Picked up the Aztec from annual, and in my test flight, twice the flaps didn't go down. On the preflight then went down fine with the hand pump. They never had a problem going up. Also the first time I tried to use them in the air on the test flight, then went down just fine. And the times they didn't go down the first time, raising and lowering the flap handle cured it within a couple cycles. After the two times I had an issue, it worked after that and I must have put it through 20+ cycles... both in the air and on the ground. Never an issue. Gear never had an issue. We replaced the hydraulic filter as part of the annual.
I also had observed this one time before the annual... at the conclusion of an IFR flight in very cold weather. Same symptom and resolution. As a result I didn't reject the annual and we both decided to keep an eye on it/research it.
In any case, my question is what might cause this/what should I look for/what resolutions exist? Presuming we are talking about a powerpack rebuilding... I've heard they are kinda expensive... so alternatives to that are welcome (like a field replacement of all the O rings?).
I also had observed this one time before the annual... at the conclusion of an IFR flight in very cold weather. Same symptom and resolution. As a result I didn't reject the annual and we both decided to keep an eye on it/research it.
In any case, my question is what might cause this/what should I look for/what resolutions exist? Presuming we are talking about a powerpack rebuilding... I've heard they are kinda expensive... so alternatives to that are welcome (like a field replacement of all the O rings?).
