Why the Air Force uses a ‘chicken gun’ to launch bird carcasses at its own aircraft
“The best thing to use to simulate a bird strike is a bird. And chickens are the easiest to come by.”
Thanksgiving is just around the corner, but before you sit down to enjoy a freshly-cooked turkey, picture this: a chicken carcass flying out of an eight-inch naval gun at more than 700 miles per hour and into a glass canopy like the ones found on fighter jets. As strange as the image seems, it played out more than 1,000 times at Arnold Air Force Base, Tennessee, home of the S-3 Bird Impact Range, better known as the ‘chicken gun.’
First fired 50 years ago this fall, the chicken gun at Arnold has been used to test glass canopies, windshields and other materials for some of the most famous U.S. military aircraft, including the A-10 attack jet, the C-130 transport plane, and the F-15, F-16 and F/A-18 fighter jets, according to a recent Arnold Air Force Base press release celebrating the gun’s 50th birthday.
While it may seem ridiculous that the military launches dead chickens at its aircraft, it is for a very good reason: bird strikes are some of the most dangerous threats to even the military’s most sophisticated flying machines. At best, bird strikes can cause thousands or millions of dollars worth of damage to planes, which must then sit on the sidelines as they await repair. At worst, a bird strike can cause catastrophic damage that destroys the plane and kills its crew, as a flock of Canada geese did in 1995 when it collided with an E-3 Sentry aircraft just after take-off, killing all 24 crew members on board.
As the E-3 accident proved, bird strikes on jet engines can be particularly dangerous, “like throwing a rock into the engine,” as one airman said in 2009. But bird strikes against an aircraft’s glass canopy or windscreens can also kill or injure aircrew from impact, debris or cabin decompression. Force is calculated by mass and acceleration, so even a small bird can cause catastrophic damage at the breakneck speeds of a jet aircraft.
While the problem of bird strikes is not new to aircraft (aviation pioneer Orville Wright hit one as early as 1905), it became a more pressing issue for the Air Force during the Vietnam War, where the branch flew the F-111 Aardvark. The F-111 had been designed to fly very low to the ground at very high speeds while carrying nuclear weapons behind enemy lines, but in Vietnam the jet took on a strike role for hitting targets with conventional weapons. The problem was that the high speed and low altitude “resulted in many mid-air encounters between the aircraft and Southeast Asian avifauna,” Arnold Air Force Base wrote in its press release.
The Air Force wanted to mitigate the damage caused by bird strikes, but simulating a bird hitting an aircraft at high speed in a controlled environment is a tough challenge. The Aeronautical Systems Division at Wright-Patterson Air Force Base Ohio teamed up with ballistic range experts at Arnold to build a chicken gun from scratch, including an 8-inch naval gun that Arnold Air Force Base happened to have on hand, the press release explained.
The chicken gun’s 60-foot barrel had a 10-cubic foot chamber at one end that could be filled with pressurized air, the press release said. The chicken carcass would then be loaded into a type of wooden case called a sabot, which was then loaded into the barrel. Separating the barrel from the pressurized air chamber was a thin plastic diaphragm. When it was time to launch the chicken, the diaphragm would be ruptured, letting air enter the barrel and push the sabot down and out the other end.
“A tapered and threaded section stripped the sabot away, stopping it and then allowing the bird within to continue its flight toward the test target,” the press release said.
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The chicken gun at Arnold, also known as the Rooster Booster, was not the first in the world. A similar device developed in the early 1940s by the Civil Aeronautics Administration (precursor to the Federal Aviation Administration) in Pittsburgh, Pennsylvania could launch 17-pound carcasses as fast as 400 miles per hour, Flying Magazine reported in 1943. But the Arnold facility was a step up in terms of speed, and it helped American aircraft designers make major gains in the decades since it was first fired at an F-111 crew escape module in the fall of 1972.
When the chicken carcass hit the test subject, high-speed cameras capturing thousands of frames per second helped engineers analyze the mayhem and design stronger materials. But preventing canopies and windshields from breaking was only part of the battle: engineers also had to prevent them from bending inwards, too.
“Even if the windshield or canopy survives, if it hits the pilot in the head, he’s dead,” Randall Watt, then-project manager for the Arnold Bird Impact Test Facility, said in 1996, according to the press release. “And sometimes the pilot’s head is within an inch or two of that bubble canopy.”
