Re: Large HDG and ATT deflections when testing Sta
Doesn't sound too serious. The maths inside the the unit uses a whole host of inputs to arrive at an output attitude, and changing any one of the will cause a change in attitude (and heading).
Think out what you're doing - the Efis is stationary, and level. Suddenly, it's 500' higher than it was, and has a forward speed (there is a measured difference between the pitot and static pressures). The only way an aircraft can do that is to pitch up and climb, but because there's a small forward speed, the pitch required to get there is pretty steep. But once you're airborne, and have an active forward speed, everything behaves as the maths expects it to, and it should look normal again.
The heading is affected because the efis actually measure the magnetic field in 3D and projects the field down on to a horizontal plane (which it has calculated using the attitude it's worked out), and measures the angle between the field lines and 'forward'. When the calculated plane is not actually horizontal, the projection of the field lines goes a bit awry (unless you're facing exactly magnetic North or South), and the result can be a very skew heading.
But all these problems should go away once airborne and sane airspeed and static pressures are available.
My advice: take the unit flying. If it's still wonky, then it sounds like a serious problem. If it looks ok, then what you've observed is probably perfectly normal. My unit behaves in this way on the ground and when I'm messing around with the static, but once airborne it's perfect.
Hope that helps
Etienne
