Introduction
Rapidly emerging classification of unmanned aircraft. Controlled remotely by a GCS (Ground Control Station) or CGS (Common Ground Segment,) vehicles operate at varying altitudes just above the surface of the Earth to several tens of thousands of feet dependant on airframe and constitution of the given mission.
Primarily operated by military and intelligence apparatus in the capacity of clandestine surveillance units, most vehicles can be moved, unloaded and launched anywhere within the world in a twenty-four hour period.
Initially used in combat during the Gulf War by the United States Navy primarily for OTH (over-the-horizon) spotting for battleship NGS (Naval Gunfire Support,) mine hunting and as organic BDA (Bomb Damage Assessment) assets. Since then the U.S. military has significantly expanded the active use of UAV/UCAV airframes in combat and intelligence gathering operations. In particular the United States Air Force has advanced the fastest in terms of UAV/UCAV development, laying groundwork for later Army and Navy systems acquisition. This includes UAV operations during the Bosnian conflict where UAVs are rumored to have actually laser-designated for F-16 strike missions. This is perhaps most evident in the rapid proposal, approval, development and pending acceptance into open service of highly advanced vehicles such as the RQ-3A Dark Star and RQ-4A Global Hawk.

Definitions of Acronyms
CGS- Common Ground Element
GCS- Ground Control Station
EO- Electro-optical
FLIR- Forward Looking Infrared
FSAT- Full Size Aerial Target
HALE- High Altitude, Long Endurance
IR- Infrared
LLTV- Low Light Television
MALE- Medium Altitude, Long Endurance
MMW- Millimeter Wave
RPH- Remotely Piloted Helicopter
RPV- Remotely Piloted Vehicle
SAR- Synthetic Aperture Radar
STOL- Short Takeoff and Landing
TV- Television
UAV- Unmanned Aerial Vehicle
UCAV- Unmanned Combat Aerial Vehicle. Subcategorized into UCAV-H (high altitude,) UCAV-M (medium altitude,) and UCAV-L (low altitude.)
VTOL- Vertical Takeoff and Landing

