UCAV outside a hangar

The new Russian UCAV sports a fairly blunt leading edge while all the other UAVs in the same category have sharp leading edges.

head on shot of a UAV with a sharp leading edge

in flight view of a UAV with what appears to be a sharp leading edge


1 Answer 1


This seems like a hint that for this design, flight characteristics are more important than stealth. Generally, in subsonic flight, anything with sharp leading edges will have poor transitions from negative to positive lift and a sharp, unforgiving stall -- and given appropriate materials, there may be little to gain even from a stealth standpoint with modern design optimizations (the B-2 has much more rounded leading edges than the F-117, for instance).

Since few stealth designs are intended to fly supersonic (shock waves and compression heating are prone to give away your presence, never mind the much higher exhaust temperature that tends to go with supersonic flight), it makes sense to optimize away sharp leading edges if doing so doesn't compromize observability.

  • $\begingroup$ will the sharp edges not help in vortex lift? Is vortex lift not necessary for delta winged planforms? $\endgroup$
    – Mridul
    Commented Dec 17, 2021 at 17:06
  • $\begingroup$ As I understand it, vortex lift is very helpful for high AoA to allow reasonable landing speeds, but drones may not care as much about that (the controlling computer has much faster reflexes than a human, hence ability to fly a statically unstable airframe). $\endgroup$
    – Zeiss Ikon
    Commented Dec 17, 2021 at 17:15
  • $\begingroup$ UAVs also don't have anyone on board to complain about rougher landings or hard breaking that may come from higher landing speeds. $\endgroup$
    – FreeMan
    Commented Dec 17, 2021 at 18:01
  • $\begingroup$ It may be that this particular drone has been optimised for "time on station", requiring it to operate at the lowest possible airspeed which would involve a high angle of attack, or even a STOL capability. This design decision may also be prompted by increased internal volume for fuel, sensors, novel antenna shapes or weapons. Everything about aircraft design is a compromise between competing criteria. $\endgroup$
    – Mackk
    Commented Dec 18, 2021 at 23:47

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