Last week, a research team from the Alliance for System Safety of UAS through Research Excellence (ASSURE) released a report concluding that drone collisions with large manned aircraft can cause more structural damage than birds of the same weight for a given impact speed.

The FAA will use the research results to help develop operational and collision risk mitigation requirements for drones. ASSURE conducted its research with two different types of drones on two types of aircraft through computer modeling and physical validation testing.

Kiran D’Souza, assistant professor of mechanical and aerospace engineering at Ohio State, led the engine ingestion portion of the first-of-its-kind study.

“Even small unmanned aircraft systems can do significant damage to engines,” D’Souza said.

Reports of close calls between drones and airliners have surged. The FAA gets more than 100 sightings a month of drones posing potential risks to planes, such as operating too close to airports. The FAA estimates that 2.3 million drones will be bought for recreational use this year, and the number is expected to rise in coming years.

Unlike the soft mass and tissue of birds, drones typically are made of more rigid materials. The testing showed that the stiffest components of the drone — such as the motor, battery and payload — can cause the most damage to the aircraft body and engine.

Led by Gerardo Olivares, director of Wichita State University’s National Institute for Aviation Research, the team evaluated the potential impacts of drones weighing 2.7 to 8 pounds on a single-aisle commercial transport jet and a business jet.

They examined collisions with the wing leading edge, the windshield, and the vertical and horizontal stabilizers. The windshields generally sustained the least damage and the horizontal stabilizers suffered the most serious damage. The severity levels ranged from no damage to failure of the primary structure and penetration of the drone into the airframe.

An expert in gas turbine dynamics, Ohio State’s D’Souza conducted computer simulations to evaluate the potential damage of a drone entering a generic mid-sized business jet engine, including damage to fan blades, the nacelle and the nosecone.

The simulations revealed that the greatest damage and risk occurs during takeoff, since the fan is operating at the highest speed at this phase of flight. The location of the drone’s contact on the fan is a key parameter, with the most damage occurring when the impact is near the blade tip.

According to D’Souza, the next step is the development of a representative commercial jet engine model for ingestion simulations, as well as full-scale testing to verify and validate the simulations. The team is planning additional research on engine ingestion in collaboration with engine manufacturers, as well as additional airborne collision studies with helicopters and general aviation aircraft.

The researchers concluded that drone manufacturers should adopt “detect and avoid” or “geo-fencing” capabilities to reduce the probability of collisions with other aircraft.

The findings are important because of mistakes made in what traffic engineers call the “dilemma zone” — the area in which a driver isn’t sure whether to stop or keep going when the light turns yellow.

A traffic signal countdown timer, or TSCT, is a clock that digitally displays the time remaining for the current stoplight indication — i.e., red, yellow or green.

Widely adopted by roughly two dozen countries around the world, traffic signal countdown timers are not used in the U.S. Crosswalk timers for pedestrians are allowed, but TSCTs are prohibited by the Department of Transportation.

“When you introduce inconsistencies — sometimes you give drivers certain information, sometimes you don’t — that has the potential to cause confusion,” said David Hurwitz, transportation engineering researcher in OSU’s College of Engineering and corresponding author on the study.

There were more than 37,000 traffic fatalities in the United States in 2016. Around 20 percent of those occurred at intersections, he said.

It’s not known exactly how many U.S. intersections are signalized because no agency does a comprehensive count, but the National Transportation Operations Coalition estimates the number to be greater than 300,000.

A significant percentage of those feature fixed-time signals, which are recommended in areas with low vehicle speed and heavy pedestrian traffic.

Traffic signal countdown timers work well at fixed-time signals, Hurwitz said, but they may not be practical for actuated signals; at those intersections, he said, a light typically changes only one to four seconds after the decision to change it is made — not enough time for a countdown timer to be of value.

In this study, which used a green signal countdown timer, or GSCT, in Oregon State’s driving simulator, the clock counted down the final 10 seconds of a green indication.

A subject pool of 55 drivers ranging in age from 19 to 73 produced a data set of 1,100 intersection interactions, half of which involved a GSCT. The presence of the countdown timer increased the probability that a driver in the dilemma zone would stop by an average of just over 13 percent and decreased deceleration rates by an average of 1.50 feet per second.

“These results suggest that the information provided to drivers by GSCTs may contribute to improved intersection safety in the U.S.,” Hurwitz said. “When looking at driver response, deceleration rates were more gentle when presented with the countdown timers, and we did not find that drivers accelerated to try to beat the light — those are positives for safety. Drivers were significantly more likely to slow down and stop when caught in the dilemma zone. The results in the lab were really consistent and statistically convincing.”

The findings, published recently in Transportation Research Part F: Traffic Psychology and Behaviour, build on a 2016 paper in Transportation Research Part C: Emerging Technologies.

The earlier results, which arose from a related research project, showed drivers were more ready to go when the light turned green at intersections with a red signal countdown timer, which indicates how much time remains until the light goes from red to green. The first vehicle in line got moving an average of 0.82 seconds more quickly in the presence of a timer, suggesting an intersection efficiency improvement thanks to reduction in time lost to startups.

The papers comprised dissertation work by then Ph.D. student Mohammad Islam, who now works for a Beaverton, Oregon-based company, Traffic Technology Services. Amy Wyman, an OSU Honors College undergraduate who completed her degree in 2017, collaborated on the publication.

TTS, whose chief executive officer, Thomas Bauer, is also an OSU College of Engineering alumnus, has developed a cloud-computer-connected countdown timer for the automotive industry.

Several cars in the German luxury carmaker Audi’s 2017 lineup already feature the timer, which can be viewed both on the instrument panel and via a heads-up display. The system is currently operational in several U.S. cities including Portland.

Unlike the traffic-signal-mounted timers, the onboard clocks are allowed in the U.S.

With a drone, things like letters, medicine, first-aid supplies and food can be delivered quickly, cheaply and autonomously without having to worry about traffic, blocked roads or a lack of roads. Some companies will surely come to rely on these drones. And engineers will be called on to develop ever more sophisticated models to keep pace with this new facet of e-commerce.

The drone, which has been designed in EPFL’s Laboratory of Intelligent Systems with funding of NCCR Robotics, is equipped with several innovations that make it particularly safe, autonomous and easy to transport.

The unique idea here is that the drone becomes the package that wraps around the cargo before flight, just like a mail package. The foldable carbon-fiber cage protects the drone and the cargo in case of a collision or fall. What’s more, the recipient can catch the drone mid-flight without being injured by the propellers, which are located within the structure and have a safety system so that they stop when the cage is opened.

The origami-inspired design means that the frame can be folded and unfolded in a single movement. It can be flattened in just a few seconds, reducing the drone’s volume by 92% so that it can easily be slipped inside a backpack.

An accurate, self-flying drone

The drone — a multicopter with four propellers — can take off and land vertically, which enhances its accuracy. And it can carry a package weighing up to 500 grams over a distance of 2 kilometers.

The drone contains specially designed self-flying software to program the delivery. A flight plan is created to ensure it avoids obstacles such as trees and buildings. The drone can then be tracked in real time on a tablet or smartphone. And once the package has been delivered, the drone makes its way back on its own. The device also has a safety system to prevent it from being hacked.

“This project is a work in progress — in addition to strengthening its ability to detect and avoid objects, we are exploring possibilities to increase the drone’s payload capacity and enhance its autonomy, “says Przemyslaw Kornatowski, who developed the drone. “Throughout the summer, we tested our human-friendly, drone-delivery system on the EPFL campus, delivering items to people over 150 test flights.” The drone will also have a parachute to increase its safety in the event of a breakdown.