NASA - National Aeronautics and Space Administration

NASA Dryden's DROID small unmanned research aircraft executes a hard right climbing turn to avoid crashing into a rocky desert ridge during flight tests of a miniature ground collision avoidance system for small unmanned air vehicles. The DROID -- short for Dryden Remotely Operated Integrated Drone -- provided good data for project engineers as they flight-validated the collision avoidance software Installed in a smartphone connected to its autopilot that enabled automatic fly-ups or turns when the aircraft neared terrain.› View larger image

This graphic depicts how the automatic ground collision avoidance system (Auto-GCAS) software application, tied to a small autopilot, can command the flight controls to alter the flight path of an aircraft when it is facing the imminent threat of a collision with the ground. (NASA graphic)› View larger image Project officials at NASA's Dryden Flight Research Center are hailing the success of recent flights tests of a miniature automatic ground collision avoidance system (Auto-GCAS) for small unmanned aircraft, after the smartphone-assisted system repeatedly executed pull-ups or sharp turns of the test aircraft to avoid imminent impact with terrain in its flight path.

During final test flights of the software integrated into an autopilot on the Dryden Remotely Operated Integrated Drone (DROID) research aircraft in May, the system consistently commanded evasive maneuvers when it sensed the aircraft was getting too close to rocky, mountainous terrain or ridgelines.

The software has been adapted by the project team into an application for a smartphone using the Android operating system linked to a small Piccolo autopilot. The last flight tests were flown with the smartphone containing the developmental software installed in the aircraft.

“For these last flights, the smartphone aboard the aircraft eliminated the need for the ground control station link to be in constant communications with the aircraft,” said Dryden's project manager Mark Skoog. “On these flights the system performed very reliably, consistently initiating recoveries close to the last possible moment, even in the face of numerous losses of communications with the ground control station right at the critical point of needing to avoid the colliding with the mountain,” Skoog said.

NASA Dryden's DROID small unmanned research aircraft executes a hard right climbing turn to avoid a ridgeline during flight tests of a miniature ground collision avoidance system for small unmanned air vehicles. › View larger image The last two flights, conducted at a remote dry lake surrounded by hilly desert terrain northeast of Edwards Air Force Base, Calif., saw the system successfully execute five mountainous terrain collision avoidance fly-ups, five ridge crossings executed with and without the software’s multi-trajectory mode on, and a clockwise and counter-clockwise “patrol” over the valley with the multi-trajectory mode off.

The last flights were not without a few glitches that are often the hallmark of experimental flight testing and software development, ranging from computer cooling issues in the ground control station van, to a non-responsive left actuator on the DROID research aircraft. The latter challenge forced the project team to disassemble the aircraft’s wing, where they discovered wires had separated. Innovative repairs were made in the field requiring a creative use of the minimal resources available, and the aircraft was again ready to fly.


Test objectives of the final flights included phone-on-aircraft testing of the team’s latest software changes for failure mode logic of the collision avoidance system. The project team also collected terrain influences on wind for trajectory prediction, and verified the software’s nuisance evaluation of single-trajectory versus multi-trajectory flight options.

Several NASA Dryden Remotely Operated Integrated Drone (DROID) project team members secure the aircraft’s single-piece wing during flight tests of the project’s miniature ground collision avoidance system for small unmanned air vehicles. › View larger image In all, the phone-on-aircraft software changes functioned well, with the software’s multi-trajectory capability providing noticeable nuisance-free flight improvements over its single-trajectory mode.

The flights were conducted within Dryden's Western Aeronautical Test Range, which is part of the restricted military flight-test ranges over Edwards Air Force Base and Southern California's high desert.

“Our last flights represent well over a year of hard work by a highly skilled and dedicated team who have made important steps towards the elimination of controlled flight into terrain accidents,” said Jack Ryan, the project’s chief engineer.

The Auto-GCAS -- DROID project team will now complete analysis of the flight data and begin the report writing process.

When fully developed and matured, the miniaturized Auto-GCAS technology could have wide applications for potential use in general aviation aircraft, including both manned and remotely and autonomously operated unmanned aircraft systems.

Banking hard to starboard after a very close pass near a ridgeline, NASA Dryden's DROID research aircraft provided good data for project engineers during flight tests of a miniature ground collision avoidance system for small unmanned air vehicles. › View larger image Development and adaptation of the automatic ground-collision avoidance software into a smart phone application for unmanned aircraft was sponsored by NASA Dryden and the Defense Safety Oversight Council of the U.S. Department of Defense.

Learn more:
  Are These the DROIDs You're Looking For?
  Dryden Validates Auto-GCAS Smartphone Software



Gray Creech, Public Affairs
NASA Dryden Flight Research Center