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E-8C JSTARS
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The USA’s E-8 JSTARS is a Boeing 707-300 derivative that provides a picture of the ground situation analogous to the E-3 AWACS’ picture of the air situation. JSTARS aircraft use their radars to determine the direction, speed and patterns of military activity of ground vehicles, helicopters, and even groups of people. They then send this information via secure data links with air force command posts, army mobile ground stations and centers of military analysis around the world. These surveillance and communications relay capabilities are somewhat unique, and have proven extremely useful in a series of conflicts from Desert Storm in 1991 to the present day. Europe originally intended to field a similar, smaller AGS aircraft based on the Airbus A321, but that project has now been cut to a small fleet of RQ-4 Global Hawk UAVs. With the Global Hawk limited by its payload capacity, and the USA’s E-10A program canceled, the USA’s 17 aircraft JSTARS fleet is likely to remain very popular for some time to come.

The question is how to keep that fleet relevant, flying, and allocated among all of the units clamoring for their attention. A range of upgrades were ordered in 2005, and a recent study claims that the structural improvements and other modifications could allow the aircraft to fly safely for another 50 years. The E-10’s demise may yet see the work on that plane’s full size MP-RTIP radar transferred to the E-8 fleet, a move that would improve the JSTARS’ ability to find ground targets by a factor of 5-10. The number one issue with the JSTARs fleet, however, remains its old JT3D-3B engines, whose core design was first introduced in the 1950s. An upgrade program is underway to address that…

The Engines

CFM56-7B engine
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The choice facing the US Air Force involved 2 candidates:

One was GE’s very popular CFM56 high bypass tubofan, which flies on a wide variety of commercial jets including the entire Airbus 320 family, the A340, and Boeing’s 737-300+) and has been used to re-engine the USA’s 707-derived KC-135 Stratotanker fleet. The new KC-135Rs have demonstrated about a 27% fuel savings since the switch, in addition to lower maintenance costs, compatibility with the KC-135 fleet, and the ability to leverage a wider commercial skills base.

The other option would be Pratt & Whitney’s JT8D-219, based on an engine design that was introduced in the mid-1960s and powers DC-9, MD-80, Boeing 727, and early-model 737 aircraft. While the fuel savings would be slightly smaller, the JT8 has an advantage of its own: no significant aircraft modifications are required, because the engine has the same weight and center of gravity as the older JT3D engines in current use. This seemingly minor feature offers significant capital and time savings for the re-engining program.

In an environment characterized by high availability needs and a cash crunch for investment, the Pratt & Whitney offering won.

Contracts & Events

JT-8 cutaway
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May 13/08: Northrop Grumman announces 2 unfinalized USAF contracts worth $300 million. Their team will complete non-recurring engineering, flight test, and certification of new PW JT8D-219 engines for the service’s E-8C JSTARS fleet, and begin engine production. Work will begin immediately, with the test bed aircraft in Melbourne, FL being the first E-8 to convert to the Pratt and Whitney JT8D engine and begin military flight certification later this year. Concurrently, production startup activity begins with Northrop Grumman’s principal subcontractors to produce the propulsion pod system.

The first retrofit to the Joint STARS fleet is set for late 2010. All refits will take place during routine periodic depot maintenance schedules, in order to ensure the least amount of down time for the in-demand JSTARS fleet. NGC release.

Jan 18/07: Northrop Grumman selects Pratt & Whitney’s JT8D-219 engine to power the E-8 JSTARS conversion project. The effort will be a joint venture involving United Technologies’ subsidiary Pratt & Whitney and Seven Q Seven (SQS), will produce and deliver the complete JT8D-219 propulsion system. Pratt & Whitney will be responsible for delivering the engines, and SQS will work with its key suppliers Goodrich Corporation and The Nordam Group to supply the propulsion pods the engines rest in, including the struts, cowl doors, inlets, reversers and systems. Pratt & Whitney release.