NTSB Factual Report

On January 27, 2014, at approximately 11:18 p.m. Pacific Standard Time (PST), a General Atomics MQ-9 unmanned aircraft system (UAS) operated by the U.S. Customs and Border Protection (CBP), registered as CBP159, was substantially damaged following an intentional ditching 23 miles west of Point Loma, California. The aircraft experienced a generator failure approximately one hour prior to the ditching. The crew elected to ditch the aircraft upon determining there was insufficient battery power to transit the aircraft to the nearest recovery site at Fort Huachuca, Arizona. The flight was conducted as a non-military public aircraft operation under the provisions of Title 49 of the United States Code (U.S.C.) Sections 40102 and 40125, and a Federal Aviation Administration (FAA) Certificate of Authorization (COA). The flight operated under instrument flight rules inside Warning Area (W-291) and visual meteorological conditions. There were no injuries.

According to the operator, the aircraft was en route to the assigned operational areas at FL280. An audible alarm sounded followed by the "battery-sourcing current, 28 V bus - voltage approaching lower limit, and "power system/fault- payload shed" warnings. These are all indications of a generator failure. The pilot immediately reversed course and called for the Dual Generator Failure Checklist. The checklist was completed without restoration of generator operation. Throughout the remainder of the flight, the pilot attempted multiple unsuccessful generator resets. The crew analyzed the power supply options and determined that the aircraft lacked sufficient backup battery power to sustain flight for the time required to return to base, which would require a transit across populated areas. The crew proceeded to the Flight Termination Point (FTP) on the eastern side of W-291 to complete an intentional ditching of the aircraft. The aircraft was being controlled via Ku satellite communication (SATCOM) and the crew elected to leave most of the electrical equipment on to ensure sufficient electrical power was available to control the aircraft throughout the ditching evolution.

While en route to the FTP, the pilot descended the aircraft from FL280 to 5,000 feet mean sea level (MSL) and then continued the descent to get below a marine overcast layer that was at approximately 2,000 feet to ensure the intended FTP was clear. Once it was determined that the ditch area was clear of maritime traffic, the pilot positioned the aircraft to the south of the FTP and initiated a descent. At approximately 600 feet MSL, the crew lost link with the aircraft due to a low voltage condition that caused an automatic reset of the Interim Link Manager Assembly (ILMA). After approximately two minutes, the crew was able to re-establish return link and found that the aircraft was climbing through 2,000 feet MSL on its lost link profile (last set to 5,000 feet MSL). The crew re-established the command link and positive control. The pilot maneuvered the aircraft back towards the FTP, actuated the condition lever to stop the engine and completed the ditching. The aircraft impacted the water approximately 1.7 miles north of the FTP, destroying the aircraft.

A full CBP report of this accident is available in the public docket for this case.

NTSB Probable Cause

intentional controlled ditching of the aircraft due to failure of the starter/generator supplying electrical power to the aircraft.