Every year, the U.S. Air Force's 82nd Training Wing at Sheppard Air Force Base in Texas prepares thousands of airmen to become maintainers and munitions specialists, or to improve their skills, and it uses a number of non-flyable aircraft to help with those training courses. But one of its permanently grounded GA-10A Warthogs is also something of a unique historical article with a rarely seen muzzle device, nicknamed "the Tickler," on its 30mm GAU-8/A Avenger cannon, which operational units only ever used briefly decades ago. On Oct. 10, 2018, the 82nd's public affairs office posted otherwise unassuming pictures online of trainees from the 362nd Training Squadron using the GA-10 to practice conducting a landing gear function check. The add-on muzzle device it has was originally supposed to help mitigate the shock and blast of firing the massive gun and help deflect and disperse fumes that could choke out the aircraft's engines, but proved to be problematic in its own right.

We reached out to the Wing for more information about this particular Warthog and they confirmed that it is an instructional trainer airframe. At the time of writing, they had not yet been able to provide the plane's specific serial number or explain why it still has the muzzle device installed. The unit has received a number of grounded Warthogs over the years, including some of the earliest developmental examples. "The A-10 is one of the hardest planes to take down [for maintenance]," one of the 362nd's instructors said, according to a caption for one of the pictures. This is "because of all the back-up/emergency systems it has that the pilot can fall back on when worse comes to worst."

USAF A trainee assigned to the 362nd Training Squadron sits in the GA-10A with GFU-16/A at Sheppard Air Force Base.

Defense contractor Battelle developed the Tickler, also known more formally as the Gun Gas Diverter or the GFU-16/A, as another safety measure. During development of the Avenger cannon, which occurred in parallel with that of the A-10 itself, it quickly became apparent that without any sort of flash hider or muzzle brake on the end, the gun would blind the pilot during firing. Soot would also build up on the windshield, eventually blocking the pilot's view in general. On top of that, the gasses the weapon produced as a by-product of firing could end up getting sucked into either of the Warthog's two engines. These fumes contained no oxygen, which could starve the jets of air and cause them to stall, and might have unburnt gunpowder in them, which could cause even more serious problems. The A-10's manufacturer, Republic, and the Air Force spent considerable effort during the plane's developmental period and early service life searching for ways to solve these issues, which we at The War Zone have explored in detail in the past. Battelle's GFU-16/A was the last of these projects, with work related to the device continuing into the late 1980s. The muzzle brake has two sets of baffles inside intended to eliminate the flash from firing and help disperse the gun gasses before they exit the device. By all accounts, it was quite successful in performing both of these functions. The Air Force sent the GFU-16/As out to various A-10 units, which dutifully installed them on their aircraft.

USAF A close-up showing the rear of the GFU-16/A with its two sets of baffles.

Unfortunately, the devices also created new and problematic turbulence at the muzzle and magnified the gun's already severe vibration. This, in turn, led to severe cracking in portions of the forward fuselage, especially inside the gun bay, which became more apparent as time went on. "Although at this time this cracking is not believed to be a flight safety problem, it is a maintenance burden and could have an impact on the operational readiness of the A-10 force," one 1986 report explained. At that time, the Air Force had initiated a program to "find a solution to the A-10A gun bay fatigue problem by determining the source of the structural fatigue and applying and verifying airframe modifications to achieve the desired structural design life."

CORBIN H. VIA NETWORK54.COM A rare, but low-quality image of the Battelle Gun Gas Diverter installed on an operational A-10 in the 1980s.