Longitudinal drop-water response analysis of low-flat-tailed firefighting aircraft

低平尾灭火机投水纵向响应问题分析研究

Unit 95885 of People's Liberation Army, Xi'an 710089, China

Received: 23 May 2025

Abstract

The low-flat-tail conventional-layout firefighting aircraft produces the obvious longitudinal head-up response when the gravity water-drop system is used. In order to solve this problem, through the theoretical study of the aerodynamic characteristic change principles during the aircraft's firefighting, a rigid water body assumption method is put forward to simulate the effect of the water body on the aerodynamic characteristics of the firefighting aircraft, and the intrinsic mechanisms of the water body are preliminarily revealed. On this basis, the spatial flow field is analyzed, and the optimal vortex generator layout is given and theoretically verified. The water-drop trial flight verification results show that the installation of a vortex generator can effectively mitigate the head-up moment caused by the presence of water bodies and that the mitigation measure is a low-cost and high-efficiency aerodyna-mic mitigation measure, which significantly reduces the magnitude of the instantaneous pushrod force of the water drop and guarantees the safety of a firefighting aircraft's flight, providing a design and modification reference for the development of other fixed-wing firefighting aircraft.

摘要

针对低平尾常规布局灭火机在采用重力投水系统时出现的纵向抬头响应问题, 通过分析灭火机作业过程中气动特性的变化机理, 提出了一种刚性水体的假设方法, 用以模拟水体对飞机气动特性的影响, 初步揭示了该现象的内在机理。在此基础上对空间流场进行分析, 给出最优的涡流发生器布局并进行了理论验证。投水试飞试验结果表明, 安装涡流发生器能够有效减轻由水体引起的抬头力矩, 显著降低投水瞬间的推杆力大小, 保障灭火机飞行作业安全, 为其他固定翼灭火机的研制提供设计与改装参考。