Commercial drone flights are set to become a widespread reality in the United States, starting next year, under a 2012 law passed by Congress. Drone flights by law enforcement agencies and the military, which already occur on a limited basis, are projected to surge.

The documents obtained by The Post detail scores of previously unreported crashes involving remotely controlled aircraft, challenging the federal government’s assurances that drones will be able to fly safely over populated areas and in the same airspace as passenger planes.

Military drones have slammed into homes, farms, runways, highways, waterways and, in one case, an Air Force C-130 Hercules transport plane in midair. No one has died in a drone accident, but the documents show that many catastrophes have been narrowly averted, often by a few feet, or a few seconds or pure luck.

“All I saw were tents, and I was afraid that I had killed someone,” Air Force Maj. Richard Wageman told investigators after an accident in November 2008, when he lost control of a Predator that plowed into a U.S. base in Afghanistan. “I felt numb, and I am certain that a few cuss words came out of my mouth.”

Investigators were unable to pinpoint a definitive cause for the accident but said wind and an aggressive turn by the pilot were factors. Wageman did not respond to a request for comment through an Air Force spokeswoman.

Several military drones have simply disappeared while at cruising altitudes, never to be seen again. In September 2009, an armed Reaper drone, with a 66-foot wingspan, flew on the loose across Afghanistan after its handlers lost control of the aircraft. U.S. fighter jets shot it down as it neared Tajikistan.

The documents describe a multitude of costly mistakes by remote-control pilots. A $3.8 million Predator carrying a Hellfire missile cratered near Kandahar in January 2010 because the pilot did not realize she had been flying the aircraft upside-down. Later that year, another armed Predator crashed nearby after the pilot did not notice he had squeezed the wrong red button on his joystick, putting the plane into a spin.

While most of the malfunctioning aircraft have perished in combat zones, dozens have been destroyed in the U.S. during test and training flights that have gone awry.

In April, a 375-pound Army drone crashed next to an elementary school playground in Pennsylvania, just a few minutes after students went home for the day. In Upstate New York, the Air Force still cannot find a Reaper that has been missing since November, when it plunged into Lake Ontario. In June 2012, a Navy RQ-4 surveillance drone with a wingspan as wide as a Boeing 757’s nose-dived into Maryland’s Eastern Shore, igniting a wildfire.

Defense Department officials said they are confident in the reliability of their drones. Most of the crashes occurred in war, they emphasized, under harsh conditions unlikely to be replicated in the U.S.

Military statistics show the vast majority of flights go smoothly and that mishap rates have steadily declined over the past decade. Officials acknowledge, however, that drones will never be as safe as commercial jetliners.

“Flying is inherently a dangerous activity. You don’t have to look very far, unfortunately, to see examples of that,” said Dyke Weatherington, director of unmanned warfare for the Pentagon. “I can look you square in the eye and say, absolutely, the [Defense Department] has got an exceptional safety record on this and we’re getting better every day.”

The Post’s analysis of accident records, however, shows that the military and drone manufacturers have yet to overcome some fundamental safety hurdles:

• A limited ability to detect and avoid trouble. Cameras and high-tech sensors on a drone cannot fully replace a pilot’s eyes and ears and nose in the cockpit. Most remotely controlled planes are not equipped with radar or anti-collision systems designed to prevent midair disasters.

• Pilot error. Despite popular perceptions, flying a drone is much trickier than playing a video game. The Air Force licenses its drone pilots and trains them constantly, but mistakes are still common, particularly during landings.

• Persistent mechanical defects. Some common drone models were designed without backup safety features and rushed to war without the benefit of years of testing. Many accidents were triggered by basic electrical malfunctions; others were caused by bad weather. Military personnel blamed some mishaps on inexplicable problems. The crews of two doomed Predators that crashed in 2008 and 2009 told investigators that their planes had been “possessed” and plagued by “demons.”

• Unreliable communications links. Drones are dependent on wireless transmissions to relay commands and navigational information, usually via satellite. Those connections can be fragile. Records show that links were disrupted or lost in more than a quarter of the worst crashes.

Among the models that crashed most often is the MQ-1 Predator, the Air Force drone manufactured by General Atomics Aeronautical Systems, of San Diego. Almost half the Predators bought by the Air Force have been involved in a major accident, according to purchasing and safety data.

Frank Pace, president of aircraft systems for General Atomics, the leading producer of large military drones, said the Predator has exceeded expectations for reliability. It was designed to be lightweight and inexpensive, costing less than $4 million apiece. During the early years of the wars in Afghanistan and Iraq, he said, nobody expected the Predator to last very long.

“It was more of a mind-set that you were going to get shot down or have other losses, so you don’t want to put all this money into a redundant system,” Pace said, referring to backup systems designed to kick in when a failure occurs.

He emphasized that none of the Predator accidents have been fatal.

“We’ve never reported a loss of life,” he said, “so we’re doing pretty good.”

Accidents span globe

Drones have revolutionized warfare. Now they are poised to revolutionize civil aviation. Under the law passed by Congress, the Federal Aviation Administration is scheduled to issue rules by September 2015 that will begin the widespread integration of drones into civilian airspace.

Pent-up demand to buy and fly remotely controlled aircraft is enormous. Law enforcement agencies, which already own a small number of camera-equipped drones, are projected to purchase thousands more; police departments covet them as an inexpensive tool to provide bird’s-eye surveillance for up to 24 hours straight.

