The A-10 Warthog owes its distinctive noise to its GAU-8/A Avenger cannon. Supersonic speed, rate of fire, acoustics: here’s the explanation for the BRRRRT.
The close air support aircraft and its mission
The Fairchild Republic A-10 Thunderbolt II was designed for close air support. It flies slowly, stays in the air for long periods of time, and can withstand damage. Its two TF34 turbojet engines each deliver 40.3 kN of thrust (9,065 lbf), allowing it to take off from rough runways and maneuver at low altitudes while protecting the pilot with a titanium “tub”. In this context, the BRRRRT’s place in the A-10’s reputation is no mere anecdote: the sound has become the audible signature of a specific tactical function, striking quickly and accurately close to friendly troops. The A-10 Warthog remains the archetype of an aircraft designed around a dedicated weapon technology: the A-10’s GAU-8 Avenger cannon.
The heart of the system: a unique rotary cannon
At the center of the aircraft is the GAU-8/A Avenger, a 7-barrel rotary Gatling cannon with 30×173 mm rounds. The complete system, with its drum and linkless feed, weighs approximately 1,828 kg (4,029 lb) and is approximately 5.93 m (19 ft 5.5 in) long. The drum can hold 1,174 rounds (typical load 1,150). The rate of fire has been stabilized at around 3,900 rounds/min (or 65 rounds/s). At this speed, a 1-second burst fires ≈ 65 projectiles; a 2-second burst fires ≈ 130. To prevent overheating and maintain accuracy, firing doctrines favor short bursts.
The velocity of the A-10’s projectiles is decisive: a PGU-14/B armor-piercing shell leaves the muzzle at ≈ 1,010 m/s (3,324 ft/s). The typical dispersion is 5 mils (80%), which corresponds to a circle of approximately 12 m (40 ft) at 1,200 m (4,000 ft). The effectiveness of the A-10’s gun is based on superior ballistics and a projectile mass of ≈ 395 g, much higher than a conventional 20 mm gun. In terms of ammunition, the US Air Force has historically used a mix of PGU-14/B AP-I (depleted uranium core) and PGU-13/B HEI, a combination optimized against armor and hard targets.
Key points to remember: 3,900 rounds/min, ≈ 65 shells/s, ≈ 1,010 m/s at the muzzle, 1,174 rounds carried. These parameters define the firepower of the A-10… and set the stage for the sound of the A-10’s gunfire, which has become legendary.
Mounting, recoil, and trajectory
The role of the A-10’s rotary cannon requires a specific mounting. The GAU-8 is offset slightly to port, but the active gun passes over the longitudinal axis at the moment of firing. This positioning centers the average recoil of approximately 44.5 kN (10,000 lbf), avoiding yaw or pitch torque that could open the dispersion cone. The nose gear is offset to starboard to make room for the drum.
The recoil is massive but manageable: when level, a short burst only slows the aircraft by a few knots, the main effect being a characteristic vibration. Another known constraint is that the oxygen-poor exhaust gases can disrupt the flow over the air intakes. Initial tests had shown a risk of flameout, so the USAF installed automatic igniters and exhaust gas management procedures. These elements explain some of the flight path details and… indirectly contribute to the sound signature of the A-10 Warthog.
The famous “BRRRRT”: what your ears hear
The characteristic noise of the A-10 is not just a “sewing machine.” It is a mix of acoustic phenomena:
- Supersonic shock waves: each 30 mm projectile is supersonic when it leaves the muzzle. It generates a Mach cone that produces a sharp ” crack“ that can be heard as soon as the projectile passes close to the observer. Multiply this ”crack” by 65 per second and you get a continuous texture that contributes greatly to the A-10’s nickname, BRRRRT.
- The bullet velocity/speed of sound ratio: for an observer on the ground, the impacts and/or the “crack” as it passes can be heard before the muzzle blast. At 1,000 m from the point of impact, a shell traveling at 1,010 m/s arrives in ≈ 1.0 s, while the sound of the cannon takes ≈ 2.9 s to travel the same distance (speed of sound ≈ 343 m/s). This explains the double sound: first the claps/impacts, then the low hum from the aircraft.
