The purpose of the In-situ Turbulence Reporting Project is to develop, demonstrate, and implement a means to collect and report real-time turbulence metrics using the Aeronautical Radio, Inc. (ARINC) Aircraft Communications Addressing and Reporting System (ACARS) downlink capability and the Meteorological Data Communicating and Reporting System (MDCRS) weather data dissemination system. The turbulence metric is derived from in-flight aircraft accelerations sensed by onboard accelerometers. An algorithm developed by L. Cornman is being employed to remove aircraft, pilot, and autopilot dynamic responses such that the turbulence metric approximates the eddy dissipation rate.
The MDCRS employs ACARS bandwidth to downlink atmospheric variables, such as winds, temperature, and relative humidity. These parameters are used as real-time updates to meteorological data assimilation models, such as the National Center for Environmental Predition's Rapid Update Cycle (RUC). It is anticipated that enhanced real-time updates to the models will greatly improve the quality and temporal/spatial resolution of future aviation weather forecasts. Rapid turnaround of a raw turbulence metric will also permit airlines and pilots to strategically and tactically plan their flights around turbulent volumes. The real-time turbulence measurements will also be incorporated into numerical weather models and nowcasting models, thereby increasing the accuracy of subsequent turbulence forecasts.
The critical technology which makes reporting of a raw turbulence metric possible is an algorithm developed by Cornman which transforms aircraft acceleration into the eddy dissipation rate. The algorithm employs dynamic response models that remove inputs from the pilot, the aircraft, and the autopilot. This capability requires no new hardware for most commercial aircraft flying today. The algorithm is implemented as software resident within the Aircraft Condition Monitoring System (ACMS) partition of the Flight Data Acquisition and Management System (FDAMS), and communications protocol to the ACARS system. These software changes are designed to exploit near-term enhancements to ACMS systems which are already planned by avionics manufacturers. For this reason, there is a window of opportunity to demonstrate this capability with minimal implementation cost. Certification costs will also be zero, since software additions to include this capability can be made independent of flight-critical functions within the Flight Management System (FMS).
The algorithm has been developed and is ready for operational demonstration. The in-situ turbulence capability can be operationally implemented immediately following the operational demonstration.
United Airlines has agreed to be the airline industry lead in validating and using this important new capability. Project team members include:
| NCAR-RAP |
| United Airlines |
| Allied Signal Aerospace, Redmond WA |
| ARINC |
| Aviation Weather Center, Kansas City |
| Air Line Pilots Association |
Allied Signal completed software installation and bench testing in September of 1997. United installed the software on two of its Boeing 737-500s in late September 1997. Aircraft data are now being collected to be used in validating and calibrating the algorithm, which should take about two months. Objectives of this evaluation include:
Once this evaluation period is over and a final software build is complete, the NCAR algorithm will be installed on over 200 United Boeing 737 and 757 aircraft. Other interested airlines include Northwest Airlines, Delta Airlines, US Airways, QANTAS, and American Airlines.
Once the United fleet campaign is complete, NCAR will "productize" the downlinked turbulence metrics into a real-time turbulence display. It is anticipated that this information will be presented to the participating airlines on a common ARINC extranet. In addition, research aimed at using the eddy dissipation rate metric in numerical models and new integrated turbulence nowcasting algorithms is being sponsored by the Federal Aviation Administration (FAA).