Altimiter

[Mark Shayne]

Does anyone know what the proper altimeter might be for a 1940 Collegiate? 
Ours is odd in that there is no pressure window to set for the current baro pressure. One sets the faceplate to align with the needle for the known field elevation before take off. Not a lot of help if one is flying to a higher or lower pressure area. See attached photo which was taken in flight at 2,500 asl.
Thanks! Mark

[Andy Gelston]

Oh Mark, welcome to our wondrous world of flying visually, low and slow by the seat of your pants!

Our altimeters aren't odd, they're just old. The proper altimeter has the adjustment knob at the six o'clock position, and like yours, the knob moves the face and not the needle. Most prewar light planes had these altimeters and were "upgraded" later in their checkered pasts.

Our old gals don't have the range to need such modern conveniences as Kollsman windows in our altimeters. If you're flying where you need to adjust for ambient pressure changes enroute, the winds would be so high you probably shouldn't be flying then anyway.

[Lance Fisher]

I put a small arrow (actually more like an inverted 'V') on the panel close to the altimeter bezel that points to the barometric pressure on the altimeter dial.   This is only accurate to around 0.1 or 0.05 inHg but given the resolution of the single pointer altimeter that's plenty good enough.  I "calibrated" the arrow by placing it so it pointed to the ATIS altimeter setting (ignore the first and last digit) with the altimeter already set to the field elevation.  For example if the field elevation is 900 MSL and the baro setting is 29.92, place the arrow so it's pointing to 9900 feet.  To adjust the altimeter on a different day or in the air when the local baro setting is changed by more than 0.05 inHg drop the first and last digits of the new setting and rotate the altitude card until the altitude matches the resulting 2 digit number (e.g. if the new baro setting is 30.21, turn the card so the pointer is at 200 MSL).