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DEmonstration of LIdar based Clear Air Turbulence detection

Final Report Summary - DELICAT (DEmonstration of LIdar based Clear Air Turbulence detection)

Executive Summary:
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, cannot be detected by any existing airborne equipment, including state-of-the-art weather radar; this explains why the number of turbulence accidents has been growing by a factor of 5 since 1980, 3 times faster than the increase of the air traffic.

Operational concepts for the protection against turbulence hazards include:
o 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, o Medium-range (10 km to 30 km) detection of turbulence and securing of passengers and crewmembers by seat belts fasten.

Both concepts are based on the UV LIDAR technology. The short-range concept was validated in the frame of the FP5 AWIATOR project. The objective of DELICAT is to validate the concept of LIDAR based medium range turbulence detection.
At the end of the project, we can state that the objectives of DELICAT have been globally achieved.

A LIDAR system has been designed, manufactured and tested, with performances compliant with thedesign objectives. The LIDAR system was successfully integrated on-board the test aircraft and the flight test campaign took place. During the flight tests, all systems worked and performed properly.
However, no moderate turbulence event was encountered, despite the intensive meteorological support provided by ICM and Meteo France

The flight test data analysis shows that in the favourable case, it should be possible to detect CAT with moderate severity at medium range, objective of the DELICAT project. However, it is difficult to draw definitive conclusion, because only light turbulence was encountered during the flight tests, and because the absence of Mie / Rayleigh filter, which Hovemere failed to provide, prevented the suppression of aerosol perturbation.

Regarding meteorological activities, ICM and Meteo France developed new methods of CAT prediction, which showed good potential but need more data for tuning and performances verification.

Finally, the integration of short-range and medium-range functions has been assessed.

Project Context and Objectives:
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, cannot be detected by any existing airborne equipment, including state-of-the-art weather radar; this fact explains that the number of turbulence accidents has been growing by a factor of 5 since 1980, 3 times faster than the increase of the air traffic.

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 seat belts fastening.
Both concepts are based on the UV LIDAR technology. The short-range concept was validated in the frame of the FP5 AWIATOR project.

The objective of DELICAT is to validate the concept of LIDAR based medium range turbulence detection.

This validation of medium range turbulence detection is based on the comparison of the information on a turbulent atmospheric area, provided on one side by the remote UV LIDAR and on the other side by the aircraft sensors (acceleration, air speed, temperature). This validation includes the following steps:

o A UV LIDAR system is designed and manufactured, tested in laboratory on the ground, and then installed on-board a research aircraft. This LIDAR system includes the following sub systems
- LIDAR Transmitter
- LIDAR Receiver
- Beam Steering system

o During the flight tests, the atmosphere is analysed by the UV LIDAR and also by the aircraft on-board sensors, which is intended to fly in turbulent and non-turbulent conditions

o The data obtained from the LIDAR and from the aircraft sensors are compared off line once the aircraft on the ground. The correspondence between LIDAR backscattered energy fluctuations and turbulence experienced by the aircraft, for a given atmosphere area, is assessed and evaluated.

In parallel to the LIDAR based activities, the meteorological partners of the DELICAT consortium have specific activities with the objective to improve the understanding of Clear Air Turbulence atmospheric phenomenon and to improve the CAT forecasting capabilities.

Finally, The DELICAT project also includes the analysis of the integration of short-range and medium range functions.

Project Results:
In WP1000, a description of the turbulence hazard has been done, regarding the following aspects:
- Impact of turbulence on aviation transport industry
- Turbulence severity classification
- Clear Air Turbulence protection needs
- Overall experimental system requirements

Main results and foreground for WP2000: Lidar
- Overall LIDAR system structure
- Simulation of the performances of the DELICAT experiment
- Design of the Transmitter unit
- Receiver system
- Beam steering device
- Integration of the LIDAR in the Aircraft
- Design review
- Laser transmitter subsystems and analogue detection chain (DLR)
- Initial Receiver subsystem and data acquisition system (HVM)
- Alternative receiver (DLR)
- Integration of manufactured sub-systems for the setup of the final lidar system (DLR)
- Mirrors
- Mirrors mechanical mounts
- Beam Steering Control
- Beam Steering Control
- Ground-based synthesis test of complete LIDAR system (DLR)
- Comparison of measured LIDAR signals to simulation runs

