Capt. Geoffrey Thorpe wrote:
"Kyle Boatright" wrote in message
...
... I should have mentioned before that the altimeter is close to the
field
elevation when on the ground. Well within VFR limits.

One interesting test would be a low altitude pass down the runway at
cruise power and speed. If I'm 50' above the field and the altimeter shows
field level + 50' (or thereabouts) what would that tell me?

A basic question: If there was a problem with the static system, wouldn't
that cause the same discrepancy in both the altimeter and transponder?
...

That seems likely as far as static sytem design is concerned (e.g. static
port location).

If they differ only in flight, then they probably aren't seeing the same
static source due to kinks and leaks. I assume that both are really
connected to the static source (You have looked, right? No hose has fallen
off?)

Have the encoder output compared to the altimeter while sitting on the
ground - if they are the same, you have a plumbing problem. If they are
different, the problem is in the instruments, eh?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


Where the static port is located has no bearing on this issue. There
could be a kink/clog like Geoff indicates but it would need to be
between both the instruments. There could also be water in the static
line somewhere between where the altimeter and encoder are.
A leak won't do it since the altimeter and encoder are at the same
potential. They will both just read the same erroneous altitude. Also,
your airspeed would be off quite a bit since it shares the static system.

Either the altimeter or encoder is off. Your allowed 125 foot deviation
between the two to be legal.
You need to get the system checked and recalibrated. The encoder can be
recalibrated on site if it is off, but the altimeter will need to go to
the shop.

My guess if the altimeter reads the correct baro at field elevation,
then the encoder is the problem.
And if it's suddenly off by 200 feet, then it probably has more of an
issue than a calibration would permanently fix.

If your in the Dallas area, let me know and I can give you a hand to
figure this out. I run/own a repair station for doing this sort of thing.

A cheap and dirty way to check for static leaks (that makes a
difference) is to open a window in flight and see if the airspeed and
altimeter jumps around. If the system is tight, there should be no change.

Good luck

Dave

www.craigmileaviation.com