How One Mechanic’s “Stupid” Wire Trick Made P-38s Outmaneuver Every Zero

The Tensioner: How One Mechanic Changed the War

It was a quiet morning at Doadorura Airfield in New Guinea on August 17th, 1943, as Technical Sergeant James McKenna crouched beneath the wing of a P-38 Lightning, observing his pilot, Lieutenant Robert Hayes, prepare for another dangerous mission. The airfield was alive with the usual sounds of engines firing up and pilots getting ready for another round of combat, but McKenna couldn’t shake the feeling that this mission might be different.

Hayes was a young pilot—just 23 years old—who had flown six combat missions and still had zero kills to his name. The Japanese were sending 18 Mitsubishi A6M Zero fighters to intercept the morning patrol, and Hayes would be flying straight into them. McKenna had been maintaining P-38s for eight months, and over that time, he had seen enough to know that Hayes was facing odds stacked against him.

The P-38 Lightning was a powerful aircraft, fast in a straight line, and a formidable fighter at high altitudes. However, McKenna knew its biggest flaw—the P-38 was not a good turner. It couldn’t match the agility of a Zero in a dogfight. The Zero, with its lightweight frame and exceptional turning radius, could outmaneuver the P-38 every time. That was a deadly advantage for the Japanese pilots, who knew how to bait American pilots into a turn and then cut inside their radius to get a kill.

American doctrine warned P-38 pilots to avoid turning with a Zero. Instead, they were instructed to use speed and altitude to their advantage—hit fast and high, then climb away. The key was to stay out of a turning fight. But Hayes had already tried this five times, and it hadn’t worked. The Zeros were smarter than that. They baited the American pilots into turns, then cut them off before they could escape.

The 5th Air Force had already lost 37 P-38s in just the past six weeks. Most of those pilots had been caught in a turning fight they couldn’t escape. McKenna had witnessed enough of his fellow airmen die in the skies. Some he had known well, some only briefly during pre-flight checks, but the result was always the same. They climbed into their P-38s, thinking they had the advantage, only to return in pieces—or not return at all.

McKenna had a theory. He wasn’t a pilot, but as a mechanic, he knew the P-38 inside and out. The issue wasn’t with the pilots, it was with the aircraft itself. The problem lay in the control cables. The aileron control cables on the P-38 were routed through the twin booms to the tail section, then forward through pulleys to the wing control surfaces. There was a small amount of slack in the system—just 3/8ths of an inch at full deflection. That tiny delay caused by the slack was enough to make all the difference in a high-speed turn. The P-38 couldn’t outmaneuver a Zero because it couldn’t respond fast enough during a tight turn.

McKenna had brought this up to the engineering officer two months ago. He had suggested that the cables might need tighter tension. But the officer had dismissed it, saying the cables were within factory specifications, and modifying them would void the warranty on the aircraft. As a mechanic, McKenna had no authority to make such modifications. But as he watched pilot after pilot die in combat, he couldn’t ignore what he knew had to be done.

It wasn’t until August 16th, 1943, when McKenna saw Lieutenant Hayes prepare for another mission, that he decided to take matters into his own hands. Hayes came to McKenna, his face drawn with concern, asking if there was anything McKenna could do to make the aircraft roll faster. McKenna had no official solution, but the idea of Hayes’s certain death if something didn’t change weighed heavily on him. Hayes wasn’t the first to ask. McKenna had heard similar requests from other pilots who had flown with him, each asking the same thing: Could they make the aircraft roll better, turn faster?

McKenna made a decision that would change the course of history. He worked through the night, staying up long after everyone else had gone to bed. He grabbed a piece of piano wire from a damaged aircraft that had been written off and bent it into a Z-shape. This small piece of wire, just six inches long, would act as a tensioner for the aileron control cable. It would eliminate the slack and improve the responsiveness of the aircraft. It wasn’t authorized, and it could get him court-martialed, but McKenna didn’t care. Hayes’s life was on the line, and the standard procedure was killing pilots.