Main results and foreground for WP3000: Met activities
- Review of previous studies
- Preliminary selection of the test areas and times of year based on existing climatology
- Aerosol climatology based on MOCAGE output
- Preparation of the real time support for the flight test
- ICM Website
- ICM development
- Meteo-France development
- Verification method
- Observation data-set
- Forecasted data-set at Meteo France
- Statistical indices
- Results

Main results and foreground for WP4000: Flight tests
- Flight preparation
- Aircraft installation and modification
- Flight campaign

Main results and foreground for WP5000: Data Processing
- Data extraction
- Identification of useful time ranges
- Detection algorithms

Potential Impact:
The objective of the DELICAT project was to validate the concept of Clear Air Turbulence detection at medium range (10 km to 30 km), using a UV Lidar.
This validation included the development of a UV LIDAR system, tested in laboratory on the ground,and then installed on-board a research aircraft. This Lidar system is composed if 3 sub-assemblies:
o A Transmitter,
o A Beam Steering system
o A Receiver, including a Mie / Rayleigh separation filter

The Transmitter and Beam Steering systems performed according to the project needs.
Regarding the Receiver and especially the Mie / Rayleigh separation filter, Hovemere was not able to develop a system suitable for the DELICAT project experimental needs.
Regarding meteorological activities, ICM and Meteo France developed new methods of CAT prediction, which showed good potential but need more data for tuning and performances verification before those new methods can be actually used for CAT prediction on a regular basis.
Based on those facts, the potential direct exploitation of the results of the DELICAT project is described hereunder.

Further processing of the flight test data

Both Lidar data and aircraft data were recorded during the flight tests. Those data were processed (off-line) by the DELICAT project partners in the frame of WP5000 in order to define and test CAT detection algorithms.
In addition to the work already performed within the DELICAT project, further processing could be performed on the flight test data in order to improve the understanding of all phenomenon observed during the DELICAT experiment, as well as to improve the statistical aspect and the completeness of the data processing.

Further flight tests using existing hardware and newly developed Mie / Rayleigh separation filter
In general CAT conditions were not favourable during the DELICAT flight test experiment. This was mainly due to the project planning, which made it impossible to perform the tests in the forecasted more encouraging seasons

During flight execution the intensity of CAT areas found was dominantly light: the maximum turbulence observed was in the order of 5 m/s2 (or 0.5 g) in very rare occasions (max. CAT level mostly was below 0.2g). In addition, only very few turbulence events were encountered, even though the encountered turbulences were of light severity.
The absence of a Mie Rayleigh separation filter was another major obstacle for the analysis of the flight tests data and the definition of CAT detection algorithms.

It would then be very useful to perform complementary flight tests in order to draw more definitive conclusions about the capability to detect CAT at medium range using a UV Lidar.
o The Lidar Transmitter already exists and is compliant with the experimental needs. The Transmitter can be re-used for further flight tests without any modification,
o The Beam Steering system already exists and is compliant with the experimental needs. It may be adapted to comply with the specific conditions of a possible new experiment, if any,
o The Lidar Receiver, and especially the Mie / Rayleigh separation filter, needs to be redesigned in order to comply with the experimental needs. The thermal principle of the filter designed by Hovemere is clearly not adequate and needs to be reconsidered,
o Finally, the aircraft modifications have been implemented, and the certification authorities have granted a ‘Supplemental Type Certificate’ (STC), based on which the aircraft is able to perform a flight tests campaign,
o With the lidar data being analysed in detail, many improvements may be contributed to the system developed within DELICAT.


Further analysis regarding new methods of CAT prediction
ICM and Meteo France have developed, within the DELICAT project, new methods of CAT prediction that could be very useful in the context of the development of the European aeronautical transport.
However, more data and research is necessary before these methods could go operational.
Those complementary analysis and research could use, for example, more commercial flight data provided such flight data can be made available for the study.

The dissemination activities were mainly directed toward the scientific community, with the exception of the presentation of the DELICAT project in the frame of the Aerodays 2011 event, organised by the European Community with a larger audience including the aeronautical industry stakeholders and the public audience.The other Dissemination events are detailed in the PDF version fo the Final Report.

List of Websites:

The web site has been established by INOE and is available at the address: www.delicat-fp7.org.
The web site includes a public part and a part only accessible to the partners (through a password).

The public part contains:
o A general description of the project,
o The list of the project deliverables,
o A presentation of the project objectives,
o A presentation of the different beneficiaries and their contributions to DELICAT, as well as a point of contact,
o The public presentations and documents prepared in the frame of the DELICAT project.