O-5A Special Electronic Mission Aircraft
EO-5B Special Electronic Mission Aircraft
EO-5C Special Electronic Mission Aircraft
RC-7B Special Electronic Mission Aircraft

O-5 is the US military designation for the DeHavilland Canada DHC-7 in US Army service. The O-5 is a member of the Army's Special Electronic Mission Aircraft (SEMA) fleet and is the platform used for the Airborne Reconnaissance - Low (ARL) program, originally a US Southern Command (SOUTHCOM) requirement. The ARL system was initially broken into 2 separate systems, one for imagery intelligence (ARL-I) and another for communications intelligence (ARL-C). The carrier aircraft for the ARL-I was designated O-5A, while the aircraft for the ARL-C was designated EO-5B. The decision was subsequently made to combine the 2 systems in a multi-sensor configuration (ARL-M), with the carrier aircraft being given the non-standard designation RC-7B in 1996, a misnomer as well as the aircraft had no relationship to the C-7A Caribou other than coming from the same manufacturer. On 14 August 2004, this was officially changed to the sequentially correct designation EO-5C, though the RC-7B designation continued to appear in official documentation.

The DHC-7 aircraft was developed by DeHavilland of Canada to meet a world wide market for short to middle range Short Take Off and Landing (STOL) transports. The DHC-7 was chosen by the Army as the platform for ARL because of its ability to carry the necessary sensors, endurance, STOL performance, and multi-engine configuration. The airframe is a dual pilot aircraft modified to operate for extended 8-10 hour missions. It is an all metal, high wing monoplane powered by 4 Pratt and Whitney PT6A-50 turboprop engines driving composite construction, four bladed, constant speed, variable and reversible pitch propellers. The basic DHC-7 was an extensively modified for the ARL program to have a higher maximum gross weight and extended range capability added. At ranges to 1,500 nautical, cruise speed is 230 knots and it can loiter at speeds as low as 110 knots. The DHC-7 is capable of taking off loaded under high/hot conditions from an unimproved runway and climbing to a maximum of 20,400 feet MSL (without supplemental oxygen for crew) and 25,000 feet MSL (with crew on supplemental oxygen). Proposed future engines and "wet wing" fuel tanks were to extend the range to 2,800 nautical miles. Later aircraft featured cockpits upgraded to Airspace 2000 standards.

The aircraft were equipped with Aircraft Survivability Equipment (ASE) suitable for countering threats expected in its theater of operations. The full ASE suite included missile and radar warning systems such as the the AN/APR-39A(V1) radar warning receiver and the AN/AAR-47 infrared missile warning receiver, and the M130 countermeasure dispenser. Kevlar armor plating protected the pilots and mission crew.

In March 1991, the Army awarded a contract for one airborne imagery system (ARL-I) with options for 5 additional multifunction systems to California Microwave, Inc. (CMI), of Belcamp, Maryland. In November 1990, the US Congress had mandated the combining of the imagery system that had previously been known just by the codename Grisly Hunter with an airborne radio direction finding system also in development to form the Airborne Reconnaissance Low (ARL) program. The Grisly Hunter system had been tested on the RG-8A aircraft, and a competition had been held between the CASA 212 and the Dominion Skytrader 800 as potential platforms. The Skytrader 800 had been selected as the Grisly Hunter platform, and given the designation UV-23, before the decision was made to establish the ARL program and acquire the DHC-7, which was subsequently given the designation O-5A. The Grisly Hunter codename continued to be associated with the ARL-I portion of the ARL program and the aircraft were also referred to by that codename.

In April 1991 the Army awarded a sole source contract to ESL, Inc. of Sunnyvale, California for 2 airborne communications intelligence (COMINT) systems (ARL-C). These aircraft were subsequently designated EO-5B. The ARL-C portion of the ARL program was also known as Crazy Panther and the aircraft were also referred to by that codename.

Tragically, the single ARL-I aircraft and all 5 US crew members were lost in an accident in Colombia in July 1999. The fielding of the fourth ARL-M system (sometimes referred to as ARL-M4) aircraft in September 1999 partially offset the loss of the airframe. This aircraft contained upgraded electro-optic and infrared (EO/IR) imaging systems and a combination synthetic-aperture radar (SAR) with a moving target indicator (MTI). New equipment training on this latest system culminated in a Limited User Test in the December 1999-January 2000 time frame.

The O-5A and 2 EO-5B aircraft, intended as interim capability systems, were fielded within 2 years of contract award to USSOUTHCOM. The Army subsequently exercised its contract option with CMI and procured 3 multifunction (ARL-M) systems, which combined the ARL-I and ARL-C capabilities. The ARL-M carrier aircraft were subsequently designated RC-7B, though this was changed in 2004 to EO-5C. In December 1996, the Army exercised its contract option again and procured 2 additional ARL-M systems with delivery scheduled in December 1998. RC-7B/EO-5C aircraft continued to serve in the US Army into the 21st century and by 2012, aircraft were operating in support of US Southern Command and US Forces Korea, as well as in support of Operation Enduring Freedom.