“Urban air vehicles” have been hailed as the next revolution in aviation. Prototypes of various sizes have been flown to demonstrate basic flight (hover and climb), but in most cases there is no demonstration of full flight capability, for example conversion from vertical to level flight (conversion corridor). There are proposals for vehicles in a wide range of scales: from drones specifically designed to deliver goods, to full size vehicles for manned transportation. Most of the concepts proposed include full electric propulsion, multiple (often convertible) rotors (ducted or un-ducted, counter-rotating), and widespread use of composite materials. Start-up companies are seeking funding with high-profile demonstrations in front of the media, but many unresolved technical problems are not been solved. Large aerospace companies have joined the fray. These initiatives are fuelling expectations that achieving the next milestone is within easy reach. This paper aims to fill some gaps in understanding and curb optimism. It takes a holistic view in order to establish a scientific basis for design, manufacturing, operations.

中文翻译：

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城市空中机动性旋翼机系统：现实检验

“城市飞行器”被誉为航空业的下一次革命。已经飞行了各种尺寸的原型机来演示基本飞行（悬停和爬升），但在大多数情况下，没有演示完整的飞行能力，例如从垂直飞行到水平飞行的转换（转换走廊）。有各种规模的车辆提案：从专门设计用于运送货物的无人机到用于载人运输的全尺寸车辆。提出的大多数概念包括全电力推进、多个（通常可转换的）转子（管道或非管道、反向旋转）以及复合材料的广泛使用。初创公司正在寻求资金，在媒体面前高调展示，但许多悬而未决的技术问题并没有得到解决。大型航空航天公司也加入了竞争。这些举措激发了人们对实现下一个里程碑的期望。本文旨在填补理解和遏制乐观情绪方面的一些空白。它需要一个整体的观点，以便为设计、制造、运营建立科学的基础。