Luckily, the chicken gun testing facility is nothing if not thorough. The press release described how engineers heated the test area up to 200 degrees Fahrenheit and down to several dozen degrees below zero in order to analyze how the test materials respond to large changes in climate. But one thing that stayed largely constant was the chickens. According to the press release, four-pound chicken carcasses were the projectile of choice “due to the ease with which they could be accessed,” a.k.a, from a local chicken farm. These were not just the plucked chickens you see in the grocery store either, these were whole carcasses, feathers and all.
Test engineers have tried using other types of ammo, like fake birds, but nothing simulates a dead bird colliding with a canopy as realistically as an actual dead bird.
“The best thing to use to simulate a bird strike is a bird,” Watt said in 1996. “And chickens are the easiest to come by.”
Though chickens are good for testing bird impacts on glass canopies and other aircraft surfaces, like flat steel plates, they are not the only projectiles a chicken gun can fire. The press release described how the gun fired plastic spheres in 1996 “to simulate rocket tube cover debris that could possibly impact crew [in] the cab of the U.S. Army High Mobility Artillery System vehicle following rocket launches.” After the space shuttle Columbia disintegrated upon reentering the atmosphere in 2003, the gun was also used to launch hundreds of blocks made of the insulating foam material used on the space shuttle’s exterior so that future shuttle missions would be less vulnerable.
“These shots simulated pieces of the external tank foam breaking away from the tank during flight, as happened to Columbia, and striking various parts of the shuttle, such as the solid rocket boosters,” the press release said.
Though the press release did not provide an exact date as to when the chicken gun at Arnold fired its last shot, chicken guns in general are still used to test out parts of aircraft. One video from 2009 shows a four-pound bird carcass being launched at an F-35 canopy at about 552 miles an hour at a Lockheed Martin test facility.
“As a fighter pilot who flies this aircraft I can say that it’s definitely comforting that the canopy can survive an impact like this,” said Air Force F-35 pilot Maj. Justin ‘Hasard’ Lee in a 2021 YouTube video about the test.
One chicken gun in Canada has started working on a new threat facing aircraft: drones. Just as they would with chickens, test engineers at the National Research Council of Canada’s Super Cannon “fired drones at aircraft windshields, tail surfaces and wing leading edges at speeds up to 250 knots, or close to 290 mph,” CNN reported last year. Like birds, drones can also get too close to airfields and endanger aircraft.
While technology like the chicken gun helps limit the damage caused by bird strikes, the Air Force also tries to prevent birds from hitting planes in the first place. A separate press release published this week by Aviano Air Base, Italy, described how flight safety managers use a wide array of techniques to keep wildlife away as part of the Air Force’s Bird/Wildlife Aircraft Strike Hazard (BASH) program. The techniques include keeping the grass between seven and 14 inches long to deter nesting, moving large bushes or trees and patrolling the area to find problem areas or relocate overly-curious wildlife.
“We do perimeter checks around the base fence line, making sure wildlife isn’t burrowing
beneath,” said one flight safety manager, Master Sgt. Miguel Gibson. “As well as keeping an eye on the sky.”
The airmen also use noise makers that “emit directional chirps so BASH can guide the bird to a safer location,” the press release said. The flightline also sports air cannons operated from the air traffic controller that can “swivel and shoot small bursts of air that help us clear the flightline before take-offs,” said another flight safety manager, Master Sgt. William Telschow.
When those tools do not work, local Italian wildlife experts come onto the base to help get the bird or other wildlife to a safe area, which is particularly important when an endangered species is involved. Joint Base Andrews in Maryland at one point had a border collie named Bree for chasing away birds and other wildlife.
Birds are not the only flightline intruders: deer, coyote, and wild pigs can also interrupt aircraft operations, according to a 2009 Air Force press release. Just this April, aviators at Naval Air Station Key West, Florida had to shift to a different runway after a crocodile started basking in the sun on one of its runways and did not feel like getting up again until it was wrangled off by Florida Fish and Wildlife Conservation experts.
Though efforts like crocodile wrangling, border collies and chicken guns sound like tedious projects, they are much more desirable than the alternative, which is expensive at best and fatal at worst.
“Bird strikes don’t just take an aircraft out of flight for a few days,” said Telschow. “It’s a ripple effect, our job is the prevention of man hours lost and workload increased.”
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