National Aeronca Association Bulletin Board

My altimeter seems to be accurate when I set to the field elevation. After flying it always comes back to field elevation after landing at home or a different nearyby airport (but at a different elevation).

However if I set the barametric pressure into the colsman window the reading on the altimeter is not even close. As in about 350' off. Since I only have been flying locally and for like 1 hour hops when the barametric pressure is not changing rapidly, I've just gone with the field elevation setting and ignored the barametric reading in the window.

Is there a way to adjust this to match them up? Or do I have to get the altimeter rebuilt or buy a new one?

You can adjust this out this problem. It would be wise to have a shop perform this calibration. If done incorrectly some altimeters will be damaged.
Send it out with instructions for the repair needed, it should come back with a limited release.
Paul

Where do I send this to? What kind of cost am I looking at? Is it worth getting calibrated or just buck up and buy a new one?

Also I notice in flight the altimeter seems to bounce up and down with turbulence etc. But yet after the oscilation, it seems to always come back to accurate reading.

I use the Gyro House but any shop should be able to quote this job.
Paul

Here are the instructions for doing the adjustment:

http://www.mrkent.com/flying/altimeter/index.htm

Its pretty straight forward.

Tim

flyingfool wrote:Where do I send this to? What kind of cost am I looking at? Is it worth getting calibrated or just buck up and buy a new one?

Also I notice in flight the altimeter seems to bounce up and down with turbulence etc. But yet after the oscilation, it seems to always come back to accurate reading.

I believe much of the bouncing (mine too) is because we don't have a stable static air source for our altimeters. However, unless you really use your altimeter for a precision function, or just like having it more correct, for our VFR use it doesn't have to be very accurate. I don't know when the change occured with the manufacturers, but our vintage planes were generally delivered with only a non sensitive altimeter installed. And until I got an instrument rating, setting the altimeter to field elevation was all I was ever taught, and for VFR flight all I ever do now.

tim_chow wrote:Here are the instructions for doing the adjustment:

http://www.mrkent.com/flying/altimeter/index.htm

Its pretty straight forward.

Tim

Yes and even us A&P mechanics are not allowed to do an adjustment like this. This is for instrument shops ONLY!

Anyone doing this please realize that you are on your own after doing this. We are not even legal to add fluid to a compass, so the rules are petty tight on things like this.

Not an issue for me.............as a Sport Pilot I can't even change my own oil.........The EAA is trying to loosen these restrictions on us "only" Sport Pilots. The crazy part is I own the airplane and still can't do ANY maintance. Ah well at least I can fly pretty much anywhere I want to go.

SFC Hiatt wrote:Not an issue for me.............as a Sport Pilot I can't even change my own oil.........The EAA is trying to loosen these restrictions on us "only" Sport Pilots. The crazy part is I own the airplane and still can't do ANY maintance. Ah well at least I can fly pretty much anywhere I want to go.

With your experience now, you're so darn close to being a private pilot, you might want to consider going ahead and finishing up with a PP rating. It's just so much more handy to have than the SP. Also, you mentioned looking for a plane to fly at night occasionally. You need a PP or better for that (is that true???). And on rare occasion, you might want to fly a 150 or 172 or something out of the LSA category. To me a SP rating is fine to start with, or is a great thing to have for those who might have a medical issue, or will on be focusing only on LSA totally. You seem like you will be leaving that category on occasion (biplane?). roger