Tests Show Fewer Air Pockets
ASA is conducting
early tests of a new sensor that could make air travel safer. The sensor
detects previously undetectable clear air turbulence, often referred to
as "rough air" or "air pockets" that can be felt,
but not seen.
Although seldom damaging to modern aircraft designed to withstand its stresses, clear air turbulence is an invisible public air safety hazard and is the leading cause of in-flight injuries among the flying public. Currently, there are no effective warning systems to give pilots time to take passenger safety precautions for clear air turbulence, which occurs at high altitudes near jet streams, in the vicinity of mountain ranges and as far as 50 miles or more from developing storm systems.
The sensor device, called Airborne Coherent LiDAR (Light Detection and Ranging) for Advanced In-flight Measurement, uses a laser beam, which can be envisioned as a type of infrared radar, that relies on infrared light waves. A light pulse is transmitted from a laser. Some of the light is reflected off the particles back to a sensor at the source. It analyzes a Doppler shift in frequency, which changes the wind velocity, to determine the laser beam's path.
As long as the wind velocity remains uniform, no turbulence exists. If, however, the laser beam detects changes in the velocity in regions of air ahead of the aircraft as it moves forward, an alarm is sounded as a clear indication that air turbulence is ahead.
Experiments were flown on three separate flights for a total of more than seven hours at altitudes as high as 25,000 feet. Additional flights are slated to add to the turbulence data base and to fine-tune the sensor for better measurements.
Before flying through disturbed air, the test flight crew located turbulent conditions and used the infrared laser radar to measure the changes in wind speed—a measure of turbulence. Then, the crew compared the pre-encounter measurements with the effects of the turbulence they experienced. In this way, the team is exploring the relationship between the laser radar-measured turbulence characteristics and the actual turbulence experienced by the aircraft. These tests are designed to provide an efficient checkout of the flight hardware and to help characterize turbulence measurements.
Langley Research Center in Hampton, Virginia, is NASA's lead center for the Aviation Safety Program. Other participating NASA centers include Dryden Flight Research Center in Edwards, California, Ames Research Center at Moffett Field, California, and Lewis Research Center in Cleveland, Ohio.
For more information, contact Rod Bogue at Dryden Flight Research Center.
Call (805) 258-3193, E-mail: Rod.Bogue@mail.dfrc.nasa.gov
Please mention you read about it in Innovation.
A new sensor could detect invisible clear air turbulence, reducing in-flight injuries.
