New U.S. Unmanned Aircraft Takes Shape

The U.S. Government is advancing technology for its destroyers and frigates through the development of unmanned aircraft suitable for launch from small-deck ships.

Tern, a joint program between DARPA and the U.S. Navy’s Office of Naval Research, is currently scheduled to start integrated propulsion system testing for a new unmanned aircraft in the first part of 2017. This is anticipated to culminate in a series of at-sea flight tests in late 2018.

“We’re making substantial progress toward our scheduled flight tests, with much of the hardware already fabricated and software development and integration in full swing,” said Brad Tousley, director of DARPA's Tactical Technology Office, which oversees Tern. “As we keep pressing into uncharted territory - no one has flown a large unmanned tailsitter [aircraft that takes off and lands on its tail then tilts horizontally for forward flight] before - we remain excited about the future capabilities a successful Tern demonstration could enable: organic, persistent, long-range reconnaissance, targeting and strike support from most Navy ships.”

Last year, DARPA initiated a Phase 3 project, led by the Northrop Grumman, to build a full-scale technology demonstration system. The program has since made significant advances on numerous fronts, including commencement of wing fabrication and completion of successful engine testing for its test vehicle. DARPA has now tasked Northrop Grumman with building a second test vehicle.

Additional tests are about to start. A one-fifth-scale version of the aircraft is being tested in a wind tunnel at NASA’s Ames Research Center. Data collected during this test will be used to better characterize aircraft aerodynamic performance and validate aerodynamic models.

Tern envisions a new medium-altitude, long-endurance unmanned aircraft that could operate from helicopter decks on smaller ships in rough seas or expeditionary settings while achieving efficient long-duration flight. To provide these and other previously unattainable capabilities, the Tern Phase 3 design is a tailsitting, flying-wing aircraft with a twin contra-rotating, nose-mounted propulsion system. 

The aircraft would lift off like a helicopter and then perform a transition maneuver to orient it for wing-borne flight for the duration of a mission. Upon mission completion, the aircraft would return to base, transition back to a vertical orientation and land. The system is sized to fit securely inside a ship hangar for maintenance operations and storage.

Wing fabrication 

Since Phase 3 work started at the beginning of 2016, Tern has finished fabricating major airframe components and anticipates final assembly in the first quarter of 2017. Once complete, the airframe will house propulsion, sensors, and other commercial off-the-shelf systems to make up the full-scale technology demonstration vehicle.

Engine tests 

In Phases 2 and 3, Tern has successfully tested numerous modifications to an existing General Electric engine to enable it to operate in both vertical and horizontal orientations. This type of engine was chosen because it is mature and powers multiple helicopter platforms currently in use.

Software integration 

This summer, Tern opened its Software Integration Test Station, part of the System Integration Lab that supports software development for the program. The test station includes vehicle management system hardware and software and uses high-fidelity simulation tools to enable rapid testing of aircraft control software in all phases of flight. The station is helping ensure the technology demonstration vehicle could fly safely in challenging conditions such as launch, recovery and transition between horizontal and vertical flight.