MOJAVE — Dangerous storms have forced the Voyager into so many evasive maneuvers that, for a time Wednesday, it was nip-and-tuck whether Dick Rutan and Jeana Yeager would have enough fuel left to complete their nonstop global journey, according to the designer of the experimental airplane.
But late in the day, after the latest calculations were taken, Voyager spokesman Larry Cansler said there was no longer much concern about fuel. The aircraft's front engine was stopped after running a day longer than planned to circumvent Indian Ocean storms.
"Voyager is running efficiently on one engine at 11,000 feet, and we expect fuel consumption to be much better on the second half of the flight," Cansler said.
Earlier, plane designer Burt Rutan, who is also the pilot's brother, said the Voyager has had to climb repeatedly above severe storms, forcing the plane to run on both engines up to 18 hours longer than had been expected and using up precious fuel.
Another crucial point was expected early today when the Voyager was to have passed the tip of India on its way to Africa, where it may have to climb as high as 14,000 feet to evade still more tropical storms--thus expending even more fuel.
Initially, the plan had called for the pilots to shut down the forward engine sometime during the second day of the 10-day flight, using only the more fuel-efficient rear engine. But, before the engine shutdown late Wednesday, Rutan has had to restart the forward engine three times to attain more favorable altitudes.
At one point, he had to do a 180-degree turn and retreat from a storm he had just entered so Voyager could climb above it, his brother said Wednesday. He said that was only one of many maneuvers forced on the crew by weather as the Voyager completed one-third of its journey.
Flight controllers have also had to deal with intermittent disruptions in communications with the Voyager, but those were regarded as more of a nuisance than a threat to the flight.
Late today, the Voyager is expected to pass a milestone when it completes 12,533 miles of its journey. At that point, Rutan and Yeager will have flown farther on a single load of fuel than anyone else has ever flown before. The current record was set in 1962 with an eight-engine Air Force B-52 that flew from Okinawa to Spain.
Despite the rough going, the Voyager on Wednesday was still pretty close to its scheduled Christmas Eve landing at Edwards Air Force Base near here--unless, as Burt Rutan suggested, "it has to land someplace like Barstow instead" if fuel runs out.
In order to successfully complete the round-the-world flight without stopping to refuel, the plane must land at the same place it took off.
Wednesday's earlier concern over fuel came as a surprise because Voyager officials only Tuesday had said the flight was slightly ahead of schedule and burning less fuel than had been expected because of favorable tail winds.
"We're not looking as rosy in performance as we were yesterday," Burt Rutan said Wednesday afternoon.
He said calculations based on the amount of fuel believed remaining aboard the Voyager indicated that there may not be enough to complete the trip. But he held out the possibility that the calculations may not be correct. And that proved true later in the day.
Hopes for Error in Math
The 17 fuel tanks aboard the Voyager do not have gauges, and fuel consumption is based partly on flight logs and anticipated consumption, Rutan explained.
The plane's designer blamed the increased fuel consumption on the tricky art of picking the best course in order to take advantage of tail winds generated by a storm without getting the spindly aircraft into danger.
The plane flies faster with both engines running, but the amount of fuel it burns is disproportionate to the gain in distance. The most economical way to operate the plane is with the rear engine alone, but that can be done only after enough fuel has been burned to lighten the plane's load. Wednesday, with only the rear engine operating, the Voyager's speed had dropped from an earlier high of 145 m.p.h. to about 95 m.p.h., but it was burning much less fuel.
It is the Voyager's vulnerability to turbulence that has forced the crew to fly above most storms. "Even light turbulence bounces it. It's like being in rough seas in a rowboat," Rutan said. "It's a scary environment for this frail aircraft."
Rutan noted that on an earlier test flight, Yeager "actually got bruised and cut" while riding on the narrow bunk in the Voyager's tiny cockpit.
Dr. George Jutila, the Voyager's flight surgeon, said Dick Rutan had started turning control of the aircraft over to Yeager more often, thus easing fears that he would become exhausted before the flight can be completed.
'Much Better Spirits'
"Dick has had six sound hours of sleep during the last 24 hours," Jutila said. "He is in much better spirits."
The Voyager's communications system, which was to have kept it in 24-hour contact with its home base, has been sporadic apparently because of problems with locking onto a communications satellite. The Voyager's antenna is several times smaller than the one normally used with the system, and aiming it has proved to be a challenge.