By 2:30 a.m., McKenna had completed the modification. The cables were tight. The aircraft would roll faster, respond quicker. He didn’t know if it would work, but it was the only chance Hayes had. As the morning light broke, McKenna finished his work and went to bed, unable to sleep.

At 7:42 a.m. on August 17th, Hayes climbed into his P-38 and took off. McKenna watched him disappear into the sky, hoping his gamble would pay off. Hayes was about to fly directly into a formation of Japanese Zeroes, and McKenna couldn’t shake the feeling that this mission was different—this time, Hayes had a chance.

The engagement started at 8:14 a.m. when Hayes’s flight of four P-38s intercepted 18 Japanese Zeroes. The dogfight unfolded quickly, and McKenna watched from the ground as Hayes, now in position, dove from altitude and engaged the enemy. Hayes had the advantage of the sun at his back, and he came down hard on a Zero at the rear of the formation.

He squeezed the trigger, and the P-38’s machine guns and 20mm cannon erupted. Most of the rounds missed, but a few struck the Zero’s wing. The Zero snapped left and dove to escape, but Hayes’s P-38 responded faster than ever before. The aircraft rolled in half the usual time, the controls responding instantly to Hayes’s movements. He had never felt the aircraft move like this. It was like a weight had been lifted from the controls.

Hayes didn’t hesitate. He reversed his direction and caught the lead Zero off-guard. A quick burst—another kill. Within 30 seconds, he had taken down two Zeroes. The other two Zeros in the formation tried to scissor him, alternating turns to force him into an overshoot. But Hayes stayed with them, turning with them, anticipating their every move. His P-38 moved like a fighter—quick and deadly. A third Zero went down in seconds.

After the battle, Hayes landed at Doadorura Airfield. He was exhausted, hands shaking from the adrenaline, but there was no mistaking the result. He had killed three Zeroes in less than seven minutes, a feat that had been impossible before. As Hayes climbed out of the cockpit, he made his way straight to McKenna.

“It worked,” Hayes said simply.

What neither of them realized was that Hayes’s performance had caught the attention of other pilots. Captain Frank Mitchell, who had witnessed the entire dogfight from above, immediately saw the difference. Hayes’s P-38 was rolling faster than any Lightning Mitchell had ever seen. It wasn’t just Hayes’s skill—it was the aircraft itself. Something had changed.

Word spread through the squadron, and soon, McKenna’s modification was quietly making its way from pilot to pilot, mechanic to mechanic. No one asked for permission, and no one was documenting the changes. But the results were impossible to ignore. Pilots flying modified P-38s were engaging the Zeroes with unprecedented success. The kill ratios improved. The Zeros no longer had the upper hand in a turning fight.

By September, McKenna had modified over 40 P-38s. The difference was clear. The P-38s were faster, more agile, and more deadly. The Japanese pilots began to notice, and they couldn’t figure out what had changed. Their tactics, which had worked for two years, were suddenly failing. The P-38s weren’t fighting like they used to. They were outmaneuvering the Zeros, and the Zeros didn’t know why.

The modification remained unofficial, never appearing in any reports or manuals. The engineers at Lockheed didn’t know it existed. But the pilots who had flown the modified aircraft knew the truth. It had saved their lives.

James McKenna never received official recognition for his work. He didn’t want it. To him, it wasn’t about accolades—it was about making sure his pilots survived. And survive they did. By the end of the war, McKenna’s modification had helped turn the tide in the Pacific. American pilots were no longer losing at a 2:1 ratio to the Japanese. By the end of September 1944, that ratio had flipped.

McKenna went on to continue his work in the Army Air Force until 1946, but he never spoke much about the war. He returned to Long Beach, California, where he became a mechanic, fixing cars and quietly living his life. In 2006, McKenna passed away at 88 years old. His obituary mentioned his service during World War II, but it didn’t mention the innovation that saved hundreds of pilots’ lives.

It was only years later, through the work of a historian, that McKenna’s contribution was truly recognized. But for McKenna, the recognition he valued most was the simple fact that pilots like Lieutenant Hayes had come home alive. And that, to him, was enough.

Note: Some content was generated using AI tools (ChatGPT) and edited by the author for creativity and suitability for historical illustration purposes.