Altimaster 3

[john2236 0]

I'm just finishing up my A license and starting to get my own equipment. I got an Altimaster 3 from someone I know, and had a hard landing. The glass has a small crack now. I'm wondering if a crack that allows there to be an equilibrium between the inside and outside of the altimeter would throw off the calibration? Also, where can I download a manual for it?

[gowlerk 2,206]

The aneroid that controls it is sealed inside, the crack in the lens will not affect it. The lens is also field replaceable, at least it is on the newer ones.

http://www.square1.com/manufacturers/square1/p908.asp

If service is needed, check this page.

http://forum.altimaster.com/content.php?160-Repair-of-SSE-Manufactured-Altimeters

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[john2236 0]

Thank you, gowlerk. I didn't think that the lens was the pressure barrier, but wasn't 100% sure and tried to look up the company but wasn't having any luck. Thanks again!

[mjosparky 4]

An altimeter is not a sealed unit. If it were to be sealed it would not be able to tell the change in pressure.

My idea of a fair fight is clubbing baby seals

[Alti2_Staff 0]

Hi John,

Your Altimaster III does indeed have a user-replaceable lens. Although we no longer make this product, it may still be repairable. Shoot me an email johnhawke@alti-2.com and I will help you get it sorted.

Alti-2, Inc. Staff

[john2236 0]

Didn't mean completely sealed, but there has to be a part of the altimeter that is sealed so that the pressure within the sealed part is compared relative to outside atmospheric pressure, which in turn causes the needle to turn

[john2236 0]

Thank you, the cracks isn't bad at all, and I'm okay with it, as long as the altimeter functions as it is supposed to, and it does. I'll definitely keep you in mind doing if it becomes a problem. Thanks again

[wolfriverjoe 1,523]

john2236

Didn't mean completely sealed, but there has to be a part of the altimeter that is sealed so that the pressure within the sealed part is compared relative to outside atmospheric pressure, which in turn causes the needle to turn

There is a part of the altimeter that is sealed, offering a comparison with the outside pressure. It's called the "aneroid" and the lens has nothing to do with sealing it.

This is an aircraft altimeter, because I couldn't find an inside view of a hand mounted one. But the basic principle/components are similar:

https://atpflight.wikispaces.com/file/view/altimeter.png/335452582/altimeter.png

Edit to add: Kind of a funny thought: In an airplane, the pressure for the altimeter (and other stuff too) comes through the "static pressure port" (basically a hole in the plane in a spot where they can find a good stable reading). If that gets plugged, the alti, VSI and airspeed indicator will all be wrong. I was taught that if that happens, static pressure can be let into the system by...

Breaking the lens on the altimeter.

Internal cabin pressure won't be a perfect representation of static pressure (IIRC, it's usually a bit below), but it's better than not having it.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[john2236 0]

Thanks for the explanation wolfiverjoe, I knew it had to be set up something like that, and breaking the lens in the situation you described for a plane's equipment I can see as being helpful in that type of situation to help equalize pressure more quickly in case of an emergency.