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TTEthernet Avionics Backbone a Technology Breakthrough for S-97 Raider

By Woodrow Bellamy III  | July 20, 2015
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[Avionics Today 07-20-2015] Sikorsky's S-97 Raider development and flight testing team is preparing for the second flight of its next generation aircraft, the multi-mission S-97 Raider helicopter, expected to occur next month. The helicopter features a unique integration of mature technologies based on the X2 Demonstrator, along with a technological breakthrough in the networked distributed Integrated Modular Avionics (IMA) architecture based on Time Triggered Ethernet (TTEthernet) supplied by TTTech. 
The Sikorsky S-97 Raider during its first flight. Photo: Copyright Sikorsky Aircraft Corporation. All rights reserved.
According to Dave Adams, mission systems project lead at Sikorsky Aircraft, the S-97 Raider is the first rotorcraft platform to feature TTEthernet. TTTech defines time-triggered or "deterministic" Ethernet as a networked communication technology that uses time scheduling to bring deterministic real-time communication to standard IEEE 802 Ethernet. The deterministic Ethernet uses a global sense of time and scheduling which is shared between network components. 
"We have an extremely low bus utilization there because what we’ve done on this aircraft, is really designed it as a system that has a very modernized backbone and high bandwidth connectivity and data bus architecture, so that when we go to production we can implement numerous advanced sensors and both tactical communications and weapons on this backbone bus and we'll have plenty of bandwidth to accommodate those new sensors," Adams told Avionics Magazine. "The flight control system is our third instantiation of the triplex fly-by-wire system, which is interconnected through the time triggered Ethernet as well."
TTTech first began working with Sikorsky on a networked distributed IMA based on time-triggered Ethernet in 2008, and was eventually selected by Sikorsky and Lockheed Martin to provide TTEthernet as part of the aircraft network for the Raider. 
Another innovative avionics approach included on the Raider are the integration of remote processing units with the ability to control the aircraft's electrical power systems remotely through soft bezel controls. Inside the cockpit, the Raider team also focused heavily on reducing pilot workload with no overhead switches, levers or circuit breakers. Bill Fell, chief test pilot for the Raider, said the first test flight showed that the increased automation is a huge improvement from cockpits of the past. 
"Back in the 1970s, when we had the advancing blade concept, its just dizzying to look at the number of switches and circuit breakers and levers that were in the cockpit back then," said Fell. "There were hundreds of switches and, that combined with the number of gauges, it required two pilots working very full time to manage that type of aircraft. The automation we have today, in terms of electronic circuit breakers, there’s only one physical circuit breaker in the aircraft and the rest of them are electronic and they’re managed through the glass and have a very user friendly interface that makes my job easier."
Adams said that by incorporating the TTEthernet backbone combined with the remote processing units and the digital fly-by-wire system, when Sikorsky enters the production phase with the Raider, it will be easier to become aligned with the Department of Defense's effort to lower avionics implementation costs with the Future Airborne Capability Environment (FACE) open IMA initiative. 
"We’re really truly integrated with all these pieces. The flight controls, displays, and remote processing units are all tightly coupled together and all interfaced through this high bandwidth time triggered Ethernet backbone," said Adams. "We've also provided a stepping stone into the FACE conforming architecture."
While the Raider is the first helicopter that Sikorsky has included TTEthernet on, it's likely that it will not be the last, as Adams sees it as a networked communication technology of the future for airborne platforms.

"We also implement ARINC interfaces as well for some of the subsystems were not Ethernet capable, so they were ARINC inputs and outputs so we support that architecture for digital data buses as well," Adams said. "There are [Controller Area Network] CAN buses on the aircraft as well. But really the core underlying bus is this time-triggered Ethernet bus for high-speed data and that provides the most growth. Whereas, when we add sensors and tactical features in the future they will be riding on that bus. We do not have 1553 on the Raider, we’re trying to push forward there and go toward these high bandwidth buses in the future." 

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