Airworthiness Directives; United Instruments, Inc. Series Altimeters

We propose to adopt a new airworthiness directive (AD) for certain United Instruments, Inc. 5934 series altimeters that were manufactured between January 2015 and February 2016 and installed in airplanes and helicopters. This proposed AD was prompted by reports of certain altimeters displaying higher than actual altitude due to a slow diaphragm leak. This proposed AD would require replacing the affected altimeters. We are issuing this proposed AD to prevent display of misleading altitude data, which could result in inadvertent flight into terrain.