Boeing Studies Stealth Eagle Options
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By Graham Warwick
Boeing is studying the levels of radar cross-section (RCS) reduction possible with its F-15SE Silent Eagle in advance of licensing discussions with the U.S. government on possibly exporting the stealthy fighter.
“It’s not how low can you go, it’s how low are you allowed to go, and the U.S. government controls that,” says Brad Jones, Boeing program manager for F-15 future fighters. “We can get to different levels depending on the country.”
Trade studies under way, including RCS chamber tests, will provide data for discussions with the government on what level of frontal-aspect stealth is releasable to each country interested in the F-15SE.
The studies cover both new-build Silent Eagles and retrofit of existing F-15s with stealth features, which poses additional challenges, Jones says.
A major contributor to reducing RCS is the conformal weapons bays that replace the conformal fuel tanks now carried by F-15s. These allow a mix of air-to-air and air-to-ground weapons to be carried internally.
“We need to decide what to do in various areas across the aircraft to get to a specific level” of RCS, according to Jones. “There are many different techniques involved pending on the level of what we do and where we do it.”
Boeing is working to complete the RCS studies as soon as possible so it can start the licensing process, he says, adding that the first request for proposals from a potential customer is expected between mid-2010 and 2011 from South Korea.
The company is hoping the U.S. government will agree to release a frontal RCS level equivalent to that offered by the F-35 Joint Strike Fighter. “Internationally we are looking for a level playing field,” Jones says.
Meanwhile, trade studies are also under way for design of the F-15SE weapons bays, including whether electric, hydraulic or pneumatic power, or some combination, should be used to actuate the doors and deploy the weapons quickly.
These studies could involve potential international partners, and may take longer, Jones says. Some potential customers are interested in using the internal bays to house other payloads, including side-looking radar and broadband electronic-warfare jammers.
Since unveiling the F-15SE in March (Aerospace DAILY, March 18), based on customer interest, Boeing has done more work on a possible retrofit option, and the effect on the range of replacing the conformal fuel tanks.
A retrofitted F-15E, with the original straight tails, would lose 220-240 nautical-miles-radius of action depending on its mission. A new-build F-15SE would lose 180-200 miles because of the new canted tails and digital fly-by-wire and electronic warfare (EW) systems.
“We take 1,500 [U.S.] gallons off the aircraft [by removing the conformal tanks], but the digital EW shrinks three systems into one so we can put fuel back in,” Jones says. “In the end we take 950 gallons off the aircraft.”
Digital fly-by-wire allows removal of the mechanical flight controls and saves weight and volume, while the canted tails generate lift at the back of the aircraft and allow 400-500 pounds of ballast to be removed from the nose.
Jones says Boeing still plans to fly a Silent Eagle demonstrator in early to mid-2010 to show capability ahead of any international customer issuing a request for proposals. “International customers want low risk, and to see us test this before an RFP,” he says.
Photo: Boeing
