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A Defense Technology Blog
Silent Eagle Sneaks into the Market

Boeing unveiled a stealthy version of the F-15, dubbed the "Silent Eagle" today at its St Louis plant. (Update: Full story here.) The aircraft has two conformal fuel tanks reconfigured to carry up to two air-to-air or air-to-ground weapons, and tail fins canted outwards 15 deg. to reduce radar cross-section.

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Photo: Boeing

Added to these is a new digital electronic warfare designed to work with the F-15's active electronically scanned radar. Radar absorbing coatings and inlet radar blockers could be added to make the fighter more stealthy, says Boeing.

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Photo: Boeing

Brad Jones, F-15 future programs manager here in St Louis, hopes to sell as many a 190 of the new F-15s to South Korea, Singapore, Japan, Saudi Arabia and Israel. 

Not on the list is the U.S. Air Force, which has been solidly focused on buying only fifth-generation fighters for its future fleet. Boeing officials, not wanting to raise the ire of the service, say they are targeting only international customers.

Cost of the Silent Eagle is expected to be around $100 million for a new-build aircraft. You think the Air Force will bite, or hope this one doesn't muddle the F-22/F-35 plan?

blog post photoPhoto: Boeing

Graham Warwick writes:

Silent Eagle would seem to prove wrong the adage that stealth can't be retrofitted. It has been before, witness the coated canopies and RAM-lined inlets on F-16s, only not on this scale (at least not publicly). And it appears to be limited to front-aspect stealth.

The modification seems designed to compound the range advantage provided by the newest F-15E's powerful active electronically scanned array radar and sensitive digital electronic warfare system by making it harder for enemy aircraft and air defenses to detect and track the big fighter.

There have to be penalities. Concealing weapons inside the conformal fuel tanks must reduce their capacity, and to preserve stealth external tanks and weapons cannot be carried under the wing. But reinstalling the original conformal tanks would restore the F-15E to its old long-range, heavy-payload self.

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AMRAAM deployment from the internal bays. Artwork: Boeing

My question has to be, can anyone follow suit and retrofit stealth to their fighter? Boeing's own F/A-18E/F already has some stealth features, including inlet blockers and edge treatments, but it does not have those convenient conformal tanks in which to hide weapons - or any obvious place to put an internal weapons bay.

It is similar for F-16, which is also unlikely to get a stealth makeover as it would compete with Lockheed Martin's F-35. Gripen, Eurofighter and Rafale do not have any obvious places to hide weapons, although there is work afoot on stealthy pylons to reduce the radar cross-section penalties of carrying external weapons.

So is this the start of a trend, or is there more - or less - to Boeing's bolt-on stealth than meets the eye?

blog post photo
Photo: Boeing

Tags: ar99BoeingF-15Estealth
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Marcase wrote:
"...My question has to be, can anyone follow suit and retrofit stealth to their fighter?..."

The easy way to stealth up a combat aircraft is to *stealth* its outboard combat load. Putting ordnance inside large RAM coated 610-US gal fuel tanks (such as the NCADE missile) is an idea. Two or more SDBs might even fit as well.

Spraying it all with "off-the-shelf, exportable RAM" could work, if it just wouldn't be so maintenance intensive.

I think the F-15 is unique because of its boxy design. The curved lines of for example the F-16 won't allow any underwing modding (although it can carry CFTs on top; sidewinders Jaguar style...?).

Neat trick though, strike aircraft by day, stealth aircraft by night. AESA, good range and payload, 1:1 thrust ratio - what more would you want?

Now if it just didn't break-up in flight...;)
3/17/2009 3:23 PM CDT
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Corvan wrote:
Ooooh! Nice sting in the tail Marcase!

It would be great to see a "hard core" stealth version of this, even if it's just a few well thought out images.

It's silly to say stealth cannot be retrofit unless that statement also defines closely what is meant by "stealth" & "retrofit". If you just want better X band front axis cover and you're willing to replace some flight structures, redesign others, stealth sure can be retrofit. If you want good wide-band all aspect stealth or don't want to have to buy any new parts, stealth sure can't be retrofit.

At any rate, this is a good move by Boeing so I hope it pays dividends.
3/18/2009 4:02 AM CDT
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ghemago wrote:
Let's not forget that most tracking radars work in X and Ku bands and usually you aim toward them. In addition even if they can detect you, a lower RCS means less range and possibly random unlocks of the tracking radar.
All inclusive, it lowers kill probability.
3/18/2009 6:49 AM CDT
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Bill Sweetman wrote:
Also, remember that detection range declines with the fourth root of RCS, while burn-through range against jamming declines with the square root. So if you combine this treatment with the new digital EW system (or with the Elisra kit on the Singapore and Israeli aircraft) the hostile radar's going to have a much more difficult time.
3/18/2009 8:12 AM CDT
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Talyn wrote:
There's still alot of potential in this platform so I'm glad Boeing is making an effort. However, I wish they would have considered the old "big-wing" proposal from a few years back. As with the "new" tail fins they could have mocked up a set and bolted them on since that's relatively easy on the F-15.
3/18/2009 1:37 PM CDT
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Talyn wrote:
BTW - the "big-wing" could have gained back the lost fuel capacity in puting the internal bays in the conformal tanks.
3/18/2009 1:38 PM CDT
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