What is a significant issue with accelerometer-based altimeters?

The significant issue with accelerometer-based altimeters revolves around their performance in non-vertical flight conditions. These altimeters measure altitude based on changes in acceleration, typically derived from the rocket's vertical motion. When a rocket follows a flight path that deviates substantially from vertical—such as during angled launches or in the case of weather conditions causing lateral drift—acceleration data can become less reliable. This misinterpretation of data can lead to improper calculations of altitude and, consequently, result in failure to deploy recovery systems like parachutes at the appropriate time. This nuance highlights the importance of understanding how the orientation and trajectory of a rocket can critically impact the functioning of an accelerometer altimeter in practical applications.