Kollsman Drum-Type Altimeter

Kollsman Altimeter has been a major challenge. I used a broken spare unit to test a stepper motor on it. The axis for the QNH setting needs to be lengthened to turn a potentiometer. The white flag on the altimeter scale for the KIFIS system can be biased out of view with a fixed voltage. Note the prototype Kollsman altimeter is from a Caravelle III and does not have the white flag (triangle / chevron).

Position error in static pressure as sensed by the airplane’s normal static systems is corrected by the computer units, and scale error of the altimeters is corrected in the scale error correctors. These corrections are combined and fed to the altimeters in the system; Corrections are continuously applied at altitudes between 8000 feet and 50000 feet. A small flag in the shape of a chevron (or triangle see below) will appear on the face of the pilot’s and copilot’s altimeters when the KIFIS correction is removed or lost.


Original 707 Kollsman Altimeter. Note the White flag when no KIFIS correction is applied.


Potentiometer for the QNH setting