The U.S. Air Force denies its Thunderbirds went supersonic while practicing for the Chicago Air and Water Show on Friday, despite two blasts heard across the North Side that possibly shattered several windows in Lake View.
But videos of the F-16 jets show an obvious sonic boom, according to one aeronautics professor.
“Those were clearly sonic booms,” Matthew Clarke, assistant professor at the University of Illinois Urbana-Champaign’s Grainger College of Engineering, told the Sun-Times.
It is possible that part of a plane, and not the whole aircraft, exceeded the speed of sound to create shock waves that can be perceived as booms, Clarke said. This is possible when lift is created by air going over the wing, Clarke said.
“Even though the global flow may not be faster than the speed of sound, there are places locally faster than the speed of sound, creating shock waves,” he said. “While I can’t say that the whole plane went supersonic, I can say — from the video — shock waves [were created] from parts of the aircraft.”
The U.S. Air Force released a statement late Friday saying “a review of the practice determined the Thunderbird jets did not go supersonic at any point during the demonstration.” An Air Force spokeswoman did not immediately have a comment Monday when asked if it was possible that only part of the aircraft had gone supersonic.
On Friday, Lake View residents described the booms to the Sun-Times as an “earthquake,” “a massive jolt” and “kinda scary.”
The phenomenon has happened before with the Thunderbirds’ counterpart at the U.S. Navy: The Blue Angels.
In 2021, a Blue Angel pilot caused more than $180,000 in damage during a practice run after veering off course and passing within 100 feet of buildings while nearing the speed of sound at the Naval Air Facility El Centro in California, according to The Seattle Times.
A Navy investigative report found the F-18 Super Hornet unleashed a “noticeably larger localized sonic airflow signature,” in part because of the placement of a rear-facing camera that increased the planes sonic pressure wave beyond Mach 1, even when the pilot’s controls said the plane was flying slower. The blast injured a dozen people.
The Blue Angels, which sometimes perform at the Chicago Air and Water Show, even have a warning on its online FAQ page: “On occasion, spectators may have mistaken the sound of engines at a high-power setting approaching the speed of sound for a sonic boom.”
Ald. Bennett Lawson (44th) said residents have told him the boom was louder than any they had ever heard at an air show. He said the window damage was primarily confined to the first floors of four residential high-rises along the lakefront: 3180, 3600 and 3950 North Lake Shore Drive and 4200 N. Marine Drive.
Lawson said he has advised residents and managers of those buildings to file a claim with the city because the Air and Water Show was a “city-sponsored” event.
“My understanding is the Air Force released a statement like they didn’t do anything differently than before, but those buildings pre-date the air show and never had this problem ever before. So I don’t think the buildings should be required to pay for it. And they shouldn’t have to go through insurance first when it was something that the city sponsored and the performers created,” Lawson said.
Since the shattered windows were confined to lobbies in the four buildings, damage estimates are not expected to be too costly.
@rsavillo13 My eardrums are still recovering after this #chicago #airandwatershow #foryou #fyp ♬ original sound – Raemon Savillo
The city’s Office of Emergency Management and Communication did not immediately respond to a request for comment. OEMC has told Lawson’s office that it was “looking into” the window-shattering incident.
The Department of Public Health has not responded to Lawson’s calls.
Lawson also said inspectors responsible for enforcing the city’s noise regulations still “haven’t migrated over” from the Health Department to the newly resurrected Department of Environment.
He said no city ordinance does a good job of enforcing noise restrictions. “I don’t know that anyone does noise very well in this city,” he said.
The Federal Aviation Administration on Monday referred questions to the Air Force.
Lake View resident Ari Barjesteh captured both blasts on video and said he believed the jets went supersonic. Barjesteh uploaded the videos to TikTok, and they have garnered thousands of views since Friday.
“In the comments, it’s like a 50-50 split between people who say it was or wasn’t a sonic boom. I truly believe it. Both of them were sonic booms. Like, they’re very distinct, they sounded like bombs going off,” he said. “Jets are loud, but they don’t normally sound like a bomb went off. It shook windows and shook the building, and you heard the car alarms go off up and down Lake Shore Drive.”
In 2012, the Thunderbirds accidentally went supersonic during practice at Davis-Monthan Air Force Base, southeast of downtown Tucson, Arizona, according to Tucson News Now. In that case, the Air Force accepted responsibility for the sonic boom and set up a claim center, eventually paying more than $22,000 for damage. The Air Force said the pilot went supersonic for 9 seconds while turning.
In 1988, two F-4 Phantom fighter jets with the Indiana National Guard went supersonic over downstate Kankakee, causing a boom that could be heard on the South Side of Chicago.