Managing uncertainty through margins: Insights from aerospace engineering practice

Journal article, 2026

In safety-critical industries such as aerospace, managing uncertainty is important, both to ensure airworthiness and to control business risk. Although design margins are widely used to support safety, reliability and regulatory compliance, they are often applied conservatively, with rationales that are implicit, inconsistently documented or unevenly interpreted. While the use of margins is necessary from a safety, reliability and regulatory perspective, excessive use of margins can lead to undesirable effects such as overdesign, consequently leading to heavier parts and therefore design inefficiencies. While the role of margins in this context is well appreciated, there is a gap between the theoretical understanding of margins and their use in practice, especially in relation to uncertainty. This paper investigates this gap through a qualitative study involving 11 in-depth interviews with experienced engineers and managers at a leading aerospace component design and manufacturing company. The interviews explore the current industrial practices, cultural barriers and decision-making heuristics surrounding the practice of design margins. The findings reveal a reliance on legacy practices and tacit knowledge, which may limit margin transparency and potentially contribute to margin stacking. We conclude with actionable implications for the proper documentation and use of margins in engineering design.