N602RN

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 DEN08FA160.

HISTORY OF FLIGHT

On September 24, 2008, at 0841 Pacific daylight time, an experimental Raytheon Cobra, unmanned aircraft system (UAS), N602RN, was destroyed when it lost engine power and subsequently impacted in desert terrain near Whetstone, Arizona. 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 airstrip at the Unmanned Vehicles International (UVI), Incorporated facility near Whetstone, Arizona, at approximately 0809.

The purpose of the flight was to test a photo-mapping package for the U. S. Army Corp of Engineers. The Cobra UAS was to serve as an aerial platform for the device. The test consisted of the aircraft performing an automatic takeoff and climb to 1,000 feet above ground level (agl), fly a programming leg on which the internal mapping system would align, and then enter a grid series of 17 parallel, 5 mile long north-to-south, south-to-north legs that progressed west to east along which the camera would photograph and record the terrain over which it was being flown. Following the mapping legs. The aircraft then was to descend to pattern altitude and enter a non-standard traffic pattern from which it would execute an automatic landing.

The aircraft was computer controlled through software that established altitudes, airspeeds and GPS waypoints for the aircraft to fly. Commands to the vehicle were sent via omni radio and executed by an internal pilot that sat at a control console located in the back of a company half-ton truck. For this flight, a Raytheon internal pilot was instructing a U. S. Army student pilot, who manned the computer console, monitored the wing camera display, and held the remote control box in case it was needed. Other persons associated with the vehicle operation were a Test Director, a company observer, a company crew chief and a U. S. Army crew chief in training. All of these persons were in radio communication with the internal pilots in the truck.

The aircraft underwent preflight and systems tests. The aircraft's engine was started at 0805 and the aircraft's left wing-mounted camera was activated. Following automatic and manual engine run ups, the aircraft was taxied to a position on the UVI runway at which time the student pilot entered the command for an automatic takeoff. The aircraft took off to the south and climbed to 5,200 feet msl (1,000 feet agl), and began its programmed mission.

Following the final pass, the aircraft was to enter a single figure-eight pattern that was to set it up for landing. During the turn from north to east, the aircraft engine lost all power. The autopilot then commanded the aircraft to descend to hold airspeed and maintain it's ground track profile. An observer watching the aircraft from the ground queried the internal pilot at the command station regarding the aircraft's continuing descent. The internal pilot then noted the red-highlighted warning on the console indicating the engine RPMs were at zero. The autopilot executed a turn to the south, which aligned the aircraft with the runway at an altitude approximately 800 feet above the ground. The internal pilot told the student pilot at the console to input the "Land Now" command. The student pilot switched the remote control box to "manual" instead and the aircraft pitched down approximately 45 degrees and descended rapidly. The Test Director, who was also watching from the ground, radioed the command to "pull up." In the wing camera monitor, the runway was visible and coming up fast. The internal pilot switched the remote control box back to "automatic." The aircraft leveled off and corrected back over the runway at an altitude of approximately 60 to 70 feet. At approximately 1,400 feet down the runway, the aircraft entered a steep right diving turn and impacted the terrain.

PERSONNEL INFORMATION

The aircraft was automatic piloted on a pre-programmed schedule. A company-trained internal pilot and a student pilot monitored the aircraft's progress through laptop software programmed into the aircraft's autopilot.

Internal Pilot

The internal pilot was a Raytheon employee and held a commercial pilot's certificate with single-engine land, instrument airplane, and glider ratings. The internal pilot also held a flight instructor's certificate for single-engine land airplanes and gliders.

The internal pilot held a second class medical certificate with no restrictions, dated May 15, 2008.

The internal pilot reported having approximately 4,000 total flying hours, 3,000 of which he stated were in single-engine airplanes. The internal pilot reported having about 1,000 hours in gliders and approximately 60 hours piloting Cobra aircraft.

Student Pilot

The student pilot was an employee of the U. S. Army Corps of Engineers. The student pilot reported no civilian flight certificates or ratings.

The FAA special program letter covering Raytheon's operation of the Cobra UAS at UVI required that the internal pilot hold at least a private pilot certificate, a third class medical certificate with no limitations, and have a minimum of three years experience operating radio-controlled aircraft.

AIRCRAFT INFORMATION

The aircraft was serial number 002. It received an experimental airworthiness certificate from the FAA on January 12, 2007. The aircraft was being operated under a special program letter authorizing Raytheon Missile Systems to fly the Cobra aircraft within the confines of the UVI facility.

A Certificate of Authorization (COA) was not required for the flight. The flight was approved through the experimental certificate program letter. Although carrying a military program package, the flight was considered civilian and not military.

The aircraft was 9 feet long and had a wingspan of 10 feet. The aircraft's empty weight was 65 pounds. The maximum gross weight of the aircraft was 110.3 pounds. The gross weight of the aircraft on the day of the accident was approximately 106 pounds at takeoff. The center of gravity was at 29.09 inches with a mean aerodynamic chord of 26.3 percent, placing the vehicle within its operating envelope.

A single 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. The engine, serial number DA2178, had a total operating time of 35.9 hours at the time of the accident. The company's established time between overhauls for the engine was 250 hours.

The aircraft was controlled by a ground-based command center. This consisted of Piccolo II software run by a laptop computer, into which commands were programmed and then sent to the autopilot through an omni radio transmitter. The signals were then received and integrated with the aircraft's on-board Global Positioning system (GPS) receiver, which in turn provided commands to the autopilot. A remote control box with manual power and steering controls was also available and served as a backup control system to the command center.

The aircraft underwent a condition inspection on January 31, 2008. At that time the aircraft had 16.1 hours total flying time. Prior to the accident, the aircraft had flown 57 times. At the time of the accident, the aircraft had logged a total flying time of 25.7 hours.

METEOROLOGICAL INFORMATION

At 0755, weather conditions at the Sierra Vista Municipal Airport (KFHU), Sierra Vista Arizona, 10 miles south of UVI were clear skies, 70 statute miles visibility, variable winds at 1 knot, temperature 70 degrees Fahrenheit (F), dew point 41 degrees F, and altimeter 30.21 inches.

At 0855, weather conditions were clear skies, 70 statute miles visibility, winds 100 degrees at 8 knots, temperature 75 degrees F, dew point 45 degrees F, and altimeter 30.22 inches.

WRECKAGE AND IMPACT INFORMATION

The aircraft came to rest 1,417 feet from the approach end of the runway and 118 feet, 8 inches right of the runway centerline in sage brush covered desert terrain. The wreckage and debris trail fell along a 290-degree magnetic heading.

The primary impact point was a 4-foot long, 6-inch wide and 1-inch deep ground scar that ran along a 281-degree magnetic heading. Small pieces of fiberglass consistent with the wing structure were found along the ground scar. The ground scar ended approximately 21 feet prior to the aircraft main wreckage. Small pieces of fiberglass and foam filler material rested between the ground scar and the main wreckage along a 290-degree path.

The aircraft main wreckage consisted of the payload compartment that contained the photo-mapping package, fuel tanks, avionics and the engine, the left wing, the tail boom and empennage, the landing gear, and propeller.

The forward portion of the payload compartment was crushed inward. The nose gear was broken aft. All three propeller blades were fractured. Two blades were broken rearward at the hub. One propeller blade rested just in front of the main wreckage. The left main landing gear was broken aft. The right main landing gear was broken aft and separated. The vehicle's right wing was broken aft from the carry through spar and separated. The spar was bent aft. The left wing was broken aft and downward, but remained attached to the payload compartment. The left wing aileron was broken at the inboard hinge. The outer two-thirds o...