Since the rise of UAV, there has been many questions about the dangers posed to aircraft. The recent incident of a drone striking a King Air 100’s wing in Canada has increased interest in further understanding the extent of that danger. Enter FAA’s Center of Excellence for UAS Research Alliance for System Safety of UAS through Research Excellence (ASSURE).
ASSURE and the FAA have released a report titled, “The sUAS Air-to-Air Collision Severity Evaluation Final Report.” The team utilized research from Mississippi State University, Montana State University, Ohio State University and Wichita State University to study impact scenarios between drones and planes (in this case, jets).
“While the effects of bird impacts on airplanes are well documented, little is known about the effects of more rigid and higher mass [small UAS] on aircraft structures and propulsion systems,” said Mississippi State University’s Marty Rogers, the director of ASSURE. “The results of this work are critical to the safety of commercial air travel here in the United States and around the world.”
According to ASSURE, small quadcopters and light fixed-wing drones were chosen for the study since they are the mostly-likely threats to fixed-wing aircraft.
ASSURE made the discovery through collision simulations that small drones inflict more damage on an aircraft than collisions with birds. While the structural components of OEMS did a good job withstanding bird strikes, they were not up to par when it came to withstanding drone strikes. This was mostly due to drones being more condensed and stiffer due to hardware components.
“Therefore, bird-strike certification regulations are not appropriate for unmanned aircraft,” ASSURE said. “Additionally, regulators do not require and manufacturers do not design commercial and business aircraft to withstand collisions from other aircraft.”
If that wasn’t bad enough, ASSURE also noted lithium batteries contained with drones can increase fire risk upon collision. However, at typical high speeds, the battery completely destructs and cancels any risk of battery fire due to a shorted battery.
The collision simulations were performed on the fan section of an existing business-jet-sized, turbofan-engine model that the FAA previously used for fan blade-out testing.
“Conducting this study through full-scale physical tests would not have been possible from a cost and time perspective due to the immense complexity of the task. On the other hand, simulation enabled us to study over 180 impact scenarios in a 12-month period,” said Gerardo Olivares, director of crash dynamics and computational mechanics laboratories at Wichita State University. “To ensure results accurately predict the actual physical behavior of collisions, we have spent a lot of time developing, verifying, and validating detailed models of manned and unmanned aircraft. Once the models are validated, we can use them in the future to investigate other impact scenarios.”
ASSURE has hopes the drone industry will develop detect-and-avoid technology to make collisions far more rare. Continued studies will run through 2021 including one targeted toward turbo-props such as the King Air. A full version of the report can be found here.