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World News & Analysis

Fosset Pilots GlobalFlyer Around the World
Aviation Week & Space Technology
03/07/2005, page 26

Michael A. Dornheim
Los Angeles

Even with 15% of fuel vanishing, GlobalFlyer circles the world

Range Factor

Steve Fossett's solo flight around the world springs from a remarkable achievement in aircraft design that far exceeds the range performance of any other jet aircraft.

Scaled Composites built the Virgin Atlantic GlobalFlyer, and the team led by chief engineer Jon Karkow was able to achieve two contradictory things at once--a sailplane-like lift-to-drag ratio (L/D) of about 37, and a zero fuel weight only 18% of the takeoff weight. Compared to a modern jet transport, the L/D is roughly 50% better and the empty weight is less than half (AW&ST Jan. 3, p. 46). Karkow estimates the still-air range is 19,000 naut. mi., compared to the 19,864-naut.-mi. ground distance of a tropic line that is the Federation Aeronautique Internationale's (FAI's) definition of "around the world." Tailwinds averaging above 12 kt. are required.

LOW DRAG AND THE ABILITY TO STUFF GlobalFlyer with fuel gave it so much range that Fossett was able to complete his circumnavigation even though 15% of the fuel mysteriously leaked out shortly after takeoff.

Fossett took off from the Salina, Kan., municipal airport at 6:47 p.m. CST on Feb. 28, flew around the world eastbound, and landed there at 1:48 p.m. on Mar. 3 for a 67-hr. 1-min. flight. The actual ground distance had not been filed as of late last week, but the route plan was about 22,915 stat. mi. (19,913 naut. mi.), says Arthur W. Greenfield, director of contests and records at the National Aeronautic Assn., which represents the FAI in the U.S. That would keep the absolute distance record with Dick Rutan and Jeana Yeager, who in 1986 flew the piston-powered Voyager for 24,987 stat. mi. unrefueled.

Instead, what Fossett will likely get from the FAI is the absolute speed record around the world, unrefueled and nonstop, which works out to 341.9 mph. using the route plan distance. Within the jet category, he will likely also receive the distance-without-landing and closed-circuit record. "The milestone--what people remember--is that he did it solo," Greenfield says. The FAI does not base categories on the number of crewmembers.

FOSSETT HAS SET FASTER RECORDS around the world stopping and refueling in his Citation 10 business jet, which was used as a chase on this flight.

The takeoff weight was about 22,100 lb., comprising 18,100 lb. of JP-4 low-freezing-point fuel and a 4,000-lb. zero fuel weight. This was confirmed with a scale. The Williams FJ44-3 ATW turbofan engine produces 2,300 lbf. sea-level takeoff thrust, for a meager thrust-to-weight ratio of 0.1. The highest prior takeoff weight was 19,000 lb. at the giant Edwards AFB, Calif., runway with Karkow at the controls, and project members considered the record flight takeoff to be perhaps the most dangerous aspect of the trip. But it appeared to be relatively uneventful.

However, shortly after takeoff 2,600 lb. of fuel leaked from GlobalFlyer in about a 1.3-hr. period. As of late last week it was still a mystery how this happened--post-takeoff chase aircraft saw nothing, but takeoff was 25 min. past sunset. Engineers at mission control in Salina noticed the discrepancy between the tank gauges and fuel used by the engine, and for a while thought they had made a computational error. But later observations by Fossett of the pitch attitude and elevator position at a given airspeed confirmed the loss.

Also, there were early problems with GPS navigation receivers. They were necessary to continue the mission. Fortunately the team identified an interference issue that could be largely eliminated.

The fuel loss particularly hit home as the aircraft left Asia to cross the western Pacific Ocean. Fossett was depressed, but pushed on to Hawaii where a decision would be made whether to continue another 2,500 mi. over ocean to the U.S., or land on the island.


Steve Fossett took GlobalFlyer over the Atlas Mountains of northwest Africa less than a day after takeoff from Salina. More than 75% of the fuel is carried in the twin boom tanks.
Credit: VIRGIN ATLANTIC AIRWAYS

Luck arrived in the form of stronger-than-expected tailwinds of 100-130 kt. underway to Hawaii, providing enough range to make the west coast of the U.S. with confidence, and a so-so chance of reaching Salina. The GlobalFlyer has a gliding range of more than 200 mi. from its 45,000-50,000-ft. cruise altitude, which will reach an airport almost everywhere in the U.S., but a larger concern was the rapid loss of cabin altitude that would go with an engine failure. Oxygen was available in the cockpit, but the low descent rate would have lingered Fossett at altitudes at which even 100% oxygen may be inadequate.

The route took a big dip to the south between Hawaii and the mainland, intended to add enough ground distance to ensure the FAI minimum was met. But this took the aircraft away from good winds and added to the anxiety.

Fossett crossed the California coastline on Thursday morning and had enough fuel to make his way to the early afternoon landing at Salina. As of late last week, officials had not announced the amount of fuel remaining, but it is clear that had the 15% of fuel not leaked out, GlobalFlyer could have flown past Salina by thousands of miles.

 
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