Growing interest in unconventional aircraft designs coupled with miniaturization of electronics and advancements in manufacturing techniques have revived the interest in the use of Sub-scale Flight Testing (SFT) to study the flight behaviour of full-scale aircraft in the early stages of design process by means of free-flying sub-scale models. SFT is particularly useful in the study of unconventional aircraft configurations as their behaviour cannot be reliably predicted based on legacy aircraft designs. In this paper, we survey the evolution of various design approaches (from 1848 to 2021) used to ensure similitude between a sub-scale model and its full-scale counterpart, which is an essential requirement to effectively perform SFT. Next, we present an exhaustive list of existing sub-scale models used in SFT and analyse the key trends in their design approaches, test-objectives, and applications. From this review, we conclude that the state-of-the-art sub-scale model design methods available in literature have not been used extensively in practice. Furthermore, we argue that one sub-scale model is not sufficient to predict the complete flight behaviour of a full-scale aircraft, but a catalog of tailored sub-scale models is needed to predict full-scale behaviour. An introduction to the development of such a catalog is presented in this paper, but the development of a formal methodology remains an open challenge. Establishing an approach to develop and use a SFT catalog of models to predict full-scale aircraft behaviour will help engineers enhance confidence on their designs and make SFT a viable and attractive testing method in the early stages of design.

对非常规飞机设计的兴趣与日俱增，再加上电子设备的小型化和制造技术的进步，重新激发了人们对使用小规模飞行测试 (SFT) 研究全尺寸飞机在设计过程早期阶段的飞行行为的兴趣。自由飞行的子尺度模型的手段。SFT 在非常规飞机配置的研究中特别有用，因为它们的行为无法根据传统飞机设计可靠地预测。在本文中，我们调查了各种设计方法（从 1848 年到 2021 年）的演变，用于确保子尺度模型与其全尺度模型之间的相似性，这是有效执行 SFT 的基本要求。下一个，我们提供了 SFT 中使用的现有子尺度模型的详尽列表，并分析了其设计方法、测试目标和应用程序的主要趋势。从这篇综述中，我们得出结论，文献中可用的最先进的子尺度模型设计方法尚未在实践中广泛使用。此外，我们认为一个子尺度模型不足以预测全尺寸飞机的完整飞行行为，但需要一个定制的子尺度模型目录来预测全尺寸行为。本文介绍了这种目录的开发，但正式方法的开发仍然是一个开放的挑战。