Notwithstanding this spring’s violent (and numerous) tornadoes, forecasters in the Midwest are able to make more accurate local weather predictions thanks to an airborne sensor being tested by NASA’s aviation safety program. Researchers at the agency’s Langley Research Center in Hampton, Va., leading a team that has installed so-called tropospheric airborne meteorological data report (Tamdar) instruments on dozens of Mesaba Saab 340s, are turning the regional airliners into veritable flying weather stations.
The Tamdar instrument allows aircraft to sense and report atmospheric conditions automatically as they fly. A satellite transmits the airborne, real-time observations to a ground data center that processes and distributes up-to-date weather information to forecasters, controllers and pilots.
“Initial research shows the airborne sensor makes a 10- to 20-percent improvement in forecast error in numerical models, and that’s just with temperature,” said NASA project leader Taumi Daniels. The onboard sensor also measures humidity, pressure, wind, icing and turbulence, as well as GPS-derived location, time and altitude data.
According to Jay Ladd, the president of AirDat–which makes and supplies the airborne sensor system–regional aircraft are a desirable platform for the sensors because they typically fly below 25,000 feet and have frequent cycles each day. This application, Ladd said, dramatically increases the number of observations in the lower atmosphere, with the Mesaba experiment contributing 800 daily atmospheric soundings. Contrast this with the data received by a mere 70 weather balloon sites in the continental U.S. that collect temperature, wind and moisture data from twice-daily atmospheric soundings and the potential benefit of Tamdar becomes clear.
Since the Mesaba fleet was fitted with the AirDat equipment in January last year, “Meteorologists at the National Weather Service have found the tropospheric airborne meteorological data [from the Mesaba aircraft] to be useful in forecasting severe thunderstorms, dense fog, the precipitation types of winter storms and
low-level wind shear,” said National Weather Service meteorologist Richard Mamrosh.
AirDat’s goal is to expand the geographical coverage of the airborne sensor network, Ladd said. Horizon Air will soon be equipping its regional turboprops with the 6.5-pound sensor system, which includes both the sensor and a two-way satellite communication/datalink system. Regional aircraft aren’t the only suitable platform for the airborne sensors, according to Ladd. He cited fractional fleet aircraft and air-taxi operations as possible candidates for the devices because such operations involve “a lot of landings and takeoffs.” In fact, Ladd said he’s talked with air-taxi start-up DayJet about equipping its Eclipse 500s with the AirDat airborne sensor package.
The system can also be used for real-time tracking of company aircraft, as an “ACARS-like” communication system and to downlink maintenance data. Besides adding no drag or weight penalty, the package’s communications system antenna provides a double benefit since it can also be used as an antenna for satellite (XM or Sirius) graphical weather services.
Ladd added that the package is not limited to the above-mentioned uses because the AirDat system can obtain and process any data flowing over the Arinc 429 busses, in addition to data from the airborne weather sensor. This, he said, makes for a flexible system that can handle almost any data-gathering or data-processing request.
