UA-drones (short for Unmanned aerial drones) are general purpose security devices that are often equipped with various defenses and security measures. They are generally utilized for the defense of any bases. In some cases, they are equipped with a 5.56mm machine gun and will sound an alarm engage an intruder with its machine gun should the latter enter its visual field.
During the Peace Walker Incident in 1974, the CIA mercenary group Peace Sentinel and the Soviets, when defending the Nicaragua base housing Peace Walker, placed Kidnapper drones near and inside the base as a precaution in the event that Big Boss infiltrated the base to put a halt to the Peace Walker project.
Diamond Dogs and various 1980s PMCs
During the 1980s, the Diamond Dogs developed and utilized various UA-drones to defend various forward operating bases of their main Mother Base at the Seychelles sea. It also came with nonlethal variants that fired smoke grenade or sleeping gas rounds.
Sons of Liberty
During the Big Shell Incident in 2009, the Sons of Liberty terrorist group utilized Cypher drones to guard the Big Shell, including a then-newly developed version called a Gun Cypher, with the FOXHOUND operative Raiden having to evade them during his mission and even neutralizing one due to it being part of a trap at the Shell Connecting Bridge.
Behind the scenes
UA-Drones were a recurring trap in the Metal Gear series. They were mostly hinderances to the player, although in Metal Gear Solid V: The Phantom Pain, because of the FOB gameplay element, they also can prove to be an invaluable defense system. The UA-drone is considered a Grade 3 security device, it requires 300000 GMP to develop, as well as a minimum R&D Team and Security Team level of 24. A Grade 4 variant can also be developed at 400000 GMP, a minimum R&D and Security Team of 30, and requires someone with the Gunsmith (Grenade Launcher) specialist ability and the [UA-DRONE] Blueprint.
General purpose unmanned security device.
A drone that conducts aerial surveillance of a fixed area. Equipped with a 5.56mm machine gun. If an intruder enters its visual field, it sounds an alarm and also engages the intruder with its machine gun."
- ―UA-drone menu description in Metal Gear Solid V: The Phantom Pain Gamescom 2015 Mother Base/FOB gameplay demo.
On March 1, the Sleep Grenade UA-drone variant was added to development. On May 10, a variant was added to development that was able to leech battery power from another player when in close proximity.