This research paper addresses the designing of high speed free fall detection and primary trigger generation problem as a part of an in-flight emergency technology developments for unmanned aerial vehicles. The primary trigger is the very first to be detected and to be generated with high speed and accuracy in designing protection mechanism. This trigger indicates that UAV started falling. Sequences of resulting mechanism such as airbag inflation comes secondly. Speed requirement is a deterministic factor when the flight altitude is low. In this paper a high speed analog module is proposed to achieve the primary trigger and performed relevant validation tests on linear free fall and rotational free fall which covers the majority of free fall patterns. The positive test results verify the design as a primary trigger generation module for linear and rotational free fall detection in low altitude UAV missions or which could be enhanced with additional features to form more complex system of airbag inflation in UAV in-flight emergency technology development.