At 4:58 this morning, in the foggy solitude of San Pedro Bay, a two-way radio started squawking in the engine control room of this 64,000-ton cargo ship with an alarming message from the captain: "Ron, the engine is not responding."

That same instant, a piercing klaxon and a series of flashing lights alerted Chief Engineer Ron Gerde to the crisis at hand: The Singapore, hauling 1,109 massive steel containers stuffed with everything from tennis shoes made in Malaysia to stereo equipment from Taiwan, had hit a digital iceberg. A year 2000 computer glitch had crashed a critical electronic system that controls engine thrust, causing the vessel, whose bow-to-stern measurement exceeds the length of three football fields, to head uncontrollably toward the Port of Los Angeles.

This time, though, the computer failure was only a simulation. The Singapore's owner, APL Ltd., was staging this emergency at the behest of the U.S. Coast Guard. Today's drill, the first in a series of port inspections nationwide, illustrates a new focus in year 2000 mobilization.

Many businesses and government agencies are in the home stretch in repairing and testing their computer systems. They've done everything they can to become "Y2K-compliant." But suppose that's not enough? Facing the prospect of computer crashes despite all of their preparation, they are staging elaborate simulations to get ready for the worst.

This morning Gerde and his staff faced the daunting task of demonstrating that the Singapore, which has computer systems rivaling those of an airplane, could hastily operate the old-fashioned way. They would have to communicate with the captain, standing six decks above on the bridge, with a non-electric telephone. They would have to descend into the depths of the engine bay and use an antiquated crank to slow down the ship. They would have to rely on analog gauges and paper charts instead of the sophisticated computer images they use now.

With that challenge ahead, Gerde radioed up: "We're going to take control down here."

Like many large businesses, the Singapore already has tested its computer systems for Y2K problems. On Friday, for instance, while the vessel was leaving Seattle, its veteran captain, Jon Harrison, ordered that the master clock be rolled forward to 11:50 p.m. on Dec. 31. Ten minutes later, "nothing happened," he said.

Despite the positive test results, the Coast Guard wants to make sure ships are ready for any unforeseen problems that might arise on Jan. 1. "Rolling the clocks forward doesn't guarantee that a system will work just fine in the new year," said Coast Guard Rear Adm. George N. Naccara, who supervised today's drill. "You have got to be able to deal with the contingency that your computers won't work -- and you need to practice how you'll react to that."

Along those lines, the electric-power industry is planning to conduct a two-day drill in September, demonstrating how utilities would deploy extra staff, if needed, on New Year's Eve. The simulation also will test power companies' abilities to communicate with each other using backup radios should telephone service be interrupted.

Similarly, the Metropolitan Washington Council of Governments has scheduled a region-wide Y2K preparedness exercise on Sept. 1 that will involve the activation of emergency response teams in every local jurisdiction. COG plans to simulate several date-related computer failures, said Bruce Romer, Montgomery County's chief administrative officer. "This is not just about software and hardware," he said. "If Y2K results in an outage or a shortage, you need to be ready to deal with that from a non-computer perspective."

And today in Fairfax County, officials gathered around a table in the emergency management center to explain how their departments would respond in the event of a 33-inch snowfall on New Year's Eve combined with a power failure due to Y2K. [Story, Page B4.]

For some organizations, the contingency plans involve replacing instant electronic processing with tedious human labor. The Social Security Administration, for instance, will have employees on standby in its field offices over the New Year's holiday, ready to hand-write benefit checks to people who say they face a financial emergency. And large corporations are making plans to relocate critical operations in case of spot outages.

Government and industry officials acknowledge that their contingency efforts, which assume worst-case scenarios, could breed a fear of severe social and economic disruptions at the year's end. As a result, many organizations, particularly federal agencies, have been reluctant to disclose their plans publicly. "There is a public perception issue," said Stephen Frycki, the managing director of Y2K services at DMR Consulting Group Inc. in Edison, N.J. "But eventually people will realize that these efforts are intended to ensure that daily life can continue like normal even if something does happen."

The year 2000 problem stems from the fact that millions of electronic devices, from mainframe computers that process payroll checks to heart monitors in hospital intensive-care units, were programmed to recognize only the last two digits of a year and to assume that the first two would be 1 and 9. When Jan. 1, 2000, arrives, unprepared machines will understand the year "00" not as 2000 but 1900, potentially causing them to shut down or stop working properly.

But even some systems thought to have been fixed could encounter problems if some date-related functions were overlooked in the repair and testing efforts. And yet other machines could be crippled by external factors, such as a disruption in telephone service or glitch es with another system on the same data network.

Aboard the Singapore, Capt. Harrison feels confident that Y2K will create barely a ripple for him. Most of the ship's computers, though they rely on time-related data, do not have a running clock that tracks the year. And they all have been checked, with small green "Y2K" stickers placed on them to indicate compliance. Nevertheless, the Coast Guard and APL agreed that it would be prudent to emphasize "manual work-arounds" should they be needed.

So, in the early-morning darkness, three miles off the Los Angeles coast, the Singapore went through the motions this morning. The simulation was a failure of the "engine telegraph" system, a gearshift-like device in the bridge that lets the ship's officers control the speed.

Normally, a movement of the shifter automatically tells the 67,000-horsepower engine to provide more or less juice. This morning, though, with the vessel gliding along at five knots, the Coast Guard officers on board told Harrison to assume the system -- and another electronic backup -- had crashed. And, they said, he needed to quickly put the boat in reverse before it entered the busy Los Angeles harbor.

Though the drill began on the darkened bridge, which towers over the ship's payload of truck-size containers, the action quickly shifted to the below-decks engine control room, where Gerde and three deputies were getting ready to end a 42-day journey that included stops in Singapore, Malaysia, China and Taiwan.

After the first alarm sounded, Gerde reached for the vessel's most primitive backup means of communication -- a "sound-powered" phone. The device, which uses no electricity, is much like two tin cans with a string connecting them.

"They're going down there now," Gerde reported up to the bridge. At that moment, the ship's deputy engineer, Vic Raines, and an electrician flew down two sets of narrow metal stairs to the deafeningly loud engine bay. There they dashed toward the pie-size crank, which, after a switch was flipped and a safety pin was removed, would control the engine speed.

It was a moment in defiance of all the technological marvels on the 13-year-old ship. "We're bypassing all these computers," Gerde said gleefully, pointing to two large electronic monitors. Raines would be driving the behemoth the way turn-of-the-century engineers did their coal-fired merchant vessels.

The first priority was to turn the handle counterclockwise to slow the ship, something Raines did with ease. Then, an additional command rumbled over the sound-phone from the captain: "Slow astern" -- put it in reverse.

Fifteen seconds later, Gerde radioed up that the duo in the engine room had succeeded in reversing the propeller blades. With that, Harrison told the control room, "We're finished." Naccara and other Coast Guard officials quickly pronounced themselves satisfied with the crew's performance. "These guys did a first-rate job," Naccara said.

Come Dec. 31, Harrison figures he'll be somewhere out in the Pacific. As the New Year's celebrations begin, the skipper predicted, "the only thing we're going to have to worry about is blowing the whistle."

CAPTION: The Coast Guard's Terrence McGuigan, left, observes as the Singapore's chief engineer, Ron Gerde, instructs the crew during a year 2000 drill.

CAPTION: Tom Campbell, left, relays messages to deputy engineer Vic Raines, right, as they operate the ship without electronic instruments, under the watchful eye of Coast Guard Chief Warrant Officer Terrence McGuigan.