The development of full authority digital engine control （FADEC） software， characterized by its safety-critical nature， is a pivotal task in advancing control systems for large aircraft aero-engines. This study tackles key challenges in requirement analysis and testing encountered during FADEC software development. It introduces a formal modeling method based on the variable relation model （VRM） for specifying FADEC software requirements that are initially described in itemized natural language. The work further investigates techniques for automatically generating test cases from the resulting requirement model and demonstrates the entire approach through a functional case study based on the start fuel control （SFC） software within a FADEC system. The methodology encompasses： The structured preprocessing of natural language requirements to build a domain concept repository；the establishment of a formal modeling framework through requirement standardization， the mmulti-paradigm analysis using the VRM， the automated test case generation， and a critical analysis of domain-specific challenges in FADEC requirement modeling and validation. This paper provides engineering experience for modeling and test of FADEC software require ments.