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DEmonstration of LIdar-based Clear Air Turbulence detection

Tags: Air

State of the Art - Background

Atmospheric turbulence encounters are the leading cause of injuries to passengers and flight crews in non-fatal airline accidents. A whole class of turbulence, representing 40% of turbulence accidents, and designated as Clear Air Turbulence (CAT), cannot be detected by any existing airborne equipment, including state-of-the-art weather radar. The number of turbulence accidents has been growing by a factor of 5 since 1980, three times faster than the increase in air traffic.

Studies conducted during various projects (FP5 AWIATOR, FP6 FLYSAFE, etc.) have shown that operational concepts for the protection against turbulence hazards include:

- Short-range (50 m to 300 m) measurement of air speed ahead of the aircraft, and action on the aircraft flight controls to mitigate the effect of turbulence;

- Medium-range (10 km to 30 km) detection of turbulence, and securing of passengers and crewmembers by fastening seat belts.

Both short and medium-range concepts are based on the UV LIDAR technology (Light Detection And Ranging), and there would be a great interest in integrating both functions into a single LIDAR system, for both operational (medium-range detection increasing the overall reliability and integrity of the system) and economical reasons.


The short-range concept for protection against turbulence has been validated in the frame of the Fifth Framework Programme AWIATOR project.

The technical objective of DELICAT is to validate the concept of LIDAR-based medium-range turbulence detection. This validation will be based on comparing the information on a turbulent atmospheric area, provided on one hand by the remote UV LIDAR and on the other by the aircraft sensors (acceleration, air speed, temperature, etc.).

Description of Work

The validation of the LIDAR-based medium-range turbulence detection includes the following steps:

- A UV LIDAR mock-up will be designed and manufactured, tested in a laboratory on the ground, and then installed onboard a research aircraft, which will fly in both turbulent and non-turbulent conditions.

- During the flight tests, the atmosphere will be analysed remotely by the UV LIDAR, and by the in situ aircraft onboard sensors.

- The data obtained from the LIDAR and from the aircraft sensors will then be compared off-line once the aircraft is on the ground. The correspondence between the LIDAR backscattered signals and the turbulence experienced by the aircraft for a given atmospheric area will be assessed and evaluated.

- Conclusions will then be drawn on the capabilities of the LIDAR technology, regarding Clear Air Turbulence detection, and a preliminary equipment architecture will be defined, for both short and medium-range concepts.

DELICAT will take advantage of existing hardware (laser sub assemblies, test aircraft fairing) to achieve its goal at the lowest possible cost.

Expected Results

The DELICAT project will directly contribute to the validation of an advanced technology for aircraft protection against Clear Air Turbulence hazards. This will increase both customer comfort and aviation safety.

Based on traffic and accident statistics, one can estimate that such a UV LIDAR turbulence protection equipment would have avoided between 8 and 10 turbulence accidents in 2005 and will reduce by up to 20 (or 40%) of the number of turbulence accidents per year, once this system has been developed by DELICAT's industrial partners.

The DELICAT project will also contribute towards increasing the knowledge about Clear Air Turbulence phenomenon, and the capability to forecast such hazardous phenomenon.

Dissemination of DELICAT will be ensured by setting up a website, and by gathering an External Experts Advisory Group (EEAG). Through the EEAG and the website, the external stakeholders (airlines, aircraft manufacturers, meteorological service providers) will be informed about the objectives and progress of DELICAT, they will be able to provide feedback and also to update and refine their needs regarding protection against turbulence (both for short-range and medium-range concepts).