European researchers are trialling a laser-based system to detect clear air turbulences in an aircraft's flightpath.
A modified Cessna 550 Citation II research aircraft by the Netherlands' national aerospace laboratory NLR is conducting test flights with the demonstrator system from Amsterdam across Europe until the end of August.
The equipment - which involves light-detecting and ranging (LIDAR) technology - has been developed by Germany's aerospace research institute DLR as part of the EU project DELICAT (demonstration of LIDAR-based clear air turbulence detection).
The system projects ultraviolet light ahead of the aircraft to determine atmospheric parameters - such as air density and the speed of moving air - by measuring the scatter of light that has been reflected by air molecules.
High-altitude turbulences can be generated at the boundary of jet streams where air masses - which may move in different directions at different speeds - build up waves. This cannot be detected by weather radar equipment.
The researchers are evaluating short- and long-range measurements. The former assess air speed 50-300m (165-985ft) ahead of the aircraft, which could be used for flight-control inputs to mitigate the effect of turbulences. Long-range measurements should determine turbulences at a distance of 10-30km (5-16nm), which would create the opportunity to instruct passengers and cabin crew to fasten their seatbelts.
Around 40% of turbulence-related accidents on aircraft are caused by clean air turbulences. DLR says that the weather phenomenon is set to increase in future due to climate change.
Part of the trial is to compare the observational data from the LIDAR system with measurements of the actual turbulences the research aircraft encounters. This is to refine the models used to determine any potential turbulences.
DLR says that the "long-term" goal is to develop an integrated detection system to avoid clean air turbulences.
The DELICAT project began in 2009 and is to be completed in March 2014. It involves 12 research partners from seven European countries, including France's Office National d'Etudes et de Recherches Aérospatiales (ONERA) and Warsaw University's Interdisciplinary Centre for Mathematical and Computational Modelling. The project co-ordinator is French avionics and electronics specialist Thales.