v1.2.3 / chapter 2 of 4 / 01 may 07 / greg goebel / public domain
* While the sensor suite of the Mohawk was state of the art for its time, sensor capabilities have improved dramatically since the 1960s. In the early 1990s, the US Army decided to obtain a new surveillance platform, the RC-7 "Airborne Reconnaissance Low (ARL)" aircraft, based on the De Havilland Canada Dash-7 airliner, to exploit these new technologies. The RC-7 proved so useful that the Army obtained an improved version, the RC-7B "ARL Multifunction" (ARLM). This chapter describes the RC-7 and RC-7B, and discusses efforts to obtain a successor.
* During the 1950s and 1960s, the aircraft manufacturer De Havilland Canada (DHC) acquired extensive experience in the construction of small and medium capacity transports with short takeoff & landing (STOL) capabilities, such as the "Otter" and "Caribou". The US Army was one of their customers, and the two organizations developed a good long-term relationship.
In the early 1970s, the company decided to build a larger STOL transport for use as a mid-sized commercial regional airliner, operating on intercity routes between major metropolitan areas from small local airports. This requirement dictated a design that had good short-field capability and a low noise signature. Construction of prototypes of what would be the "DHC-7 / Dash-7", began in late 1972, with two prototypes taking to the air in the spring of 1975. The type received Canadian certification in the spring of 1977, with the first production aircraft flying shortly afterwards. The first customer delivery was in early 1978.
The Dash-7 is powered by four Pratt & Whitney Canada (PWC) PT6A turboprops, each rated at 835 kW (1,240 SHP) at takeoff and driving a four-blade Hamilton Standard propeller. The propellers are very wide, with a diameter of 3.4 meters (over 11 feet), to allow them to provide adequate thrust at relatively low RPM, reducing noise. The aircraft features a high wing, tee tail, and an aerodynamic lift enhancement system that features double slotted flaps over 80% of the wingspan, along with an outboard spoiler on each wing to provide additional control as needed. With these features, the Dash-7 can take off and land in less than 700 meters (2,300 feet). In contrast, a Boeing 737-300, which has a degree of short-field capability in the form of thrust reversers and triple slotted flaps, requires about 1,400 meters (4,600 feet) for takeoff and landing.
The initial Dash-7 model was the "Series 100", which was a pure airliner typically fitted with 50 seats. There was a complementary "Series 101" variant, with a large freight door just aft of the cockpit, that could be configured as a cargolifter or mixed cargo-passenger transport. These variants were followed by the "Series 150" airliner and the complementary "Series 151" cargo lifter or cargo-passenger transport. The 150/151 are essentially identical to the 100/101, except for increased fuel capacity and a higher take-off weight rating.
Stretched variants were considered but never built. While the Dash-7 was an attractive and well-built aircraft, the urban STOL market that DHC had anticipated never materialized, and the Dash-7 didn't sell. When Boeing bought out DHC in 1986, new efforts were focused on stretched versions of the less specialized twin-turboprop "Dash-8" transport. 108 Dash-7s had been sold by 1987. It is now out of production.
* Although the Dash-7 was something of a noble failure, it was still a fine aircraft that was well suited to certain applications. In the early 1990s, the US Army Southern Command (SOUTHCOM), with its domain of responsibilities in Latin America, determined a need for a "low profile" intelligence platform to participate in counter-drug operations and other missions that fell outside of the Army's traditional battlefield operations role.
The Dash-7 was an excellent choice for this purpose. As noted, the US Army had long and happy experience with DHC aircraft, and the Dash-7 coupled good endurance and load-carrying capacity with very good short-field performance. Besides, it looked like a civilian airliner and made relatively little noise, which fit the Army's need for an aircraft that didn't attract attention.
The initial contract for converting the Dash-7 into an intelligence aircraft was awarded to California Microwave Incorporated (CMI, now a part of Northrop Grumman) in the spring of 1991, with the first "RC-7 Airborne Reconnaissance Low (ARL)" aircraft delivered two years later. Three RC-7s were provided to SOUTHCOM, with two of them optimized for signals intelligence (SIGINT) and one for imaging intelligence (IMINT). These initial RC-7 variants were used in the Haiti intervention in 1994, Bosnian peacekeeping duties, operations against drug producers and smugglers, and in support of disaster relief operations.
