The Smithsonian's National Air and Space Museum has scrapped plans to have a radio-controlled replica of a pterodactyl circle the Mall, and instead will introduce its flying dinosaur to Washingtonians on May 17 in the skies above Andrews Air Force Base.

A 44-pound, battery-powered scale model of the pterodactyl (the "p" is silent) was built in California at a cost of $500,000 by a team of paleontologists, aeronautical engineers and robotics experts. The idea was to simulate the flight of the prehistoric giant reptile, the largest flying creature known to man.

But the Mall, once deemed an appropriate staging area for the flight, has been vetoed because of some obvious down-to-earth problems.

"We decided there wasn't enough space," museum spokeswoman Joyce Dall'Acqua said yesterday. "It needs to be towed 1,000 feet just to get it in the air."

The museum also was concerned that trees on the Mall would block the view of the flight and that other radios might interfere with its operations.

"If the signal was scrambled, it could be devastating," Dall'Acqua said.

The man-made pterodactyl was modeled after the Quetzalcoatlus northropi, a gawky-looking creature that soared during the so-called Age of Dinosaurs and disappeared about 65 million years ago. Fossil remains indicate it had a long neck, a large head and a wingspan of 25 to 40 feet. The largest ones weighed about 150 pounds.

Although initial plans called for constructing a nearly life-sized model with a wingspan of 36 feet, scientists subsequently chose to build a smaller version with an 18-foot wingspan. Once the model is in the air, a computer monitors and makes adjustments based on changing wind currents, but the contraption's propulsion comes from the actual flapping of its wings.

The pterodactyl is scheduled to take to the air at Andrews at 9 a.m. on May 17, and there is a good possibility that a second flight will be made later that day. It will be the first activity of the annual Joint Services Day, an event that normally showcases the Blue Angels and other aerial demonstrations.

The model, along with videotapes of its construction and test flights, will be displayed on the Mall on May 16, and the pterodactyl will go on permanent display at the Air and Space Museum on May 19.

The recreation of the flight of the pterodactyl will be the centerpiece of "On the Wing," a film about the evolution of and relationship between natural and mechanical flight. The film's premiere at the museum theater is set for June 20.