Changes Would Hide Key Information : Details of Stealth Bomber Likely Altered in Drawing

The artist’s drawing of the stealth bomber released by the Air Force this week may be as significant for what it does not show as it is for the technical information that it discloses about the revolutionary aircraft, aeronautical experts said Thursday.

Some aircraft engineers say the artist’s drawing deletes key elements and includes deceptions, such as an obviously oversized cockpit and an unlikely flatness to the upper wing surface, intended to keep secret vital information about the aircraft’s ability to escape detection by radar and to prevent Soviet authorities from estimating the size of the aircraft.

However, a former Northrop Corp. employee who has worked on the bomber said in an interview that the picture accurately represents the overall shape of the nuclear bomber and that it takes public knowledge of the aircraft well beyond the simple speculation of the544235891wing” without a fuselage.

The Air Force plans to buy 132 of the B-2 bombers, which are designed to escape detection by enemy radar largely through their unique shape and plastic materials that do not reflect radar waves.

The Air Force’s release of the drawing “displays confidence in Northrop,” said David J. Smith, an industry consultant. “There are those at high levels in the Pentagon,” he added, “who don’t have confidence in Northrop” owing to rumored technical difficulties.

The Pentagon has been under mounting pressure from Congress to provide more information about the bomber program, which apparently explains some of the motivation for releasing the drawing. The Air Force stated no official reason for the release. In addition, if the aircraft does make its first flight this fall, as announced by the Air Force,543781920outside Northrop’s Palmdale plant, where it is being assembled.

But it is doubtful that even when the aircraft is rolled out for the first flight, the Air Force will allow the general public to get close enough to it to discern the details of design and544039284Soviet radar from detecting the bomber.

“Many times when we put artist renderings together, we take a great deal of liberty in disguising things we feel are important technologically,” said one defense industry aircraft designer who, like others who spoke on the bomber, declined to be named. “And that’s what they have done here. What they are actually doing in some fine details are probably quite different than what it looks like in the picture.”

Details You Don’t See

Another aeronautical expert observed: “The real keys to success of the aircraft will be in the details that you don’t see in the artist’s conception.”

The artist’s drawing does not show any control surfaces, such as flaps and edges, that aircraft ordinarily need to steer and control pitch. Conventional control surfaces are attached to airplanes with hinges that leave gaps, which create large radar targets that are difficult to conceal.

The undisclosed system for controlling the stealth bomber’s unusual airframe, which does not have vertical or horizontal stabilizers, is one of the craft’s most important new areas of technology.

“With new control technology, there is no reason why you can’t make a barn door fly, but I wouldn’t bet my grandmother’s diamond ring on the accuracy of that picture,” one Los Angeles aircraft executive said.

Speculation on Steering

With no tail or rudder, experts say the aircraft would be steered by using differential thrust from the engines or by using flaps called ailerons or even “spoilerons,” a type of air brake.

“It may be something even more advanced, like blowing jets of air,” one expert said.

Engineers expressed surprise over the shape of the rear or “trailing” edge of the aircraft, which one engineer described as shaped like a crank. He surmised that the pointed extensions behind each wing were included to help control the aircraft’s pitch (up and down movement of the nose). Since the bomber’s airframe length is so small, compared to its wing span, pitch control is believed to be much more difficult than in a conventional aircraft.

The picture does reveal such things as its unique pointed nose, which would not be able to accommodate a conventional, dish-shaped radar antenna. Rather, the radar is thought to be embedded in the leading edge of the wing and to utilize new “phased array” technology, reportedly from Hughes Aircraft Radar Systems Group in El Segundo, according to industry experts interviewed Thursday.

Normally Radar Targets

Another revelation is that the jet engines have small air inlets just below the main engine inlets, which are presumed to be “boundary layer gutters.” Engine inlets are normally big radar targets because they contain sharp edges and allow radar waves to bounce off engine compressor blades.

To solve that problem, Northrop placed the engine inlets on top of the wing, concealing them from ground-based radar. But that creates another problem, because the air moving along the wing surface is highly turbulent and engines need air moving in an undisturbed flow. The “boundary layer gutters” bleed off the turbulent air and allow relatively undisturbed “high energy” air to enter the engines.

The drawing does not show how many engines the aircraft has, but one engineer at a competing firm remarked: “I would bet a nice cold beer that it has four engines.”

Aeronautical experts speculated that the biggest area of deception in the drawing may involve the cockpit area--in particular, the canopy--to make the job of estimating the airplane’s size more difficult.

Disguise Scale of Aircraft

“I would guess the dimensions of the canopy center post are very misleading to disguise the scale of the aircraft,” an executive at one aircraft firm said. “To me, that cockpit looks totally out of proportion to the rest of the airplane. There is no reason to have windows that big.”

Despite the lack of details, engineers reacted to release of the artist’s conception with excitement at having finally laid eyes on what has been one of the biggest secrets in the history of the industry.

“I like the configuration just because it is radical,” one aircraft designer said.

Prof. Richard Kaplan, aerospace engineer at USC, said: “It is very impressive. If I were asked to design an aircraft to do this mission, I would want to design it exactly the same way.”

But Kaplan, too, questioned the authenticity of some aspects of the drawing.

‘Don’t Do Tips That Way’

“I didn’t like the wing tips,” he said. “They are perpendicular to the wing chord (the wing width) and you don’t do tips that way. You would have winglets or edges that taper away from the airstream.”

A congressional source said the release of the picture is just the first in a series of disclosures about the program. “You are seeing the aircraft transition from the black world to the white,” he said.

The next disclosure is expected to concern how much the aircraft’s cost has grown. Congressional sources say the cost of the bomber program will be considerably more than the 1986 estimate of $36.6 billion (in 1981 dollars). Northrop has fallen an estimated one year behind schedule in the timing of its first flight.