Trekkers should be proud

Piadinhas a parte, o nome de batismo da aeronave tem tudo a ver...

Now you see it, now you won't: Boeing lifts the veil on stealthy Bird of Prey


Boeing's Bird of Prey technology demonstrator, unveiled in St Louis on 18 October after spending a decade in the world of 'black' or classified programs, is a very important step in stealth technology, combining a very low radar cross-section (RCS) with a renewed focus on visual and even acoustic signatures. The overall goal, confirmed by officials at the event, is to achieve daylight stealth.

The importance of the event was underlined both by the presence of the two top US Air Force (USAF) leaders - Air Force secretary James Roche and chief of staff General John Jumper - and by the scanty information made available. On the record, officials said only that the program's purpose was to test 'specific' and 'breakthrough' stealth technologies, along with the rapid-prototyping techniques developed by the Phantom Works. The pilots who carried out the unusually slow-paced flight test program - 38 missions between late 1996 and 1999, barely more than a sortie per month - were identified, but the engineers who ran the program were not.

Boeing pilot Joe Felock made it clear that the Bird of Prey - named after a Klingon spacecraft from Star Trek - was a low-performance demonstrator, designed to put a representative shape into the air with minimum time and expense. Maximum speed was 260kt and the highest altitude achieved was 20,000ft. The 14.2kN Pratt & Whitney Canada JT15D-5 engine would have been working hard to propel a small-winged 3,360kg aircraft even if it were not breathing through a tortuous inlet; Northrop Grumman, using the same engine on its X-47A Pegasus unmanned combat air vehicle (UCAV) demonstrator, has reported problems in reducing duct losses.

An unusual feature of the Bird of Prey was that it was designed with an all-manual control system, with pushrods and a mechanical mixer box linking the stick and rudder pedals to four control surfaces - elevons on the inner wings and 'rudderons' on the outer wing panels. The landing gear used modified components from Beech King Air and Queen Air aircraft.

The project formally started in 1992. The US$67 million development cost was provided by McDonnell Douglas (acquired by Boeing in 1998), but the USAF agreed to provide flight-test facilities and security, including chase aircraft and access to the secure flight-test center at Area 51 in Nevada.

The Bird of Prey would have been one of the first major Phantom Works projects. It was parallel and complementary to the X-36 unmanned tailless demonstrator. While the latter was aimed at validating technologies that McDonnell Douglas was offering for the supersonic, agile Joint Strike Fighter, the Bird of Prey clearly represents an all-out stealth approach in a vehicle with lower flight performance.

Many features of the Bird of Prey support the hypothesis that it was designed for unprecedented RCS levels: possibly an RCS of -70dBsm, or rather smaller than a mosquito.

The shape of the aircraft, too, is - accidentally or intentionally - laid out to avoid shadows. This suggests strongly that the Bird of Prey is a demonstrator for visual stealth technology.