Improving the DH-4 “Liberty Plane”
1918–1919
Fleet helped correct the deadly flaws of the DH-4, transforming a notoriously dangerous aircraft into a safer, more reliable military machine.
Improving the DH-4 “Liberty Plane”
Fixing America’s Most Controversial Wartime Aircraft
During World War I and the years immediately following, the De Havilland DH-4—built in the United States as the Liberty Plane—was the primary American-made combat aircraft. But it had a terrible reputation. Pilots called it the “Flaming Coffin” because its fuel system, placed between the pilot and observer, could ignite during a crash or even from minor gunfire.
When Reuben H. Fleet inspected the aircraft as part of his Army aviation responsibilities, he realized that thousands of American pilots were being placed in lethal machines. This was unacceptable to him—not just as an officer, but as a pilot who personally understood risk.
Fleet’s involvement in improving the DH-4 became a major influence on his later design philosophy and played a key role in America’s ability to field safer aircraft.
The Problem: A Dangerous Design
The U.S.-built DH-4 suffered from several major issues:
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Fuel tank placement: a large gravity-fed tank behind the engine made the aircraft prone to fires.
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Poor balance and stability: it tended to stall abruptly.
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Weak structural components: several airframes were poorly built due to rushed wartime production.
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Inconsistent manufacturing standards: different plants produced parts that didn’t always match.
These flaws caused accidents, fatalities, and widespread distrust among pilots.
Fleet confronted the problem directly.
Fleet’s Reforms and Improvements
Working with Army engineering units and industry partners, Fleet pushed for immediate corrections. His improvements included:
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Relocating fuel lines and fittings to reduce fire risks.
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Reinforcing structural components to improve crash survivability.
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Redesigning the cockpit arrangement for better crew communication and safety.
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Improving weight distribution for more predictable handling.
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Establishing uniform production standards across all contracted factories.
Fleet insisted on extensive testing, reworking, and re-certification of each change. He did not accept partial solutions—he demanded aircraft pilots could trust.
These efforts dramatically reduced DH-4 fatal accidents and stabilized its performance.
The DH-4B: A Safer, More Capable Aircraft
Thanks in part to Fleet’s influence, the improved DH-4B emerged:
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safer
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more stable
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structurally stronger
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better suited for training and early transport roles
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trusted by pilots who once feared it
The DH-4B later became the backbone of the early U.S. Airmail Service, the same system Fleet launched in 1918.
His improvements helped transform a flawed wartime design into a dependable peacetime workhorse.
How the DH-4 Experience Shaped Fleet’s Future
Working on the DH-4 convinced Fleet of several truths that would define his entire engineering philosophy:
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A pilot’s life depends on design choices made on the factory floor.
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Safety cannot be bolted on later—it’s built in from the start.
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Aircraft must be structurally reliable, not merely fast or powerful.
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Manufacturing consistency is a moral obligation, not a convenience.
These lessons guided him when he:
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founded Consolidated Aircraft
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designed trainers, transports, and flying boats
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demanded structural integrity in every B-24 and PBY
The DH-4 experience forged the principles that would make Consolidated the safest and largest aircraft producer in America.