* The RC-7 met SOUTHCOM's requirements very well, and the Army went on to initiate the acquisition of a more advanced version in the summer of 1993, designated the "RC-7B ARLM (ARL Multifunction)", that merged the SIGINT and IMINT functions of the two types of RC-7, along with new capabilities, to provide a comprehensive sensor suite. The first two RC-7Bs were delivered in the fall of 1996, and were deployed to Korea to observe North Korean military activities. They replaced the retiring Grumman OV-1D Mohawk. More RC-7Bs were delivered in the following years.
The RC-7B carries a crew of pilot, copilot, and four systems operators. The
electronics systems are highly automated to reduce crew workload. The RC-7B
can be regarded as sort of a combination poor-man's E-8 "Joint-STARS"
battlefield surveillance platform (described in the next chapter), and RC-135
"Rivet Joint" signals intelligence aircraft. While it does not have nearly
the capabilities of these two larger Boeing four-jet intelligence platforms,
the ARLM is adequate for low-intensity missions, and much cheaper to operate.
RC-7 ARL:
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spec metric english
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wingspan 28.4 meters 93 feet
wing area 79.9 sq_meters 860 sq_feet
length 24.5 meters 80 feet 6 inches
height 8 meters 26 feet 2 inches
max loaded weight 21,300 kilograms 47,000 pounds
cruising speed 425 KPH 265 MPH / 230 KT
service ceiling 7,600 meters 25,000 feet
endurance 7.5 hours
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CMI bought each aircraft for less than $4 million USD, modified them for
about the same amount, and then crammed each bird with $17 million USD in
electronics. At a total of about $25 million USD, the RC-7B couldn't be
regarded as cheap, but it was about the same price as an F-16 fighter, and
far cheaper than a Joint-STARS or Rivet Joint. Its operational costs are
similarly lower, about 15% of those of the RC-135. The RC-7B can typically
operate for 7.5 hours at 250 KPH, though it can be configured for 10-hour
flights.
The RC-7B's payload includes:
The MTI display shows targets on a map background, with those moving towards the aircraft displayed as red dots and those moving away as green dots. A target that stops moving will remain on the display for three minutes and then disappear. The MTI operates in three modes: a 90 degree / wide-area search mode; a 5 degree / narrow sector search mode; and a 2 degree single-beam "spotlight" mode for examining individual targets.
The signals intercept system can be configured in flight to sort out signals with different characteristics. While it can't analyze burst communications or decipher signals with advanced voice encryption, it can store them on tape and transmit them to US National Security Agency stations for analysis.
The current direction finding gear on board the RC-7B cannot link particular communications to specific vehicles, except if the aircraft is operating in conjunction with direction finding equipment on other aircraft or ground stations.
The Army has considered adding a "measurement & signature intelligence (MASINT)" system to the RC-7B that could perform remote chemical analysis of factory smoke, rocket exhaust plumes, and waste water runoff. The MASINT system would use "hyperspectral" sensing techniques that perform observations over a large number of infrared and optical bands.
The RC-7B's sensing and comlink capabilities permit realtime targeting of adversary assets, allowing ground forces to react quickly to distant threats. Intelligence collected by space satellites may take up to three days to reach its ultimate users, but battlefield commanders down to the battalion level can obtain near-realtime SAR-MTI displays from the RC-7B to give them a view of their tactical environment.
The RC-7B, while hardly invisible to radar or other sensors, has adopted a clever kind of "stealth" of its own. The aircraft's "Low" designation implies "low profile", and it is rigged in such a way as to attract little attention. There isn't much in its external appearance to distinguish it from an ordinary Dash-7, since most of the antennas and other sensors are retractable. It is painted to look like a commercial airliner, with military markings kept to a discreet minimum. During Haiti operations, Caribbean charter pilots took the RC-7 for a new competitor.
* On 23 July 1999, one of the original RC-7s was operating under low-visibility conditions in support of "anti-narcotic" operations in Colombia when it flew into a mountainside. All on board, including both US Army and Colombian military personnel, were killed. The incident revealed both the use of the aircraft in low-profile military operations and the US involvement in the guerrilla war in Colombia.
