After several consultations with Dr Ho and seniors, we realised that gliding may not be as power efficient as we envisioned.
As the glider drone has to expend power to climb before gliding without power, as shown in the diagram above, doing so regularly may not be as power efficient as horizontal flight over the same range. This is because vertical flight usually consumes more power than horizontal flight.
We performed some calculations to find out which flight path saves more power in the end. In the working below, subscript ‘V’ denotes vertical and subscript ‘H’ horizontal.
Assuming that the drone travels the same horizontal distance for both gliding and powered flight, if gliding were to expend less power, the drone needs to glide at an angle of less than 20.6°. This angle is very small and difficult to maintain in flight. Also, from our observations, glider flight pattern is rather unpredictable and easily affected by many factors, hence it will be very challenging to travel similar horizontal distance as powered flight.
These reasons made us reconsider our plans to build a glider drone. We decided to investigate some alternatives that can save more power.