The reliability study of high-altitude unmanned platforms is a very important problem [1, 2]. Platforms of this
type are intended to be operational over long periods of time and are widely used in both civilian and military areas.
Multi-rotor architecture of such platforms allows for the platform with n rotary-wing engines to stay operational even
after k - 1 engines fail. However, failure of a part of the engines causes the increase in load on the others, which results
in their reliability deterioration. Moreover, the system’s operational capability depends on the disposition of the failed
engines. So, the worst case for this system is the failure of the proximately-located engines. Hence, while developing
the reliability evaluation models and finding an optimal architecture of such systems, it is necessary to consider a factor
of the “failure dependency”. Thus, the considered systems can be modeled by the k-out-of-n heterogeneous models,
which components’ failures depend on the configuration of the failed components. Due to the wide practical application
area, a lot of papers were devoted to the study of the k-out-of-n systems. In the talk a review of classic and
contemporary papers dedicated to the considered class of systems will be proposed.