At the time of the crash, the Army had a total of eight RC-7/7Bs, plus a Dash-7 used for flight training and another used as a technology demonstrator. The RC-7 that crashed was the single pure IMINT variant, while of the other seven, two were updated RC-7 SIGINT variants and five were RC-7Bs. Three of the RC-7Bs are currently deployed to Korea, where they keep an eye on North Korean military activities north of the demilitarized zone. The US Congress provided funds to replace the RC-7 that was lost and a new RC-7B has been delivered to the US Army. The fleet is expected to remain in service up to 2017.
There has been some talk of updating the two SIGINT-only variants to RC-7B specification, though so far nothing much seems to be happening, and a few years ago there was a proposal to replace the fleet's PT6A engines with the LHTEC T800 engine. This idea didn't go anywhere either, but the idea of reengining the fleet with a new turboprop engine to increase time on station and reduce maintenance costs is still attractive.
* Whether any more RC-7Bs will be ordered or what level of updates existing machines will receive is unclear. The Army did work on a successor platform, the "Aerial Common Sensor (ACS)", to replace both the RC-7B and the RC-12 "Guardrail".
The Guardrail is a SIGINT platform based on the Beech Super King Air twin-turboprop transport, known generally as the "Ute" in Army service. Predecessors to the Guardrail were based on the smaller Beech Queen Air piston twin, known generally as the "Seminole" in Army service. The Guardrail was developed in later part of the 1960s to deal with North Korean military activities, following a series of commando intrusions performed in 1967 through 1969.
There have been a confusing range of different Guardrail variants, but all have been focused on the SIGINT mission. They do little or no on-board processing of data, relaying it to a ground station for analysis. Later Guardrails carry an almost ridiculous array of antennas, doing much to clutter up the very pleasing lines of the Super King Air.
The ACS was to combine the functions of the RC-7B and the Guardrail. Concept studies for the ACS were initiated in 2000. Army specifications for the ACS essentially dictated a business jet or small jet airliner, not a turboprop like the Dash-8. The ACS was to carry a comprehensive SIGINT suite, an electro-optic sensor system, SAR-MTI, and high-speed datalinks. The Army also decided that the ACS should also be able to act as an airborne communications center.
In the summer of 2003, the US Navy signed on to the ACS program. The Navy was facing the phaseout of the service's current P-3C Orion antisubmarine warfare platform and EP-3 Aries SIGINT aircraft, and was in need of replacements. The Navy initially pressed for development of a "Multimission Maritime Aircraft (MMA)" as the replacement for both, resulting in a contract awarded to Boeing in 2004 for what would be designated the "P-8A", based on the Boeing 737-800 airliner with longer-span 737-900 wings. The Navy had been interested in the Army ACS effort, at least initially with an eye to leveraging the ACS electronics suite into the MMA. However, cost forced the Navy to accept the full Army ACS solution.
Northrop Grumman and Lockheed Martin competed on the deal, with Northrop Grumman proposing a solution based on the Gulfstream IV business jet, while Lockheed Martin proposing a solution based on the Brazilian EMBRAER ERJ-145 regional airliner. Lockheed Martin won the award in August 2004, but then the program faltered: a year later, "payload creep" finally overloaded the lift capability of the ERJ-145.
Lockheed Martin proposed using the Bombardier Global Express XRS instead, but when Northrop Grumman said that a switch to a different aircraft would trigger a legal protest, the Army decided to axe the program. It was a painful thing to do, but since Lockheed Martin hadn't been able to deliver on the contract as it had been bid, Northrop Grumman had a very good case on legal grounds for a challenge despite the fact that their Gulfstream-based solution would have run into the same trouble. The Army sensibly didn't think of trying to ignore it.
The program was effectively reset to square one, a senior Pentagon official saying it was "back to the drawing board". The Army still wants the ACS but what happens now is unclear; it appears that funding has been cut back substantially, at least for the moment. In considerable irony, it was the Navy requirements that raised the payload and forced the move to a larger platform, and the Navy may well go back to their original notion of a 737-based SIGINT platform. In early 2006, Boeing announced that the company would offer a SIGINT variant of the MMA, claiming that the platform would also be able to carry surveillance sensors and communications relay payloads.
