I've read in "How do they fly" by Rudolf Dvořák that the main constraint from inventing some kind of remote-controlled flying machine that could go all directions was the lack of theoretical background that had been significantly improved with the continuing research on insect fly technology.
Is this true or were there much bigger constrains that were making it hard to construct drones apart from the lack of knowledge on aerodynamics?
Drones fly on the same principles as the ordinary airplanes or helicopters. So the main difficulty in developing of drones was the problem how to control them, not how to make them fly. And this problem of control has nothing to do with birds or insects.
Actually airplanes have also little to do with birds and insects because they use different aerodynamic principles. Airplanes (gliders) can be only compared with some large birds which glide for long periods of time. Attempts to imitate birds and insects with artificial devices were made but they were not very successful.
