Terminal Doppler Weather Radar (TDWR)
Air Traffic Control (ATC) uses Terminal Doppler Weather Radar (TDWR) to increase the safety of the National Airspace System (NAS).
For air traffic controllers who manage arriving and departing flights in the terminal area, TDWRs provide vital information and warnings about
- hazardous wind shear conditions
- gust fronts
Massachusetts Institute of Technology's Lincoln Laboratory developed TDWR, a Doppler weather radar system, in response to several disastrous jetliner crashes in the 1970s and 1980s. The crashes occurred because of wind shear, a sudden change in wind speed and direction. Wind shear is common in thunderstorms due to microbursts, which are downward rushes of air.
TDWR's primary purpose is to timely and accurately detect hazardous wind shear in and near terminal approach and departure corridors as well as to report this information to pilots and local air traffic controllers. TDWR also provides warnings of sustained wind shifts and hazardous weather, including turbulence, to ATC supervisory employees to improve airport operation. We anticipate that NextGen Surveillance and Weather Radar Capability, a NextGen capability, will replace TDWR. Until then, we must properly maintain the TDWR system to comply with service availability requirements.
Benefits and Challenges
The TDWR system has been in service since 1994. It has a large number of proprietary software and hardware parts, many of which have become obsolete and present significant supportability problems that worsen with time. The last wind shear related accident occurred at Charlotte/Douglas International Airport on July 2, 1994, before its TDWR was installed and operational (Aircraft Accident Report 95-03). In addition, weather related delays have been reduced, allowing savings in aviation fuel consumption.
Operational benefits of the system include the real-time detection of microburst, gust fronts, wind shifts, and precipitation, as well as prediction of wind changes that allow improved airfield efficiency when making runway changes. The program will continue to deploy improvements that will lower TDWR operations costs and improve its reliability.
Forty-five TDWR systems protect 46 high-capacity airports, throughout the United States and Puerto Rico, which are prone to wind shear events. Two additional systems at the FAA's Mike Monroney Aeronautical Center in Oklahoma City provide engineering support and training. No wind shear accidents have occurred at any TDWR-protected airport since TDWR was commissioned in 1994. FAA automation systems and 34 National Weather Service forecast offices receive TDWR weather data.
TDWR Service Life Extension Program (SLEP)
The TDWR SLEP program is an ongoing effort to modernize the existing TDWR capability so that the TDWR continues to benefit the NAS and the FAA's Enterprise Architecture. The main purpose of the various individual projects funded by the TDWR SLEP funding stream is to improve TDWR’s availability.
TDWR SLEP will support safety by sustaining operations of terminal weather and wind shear services at target levels. The TDWR SLEP will address issues of obsolete and unsupportable parts to maintain required service levels and remain operational until NextGen capability replaces it.
So far, the SLEP eliminated outages due to antenna gear failure and maintained service by replacing parts of the system that are difficult to maintain and support.
Also, FAA has an agreement with the National Weather Service to provide TDWR data. This information is further distributed to non-governmental organizations and companies such as Weather Underground. This distribution provides easy access to TDWR information to the public and other interested parties.