The venerable CT7/T700 family has proven a reliable engine partner for helicopter pilots for decades. Soon it will branch out to power a new breed of aircraft with non-cockpit operators.

The CT7/T700-powered Tern, a medium-altitude, long-endurance unmanned air system (UAS) sponsored by DARPA (Defense Advanced Research Projects Agency), is on track to meet a major milestone in January with its first demonstrator engine delivery.

The delivery comes 13 months after DARPA awarded the “fast works” Tern contract to Northrop Grumman, and just 10 months after GE was put on contract. The team has been tasked with designing the UAS that would take off vertically from a tail-sitting position before leveling out in the air and transitioning to horizontal flight. This design allows forward-deployed small ships without a full runway on deck to serve as mobile launch and recovery sites. Current UASs lack the ability to take off and land from confined spaces in rough seas and achieve efficient long-duration flight.

An illustration of Tern, Northrop Grummans next-generation unmanned system for maritime ISR and strike.

An illustration of Tern, Northrop Grummans next-generation unmanned system for maritime ISR and strike.

“The aircraft itself is unique,” said Christopher Smith, engineering manager – Turboshaft/Turboprop propulsion. “The biggest challenge is the aircraft control system. Trying to land the aircraft vertically on a ship that’s moving up and down in a very severe ocean state is challenging. The control system logic and how the engine integrates together is the biggest technical challenge.”

GE has developed a new version of the proven CT7/T700 family, with modifications to add FADEC controls and lube system modifications for vertical operation.

“On the engine side, from a conventional engineering aspect, the challenge has always been how to get the engine to operate vertically during takeoff and transition horizontally for flight. It needs to be able to take off like a rocket and fly like a plane,” Smith said, adding that the engine has 210 new parts and it will undergo testing in a Lube System Simulator before the end of the year.

To meet the demands of the “fast works” schedule, which has the TERN slated for shipboard landing by late 2018, the engine incorporates parts manufactured using the additive process, rather than castings that require a much longer timeframe to manufacture.

Overall, Smith said the Tern provides a chance to breathe new life into the CT7/T700 Family.

“This is a great opportunity to find green space for our existing product,” he said. “Many people are working very hard on new centerline NPI engines – they are very important – and GE and our customers spend a lot of money. But if you can put a current product in a completely new space, that’s a great opportunity at lower cost. We’re modifying a baseline engine and creating an opportunity for up to 500 CT7/T700s in the future and that’s a really effective way to grow.”

Click here to see an update on the Tern program.