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NASA News
National Aeronautics and
Space Administration
Dryden Flight Research Center
P.O. Box 273
Edwards, California 93523
Phone   (661) 276-3449
FAX (661) 276-3566 
                        __
July 10, 2003

Alan Brown
NASA Dryden Flight Research Center
(661) 276-2665
alan.brown{at}dfrc.nasa.gov

RELEASE 03-40

HELIOS INVESTIGATION TEAM WRAPS UP FIELD WORK, ANALYSIS BEGINS

The NASA Mishap Investigation Board (MIB) that is probing the
causes of the in-flight mishap that led to the loss of the Helios
Prototype solar-electric aircraft June 26 has completed the on-site 
portion of their task at the U.S. Navy's Pacific Missile Range 
Facility (PMRF) on the Hawaiian island of Kauai, and will now turn 
towards coming up with a probable cause of the accident.

    While the investigation is continuing, both NASA and Helios 
manufacturer and operator AeroVironment, Inc., are moving ahead with 
planning for follow-on activity to mature the solar and fuel cell 
propulsion systems technology developed for the Helios, while 
incorporating lessons learned from the mishap investigation in the 
planning effort.

    An interim status report released by the Mishap Investigation 
Board July 8 indicates the Helios Prototype appeared to have 
experienced undamped pitch oscillations that led to a partial breakup 
of the aircraft in mid-air while flying at about 3,000 feet altitude 
in restricted test range airspace over the Pacific Ocean about 10 
miles west of Kauai. The Helios Prototype had been aloft for about a 
half-hour on the second of two checkout flights leading to a planned 
long-endurance flight demonstration later this summer, using power 
from its solar arrays by day and from an experimental fuel cell 
system at night. The fuel cell system had not yet been turned on when 
the mishap occurred.  

    According to the interim status report, the board believes 
the undamped pitch oscillations may be related to the complex 
interactions between the aerodynamic, structural, stability and 
control and propulsion systems on a flexible aircraft. However, the 
board emphasized that this hypothesis is still preliminary, and much 
work needs to be done to discover the primary causes of the mishap.

    The five-member board led by Dr. Thomas E. Noll of NASA 
Langley Research Center completed their field work July 7. During 
their nine days at PMRF where the Helios Prototype was based during 
the summer flight deployment, the team collected all of the 
"perishable data," including witness interviews and statements, 
reviewed available program information, developed a fault-tree 
analysis, and developed several potential contributing causes to the 
mishap. The board's investigation is being aided by good telemetry 
data received during the flight, as well as video and still photos 
that recorded much of the incident from a chase helicopter. 

    Over the next few weeks, the team, assisted by several 
ex-officio members and support staff from NASA Dryden Flight Research 
Center and AeroVironment, Inc., will continue reviewing available 
data, initiate independent analyses and tests to further investigate 
certain technical areas, and will begin drafting parts of the mishap 
report.  The board will reconvene at AeroVironment's facility in Simi 
Valley, Calif., the first week in August to review the independent 
analysis and to further develop possible causes, recommendations and 
lessons learned.

    AeroVironment's Helios team has also begun a parallel 
investigation into the possible causes of the mishap and will be 
providing input to the MIB as it progresses through its independent 
effort. The MIB's final report is due by Sept. 30.

    About three-fourths of the Helios Prototoype wreckage has 
been recovered from the ocean, and will be shipped to California in 
the near future to aid in further investigation of the accident.
   
    "The Helios Prototype project has made great strides in 
advancing the technology of solar-powered aircraft, as evidenced by 
the record altitude flight in 2001," commented John Del Frate, Helios 
project manager at NASA Dryden. "The value of the program is not only 
in development of the aircraft platform, but in the related 
technologies, i.e., solar and fuel cell systems, for both airborne 
and terrestrial applications. We will use results of the accident 
investigation to improve the next generation of the Helios."

    Based on requirements of NASA, Defense Department, and 
commercial users of future extreme-duration aircaft, the effort will 
focus on investment in technology development and demonstration of 
extreme-duration UAV flight in the stratosphere, added Bob Curtin, 
vice president in charge of Aerovironment's UAV Design Development 
Center.

    "The plan will get a jump start from the fuel cell and 
electric propulsion technologies developed for Helios and its 
predecessors," said Curtin. "Although saddened by the loss of Helios, 
the AeroVironment team will respond to the loss as a challenge to 
learn from the incident and incorporate Helios technologies into a 
new and better extreme-endurance UAV."

- NASA

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