Aviation Accident Summaries

Aviation Accident Summary DCA09FA028

Sierra Vista, AZ, USA

Aircraft #1




At the time of the accident the flight was operating as a Launch Recovery Element training mission, performing touch-and-go landings on runway 26. Customs and Border Protection had resumed pilot training following a Federal Aviation Administration-imposed suspension as a result of an accident 2 days prior. The accident landing was the seventh of eight planned landings. As the student pilot rotated the aircraft into the landing flare about six feet above the touchdown zone, a tailwind of approximately 9 knots was recorded. The instructor told the student to increase the pitch to arrest the descent rate and increase power to begin a go-around. However, the aircraft touched down hard on the main gear and lower vertical stabilizer and porpoised a number of times. The instructor then took over, executing a go-around and landing with no further incident. The aircraft sustained damage to the propeller, left main landing gear, vertical fin and the lower cowl. There was no evidence of any preexisting anomalies with the aircraft.

Factual Information

HISTORY OF FLIGHT On February 19, 2009, at approximately 1318 MST, a US Customs and Border Protection (CBP) General Atomics MQ-9 Predator unmanned aircraft, registration CBP-108, experienced a hard landing and tailstrike resulting in substantial damage to the lower vertical stabilizer and propeller. The hard landing occurred during Launch and Recovery training while conducting the seventh of eight planned touch and go landings. At about 1314:19 the aircraft began its descent from pattern altitude of approximately 1,200 feet above ground level (agl) at an indicated airspeed of 95 knots. The aircraft was being hand-flown with autoflight modes off. Vertical speed during the descent averaged about -377 feet per minute (fpm), but varied between 957 fpm and -1,536 fpm. Pitch angle was about -3.74 degrees. At about 1316:19, the aircraft was descending through about 400 feet agl, flaps at 30 degrees and power reduced to 27.4%. At 1317:10, the pilot reduced power to idle and pitched to about +1.5 degrees, indicated airspeed was 84.5 knots and altitude about 6 feet. Airspeed was further reduced to about 74 knots as a result of a pilot commanded nose up pitch to about 12 degrees. Data logger computed wind at this time was 106 degrees at 9.5 knots, resulting in a tailwind component of about 9 knots. The instructor told the student to flare more to arrest the descent rate and to add power to initiate a go around. At 1317:20 a peak acceleration of +3.76g occurred, likely coincident with the first hard touchdown. The instructor reported that he placed his hand on the controls to help with the flare but the aircraft stalled and impacted the runway. The pilot commanded a pitch up to about 15 degrees at the same time. The aircraft pitched up to about 17.5 degrees and the pilot commanded a nose down -3.2 degrees of pitch. At 1317:22, the pilot commanded full power just prior to a second increase in normal acceleration of 4.8g, The aircraft pitch angle was +1.5 degrees while the pilot's pitch command was 16.7 degrees. The indicated airspeed was 71.3 knots, calculated stall speed was 74 knots, and angle of attack was +6.6 degrees. Engine torque was at 53.2% and increasing. The instructor reported that as the aircraft bounced and became airborne it entered heavy pitch and roll oscillations and he took over control of the aircraft. During the bounces the aircraft pitched as high as +17.3 degrees with an angle of attack of +20.2 degrees. The oscillations in pitch and roll, opposite the control inputs according to data logger information, continued over approximately the following 15 seconds. At about 1319:36, the indicated airspeed increased above the calculated stall speed, and the aircraft began to increase in altitude. The instructor maintained control of the aircraft and climbed to pattern altitude. The sensor operator maneuvered the payload ball to inspect the aircraft and saw no catastrophic damage. The instructor advised air traffic control to forgo a normally required foreign objects and debris check of the runway because the aircraft’s flight characteristics were affected, and he did not want to risk any delay. He completed a full stop landing on runway 26. There was no further damage, and no injuries. DAMAGE TO AIRCRAFT The vertical fin, including the rudder and tailwheel, was damaged affecting the flight control of the aircraft. Additionally, the propeller blades were bent, the left main landing gear wheel hub exhibited crush damage, and there were two cracks in the lower cowl. PERSONNEL INFORMATION The student pilot was receiving training for Launch and Recovery Element (LRE) operations. He held FAA Airline Transport Pilot and U.S. Military pilot certificates with multi-engine land, and instrument ratings. He was type rated in the Cessna Citation 550, Beechcraft King Air 200, and Lockheed L-188 (C130). He had a total of 2,325 hours with 1,084 hours pilot in command. He had logged 76 hours of time on the MQ-9 in Mission Control Element (MCE). He held a current FAA First Class medical certificate with no limitations or waivers. The Instructor Pilot (IP) held FAA Commercial Pilot and Flight Instructor certificates, with instrument multi-engine land ratings. He had logged a total of 4,650 hours total time including 322 hours as