N601RN

Note: This case was reclassified from an accident to an incident as a result of applicable revisions to 49 Code of Federal Regulations Part 830.2, as amended at 75 FR 51955, Aug. 24, 2010. The case was previously identified under accident number DEN08FA130.

HISTORY OF FLIGHT

On July 28, 2008, at 1231 mountain daylight time, an experimental Raytheon Cobra, unmanned aircraft system (UAS), N601RN, sustained substantial damage when it collided with a stadium light pole while maneuvering for a pre-programmed landing near Colorado Springs, Colorado. The aircraft was registered to and operated by Raytheon Missile Systems Advanced Programs of Tucson, Arizona. There were no injuries to persons on the ground. Visual meteorological conditions prevailed for the Title 14 Code of Federal Regulations Part 91 test flight, and no flight plan was filed. The aircraft had departed from a paved road paralleling one of the athletic fields on the grounds of the United States Air Force Academy at 1208, and was returning to that location when the accident occurred.

The purpose of the flight was to test the system before demonstrating the Cobra to Air Force Academy staff. The staff at the Air Force Academy wanted to evaluate the aircraft's potential as part of an advanced airmanship curriculum course on UAS for the cadets. Prior to the flight, the Raytheon flight test team surveyed the road, the athletic fields, and the terrain north and south of the takeoff area. They then programmed the Global Positioning System (GPS) flight profile waypoints into the autopilot.

The aircraft underwent a preflight and systems tests. The aircraft's engine was started at 1206. It was also at this time that the aircraft's left wing-mounted camera was activated, which recorded the 25 minute, 5 second flight. Following automatic and manual engine run ups, the aircraft was taxied to a position on the road from which the command for an automatic takeoff was entered. The aircraft took off to the north and climbed to 8,000 feet above mean sea level (msl) or 1,000 feet agl. It then turned east to enter a counter clockwise, east-to-west rectangular flight pattern profile over the athletic fields north of the Air Force Academy's cadet area, as programmed. The aircraft then climber to 9,000 feel msl (2,000 feet agl) and continued the rectangular patterns.

The Cobra UAS performed several rectangular patterns over the athletic field with no problems noted. Part of the demonstration showed that the UAS could fly on its pre-programming in the event of a "lost-link" or loss of signal between the ground station and the aircraft.

After the aircraft had performed all of its maneuvers, it entered a north upwind leg for a right hand traffic pattern. The aircraft made several patterns at 8,000 and 7,600 feet before it was descended on the downwind leg for landing. The south-to-north landing pattern was set up so that a downwind to dogleg, dogleg to base, and base to final pattern would be flown. During the turn to final for landing, the aircraft undershot the final approach. The supplemental pilot and observer both called for a "wave off" (abort) and the internal pilot (aircraft operator in the truck manning the control console) selected the "abort" command, which sent the aircraft to the upwind waypoint to re-enter the traffic pattern. The aircraft established itself on crosswind and then flew a descending downwind, dogleg, base leg and turn to final. During the turn to final on the second landing pattern, the aircraft undershot the turn again. The supplemental pilot and observer both called for an abort and the internal pilot again selected the abort command and the aircraft again proceeded to the upwind waypoint. On the third traffic pattern, the aircraft overshot the final turn waypoint flying approximately 89 feet west of flight path centerline. The Raytheon supplemental pilot elected not to take over manual control of the UAS because both he and the observer thought the aircraft would correct back to the programmed flight path and miss the stadium lights. The aircraft's wing-mounted camera showed the UAS fly west of and above a first of three 80-foot tall stadium lights that aligned the east side of a soccer field. The camera then showed the UAS in a 45-degree bank descending turn, heading toward the middle set of stadium lights. The last image recorded by the aircraft's wing camera had the stadium lights within feet of the camera. The aircraft impacted the top of the lights. The aircraft's right wing fractured and remained in the top bank of lights. The remainder of the aircraft fell to the ground impacting terrain within feet of the base of the light pole. The right wing was subsequently dislodged by the wind and fell to the ground.

AIRCRAFT INFORMATION

The aircraft was serial number 001. It received an experimental airworthiness certificate from the FAA on September 29, 2006. The aircraft was being operated under a special program letter authorizing Raytheon to fly the Cobra over the U. S. Air Force Academy.

