Drucella Andersen
Headquarters, Washington, D.C.                                           
September 17, 1993
(Phone:  202/358-4727)

Don Haley
Ames-Dryden Flight Research Facility, Edwards, Calif.
(Phone:  805/258-3456)


RELEASE: 93-163

NASA TESTS NEW LASER AIR DATA SYSTEM ON SR-71 BLACKBIRD

     A NASA SR-71 "Blackbird" research aircraft today made the 
first triple-sonic flight test of a laser measurement system that 
could give pilots more accurate data on their air speed and 
aircraft attitude.

    The Optical Air Data System focused laser light beams several 
feet away from the side of the SR-71 as it flew at more than three 
times the speed of sound.  As microscopic particles passed between 
the beams in undisturbed air, the system measured their direction 
and speed and turned that information into standard air speed and 
attitude data. 

     "Because the system doesn't use tubes or openings that can 
disturb the airflow, we expect it to be more accurate than current 
systems," said Dave Lux, SR-71 Project Manager at NASA's 
Ames-Dryden Flight Research Facility, Edwards, Calif., where the 
flight took place.  "It could apply to both civilian and military 
aircraft flying at high speeds."
 
      Air data systems give pilots speed information and attitude 
references such as angle of attack (up and down) and sideslip 
(side to side).  Current systems use small tubes and vanes that 
extend into the air stream or tubes that have openings flush with 
the aircraft's outer skin.  

     But external tubing disturbs air flow over the aircraft, 
compromising the data.  Both external and flush openings must be 
cleaned frequently of insects and debris or they cannot collect 
accurate data.

     In contrast, the NASA SR-71 laser system is installed 
internally, so it does not affect the airstream.  The system 
projects laser beams through a small side window in the forward 
part of the aircraft and does not require any external 
maintenance.
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     Up to six flights are planned in the current test schedule.  
The SR-71 will evaluate the Optical Air Data System at a maximum 
speed of 2200 mph (3540 kilometers per hour) at altitudes of about 
85,000 feet (25,908 meters.). 

     NASA successfully tested the laser system at Dryden 2 years 
ago at speeds up to 1300 mph (2092 kilometers per hour) and at 
altitudes up to 65,000 feet (19,812 meters) on a NASA F-104 
research aircraft. 

      NASA is doing the laser air speed system study for the 
Defense Department's Advanced Research Projects Agency.
                             - end -

NOTE TO EDITORS:  Photos are available to media representatives to 
illustrate this release by calling the Ames-Dryden Public Affairs 
Office, 805/258-3456.