April 26, 2017
The end of an era: PATWAS
When inclement weather is on the way, you can find out about it, whether on your smartphone, on TV or the front page – especially if it is any risk to air travel.
While weather reporting has always been an important part of any travel equation, the method that pilots and airlines use to access weather information has evolved dramatically – from a wind sock and posted reports, to radio broadcasts and web portals.
However, as with most innovation, adopting new technologies means retiring the old.
In November 2016 NAV CANADA discontinued the Pilot`s Automatic Telephone Weather Answering Service, known as PATWAS, in favour of a combination of the widely used Aviation Weather Web Site (AWWS), Flight Information Centres (FICs), and the Collaborative Flight Planning System.
Despite its end, PATWAS was the industry standard for over a decade – using the cutting edge technology of its time to provide accurate and detailed weather and flight information to pilots through an automated text-to-voice system over the phone.
Prior to departure and/or creating a flight plan, pilots could call into PATWAS and be provided weather information along their routes or in some instances within 50 nautical-miles of their location, through a voice recording. The content of the transcriptions would always follow the same order:
2. Flight Precautions
3. Route Forecasts
4. Outlook (optional)
5. Winds Aloft
6. Radar Reports
7. Surface Weather Reports
8. Pilot Reports
9. Notices to Airmen
This automated system was first conceived in the early 1990s by Larry James and Jeff Cochrane with the Flight Information Services Automation (FISA) group of Transport Canada, Civil Aviation, but it wasn’t fully realized and implemented until the early 2000s.
The automated PATWAS system was preceded by the Transcribed Weather Broadcast (TWB) and manual version of PATWAS. These manual systems required flight service specialists to create live voice recordings that were verified and played back on a continuous loop over a radio frequency or for telephone access.
“These systems were labour intensive for FSS to maintain since anytime new weather came in on their circuits they would have to re-record the information,” recalled William Estrada, former Project Manager for PATWAS and now Director of Communications/Navigation/Surveillance (CNS) Engineering at NAV CANADA.
The PATWAS prototype was well received in the field and spread quickly, leading to the launch of the national PATWAS project.
Despite the success, there were also plenty of challenges facing the development team.
“PATWAS provided information for over a thousand airports across Canada and the US,” said Estrada. “Developing the aviation specific weather decoding capabilities, adding error handling and correction capabilities for FSS, and ensuring logistics and system design commensurate with meeting ANSP grade operational system requirements was a challenge.”
These challenges were on top of regularly recording and updating over 20 thousand speech units in English and French.
Once the development phase was over the PATWAS prototype was deployed in the spring and summer of 1998 at four airports: Buttonville, Edmonton, Winnipeg, and Vancouver.
The national deployment of PATWAS was then synchronized with the launch of the FICs throughout the early 2000’s, serving as pre-requisite to cut-over to FIC operations.
“From its heyday in the late 1990s and 2000s, when it handled over 1000 calls per week per site, PATWAS gradually was handling fewer and fewer calls with every passing year,” recalled Estrada. “In the last few years, it reached the point where, at some sites, the only calls PATWAS handled were those from the Engineering LCM and Technical Operations verifying system was working!”
The reason for the marked decrease can be easily attributed to the ease with which pilots can access weather information and graphics on smartphones and other mobile devices.
While NAV CANADA discontinued PATWAS service in November 2016, pilots continue to have the option of obtaining weather information via the Aviation Weather Web Site (AWWS), speaking directly with weather briefers at FICs at 1-866-WX BRIEF, or by using the Collaborative Flight Planning System.