- **The rate and filtering of the environment: *65 shots/s* give a fundamental frequency of 65 Hz around which harmonics (mechanical, aerodynamic, echoes from the ground) pile up. The result is this low, continuous hum, perceived as a BRRRRT.
- The “start-up” of the cannon: at the very beginning of the burst, the cannon block accelerates in a few tenths of a second. This transient adds a glissando at the start, often audible on videos.
- Echoes and topography: valleys, buildings, and hills reverberate the sound and thicken it, giving more “body” to the sound of the A-10 firing.
It is the combination of these mechanisms (ballistics, rate of fire, acoustics) that explains the unique sound of the A-10.
The physics behind the BRRRRT: simple and useful figures
A few orders of magnitude help to understand the explanation for the BRRRRT sound of the A-10:
- Flight time: at 1,200 m (4,000 ft, effective design range), a projectile traveling at 1,010 m/s takes ≈ 1.19 s.
- Sound propagation: the muzzle report of the gun takes ≈ 3.5 s to travel 1,200 m.
- Perceived delay: observers close to the target first hear cracks/impacts, then the buzz of the gun with a ≈ 2–2.5 s delay.
- Rate of fire: 3,900 rounds/min, or 65 Hz; this is in the low frequency range of the human hearing spectrum, hence the “buzzing” sensation.
- Burst: 1 s ≈ 65 rounds, 2 s ≈ 130 rounds; firing 1,150 rounds would require ≈ 18 s of continuous fire, which is rare in practice.
These values structure the sound signature of the A-10 Warthog and explain why, even from a distance, the ear can distinguish a recurring pattern.
Design at the service of the mission
When it comes to modernizing the US fighter fleet, the debate often pits specialized aircraft against multi-role aircraft. The role of the A-10 in the US Air Force has been built on a weapon adapted to CAS missions: precision, endurance, and resilience. The GAU-8 Avenger on the A-10 fires 30 mm high-energy ammunition that is stable in flight and has low dispersion. This results in a loud sound signature and immediate effects on the ground, which are particularly clear to the troops being supported.
The reason for the A-10’s unique noise is therefore as much to do with physics (supersonic + rate of fire) as with doctrinal choice: accepting a heavy cannon to achieve a superior terminal effect at short and medium ranges. This logic is as understandable as it is obvious.
Operational impact and acoustic limitations
In heavily defended environments, the A-10 Warthog must deal with ground-to-air threats. The characteristic noise of the A-10 is not a tactical handicap in itself: at the distance where it is audible, the aircraft has already fired, and its shells have reached the target area. On the other hand, penetrating a contested space requires altitude, heading, timing, and combined use (missiles, guided bombs, observation drones). The BRRRRT remains emblematic, but it is only one component of a larger weapons system.
On a technical level, the USAF has solved muzzle flash problems through automatic ignition during firing, speed/attitude guidelines, and maintenance of the gun system. The reason for these adaptations is simple: to preserve the effectiveness of the A-10’s gun while ensuring engine safety.
The place of sound in aviation history
The A-10’s nickname, BRRRRT, has become a cultural marker. In American military history, few weapons have such an immediately recognizable sound identity. Beyond the image, this sound remains an auditory shorthand for a technical reality: a stream of supersonic projectiles fired at 65 per second, guided by close air support avionics, to deliver immediate and measurable effects. This is another reason why the sound signature of the A-10 Warthog continues to fascinate both the general public and professionals alike.
One last listen, for a better understanding
The next time you hear that BRRRRT, break it down: a “crack” from nearby shock waves, a rumble from the aircraft a few seconds later, and, in between, the cadence that ties it all together. You will then have, in your ears, the best explanation of the BRRRRT sound of the A-10.
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