climb with alternate static engaged. It was not inoperative. I was operating VFR, unlimited vis and no clouds, but am instrument rated and familiar with the accuracy requirements for IFR flight.
Thanks for the helpful responses - they make sense.

91.213:

Inoperative means that a system and/or component has malfunctioned to the extent that it does not accomplish its intended purpose and/or is not consistently functioning normally within its approved operating limits or tolerances.

My altimeter was doing neither when the proper corrective actions were taken.

UAL T38 Phlyer

Nothing to see here, citizens...return to your homes.

lakehouse

Not to nit pick but you cant set the gps, it uses your distance from the sat or some crap like that to get your alt, and the transponder is off like pressure alt, so I THINK when its 29.92 out it is right, otherwise slightly off, but honestly dude its DAY VFR, I would use my Moto Droid's GPS to give me the altitude, who cares, even on a cross country you could just check what ATC is showing you at to make sure the droid is right, along with the on board GPS, the altimeter you know is working off the alt. air, and the transponder that you should be able to figure out where you want to be on, heck if you have an E6B you prol can figure out the number you want on the transponder to balance out to the current altimeter setting. I think your over thinking it for a VFR part 91 day flight.

Again Disclaimer, above is a joke, see my last disclaimer, I could never tell you do anything like I saying above legally, remember your the PIC, im just a moron who is so bad at flying everyone seems to jump out!

Planespotta

. . . huh

lakehouse

You cant put an altimeter setting into a GPS, or a transponder. My point is for day VFR I would have gone, and flown the plane, even if the alt air did not work. My friggin Iphone has a gps in it that gives me a better altitude reading then the one in any Cessna I have been in. I would just use that, I mean heck it is DAY VFR, I would use the altitude read out my crap transponder gives me.

However I have to say that the above is JUST A JOKE, since I would not openly post in writing on the internet that I would fly with a known deficiency