SEATTLE -- Boeing Co. experts Friday searched a farm southwest of Seattle for more pieces of a prototype Navy Boeing 707 communications jet that lost large chunks of its tail fin and horizontal stabilizer during a flight test to push the plane beyond its design limits.
Sherry Nebel, a spokeswoman for the Boeing Aerospace division, said more pieces were found early Friday on a farm near Centralia, about 80 miles southwest of Seattle.
The plane, which landed safely at Boeing Field in Seattle at 3:40 p.m. Thursday, was a prototype of the E-6A, a modified 707 crammed with military communications equipment designed to link submarines and national command headquarters.
The Navy is spending $1.5 billion for 16 of the aircraft, with the first to be delivered by the end of April, Nebel said. The first of the jets, built by Boeing's Commercial Airplanes division, rolled off the assembly line in December 1986.
The three-man Boeing test crew, which took off from Boeing Field at noon, was flying at 15,000 feet when it performed a 'flutter' test, in which the craft goes into a rapid descent at 530 mph to put maximum pressure on the surfaces of the plane.
During the test -- identical to two others performed earlier -- the crew heard a series of noises. Officials monitoring the flight at Boeing Field also knew there was a mishap when the stream of information they were receiving from the plane suddenly stopped, Nebel said.
'When it happened, (the crew) heard a 'thump, thump, thump' and figured something had happened. At that precise moment, the Boeing people (on the ground) stopped receiving the test information,' Nebel said.
'They got orders to come home. It wasn't until the crew was on their (landing) approach that the tower people saw a piece of the tail missing and informed the crew of the situation,' she said. 'They didn't even know it happened. It's that stable of an aircraft. That says a lot about the 707.'
A farmer about 10 miles north of Centralia reported hearing a boom. Looking up, he saw what apparently were pieces of the plane's tail falling to the ground.
Nebel said the plane had lost 8 to 10 feet -- about 30 percent -- of its vertical tail fin, and 3 to 4 feet of the right horizontal stabilizer.
Nebel said it will take some time before engineers can determine exactly how much of the plane fell off, and even longer before all the pieces and data can be analyzed to determine why the incident happened.
While it is the same model, the E-6A was not the same plane that lost a mile-long antenna and a 47-pound drogue, or drag device, while on a test flight Feb. 10 over eastern Washington, Nebel said. The antenna and drogue have not been found.
Boeing has delivered almost 1,000 707s, the majority for commercial use. One of those planes crashed Feb. 8 in the Azore Islands, killing 144 people. Investigators still are trying to determine the cause of that crash.
Boeing spokesman Craig Martin said the 707 is favored by the military because it is large without taking on the jumbo proportions of the 747, and is powered by four engines, as opposed to two on some other models.