Inertial couplings at near-critical angles of attack

Purpose This paper aims to examine inertial coupling in high-speed aircraft, particularly those operating at supersonic speeds. It investigates how the rapid increase in speed, resulting from jet engine use, introduced new dynamic behaviors like gyroscopic effects and autorotation due to changes in aircraft geometry and reduced moment of inertia. Design/methodology/approach The study compares two methods for assessing inertial coupling. The first method uses a detailed, mathematically complex model for preliminary stability assessments but struggles with defining stability conditions due to approximation challenges. The second, more simplified method allows for straightforward calculation of stability parameters, offers easier interpretation through stability diagrams and is better suited for practical applications. Findings The comparison highlights that both methods provide complementary insights into aircraft stability. The first method offers higher precision but is more difficult to use for routine stability determinations, while the second method, though less detailed, provides easier interpretation and practical utility. Both methods help in understanding the stability limits related to roll-yaw and roll-pitch couplings and can assist in mitigating phenomena like autorotation. Practical implications The study’s findings are critical for improving aircraft design, flight dynamics and pilot training, especially for aerobatic manoeuvres. Understanding inertial coupling helps prevent dangerous behaviours like uncontrolled autorotation rolls. Originality/value This study contributes to the field by comparing two distinct approaches to handling the complex dynamics of high-speed aircraft, highlighting the trade-offs between model accuracy and practical usability.