Wednesday, May 1, 1996 | 11:59 a.m.
WASHINGTON -- It flew 135 times, all in daylight, over a three-year span in the 1980s, and yet no one apparently ever spotted it. "Tacit Blue" as the experimental plane was known, turned out to be one of the military's best-kept secrets.
More than 11 years after Tacit Blue made its last test flight, the Air Force declassified it Tuesday, complete with color photos and a videotape of the airplane that in a side view looks like an upside-down bathtub with wings.
The idea behind Tacit Blue -- to build a spy plane that could not be detected on radar -- died in 1985 after the Air Force spent $165 million to manufacture and test the first and only prototype. But the secrecy lived on while the "stealth" technologies were adapted for use on today's B-2 bomber.
The plane has been in storage since 1985. It is scheduled to go on permanent public display May 22 at a museum at Wright-Patterson Air Force Base, Ohio.
The Air Force had never before acknowledged the existence of the project, which was managed at a level of secrecy -- "special access required" -- that is higher than top secret.
The plane was built between 1978 and 1982 by Northrop Corp. at its Hawthorne, Calif., plant for $136 million, Lt. Gen. George Muellner told a Pentagon news conference. Testing the plane cost about $29 million more, he said.
"It has been a pretty well-kept secret," Muellner said.
Military officials did not say where Tacit Blue was based, but it is believed that most U.S. experimental aircraft are tested at Area 51, a secret air base about 80 miles north of Las Vegas.
The government refuses to acknowledge the existence of Area 51, also known as Groom Lake or Dreamland, even though the base has been photographed and is visible from surrounding areas. Government security forces do not allow the public near the base.
Aircraft enthusiasts have speculated for years about the existence of a super-secret spy plane some dubbed "Aurora," but that plane -- which U.S. officials deny existed -- was supposed to be supersonic. Tacit Blue was subsonic.
John Pike, an aviation specialist at the Federation of American Scientists, said none of the private groups that hunt for clues to secret military programs had ever spotted Tacit Blue or speculated on its existence. Pike said the full story of Tacit Blue and other secret aircraft is yet to be told.
"I would be surprised if there weren't several more" like this yet to be declassified, Pike said in an interview.
Shaped like no other known military aircraft, Tacit Blue is 55 feet long with a 48-foot wingspan. That makes it roughly the size of an Air Force fighter jet.
The intake for Tacit Blue's two turbofan engines is on top of the fuselage. The vertical stabilizers on the rear of the plane form a "V." The plane's underside appears to form an unbroken flat surface from front to rear.
Two aspects of Tacit Blue's innovative radar-evading characteristics were adapted for use on the B-2 bomber, Air Force officials said. One is the combination of curved and linear surfaces; the other is the special composite materials used on the surfaces to absorb signals from radars trying to track it.
Muellner said the project was canceled in 1985 when the Air Force decided it made more sense to build what is now the Joint-Stars ground surveillance plane.
Joint Stars, which uses a modified Boeing 707 air frame, does not have radar-evading capability but carries a bigger radar than Tacit Blue could. The bigger radar enables Joint Stars to provide wide ground coverage while staying out of range of hostile air defenses by flying farther from the battle front.
Joint Stars planes were flown in the 1991 Persian Gulf War and in the current NATO-led peace mission in Bosnia, although it technically is still in the test and evaluation phase. It is scheduled to be officially operational in 1997.
Muellner said the Tacit Blue plane was flown only by five pilots. They operated it from several different locations, but he would not say where. There were 135 flights totaling 250 hours between Feb. 5, 1982, and Feb. 14, 1985, he said. All were in daylight.
Even though the plane stopped flying more than 11 years ago, the Air Force kept it secret because some of its unique stealth technologies were adapted for the B-2 bomber and a once-classified Air Force strategic missile. After the first B-2 entered the fleet in 1993 and the missile program was canceled in 1994, Tacit Blue no longer needed to remain secret, Muellner said.
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