Accidents involving UAVs

Lockheed Martin has confirmed that its P-175 Polecat unmanned air vehicle crashed in December on the Nevada test range after the unintentional activation of its flight termination system.

The Skunk Works-built private-venture high-altitude UAV demonstrator, first flown in secret in 2005 and unveiled at last year’s Farnborough air show, had only recently returned to flight.

Lockheed says the UAV was “functioning normally, performing well and in full positive control by the ground operators” when the failure occurred.

According to Lockheed, it was ordered by the US government not to discuss the 18 December accident until after an investigation was completed. " There was an irreversible unintentional failure in the flight termination ground equipment at the Nevada Test and Training Range. We believe the test range has corrected the potential for a similar circumstance to occur again," the company says.

Powered by two Williams International FJ44 turbofans, the 4,100kg (9,000lb) gross-weight Polecat was a low-observable, high-altitude UAV designed to demonstrate a number of advanced technologies, including low-cost composite construction and laminar-flow swept wing.The tailless flying-wing UAV was “damaged beyond repair due a failure of the flight-termination ground equipment, which caused the aircraft’s fail-safe flight termination mode to activate”, says Lockheed, adding that the automatic fail-safe system was “designed to irreversibly terminate flight” so that the UAV did not leave the range.

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Predator UAV crash: switchology mistake

< " Mark M. Newton" < newton06262@earthlink.net> >

Fri, 26 May 2006 04:56:10 GMT

The National Transportation Safety Board has released a preliminary report on the 25 Apr 2006 crash of a Predator UAV while on U.S. border patrol. " The pilot reported that during the flight the console at PPO-1 'locked up', prompting him to switch control of the UAV to PPO-2. Checklist procedures state that prior to switching operational control between the two consoles, the pilot must match the control positions on the new console to those on the console, which had been controlling the UAV. The pilot stated in an interview that he failed to do this. The result was that the stop/feather control in PPO-2 was in the fuel cutoff position when the switch over from PPO-1 to PPO-2 occurred. As a result, the fuel was cut off to the UAV when control was transferred to PPO-2."

From http://www.ntsb.gov/NTSB/brief.asp?ev_id=20060509X00531& key=1

The U.S. National Transportation Safety Board (NTSB) has concluded its first investigation of the crash of an unmanned aerial vehicle and has issued 22 safety recommendations to address what NTSB Chairman Mark V. Rosenker calls " a wide range of safety issues involving the civilian use of unmanned aircraft."

The board also has voted to convene a public forum on the safety of unmanned aircraft operations and the methodologies to use when investigating accidents and incidents involving them. The forum will take place over two to three days, with the dates and agenda to be announced once the details have been completed.

The accident investigated occurred on April 25, 2006, when a General Atomics Aeronautical Systems-built MQ-9 Predator B owned by the U.S. Customs and Border Protection (CBP) agency crashed near the airport in Nogales, Ariz. There were no injuries, and the crash was blamed on operator error.

The NTSB concluded that the pilot caused the crash when he switched operational control from a console whose lower screen had temporarily blanked out. When he hurriedly switched to another console, he didn't notice that the console settings weren't synchronized and that the one he switched to had the fuel valve cut off.

He noticed that the Predator was losing altitude but didn't know why. He shut down the ground data terminal so the vehicle would start its lost-link procedure, which called for it to autonomously climb to 15,000 feet above mean sea level and fly a predetermined course until it could reestablish contact. But the vehicle's engine was cut off so it crashed instead.

" This investigation has raised questions about the different standards for manned an unmanned aircraft and the safety implications of this discrepancy," Rosenker says. " Why, for example, were numerous unresolved lockups of the pilot's control console even possible while such conditions would never be tolerated in the cockpit of a manned aircraft?"

Rosenker also says that the pilot wasn't proficient in performing emergency procedures.

" The pilot is still the pilot, whether he is at a remote console or on the flight deck," he says. " We need to make sure that the system by which pilots are trained and readied for flight is rigorous and thorough. With the potential for thousands of these unmanned aircraft in use years from now, the standards for pilot training need to be set high to ensure that those on the ground and other users of the airspace are not put in jeopardy."

Michael Kostelnik, the assistant commissioner for the Office of CBP Air and Marine, has said that the agency put safeguards in place after the crash to make sure it won't happen again. He tells AUVSI's Unmanned Systems magazine in the upcoming November-December issue that the CBP's extensive use of Predator vehicles puts it " on the leading edge of policy" in the use of unmanned vehicles in the National Airspace System. He notes that CBP typically flies the vehicles late at night and over relatively unpopulated territory, so even when this Predator crashed no one was hurt.

