EC-135 / EC-18 ARIA

The Advanced Range Instrumentation Aircraft (ARIA) were a US Air Force fleet of telemetry and tracking aircraft converted from Boeing C-135 and 707 airframes. Eight EC-135N conversions entered service in January 1968 to support the Apollo programme, distinguished by a bulbous "droop snoot" nose radome housing a steerable 2.1 m (7 ft) antenna dish. They were later re-engined as the EC-135E and joined by four EC-18B conversions of former airline 707-320s. Over a 32-year career the fleet supported the US space programme, missile tests and treaty verification before its tasks passed to satellites and other programmes.

Development

In the early 1960s NASA and the Department of Defense required a mobile platform able to track spacecraft and receive telemetry from Apollo and unmanned flights beyond the reach of ground stations. Under a joint project, McDonnell Douglas and Bendix modified eight C-135s into Apollo/Range Instrumentation Aircraft (A/RIA), designated EC-135N. They became operational in January 1968 with the Air Force Eastern Test Range at Patrick AFB, Florida. When Apollo ended in 1972 the aircraft were renamed Advanced Range Instrumentation Aircraft. Corrosion from the salt air at Patrick was a persistent problem, and in December 1975 the fleet moved to the 4950th Test Wing at Wright-Patterson AFB, Ohio, as part of a consolidation of large test aircraft. There it underwent numerous conversions, including a re-engining that turned the EC-135N into the EC-135E; a further variant, the EC-135B, was a C-135B fitted with the enlarged nose.

To expand the fleet the Air Force bought eight second-hand Boeing 707-323Cs from American Airlines as C-18A crew trainers for the EC-18B. Four were converted to EC-18B ARIA, a modification initially designated E-7; two became EC-18D Cruise Missile Mission Control Aircraft, one the C-18B for MILSTAR support, and one was used for spares. In 1994 the ARIA fleet relocated to Edwards AFB, California, under the 412th Test Wing.

Design

The ARIA aircraft are identified by the greatly enlarged nose radome, which houses a steerable seven-foot (2.1 m) antenna dish used to acquire and track spacecraft and missiles. The cabin carries the mission electronics for receiving and recording telemetry. The EC-135N were converted from C-135 transports and the EC-135E from the EC-135N; the preserved example is a C-135A airframe with J57-59 engines. The EC-18B retained the airframe of the 707-320 airliner. Beyond telemetry reception, the fleet collected data from the Sonobuoy Missile Impact Location System (SMILS), a task also performed by Navy P-3s.

Military service

From January 1968 the EC-135N fleet tracked Apollo missions for the Air Force Eastern Test Range. After the move to Wright-Patterson and later Edwards, the aircraft gathered telemetry for the US space programme, including the Space Shuttle, supported cruise missile and ballistic missile defence tests and verified international treaties. Two aircraft were lost. On 13 June 1971, EC-135N 61-0331 of the 4950th Test Wing disappeared between Pago Pago and Hickam AFB after monitoring the French nuclear test Encelade at Moruroa; it went down in the Pacific south of Hawaii near Palmyra Island, with 24 killed, 12 of them military and 12 civilian. On 6 May 1981, EC-135N 61-0328 on an ARIA training mission from Wright-Patterson crashed near Walkersville, Maryland, after the pitch trim ran to full nose-down and the aircraft exploded at about 1,500 ft; all 21 on board, 17 crew and four passengers, were killed. By the 1990s taskings dwindled as satellite technology took over and costs rose, and the aircraft were transferred to other programmes such as the E-8 J-STARS. One ARIA, 60-0374 "The Bird of Prey", an EC-135E built as a C-135A and converted to EC-135N, was flown to the National Museum of the United States Air Force on 3 November 2000 with its mission equipment intact.

Variants

• EC-135N: eight C-135s converted by McDonnell Douglas and Bendix with the droop-snoot radome; the original A/RIA.
• EC-135E: EC-135N re-engined at the 4950th Test Wing.
• EC-135B: C-135B fitted with the enlarged ARIA nose.
• C-18A: eight former American Airlines 707-323Cs bought as crew trainers and conversion airframes.
• EC-18B: four C-18As converted to ARIA, initially designated E-7.
• EC-18D: two C-18As converted as Cruise Missile Mission Control Aircraft.
• C-18B: one C-18A modified for MILSTAR support.