A team from the Massachusetts Institute of Technology has developed a new onboard system that could protect commercial airplanes from lightning strikes, significantly reducing the risk of a plane being struck by lightning.  

Aviation experts estimate that every commercial airplane is struck by lightning at least once a year, with about 90 percent of the incidents likely triggered by the aircraft itself, requiring follow-up inspections and safety checks that could delay subsequent flights.

During a thunderstorm, a plane’s electrically conductive exterior acts as a lightning rod, sparking a strike that could potentially damage the plane’s outer structures and compromise its onboard electronics.

To avoid potentially dangerous lightning strikes, flights are usually rerouted around stormy regions.

However, when a plane flies through an ambient electric field, its external electrical state, normally in balance, shifts. As an external electric field polarizes the airplane, one end of the plane becomes more positively charged while the other end swings towards a negative charge.

As the plane becomes increasingly polarized, it can set off a highly conductive flow of plasma, called a positive leader—the preceding stage to a lightning strike.

However, the researchers believe that temporarily charging a plane to a negative level to dampen the more highly charged positive end could prevent it from reaching a critical level and initiating a lightning strike. The researchers achieved this by outfitting a plane with an automated control system consisting of sensors and actuators fitted with small power supplies.

The sensors monitor the surrounding electric field for signs of possible leader formation, while the actuators emit a current to charge the aircraft in the appropriate direction.

“We’re trying to make the aircraft as invisible to lightning as possible,” co-author Jaime Peraire, head of MIT’s Department of Aeronautics and Astronautics and the H.N. Slater Professor of Aeronautics and Astronautics, said in a statement. “Aside from this technological solution, we are working on modeling the physics behind the process.

“This is a field where there was little understanding, and this is really an attempt at creating some understanding of aircraft-triggered lightning strikes, from the ground up.”

Newer planes are partially made from nonmetallic composite structures like carbon fiber, which are more vulnerable to lightning-related damage.

“Modern aircraft are about 50 percent composites, which changes the picture very significantly,” assistant professor Carmen Guerra-Garcia said in a statement. “Lightning-related damage is very different, and repairs are much more costly for composite versus metallic aircraft. This is why research on lightning strikes is flourishing now.”

The researchers used a simple model of an aircraft-triggered lightning strike to determine whether charging the plane could reduce the risk of a lightning strike. As a plane flies through a thunderstorm or other electrically charged environment, the outside of the plane begins to be polarized, forming “leaders,” or channels of highly conductive plasma, flowing from opposite ends of the plane and eventually out toward oppositely charged regions of the atmosphere.

The team then used a mathematical model to describe the electric field conditions under which leaders would develop and how they would evolve to trigger a lightning strike.

They applied the model to a representative aircraft geometry and examined whether changing the aircraft’s potential would prevent the leaders from forming and triggering a lightning strike.

They found that averaging over field directions and intensities, the charged scenario required a 50 percent higher ambient electric field to initiate a leader, compared with an uncharged scenario.

“Numerically, one can see that if you could implement this charge strategy, you would have a significant reduction in the incidents of lightning strikes,” emeritus professor Manuel Martinez-Sanchez said in a statement. “There’s a big if: Can you implement it? And that’s where we’re working now.”

The researchers are now testing the feasibility of charging on a simple, metallic sphere and plan on carrying out experiments in more realistic environments, such as flying drones through a thunderstorm. The team also plans to increase the speed of the response time of the system.