The Smart Gunsight from 1944: One of the First Serial Analog Computers

This article explores the B-29 Superfortress's revolutionary fire control system, describing it as one of the first mass-produced analog computing systems in military aviation history.

The Problem: Accuracy in the Air

Traditional bomber gunners faced enormous challenges. Unlike fighters that effectively aimed themselves by pointing toward the target, bombers required precision from multiple gunners operating in different turrets simultaneously. The factors affecting accuracy included:

• Parallax between gun and gunsight positions
• The aircraft's own velocity affecting bullet trajectory
• Atmospheric conditions (temperature, humidity affecting air density)
• Gun barrel angle relative to the horizon
• Target velocity and distance

The author notes that German fighter pilots achieved roughly 2% hit rates despite firing thousands of rounds, illustrating just how difficult aerial gunnery was and why automated solutions became necessary.

Pilots had only two approaches: rely on experience and intuition, or "quickly and accurately calculate the necessary corrections." The first method was unreliable; the second was humanly impossible at combat speeds.

The B-29's Solution

The B-29 Superfortress introduced a centralized fire control system with five analog computer units — one per gun turret. This represented a fundamentally new approach to the problem.

Remote Operation

The turrets were unmanned (except the tail position) and could be controlled from five observation posts located throughout the aircraft. The gunner sat safely behind armored glass while servo motors moved the guns.

Smart Aiming

"The gunner only needed to keep the enemy in the gunsight — servo motors automatically directed weapons to the correct point in space." The computer calculated all necessary lead corrections, atmospheric adjustments, and parallax compensations in real time.

Cross-Coverage

Any gunner could operate any turret from their position using switchable controls. This meant that if one gunner was incapacitated, others could take over their turret without physically relocating.

System Integration

Built-in gyroscopes detected target vector and relative velocity. Navigators input atmospheric parameters — temperature, pressure, humidity — via dedicated control panels, allowing the computers to account for ballistic conditions.

Technical Implementation

The computers were "massive, electromechanical devices enclosed in centimeter-thick metal casings." They used synchros (selsyn motors) for servo control and complex mechanical calculation mechanisms to compute firing corrections automatically.

The system included safety interlocks that prevented gunners from firing toward the aircraft's own structure — a critical feature when turrets could be remotely aimed from distant observation positions.

Development and Manufacturing

Sperry Corporation initially won the development contracts, but their hydraulic-periscope designs proved problematic in practice. General Electric ultimately assumed responsibility for the system, manufacturing the computing units at IBM facilities — the very same company that was simultaneously producing early programmable computers like the Mark I, as well as military rifles. This convergence of computing and military manufacturing was a sign of things to come.

Historical Effectiveness: A Contested Legacy

The system's combat effectiveness remains debated. General Curtis LeMay famously stated that the B-29s "could take care of themselves," yet he paradoxically ordered the removal of most defensive armament to carry additional bombs on low-altitude incendiary raids over Japan.

Skeptics argue this decision demonstrates the system's unreliability — if it worked so well, why remove it? Supporters counter that Japanese fighter aviation had degraded so severely by late 1944 and into 1945 that defensive armament of any kind was simply unnecessary weight, making a fair assessment of the system's capabilities impossible.

Historical Significance

Regardless of its contested combat record, the B-29's fire control system represented a crucial technological milestone. It was "one of the first serial analog computing systems" — a mass-produced device that demonstrated the principle that automatic calculation could replace human judgment in complex, real-time targeting scenarios.

The lessons learned from these electromechanical computers fed directly into postwar computing development, contributing to the rapid advancement of both analog and digital computing systems in the decades that followed.