The book summarizes and analyzes the issues of aerodynamics, flight dynamics, aeroelasticity, vibrations and dynamic structural strength, performance of a power plant with gas turbine engines and automation, operational reliability, crew life, aviation meteorology, which determine the safety of flights of single-rotor and coaxial helicopters. Substantiation of the physical essence of the main flight limitations contained in the flight manual is given, possible errors during flight and technical operation of helicopters in various conditions are analyzed. For the first time, the behavior of the helicopter in characteristic special situations created by complicated flight conditions and failures of vital functional systems is discussed in detail, recommendations are made to ensure flight safety and investigate flight accidents.