an instructor on the MQ-9. He held a current FAA Second Class medical certificate with no limitations or waivers. AIRCRAFT INFORMATION CBP-108 was built in June of 2007 and delivered to CBP in July of 2007, it was one of six Predator-B MQ-9 UAVs operated by CBP. CBP records indicate the aircraft had approximately 561 flight hours prior to the accident flight. The Ground Control Station (GCS) was one of two located at Libby Army Airfield, two others were located at Riverside CA, and Grand Forks ND. CBP108 was configured for airborne reconnaissance in support of CBP missions. The MQ-9 was not certified by the FAA, but operates under the provisions of a Certificate of Authorization (COA) issued by the FAA. Although the aircraft is not certified, General Atomics stated that they meet the provisions of 14 CFR Part 23 whenever practicable. The MQ-9 was powered by a Honeywell TPE-331 turboprop engine. Maximum gross weight of the aircraft was 10,500 pounds, estimated weight at the time of the accident was 8,089 pounds. Aircraft records and data logger files showed no maintenance conditions relevant to the accident. METEOROLOGICAL INFORMATION Weather the time of the accident was reported as light and variable wind, sky clear, visibility greater than 10 miles, temperature 17 degrees C, dewpoint -8 degrees C, sea level barometric pressure 30.20”. AIDS TO NAVIGATION The aircraft navigated via GPS. There were no anomalies evident, no receiver autonomous integrity monitoring (RAIM) warnings, and no satellite outages. There were no anomalies noted in data uplink/downlink between the GCS and aircraft. COMMUNICATIONS There were no communications difficulties. AERODROME INFORMATION Libby Army Airfield is located within the city of Sierra Vista, Arizona. It is a joint use civil/military field. The runway in use, 8/26, was 12,001 feet long, 150 feet wide with full safety areas on each end. Runway 26 touchdown zone elevation was 4,599 feet, and the runway sloped at a 1% uphill grade toward the west. The runway condition was dry at the time of the accident, there were no reported Notices to Airmen of significance. The Air Traffic Control (ATC) Tower was in operation at the time of the event, and there were no other aircraft operating in the traffic area as required by the CBP COA. No abnormalities regarding the airport or ATC were reported. FLIGHT RECORDERS The MQ-9 GCS was equipped with a full data logger, which recorded approximately 1900 parameters of command and status information from the aircraft and ground station. All data was downloaded successfully. The UAS does not record any audio information. TESTS AND RESEARCH General Atomics – Aeronautical Systems Inc. (GA-ASI) reviewed the data logger files to determine the parameters and sequence of events that led to the mishap, and relevant excerpts were used in History of Flight. ORGANIZATIONAL AND MANAGEMENT INFORMATION U.S. Customs and Border Protection is an agency of the Department of Homeland Security. The stated mission of the CBP is to maintain the security of the U.S. border. In 2005, CBP formed the Office of Air and Marine responsible for the aviation assets of the agency, and began developing a UAS program. At the time of the accident, CBP was operating six MQ-9 aircraft from Sierra Vista airport, primarily for training and observation of the U.S.-Mexico border. GA-ASI is a unit of the General Atomics company. GA-ASI manufactures unmanned aircraft including the MQ-9 Predator-B (Reaper in US Air Force terminology), the MQ-1 Predator-A and others. GA-ASI also manufactures ground control stations, sensor hardware and software, and provides field support services to customers. ADDITIONAL INFORMATION Following an accident in November of 2008 (DCA09FA009), the FAA suspended the CBP COA to conduct training on the MQ-9 at Sierra Vista Airport. The CBP conducted an internal review of their programs and oversight, for the purposes of responding to the FAA. On December 17, 2008, the FAA reinstated the training COA and CBP resumed LRE training on February 17, 2009. On October 24, 2007, following a public forum on UAS safety, the NTSB issued recommendations A-07-065 through A-07-069 to the FAA and A-07-070 through A-07-086 to the CBP. At the time of this accident the recommendations were classified “open-response received.” CBP took further actions following this accident and the previous landing event (NTSB #DCA09FA009) to prohibit tailwind landings, increase training oversight by the national organization; and additional training improvements, including but not limited to, crew coordination training, reviews of various landing techniques via video, establishment of landing minima during training, and specific stable approach and go-around training. Following this accident and the previous landing event, GA-ASI recommended safety changes including but not limited to, a review of Field Alert Bulletin 0246 to ensure compliance with recommended approach, touchdown speeds, attitudes and response to pitch excursions experienced during landings, and implementation of system improvements such as laser altimeter/height annunciator and modification of the main landing gear to a trailing link system.

Probable Cause and Findings

The student pilot's improper flare while landing with a tailwind and the instructor pilot's delayed response.


Source: NTSB Aviation Accident Database

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