There was no Certificate of Authorization (COA) for the Academy demonstration. The flight was approved via the experimental certificate program letter. The flight was a civilian flight and not operated by the Department of Defense. FAA personnel were present at the demonstration.

The aircraft was one of nine aircraft in the Raytheon Cobra fleet. The aircraft was developed as a low cost, reliable test platform for numerous sensors, communications packages, and light weapons testing. The vehicle was also used to demonstrate UAS architectural concepts in the real world environment.

The aircraft was 9 feet long with a wingspan of approximately 10 feet. The aircraft's empty weight is 65 pounds. The maximum gross weight for the aircraft as cleared by the manufacturer is 110 pounds. The gross weight of the aircraft on that day was 79.9 at takeoff. The center of gravity was at 29.2 inches with a mean aerodynamic chord of 26.3 percent, placing it well within its operating envelope.

A Desert Aircraft DA-150 2-cycle, horizontally opposed, carbureted 16.5 horsepower engine powered the aircraft. The aircraft operated within an airspeed regime of 45 to 55 knots for climbs, cruise, descent, and landing. The stall speed for the aircraft was approximately 38 knots.

Guidance and navigation for the aircraft was provided by a Piccolo II autopilot using a Piccolo command center, a laptop software program where coordinates and actions inputted were uploaded by omni radio to the aircraft's autopilot and integrated with the onboard GPS receiver. A remote control box with manual power and steering controls served as a backup system to the command center.

The aircraft underwent a condition inspection on July 18, 2008. At that time, the aircraft had 25.6 hours total flying time. Prior to the accident, the aircraft had flown 61 times. It had logged a total flight time of 28.4 hours.

PERSONNEL INFORMATION

The aircraft was automatic piloted on a pre-programmed schedule. A company-trained internal pilot monitored the aircraft's progress through the Piccolo command center, located under a pop-up shelter adjacent to a medium-sized moving truck that was used to transport the Cobra UAS and its support equipment. The internal pilot also monitored the aircraft's wing-mounted camera display. In accordance with the FAA-issued special program letter, the internal pilot held at least a private pilot certificate, a third class medical with no limitations. According to the internal pilot, he had approximately 60 hours operating Cobra UAS aircraft.

A supplemental pilot held the manual control box for the aircraft. He was positioned along the west side of the north-south road near the start point along with an observer. The supplemental pilot possessed no flight ratings, but met the criteria for his position based on the FAA special program letter. The observer held a private pilot certificate and met the criteria for his position based on the FAA special program letter

For this flight, a test director was positioned near the internal pilot. All flight crew members were within talking/shouting distance of each other; therefore, no radio communications were used.

METEOROLOGICAL INFORMATION

At 1226, weather conditions at the Air Force Academy Airfield (AFF), 6 miles south, southeast of the accident scene were few clouds at 12, 000 feet, 10 statute miles visibility, wind conditions were 360 degrees at 12 knots, temperature was 86 degrees Fahrenheit (F), dew point 39 degrees F, and altimeter of 30.06 inches.

At 1255, weather conditions were clear skies, 10 statute miles visibility, wind conditions 020 degrees at 11 knots with gusts to 20 knots, temperature 87 degrees F, dew point 39 degrees F, and altimeter 30.06 inches.

The field elevation of the Air Force Academy Airfield is 6,572 feet. The elevation of the Air Force Academy athletic fields where the flight was conducted was 7,010 feet msl.

The density altitude based on the conditions recorded at AFF at 1226 was 10,427 feet msl.

WRECKAGE AND IMPACT INFORMATION

The aircraft wreckage came to rest approximately 15 feet east of the light pole that it impacted. The left wing was broken aft at the wing root and carry-through spar. The forward body of the aircraft was cracked and broken aft of the spinner to the payload bay. The nose gear was broken aft. The right main gear was broken off from the bottom of the payload bay. The right wing was broken downward but remained attached to the carry-through spar. Several areas along the leading edge showed aft crushing. The right aileron was separated at the outboard and middle hinges. The tail boom was broken from the aft portion of the payload and main body of the aircraft. The empennage was intact and showed no damage. The propeller spinner was bent aft and inward. The three-bladed composite propeller remained intact.

The aircraft batteries were disconnected and the...