The Navy plans next week to send a research submarine to explore the wreckage of an airship that disappeared 56 years ago off the central California coast with four spy planes aboard.

The Navy is trying to find a way to salvage one of the four vintage Sparrowhawk biplanes that went down with the airship Macon on Feb. 12, 1935.Navy officials said recently that they hope to retrieve one of the planes this summer so that it can be placed in the Smithsonian Institution in Washington.

The Smithsonian has a Sparrowhawk on display, but it was assembled from replacement parts because all the original planes disappeared in crashes before World War II.

The Macon, one of two ill-fated dirigibles the Navy built to carry spy planes to distant parts of the globe, crashed in a storm during maneuvers.

The whereabouts of the wreckage remained a mystery until last June, when the Navy located the airship's frame and cargo of aircraft 1,500 feet beneath the Pacific Ocean and about two miles west of Point Sur.

Although the fabric skin of the lighter-than-air dirigible is gone, its girders seem intact and the frames of four Sparrowhawks appeared to be in their proper places in the Macon's belly, said Navy officials.

An unmanned sub operated by the Monterey Bay Aquarium Research Institute has explored the wreckage in detail.

Underwater photographs convinced Navy officials that it is possible to retrieve one of the planes, said James Jenkins, an engineer with the U.S. Naval Civil Engineering Laboratory.

"The odds are very good of getting all or most of one of them back, if the project is approached carefully," Jenkins said.

The Navy research submarine, named the Turtle and designed for a crew of three, will gather more information so that a salvage plan can be drafted. The Turtle is normally used to retrieve fallen satellites from the ocean.