By Marina Malenic

ST. LOUISBoeing [BA] yesterday unveiled a prototype for a new configuration of its F-15 fighter jet, billed as the Silent Eagle, incorporating some stealth improvements into the nearly 40-year-old platform.

“We have looked at the future and listened to our international customers’ needs,” Mark Bass, Boeing’s vice president for F-15 programs, told reporters.

The improvements in the Silent Eagle include low-observable coatings and treatments on various parts of the aircraft; conformal fuel tanks (CFT) redesigned as weapon bays; vertical tails that produce lift on the back of the aircraft, thereby extending its range; and a digital electronic warfare system produced by BAE SYSTEMS.

“Our customers are interested in stealth,” Bass said, “but there is a tradeoff associated with stealth–both procurement cost and life cycle cost, maintenance and in terms of the weapons you can carry.”

The company began prototyping the new design in September, said Dan Korte, Boeing vice president for global strike systems. The company has invested “several million dollars” in the effort to date, according to Korte, and expects to spend some $75 million on the development effort to include flight testing.

“I’d say we’re a half or a third again cheaper than” fifth generation stealth aircraft such as the F-22 or F-35, Korte told Defense Daily. “Because this aircraft has all of its development costs behind it, it is considerably cheaper.”

Korte said the current per-unit cost of current F-15 variants is “under $100 million” and expects the new configuration will be priced at “not much more than that.”

Depending on the specific mission, the customer can use the modified CFTs to carry two 1,000-pound bombs, four 500-pound bombs or eight smaller bombs; or change back to traditional CFTs for optimum fuel capacity and external weapons carriage. Some 1,500 gallons of fuel can be carried externally, according to Boeing, while the internal tank will contain about 550 gallons.

The “modular” design allows the customer to convert a Silent Eagle into either configuration within about two hours.

Boeing plans to flight-test a prototype by the first quarter of next year and will also demonstrate a live missile launch at that time.

Company executives said stealth coatings could yield to as much front-aspect stealth as that achieved by the F-35 Lightening II Joint Strike Fighter, though Washington will make final decisions on what level of stealth is exportable to particular markets.

However, “we are not pursuing the F-22 market or the F-35 market” with the Silent Eagle, said Korte. “This is really geared toward our international customer, though we have informed the [U.S.] Air Force of what we’re doing so that there won’t be any surprises.”

Different F-15 configurations are currently flown by the air forces of Israel, Japan, Saudi Arabia, Singapore and South Korea, in addition to the U.S. mixed fleet of some 650 aircraft.