eVTOL闪电防护适航条款要求分析

2024年6月10日， FAA发布了AC 21.17-4 “Type Certification- Powered-lift” 咨询通告（AC）草案。该草案标志着FAA和EASA就eVTOL的适航条款制定和政策协调一致性取得了重要进展，FAA宣布这是与EASA在电动垂直起降飞行器（eVTOL）适航审定过程中的一个重要里程碑。

闪电防护是eVTOL适航取证中的一个重点和难点。该文件中，与闪电防护相关的主要条款包括：

闪电与静电防护

该条款主要针对飞机结构闪电直接效应防护，防止产生灾难性影响，同时要防止静电的积累。

PL.2335 Lightning and static electricity protection.

(a) The aircraft must be protected against catastrophic effects from lightning.

(b) The aircraft must be protected against hazardous effects caused by an accumulation of electrostatic charge.

能源系统闪电防护

该条款（a）(2)条提出能源系统（或电池与配电系统）的闪电防护，既要考虑闪电直接效应，又要考虑闪电间接效应影响，防止产生灾难性事故。

PL.2430 Energy systems.

(a) Each energy system must—

(2)Be designed to prevent catastrophic events due to lightning strikes, taking into account direct and indirect effects on the aircraft;

电子与电气系统闪电防护

该条款主要针对电子电气系统的闪电防护，主要考虑闪电间接效应的影响。根据系统安全性评估等级，防护要求不同，同时对IFR飞行作出要求。

PL.2515 Electrical- and electronic-system lightning protection.

(a) Each electrical or electronic system that performs a function, the failure of which would prevent the continued safe flight and landing of the aircraft, must be designed and installed such that-

(1) The function at the aircraft level is not adversely affected during and after the time the aircraft is exposed to lightning; and

(2) The system recovers normal operation of that function in a timely manner after the aircraft is exposed to lightning unless the system’s recovery conflicts with other operational or functional requirements of the system.

(b) For an aircraft approved for operation under instrument flight rules (IFR), each electrical and electronic system that performs a function, the failure of which would reduce the capability of the aircraft or the ability of the flightcrew to respond to an adverse operating condition, must be designed and installed such that the system recovers normal operation of that function in a timely manner after the aircraft is exposed to lightning.

螺旋桨控制系统闪电防护

该条款（a）(2)条提出螺旋桨控制系统的闪电防护，主要考虑闪电间接效应影响。

PL.3523 Propeller control system.

The requirements of this section apply to any system or component that controls, limits, or monitors propeller functions.

(a)The propeller control system must be designed, constructed and validated to show that:

(2) The propeller control system functionality is not adversely affected by the declared environmental conditions, including temperature, electromagnetic interference (EMI), high intensity radiated fields (HIRF), and lightning. The environmental limits to which the system has been satisfactorily validated must be documented in the appropriate propeller manuals.

螺旋桨闪电防护

该条款主要针对飞机螺旋桨的闪电直接效应提出要求，防止螺旋桨遭遇雷击后产生重大或危害性影响。

PL.3538 Lightning strike.

The applicant must demonstrate, by tests, analysis based on tests, or experience on similar designs, that the propeller can withstand a lightning strike without causing a major or hazardous propeller effect. The limit to which the propeller has been qualified must be documented in the appropriate manuals.

FAA咨询通告AC 21.17-4文件中与闪电防护相关的适航条款，与FAA之前发布的Joby JAS4–1和Archer M001专用条件中的闪电防护条款基本一致。包含了第 23、33 和 35 部的标准以及其他针对动力升力类及其上安装的电机和螺旋桨的闪电防护要求。与EASA 的SC-VTOL专用条件的闪电条款相比，AC 21.17-4文件中的闪电防护条款更为全面。

eVTOL的闪电防护设计尤为关键。目前，国内外eVTOL相关型号的专用条件均对于飞行器的闪电、静电及HIRF防护设计均提出要求。针对eVTOL的闪电防护设计，主要参考23部。但由于eVTOL与传统23部飞机的构型设计差异、飞行高度、动力系统、材料使用等存在较大的差异，采用了一些新的技术，对于eVTOL的电磁环境防护及适航审查工作也提出了新的要求和挑战。