Businesses see profitable possibilities for drones, to tend crops, move cargo, inspect real estate or film Hollywood movies. Journalists have applied for drone licenses to cover the news. Amazon.com chief executive Jeffrey Bezos wants his company to use autonomous drones to deliver small packages to customers’ doorsteps. (Bezos also owns The Post.)

The military owns about 10,000 drones, from one-pound Wasps and four-pound Ravens to one-ton Predators and 15-ton Global Hawks. By 2017, the armed forces plan to fly drones from at least 110 bases in 39 states, plus Guam and Puerto Rico.

The drone industry, which lobbied Congress to pass the new law, predicts $82 billion in economic benefits and 100,000 new jobs by 2025.

Public opposition has centered on civil-liberties concerns, such as the morality and legality of using drones to spy on people in their back yards. There has been scant scrutiny of the safety record of remotely controlled aircraft. A report released June 5 by the National Academy of Sciences concluded that there were “serious unanswered questions” about how to safely integrate civilian drones into the national airspace, calling it a “critical, crosscutting challenge.”

Nobody has more experience with drones than the U.S. military, which has logged more than 4 million flight hours. But the Defense Department tightly guards the particulars of its drone operations, including how, when and where most accidents occur.

The Post filed more than two dozen Freedom of Information Act requests with the Air Force, Army, Navy and Marine Corps. Responding intermittently over the course of a year, the military released investigative files and other records that collectively identified 418 major drone crashes around the world between September 2001 and the end of last year.

That figure is almost equivalent to the number of major crashes incurred by the Air Force’s fleet of fighter jets and attack planes during the same period, even though the drones flew far fewer missions and hours, according to Air Force safety statistics.

Reliability gripes

The original Predator was designed without redundant systems common to larger, manned aircraft. It bore only one engine, one alternator, one propeller. If any of those parts failed, the plane would come down.

Since the drone program began, the Air Force has acquired 269 Predators. Forty percent have crashed in Class A accidents, the most severe category. An additional 8 percent wrecked in Class B accidents.

As the accidents piled up, Air Force crews griped about reliability. Some of the complaints were aimed at General Atomics, the manufacturer.

“I don’t want to be the one that crashes a plane, but I hope that this causes folks, and when I say folks, I mean GA [General Atomics], I hope we hold them accountable for some of this stuff,” Air Force Maj. Elizio Bodden, a Predator instructor pilot, told an accident investigation board after a crash in Iraq on Nov. 29, 2007. “We know we are flying with some defective stuff, but we still do it.”

Pace, the General Atomics executive, blamed most Predator accidents on pilot mistakes during landings. He said that the company has made some safety upgrades to the aircraft but that adding extra engines or duplicate power systems was not practical, because it would require “a big redo.”

Army crash rates

The Reaper has fared better than the Predator, incurring 3.17 Class A mishaps per 100,000 hours over the past five years.

Air Force officials pointed out that the crash rate for Reapers now approaches the standard set by two fighter jets, the F-16 and F-15, which over the past five years have posted Class A mishap rates of 1.96 and 1.47 respectively, according to statistics from the Air Force Safety Center at Kirtland Air Force Base in New Mexico.

“We’ve learned a lot about flying [drones] because we had to,” said Air Force Col. James Marshall, the safety director for the Air Combat Command. “War is a great motivator when lives are on the line.”

The Reaper has not been immune to deficiencies.

After one crashed during a training mission in California on March 20, 2009, Air Force investigators blamed a faulty temperature control valve in the oil system. A similar incident had occurred one month before.

Further investigation revealed that sliders in the valves had been installed upside-down. Air Force inspectors were even more surprised to learn from General Atomics that the firm had bought the valves from a Houston company that did not design its products for use in airplanes.

The valve “is not of aerospace grade. In other words, the thermostatic valve was designed specifically for industrial applications ONLY,” an Air Force investigator wrote in the accident report. “This thermostatic valve was not intended for aircraft.”

Unlike the Air Force, the Army does not make the argument that its drones are nearly as safe as regular planes.

Lost links

Drones depend on wireless links for navigation and control. Pilots and camera operators issue directions to the drone by a command link, usually by satellite. Data about the aircraft’s movements and internal operations returns via a separate link.

The links can be easily interrupted by various forms of interference. Usually, the outages last only a few seconds and are harmless. Just in case, drones are programmed to fly in a circular pattern until the links are restored. In worst-case scenarios, they are supposed to return automatically to their launch base.

Records show that does not always happen. In more than a quarter of the accidents examined by The Post, links were lost around the time of the crash.

Several pilots told investigators that they were so accustomed to lost links that tended not to get nervous unless the disruptions lasted for more than a few minutes.

“I’d say after the three- or five-minute period, you sort of get the feeling that the plane just stopped talking to us and we may not recover this one,” a Predator pilot testified after an April 20, 2009, crash in Afghanistan.

Less than a month later, five hours into a reconnaissance mission over Afghanistan, a Predator lost its links and vanished in midair. Investigators never found the wreckage and were unable to determine a cause; the weather was clear, and there were no signs of mechanical problems or errors by the crew.

Satellite connections can be lost when a drone banks too sharply or drops in altitude too quickly. Electrical problems on the ground can also disrupt links.

On July 21, 2008, chaos erupted inside an Air Force ground-control station where crew members were flying three Predators simultaneously over Afghanistan. The station lost its power supply, and all its screens went black.

After several minutes, power was restored and pilots regained control over two of the Predators that had followed their programmed flight patterns and were flying in circles.

The third disappeared.