Among the additional safety recommendations sent to the U.S. Federal Aviation Administration (FAA) are:

The press release announcing the results is here, and the full text of the report is here.

Kinshasa - A Belgian unmanned aircraft (UAV) crashed in Kinshasa, when its forward and rear engines cut out, for unknown reasons, just after taking off, said an officer from the European Union force (Eufor) in the Democratic Republic of Congo (DRC) on Thursday.

One person was killed and three are suffering from burns, after the UAV burst into flames when it hit the ground, according to the latest report by EuFor. The unmanned, remote-controlled aircraft, equipped with cameras, fell on Boulevard Triomphal, near Kinshasa's main stadium, about one kilometre from the Ndolo air base, where Eufor headquarters are.

" The aircraft had just taken off when its two engines cut out. Belgian Lieutenant-Colonel Yves Vermeer, the head of the Eufor UAV unit said: " It continued to rise, then glided before falling towards the boulevard." " It is too soon to give reasons as to why the engines cut out," he added but said that it was " unlikely" to have been shot down.

Apparently, the cause of the crash has been ascribed to a " loss of situational awareness" . The UAV ground control thought the UAV had not taken off, when in fact it had, and closed down the engines. The UAV then crashed due to the operator instruction to cut engine power.

As of March 2002 the US Air Force inventory consisted of three Global Hawk Air Vehicles. Of the six that had been built, three were lost in mishaps.

Predator has been bought as a system consisting of four air vehicles, the ground-control stations and the satellite gear required. As of 2001 the Air Force was buying 12 systems, with the last two of those to be delivered by early 2002.

In addition to buying systems, the Air Force has bought attrition vehicles. As of 31 October 2001 the Air Force had received a total of 68 air vehicles, and had lost 19 due to mishaps or losses over enemy territory, including four over enemy territory in Kosovo.

At least seven Predators observing Iraq or Afghanistan crashed or were shot down over the six month period ending in January 2002. That meant that roughly one of every eight Predators in the Air Force inventory had been destroyed. At least nine Air Force Predators and one CIA drone crashed during missions in Afghanistan or Iraq in the thirteen months following the September 11th terrorist attacks.

As of late 2002 the Air Force had about 50 Predators in service, with only a few equipped to launch the Hellfire missile. The CIA has a small number of the armed drones. Newer versions of the Predator, at $4.5 million each, are being produced at a rate of about two aircraft a month.

The FY2003 budget request called for spending $158 million to buy 22 more Predators and upgrade existing ones.

A good number of them were lost due to operator error, since it is hard to land the UAV. The operator has the camera pointing out the front of the plane, but he really has lost a lot of situational awareness that a normal pilot would have of where the ground is and where the attitude of his aircraft is.

Air Force investigators have determined that human error caused an RQ-1 Predator aircraft to crash Sept. 17, 2003 at a classified forward-operating location in Southwest Asia. The loss is estimated at $3.2 million. The aircraft was assigned to the 11th Reconnaissance Squadron at Nellis Air Force Base, Nev. According to an Air Combat Command accident investigation report released today, the primary cause of the accident was that the pilot unintentionally flew the aircraft into a hazardous cloud. The pilot lost communication with the aircraft several times, but was able to re-establish communication twice. However, the aircraft failed to respond to the pilot’s commands, indicating the flight control computers were disabled by the hazardous weather conditions.

A failed pilot bearing caused an MQ-1 Predator unmanned aerial vehicle to crash in the U.S. Central Command area of responsibility 30 March 2005. The Predator, assigned to the 57th Wing at Nellis Air Force Base, Nev., was performing an intelligence, surveillance and reconnaissance mission when the propeller lost forward thrust and caused the aircraft to crash. The aircraft was severely damaged on impact. Because of the remote location of the crash, key components were removed and the remainder of the aircraft was destroyed. The loss is valued at about $4.4 million. There was no other damage to government or private property.

The pilot bearing, located within the propeller shaft, provides radial support for the push-pull shaft and allows the propeller shaft to spin freely around a fixed quill shaft. The investigation determined long and progressive failure of the pilot bearing caused the adapter, which holds the quill shaft in place, to shear. Once the adapter sheared, the quill shaft then unscrewed itself from the variable pitch propeller servo and drove the propellers to an extreme reverse pitch, causing the aircraft to endure severe drag and a high rate of descent.

Many accidents and fatalities occur during manned airborne geophysical surveys, that are related to flying just above ground level. As can be seen from the images below, the resolution of an aeromagnetic survey improves with decreasing height, so, it is very important for some geophysical survey work to fly just (such as 30 m) above ground level.