Car windshields smash drones like insects, up to a point.

Dan Carney

September 1, 2021

4 Min Read
AdobeStock_Drone Sign.jpeg
Adobe Stock

While drone strikes on aircraft are a high-profile hazard, the proliferation of autonomous helicopters increases the likelihood of collisions between them and cars. That’s why researchers at Virginia Tech have crash-tested a drone against a car windshield to learn what we can expect when this happens.

The testing was crucial to earning a Federal Aviation Administration waiver for drone flights over traffic, which was sought by State Farm insurance for the purpose of investigating claims.

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Virginia Tech’s lab is already known for its testing of helmets, toys, and cars, so it was a natural for State Farm to ask them to produce drone impact results that the FAA could use to decide whether to permit the insurance company to fly drones near traffic while adjusting claims. State Farm partnered with the Virginia Tech Mid-Atlantic Aviation Partnership (MAAP), which regularly collaborates with Virginia Tech’s acclaimed injury biomechanics researchers.

 The group is renowned for its experimental methods that precisely recreate real-world collisions. These techniques offer a realistic and, crucially, reproducible way to quantify the risk of various impacts and evaluate the efficacy of safety measures.

The FAA’s concern over drone flights near traffic is that a drone could hit the windshield of a moving vehicle and obscure the driver’s view through a broken windshield, or, even worse, injure the vehicle’s occupants.

Related:New IIHS side crash test wallops cars 82 percent harder

State Farm flies parachute-equipped DJI Mavic 2 Pro drones. In the event of a loss of power, the 2-lb. drone will float to earth beneath its ‘chute. This is when it could potentially blow into the path of a car.

DJI Mavic 2 Pro.jpeg

Without a waiver, the FAA would have required a drone operator who was assigned to inspect two houses across a busy street from each other to finish the first inspection, land, walk the drone across the street and start all over just a few feet away. The waiver allows the drone to fly from one house, across the street to the other one.

“State Farm claims inspections are the kind of operation where drones can offer huge advantages,” said Mark Blanks, MAAP’s director at the time of the testing. He has since left the program.  “What the FAA wants to see is a compelling, credible case that the operation is safe,” he explained.

“You need extensive data that are grounded in the context of how the operation will work in the real world,” Blanks continued. “There wasn’t any empirical information on what would happen during an impact between a drone and a car, so in order to craft a strong waiver application, we had to come up with research methods to obtain that information.”

Related:Want to Pinpoint Gas Leaks? Fly Surveillance With Tiny Drones

To do the crash test, the MAAP team mounted the drone to a pneumatic sled that was propelled down a linear track. In the end, the drone was pitched into a Toyota Camry windshield in a custom-built frame.

The test plan was to vary the impact speed with the expectation that increasing fast impacts would produce increasingly greater windshield damage. Surprisingly, the windshield showed no difference as impact speeds ratcheted up from 25 mph to 62.5 mph. The only result was smeared plastic and rubber from the drone as it slid up the glass.

But at 67 mph, the glass finally gave way, bowing inward, growing cracks, and throwing glass splinters onto the floor. This illustrated the critical threshold, above which drone impacts on car windshields become hazardous, informing the FAA’s decision to permit drone flight over traffic only on neighborhood streets where the speed limit is typically 25 mph or 35 mph. At those speeds, even a drone flying at its top speed of about 23 mph can’t produce an impact severe enough to damage a car’s windshield.

“If you're dedicated to thoroughly understanding and mitigating risk in their operations, having direct, quantitative data about the consequences of an impact is going to remain relevant,” Blanks said. “The fundamental principles and test methods have provided insight for standards development and rulemaking, and they’ll continue to be part of the foundation of safety that’s going to be crucial to this industry as it matures.”

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