The Fairchild AT‑21 Gunner was conceived during World War II as a specialised bomber‑crew gunnery trainer for the United States Army Air Forces (USAAF).
Early war experience highlighted the need for dedicated training in power‑turret operation, flexible gun mounts, crew coordination, and defensive procedures, prompting the U.S. Army Air Corps to issue a specification for a purpose‑built aircraft.
AT-21
Fairchild was contracted to produce two prototypes:
XAT‑13 – powered by two 450 hp Pratt & Whitney R‑1340‑AN‑1 radial engines, designed as a “scaled‑down bomber” with a glazed nose gun, dorsal turret, and tricycle landing gear.
XAT‑14 – similar layout but powered by two 520 hp Ranger V‑770 inverted V‑12 inline engines; first flew in late 1942.
Both prototypes used Duramold plastic‑bonded plywood, a non‑strategic material chosen to conserve aluminium.
A bombardier‑training derivative, XAT‑14A, removed the nose gun and turret and added a bombsight and glass observation floor.
After testing, the USAAF selected the inline‑powered XAT‑14 configuration for production as the AT‑21 Gunner, optimised for gunnery training.
AT-21
Design and Construction
Airframe and Layout
The AT‑21 was a twin‑engine, mid‑wing monoplane with:
Deep oval‑section fuselage
Twin fins and rudders
Retractable tricycle landing gear
Duramold plywood construction (prototypes and structural elements)
Its design intentionally replicated the internal workflow of a bomber crew.
The aircraft carried five personnel: pilot, co‑pilot/gunnery instructor, and three student gunners.
XAT-21
Crew Training Features
The AT‑21 incorporated:
A glazed nose position with a flexible .30‑calibre machine gun
A dorsal power turret with twin .30‑calibre guns
Internal stations for communication drills and coordinated firing sequences
This allowed students to practice turret operation, flexible gunnery, and crew coordination without using front‑line bombers or expending scarce ammunition.
XAT-21
Powerplant and Performance
The production AT‑21 was powered by two Ranger V‑770 liquid‑cooled inline engines, each producing 520 hp.
XAT-21
Representative Performance (AT‑21)
Maximum speed: ~225 mph
Service ceiling: ~22,150 ft
Range: ~910 miles
Crew: 5
Armament:
One .30‑calibre nosegun
Two .30‑calibre guns in dorsal turret
These performance figures made the aircraft adequate for training flights but marginal for advanced pilot instruction or single‑engine operation.
Variants
XAT‑13 (Prototype)
Twin Pratt & Whitney R‑1340 radial engines (450 hp each)
Nose gun + dorsal turret
Tricycle landing gear
AT-21
XAT‑14 (Prototype)
Twin Ranger V‑770 inline engines (520 hp each)
Similar armament and layout to XAT‑13
First flight: late 1942
AT-21
XAT‑14A (Prototype Variant)
Bombardier‑training configuration
Removed turret and nose gun.
Added bomb sight, autopilot, and glass observation floor.
AT-21
AT‑21 Gunner (Production Model)
Selected inline‑engine configuration
Crew of five
Built for gunnery training
AT-21
AT‑21‑BL and Other Sub‑Variants
Production was distributed among multiple manufacturers:
Fairchild (Hagerstown + Burlington): 107 aircraft
Bellanca (New Castle, Delaware): 39 aircraft (AT‑21‑BL)
McDonnell (St Louis): 30 aircraft
Total production: 175 aircraft (1943–1944)
AT-21
Operational History and WWII Context
Training Role (1943–1944)
The AT‑21 entered service in mid‑1943, assigned to USAAF gunnery schools such as Tyndall Field, Florida
Laredo Army Airfield, Texas
It was intended to replace ad‑hoc training using modified bombers by providing a standardised, economical platform for turret and flexible‑gun instruction.
AT-21
Operational Problems
Despite its specialised design, the AT‑21 proved unsuitable for its intended role due to:
Severe vibration and oscillation
Yaw instability caused by short rudder moment arm and gull‑wing geometry
Poor single‑engine performance
Landing gear failures
These issues made the aircraft difficult to fly and unreliable as a trainer.
Attempts to repurpose it as an advanced pilot trainer also failed for similar reasons.
AT-21
Withdrawal and Secondary Use
The AT‑21 was withdrawn from service in 1944, replaced by actual bombers adapted for training.
Many surplus aircraft were converted into target‑towing platforms, extending their utility but ending their role in crew training. Surviving Aircraft
Only a few AT‑21s survived postwar.
One known example (serial 42‑48053) remains in North Texas awaiting restoration.
AT-21
Summary
The Fairchild AT‑21 Gunner was a bold but ultimately unsuccessful attempt to create a dedicated bomber‑crew gunnery trainer during World War II.
Developed from the XAT‑13 and XAT‑14 prototypes, it featured Duramold plywood construction, twin Ranger V‑770 engines, and a layout designed to simulate bomber crew positions.
Although 175 aircraft were produced across multiple factories, the type suffered from instability, vibration, and poor performance, leading to its withdrawal in 1944.
It nonetheless represents an important chapter in USAAF training doctrine, illustrating the challenges of designing specialised trainers during wartime resource constraints.
