Redundancy

When the McDonnell Douglas DC-10 was introduced in the 1970s, it boasted what engineers called triple-redundant hydraulic systems—three separate circuits designed to ensure that even if two failed, the aircraft could still be controlled. It seemed like engineering genius, a feat of modern aviation safety. But buried in the design was a dangerous flaw: all three systems ran side by side through the plane’s tail section. A single well-placed rupture could wipe them all out at once—turning redundancy into illusion.

That flaw would remain hidden in technical schematics and engineering hubris until July 19, 1989, when United Airlines Flight 232 departed Denver for Chicago with 296 souls aboard.

At 37,000 feet over Iowa, the tail-mounted engine catastrophically failed. Fragments from the shattered fan disk shot outward with explosive force, slicing through the fuselage and severing all three hydraulic lines. Within seconds, the flight crew realized the unthinkable: they had lost all flight control. No ailerons. No rudder. No elevators. Nothing.

The DC-10 was now, in essence, an uncontrollable 200-ton glider.

Captain Al Haynes and his crew didn’t panic. Neither did Dennis Fitch, an off-duty DC-10 instructor who happened to be on board and volunteered to help. As the aircraft began to yaw and roll dangerously, the team discovered that by adjusting the throttle on the two remaining wing-mounted engines independently, they could influence the aircraft's direction—ever so slightly. Throttle up on the right engine, the plane veered left; throttle up on the left, it nudged right. It wasn’t precise, but it was something.

Over the next 45 minutes, the cockpit became a laboratory of desperation. Haynes, Fitch, and the rest of the crew worked in eerie coordination, managing turns, altitude, and descent with nothing more than asymmetric thrust. Passengers gripped armrests as the aircraft wobbled and dipped violently. Some wrote farewell notes. Others prayed. Flight attendants did their best to prepare everyone for impact.

They aimed for Sioux City, Iowa. Emergency services were alerted. The National Guard was mobilized. As the airport came into view, the crew attempted one last maneuver to align the plane. But they were coming in too fast and too steep. Without elevators or flaps, there was no way to soften the landing.

The DC-10 slammed into the runway, its right wing striking first. The aircraft cartwheeled, broke into pieces, and exploded into a fireball. Debris scattered across the tarmac.

And yet—miraculously—184 people survived.

Investigators later praised the crew for a performance that defied belief. Simulator tests revealed that most pilots crashed within minutes under similar conditions. Haynes and his team gave passengers 45 minutes of hope—and for many, a second chance at life. But the official report highlighted the fatal flaw: the triple redundancy was superficial. All systems were vulnerable to the same physical breach. When that section of the aircraft was compromised, the entire safety plan unraveled.

And so here lies the lesson—not just for engineers, but for anyone who thinks about the future.

In personal finance, we often tout the value of diversification and contingency planning. But redundancy has to be real. Three credit cards won’t save you if they’re all tied to the same bank that freezes your account. It’s not enough to have an emergency fund if it’s invested in the same volatile stocks you rely on for retirement. If your financial safety net depends entirely on your employer—your salary, your health insurance, your equity—you’ve created a single point of failure.

Redundancy must be layered, thoughtful, and physically separated—just as engineers now space out hydraulic lines in aircraft. The crew of Flight 232 showed us the best of human ingenuity under fire. But they also served as a tragic reminder: fail-safe systems aren’t really safe if they all fail the same way