An expensive drone crashed into a house in December when it lost its GPS signal due to interference, according to one accident investigation by the British.
Drone, DJI M600 Pro was surveying the construction site when the accident occurred. The DHI M600 Pro can weigh as much as 34lbs (15.5kg) and is listed at a price of $ 5,699 on the vendor’s website.
The accident has provided additional impetus for those in the United States who oppose the decision of the Federal Communications Commission (FCC) to allow Ligado Networks to transmit on frequencies close to GPS frequencies. US government tests show that high-precision GPS receivers, such as those used in some survey drones, may not have a reliable signal every time they are within 3,400 meters (2+ miles) of a Ligado transmitter. Drones with inappropriate general-purpose GPS receivers can be affected within a distance of 1,040 meters (0.6 miles).
Unreliable GPS drones can roam unauthorized areas and end up stuck. The bigger and heavier the drone, the more dangerous it is. Most commercial drones weigh less than 100 lbs (45kg), although some models can weigh 200 lbs (90 kg) or more.
While drones should remain in the operator’s line of sight, when GPS navigation is lost, many enter “attitude mode.” This results in the aircraft maintaining its altitude above the ground and its wing level using barometric and inertia sensors. It cannot hold its position above the ground, without GPS and will be washed away by the wind. Unless the operator takes manual control immediately, the drone can drift out of the operator’s view. That usually also means it cannot receive radio commands sent by the operator.
This is what happened in this case, according to British Aircraft Accident Investigation Agency Report.
A survey of construction sites by drones was on the second day. The first three flights without incident. On the fourth flight, the drone took off and reached about 65 feet above the ground. The pilot controller then shows the GPS compass error. At that moment, the drone stopped climbing and began to blow in the wind about 15 miles per hour. The pilot repeatedly selected the “return” function without success before the plane flew over the tree line and was not seen. It crashed into the roof of a house a few hundred meters behind the trees and fell in the backyard.
After informing the police about the missing drone, the pilot prepares another drone to look for the missing one. However, shortly after takeoff, the controller again showed an error message and the pilot immediately landed it.
Analysis of the accident report cites signal interference with GPS as a cause for the malfunction of the fallen drone and the second is to look for it. It said the source of the interference was not identified.
The report also observed that serious injury or death could occur.
… analysis shows that a mass of more than 2 kg falling from the roof of a house can result in serious or even fatal injuries to people if they are hit. The aircraft’s mass, 12.8 kg, far exceeds this figure and it is therefore very likely that serious injury will occur even if the person hit is wearing a hard hat for protection.
Interest in aviation in the United States for years has opposed the FCC giving the Ligado Networks application. Despite this and official and strong opposition from the executive branch of government, the FCC approved Ligado’s request in April.
Speaking of this accident, Brian Haynes, head of corporate strategy at the commercial drone company Airo Drone LLC, voiced concerns that seemed to represent the industry as a whole.
“As a commercial drone operator, this is a clear example of why the FCC’s decision regarding Ligado Networks must be reconsidered. We expect this type of accident, and incidents to interfere with other services, to increase dramatically with Ligado interruptions – with potentially dangerous consequences. An upgraded receiver will be expensive, if even feasible in size / weight of the drone requirements; who will take the bill, if and when repairs are available? “
FCC approval of the Ligado Network application has not silenced the opposition. But has caused opposition to spread in many industries and sectors. Vocal opponents now include agricultural, maritime, vehicle and industrial interests.
Legislation is being considered in Congress that will cause the FCC’s decision to be reexamined and prevent the Department of Defense from doing business with any company that interferes with GPS signals. Some proposals will delay FCC approval.
Senator Jim Inhofe, R-Okla., Has promised to introduce a law that will continue to get FCC approval until Ligado modifies or replaces all equipment throughout the country so that operations will have an impact.
While the drone crash in the UK can be seen as a relatively minor event, as a sign of things to come, it is likely to have a large impact in the United States.
Dana A. Goward is president of the Tough Navigation and Timing Foundation.