Advances in Detection of Volcanic Ash from Commercial Aircraft

Volcanic ash remains a continuing problem for commercial aircraft operations, sometimes leading to significant flight delays, airport closures, course deviations and damage to airframes and gas turbine engines. The brute force solution when ash encounters are expected is to either delay or cancel a flight or to drastically reroute the aircraft if the ash layers can be accurately forecast.

Commercial aircraft do not currently carry standard sensors to detect the presence of any type of airborne aerosol particles. Larger aircraft with weather radar will be able to detect clouds with hydrometeors larger than 100 µm, but ash or dust layers generally contain finer particles and are undetectable using these sensors. In addition, given that these layers are generally less than several hundred meters thick once they are more than several hours from their source region, they are visually undetectable by flight crews as they are challenging to discriminate from water clouds by eye.

The Backscatter Cloud Probes (BCP) have been flying since 2011 on six Airbus commercial airliners operated by Lufthansa, Air France, China Air, Iberia and Cathay Pacific, and measure cloud droplets, ice crystals and aerosol particles larger than 5 µm. The BCP can detect these particles and measures an optical equivalent diameter (OED) but is not able to distinguish the type of particle, i.e. whether they are droplets, ice crystals, dust or ash. However, some qualification can be done based on measured temperature to discriminate between liquid water and ice. The next generation BCP (BCPD, Backscatter Cloud Probe with polarization detection) is now undergoing performance testing and can differentiate atmospheric particle types. Given that the BCP and BCPD are both single particle detectors, this permits high sensitivity to the smallest quantities and rapid detection (within seconds) to alert flight crews.

The BCPD is being implemented as part of a near real-time, flight forecasting system that uses satellite and models, coupled with in situ measurements from the BCPD and meteorological sensors. DAEDALUS is a weather threat situational awareness system for commercial aircraft currently funded by the European Space Agency and supported by major aircraft and engine manufacturers, airlines and air navigation service providers.

This presentation will describe the essential components of DAEDALUS and how it will be implemented to optimize aircraft flight paths while minimizing potential hazards. Examples of measurements from the BCPD will be given that demonstrate its capability for detection and differentiation of atmospheric particulates, including volcanic ash, in near real-time.