U.S. UAV/UCAV Airframes and Designations
(Note: This is by far an incomplete treatment of airframes currently in service. Due to the nature of the field, some designs and uses are quite classified and therefore not publicly acknowledged to exist. Also, it should be kept in mind that this does not cover FSATs, drones, balloons, blimps or targets.)
Bell Eagle Eye
VTOL/STOL airframe patterned after the M/OV-22 Osprey airframe. EO/IR/FLIR sensors and has provisions to carry submunitions. Currently still under development.
Boston ACRW
Experimental VTOL UAV. Circular rotating wing on bottom of lengthened fuselage on top of tricycle landing gear, propelled by ducted fan motor in rear of vehicle. Sensor configuration, power plant type and other statistics not currently published.
BQM-145A
Manufactured by Northrop-Grumman Aerospace for the U.S. Navy/U.S. Air Force and designed to be launched from either an F-16 or F/A-18. Flat-bottomed low observable fuselage blending into two lateral intakes positioned on the upper aft tail section providing air for a single turbofan engine located inside of the tail of the airframe. Small swept back wings, rudder and tail planes similar to most cruise missile designs. Capable of carrying IR linescan, EO/FLIR, SAR or MMW sensing systems of various manufacture dependent on mission requirements. Data link specifications not currently published.
DRI STF-9
Daedelus Research International developed monoplane UAV used as a technology demonstration vehicle for DARPA. Currently no longer in active service.
Frontier Systems A160 Hummingbird
RPH consisting of a low radar observable slim fuselage and three long and thin rotor blades still in the conceptual design phase. Upon delivery should carry as a payload EO/linescan IR and SAR as a proof of concept vehicle for DARPA to see use in later projects.
General Atomics Gnat
Airframes consisting of a low wing monoplane with retractable landing gear blending into an inverted V tail and powered by a two-stroke motor coupled to a two bladed adjustable pitch propeller. Several variants of the successful design have been built and successfully fielded by differing agencies and organizations. Extremely flexible airframe capable of carrying any of the following sensor systems: FLIR, TV, LLTV, ESM, DF, NBC detection, or other air delivered/customer specified payloads.
Gnat 750: Initial service model with well over 1,500 successful service hours.
Gnat XP: Unknown variant supplied to unknown U.S. government customer. No details available as to capability or differentiations with other Gnat types.
I-Gnat: Improved version of the Gnat 750. Improvements include 2 external hard points, turbocharged engine, radar altimeter, air-to-air data link capability, and designed for HALE operations.
Lethal Amber: UCAV variant of Gnat designed to carry a laser designator and fire Hellfire or Stinger missiles.
General Atomics Prowler
Generally similar in structure to the Gnat with slight design modifications to see if changes would affect overall stability or success of the airframe, with two stages to the process.
Prowler I: Similar to Gnat in almost all respects with the exception of a ten-degree wing offset. (I.e. wings rotated ten-degrees off center, left wing forward.)
Prowler II: Eliminated Gnat inverted V tail plane and wing offset of Prowler I in favor of an upright rudder and more traditional elevators. Still propelled by a Gnat engine and two-bladed propeller mounted in the rear of the airframe, Prowler I and II carry the same instrumentation and sensors of Gnat.
Meggitt Sentry
Flying wing type design consisting of a high-mounted delta wing bonded to a deep center section fuselage. Unlike most UAVs, Sentry is pulled rather than pushed by a two bladed propeller mounted in the front of the vehicle, with twin tail booms terminating in a single elevator surface for both the Sentry and Sentry HP. Able to carry EO/IR sensors and either operates autonomously or from instructions received from a ground station.
RQ-1A Predator
UCAV/UAV manufactured by General Atomics and similar in size and design to the Gnat with larger fuselage size and lower wings that have provisions for hard points allowing the attachment of ordinance or external sensors. Primarily a MALE UCAV, Predator is capable of carrying a wide array of sensor systems dependent on mission including but not limited to: TV, EO/IR, SAR and FLIR. Powered by a four stroke, four-cylinder engine coupled to a two bladed variable pitch propeller mounted at the rear of the fuselage. Uses I band data link to communicate with a ground control station.
RQ-2 Pioneer
Manufactured by IAI mainly for the United States Navy. Shoulder wing pod and twin tail boom monoplane with pusher engine, fixed tricycle landing gear and arresting hook for shipboard operations.
RQ-2A: Initial production version of the Pioneer, progressively upgraded during service to meet expanding mission needs.
RQ-2B: Improved version of the Pioneer, (includes Option and 2+ models in this category,) carrying EO/IR and incorporating and automatic recovery system for use if data link contact should be severed.
RQ-3A Dark Star
HALE UAV built by Northrop-Grumman. Specifically designed to enter and loiter inside of a hostile environment, the airframe was built with an extremely low radar cross section. Extremely long, slightly forward swept wings attached to the rear of an extended lobe-shaped fuselage housing a static thrust turbojet engine. I band data link system is used to control the vehicle during flight, no data available on specific sensor systems.
RQ-4A Global Hawk
HALE UAV built by Northrop-Grumman and the second major effort to field a successful airframe of this type dedicated to a long endurance reconnaissance mission. Ground stations have the unique ability to control up to three units simultaneously allowing for constant turnover and presence over a given target. High aspect ratio wings similar in shape to the U-2 with a turbofan engine mounted in a rounded rectangular box at the rear of the fuselage. L-3 Communications manufactured wideband command and control data link system using satellite networking to pass signals to and from ground control stations should mission requirements merit OTH flight. Sensor package also mission flexible and can consist of IR/FLIR and/or SAR.
RQ-7A Shadow 200
Manufactured by IAI (Israel) under contract by the U.S. Army. Consists of a shoulder wing monoplane design, two bladed propeller coupled to a radial pusher engine and inverted V tail similar to the General Atomics Gnat. Typically carries EO/IR sensors beneath the nose of the airframe. Uses G/H band data link to communicate with a GCS within LOS of operating area.
X-45A
UCAV currently under development with Bell Aircraft presumably for service in the U.S. Air Force as a MALE asset capable of carrying and delivering precision munitions, unlike the RQ-3A Dark Star and RQ-4A Global Hawk. Has swept wing with W tail configuration very similar to that of the B-2A bomber leading into extended forward nose and fuselage section. Capable of carrying two precision guided munitions or a single 2000 pound weapon in an internal bay. Sensor configuration, power plant type and other statistics not currently published.

Sources
Jane's Intelligence Weekly, October 2000. Pgs: 61-70; Pilotless Progress Report, Mark Hewish Jane's Online, Drones and Targets Binder 15 (10October2000 update.)

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