Courtesy Photo | A chicken carcass launched at the Bird Impact Range at Arnold Air Force Base,...... read more read more
ARNOLD AIR FORCE BASE, Tenn. – Likely due to its peculiar purpose and unorthodox ammunition, its notoriety has waned little in the years since it was last fired.
The S-3 Bird Impact Range at Arnold Air Force Base, widely referred to as the “Chicken Gun,” remains a point of interest during base tours, has been the subject of numerous articles from outside media and is often a topic of discussion when Arnold is brought up in conversation.
The first fowl was launched from the Chicken Gun 50 years ago. Over the decades from this initial shot to its final blast, the facility was used to test windshield materials and full-scale canopies for various military and commercial aircraft and supported NASA in its effort to return to manned space flight.
Chicken carcasses were fired at the range to simulate in-flight bird strikes to test articles. These tests were done to research the damage caused by such strikes and to prevent harm to members of the aircrew.
Bird strikes have been an ever-present possibility since the first plane took to the skies. Over time, thousands of collisions between birds and aircraft have occurred, resulting in millions of dollars in damage, the complete loss of some aircraft and, in some instances, the loss of human life.
The hazards became much more prevalent when planes began flying lower and at greater speeds.
The catalyst for the development of a bird-impact test facility was the loss of F-111 Aardvark aircraft during the Vietnam War. These planes were equipped with terrain-following radar that allowed pilots to fly at high speeds only a few hundred feet off the ground. This mix of high speed and low altitudes resulted in many mid-air encounters between the aircraft and Southeast Asian avifauna.
In an effort to address the issue, Air Force officials tasked the Aeronautical Systems Division at Wright-Patterson Air Force Base, Ohio, with examining how to diminish the dangers associated with direct bird impacts.
The ASD leaned on the ballistic range expertise of personnel at Arnold and asked if Arnold team members could develop a bird strike test. Working together, they came up with the idea for the Chicken Gun.
The Bird Impact Range facility was built by Arnold engineers using scrap hardware, including an 8-inch Naval gun obtained previously. The barrel of the single-stage air gun they constructed was 60 feet long and contained a 10-cubic foot chamber that could be filled with pressurized air. Test articles were placed in an unenclosed outdoor shed downrange of the Chicken Gun.
Carcasses could be fired at speeds exceeding 700 mph.
The first shot from the Chicken Gun was fired in the fall of 1972 at an F-111 crew escape module.
To operate the gun, known to some as the “Rooster Booster,” a chicken carcass was placed into a balsa wood sabot which was then loaded into the barrel. Situated between the barrel and the air chamber was a thin plastic diaphragm. This diaphragm isolated the sabot from the high-pressure air until it was time to launch the chicken.
The firing of the Chicken Gun was achieved by rupturing the diaphragm, allowing air to enter the barrel and push the carcass-containing sabot down the launch tube toward the material or canopy to be tested. 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.
Engineers initially explored ways to take chicken off the menu, but experiments with water bags and other materials simulating birds were unreliable in delivering accurate data. Even the American Society for Testing and Materials standard permitted the use of imitation avian for bird impact testing. However, Randall Watt, then-project manager for the Arnold Bird Impact Test Facility, said in 1996 that there’s no substitute for the real thing, adding the Air Force typically required actual carcasses be used during testing.
“Again, the best thing to use to simulate a bird strike is a bird. And chickens are the easiest to come by,” Watt said. “The preference of most of the Special Program Offices is to simulate the event as close to reality as possible, using whole chicken carcasses.”
As Watt stated, chickens were selected as the bird carcass of choice for the facility due to the ease with which they could be accessed. Arnold AFB purchased Chicken Gun “ammo” - four-pound carcasses - from a local chicken farmer.
To obtain important information lost to the naked eye, high-speed motion picture cameras operating at thousands of frames per second captured the impacts of the simulated strikes. This visual data helped engineers better determine whether test articles could withstand the collisions.
Test engineers were not only interested in the integrity of test articles but also how well they deflected the hurtling carcasses. The force of a bird strike could cause a canopy to bend excessively rather than shatter, still posing a hazard to the pilot.
“Even if the windshield or canopy survives, if it hits the pilot in the head, he’s dead,” Watt said in 1996. “And sometimes the pilot’s head is within an inch or two of that bubble canopy.”
Climate was also taken into consideration during testing, as the properties of canopies and windshields will change depending on the weather conditions to which they are exposed. To simulate a scenario in which a plane sitting in the desert sun must quickly take to the air and just so happens to strike a bird as it’s taking off, test engineers heated the test area up to 200 degrees Fahrenheit. Conversely, the sudden takeoff scenario for aircraft in frigid areas was also studied. To accomplish this, a thermal enclosure was placed around the test area. Cooled gaseous nitrogen was then supplied, cooling the test area to several dozen degrees below zero.
Throughout its period of use, the Chicken Gun was fired well over 1,000 times. Manufacturers used data from the testing to redesign and build components better able to withstand bird strikes. Along with the F-111, canopies and other materials were tested on the majority of the Department of Defense’s aircraft inventory, including the A-7 Corsair II, A-10 Thunderbolt II, F-15 Eagle, F-16 Fighting Falcon, F/A-18 Hornet, T-6A Texan II, T-37 Tweet, B-1 Lancer and C-130 Hercules. Commercial aircraft tested included the Northrop Grumman Gulfstream V.
In addition to canopy and windshield samples, the Chicken Gun was used to test other materials, such as flat steel plates, to measure impact forces at various velocities and angles of attack. At least one test involved the use of an instrumented manikin to evaluate potential dangers to the crew of a high-performance aircraft fitted with a particular windscreen.
In 1996, the Chicken Gun was used to fire plastic spheres rather than chickens to simulate rocket tube cover debris that could possibly impact crew the cab of the U.S. Army High Mobility Artillery System vehicle following rocket launches. This marked the first time since the early 1970s that the range was used to fire anything other than chicken carcasses.
The last tests involving the Chicken Gun to date occurred in the early 2000s. The Chicken Gun was revamped to conduct testing for the NASA Space Shuttle Return to Flight program, initiated after the space shuttle Columbia disaster in February 2003. The gun was used to launch hundreds of block-shaped projectiles made of the insulating foam material used on the external tank of the space shuttle. 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.
Blocks were launched at various angles and velocities to help determine the effects of foam impacts, provide information on the ability of shuttle hardware to withstand the impacts and populate a database for future reference.
| Date Taken: | 10.27.2022 |
| Date Posted: | 10.27.2022 10:16 |
| Story ID: | 432104 |
| Location: | ARNOLD AIR FORCE BASE, TENNESSEE, US |
| Web Views: | 607 |
| Downloads: | 1 |
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