Altitude Measurement Capability as Related to Altitude Measurement Performance

Height-keeping capability is defined as an aircraft's capability to measure altitude and to hold that altitude while flying. This paper examines the difference between altitude measurement capability as designed into an aircraft and actual altitude measurement performance as measured through operational flight testing for various types of aircraft. It defines an altimetry system error model that can be used to develop system standards for both airframe error measurements and altimetry instrument errors. The paper addresses airframe-related questions of static source sensor tolerances, manufacturing tolerances, production line tolerances, calibration accuracy, and calibration repeatability. It also addresses questions of in-service use effects, such as static pressure sensing degradation for both static probe systems and flush static port systems.

The information presented in this paper is being used to develop altimetry system requirements that could allow vertical separation standards to be reduced above Flight Level 290.