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Wired For Survival – Redundant Backup Wiring in Military Aircraft

Wired For Survival – Redundant Backup Wiring in Military Aircraft

One Shot, One Kill

Back in the day, that’s all it took to shoot down an aircraft – one shot. Whether that magic projectile found the fuel or hydraulic lines or somehow disrupted the magneto, one shot was usually all that was needed to down an enemy aircraft. The line of thinking a hundred years ago, was to make the aircraft more durable, but that added too much weight. So how did the great minds of the time get around the issue of getting shot down so easily? They made nearly everything on an aircraft redundant – there was a backup system for everything.

Redundant flight systems became the norm in military aircraft at an early age, what wasn’t necessarily made redundant was the electrical wiring systems. However, as the space race of the 1960s started heating up, so did the technology installed in aircraft. By the late ‘60s, computers were an everyday occurrence in aircraft, but implementation was limited due to size and weight. It wouldn’t be until the 1970s when computers began getting smaller, while getting faster and more robust, that a serious effort was made to make computers a vital component of modern combat aviation.

The first major leap forward in combat aircraft came with the fly-by-wire (FBW) flight control system in 1972. NASA introduced digital FBW to the world on May 25, 1972 using an F-8C Crusader donated to them by the U.S. Navy. Since that day, nearly everything from jumbo jets to the latest in stealth bombers and fighters uses FBW system during flight. This historic day also meant something else for aircraft of the future – more computers and more wires.

Safety dictated that multiple computers be used for FBW flight operations, seeking to eliminate the possibility of a computer failure which could cripple the aircraft. However, multiple computers alone couldn’t solve the riddle of how to make combat aircraft more survivable. When engaged with anti-aircraft emplacements for example, a damaged wiring harness spelled doom for the pilots. Combat aircraft needed a better solution to survivability other than an aircraft’s ability to essentially fly itself.

Many modern aircraft now have what’s called a multi-redundancy wiring configurations. Using the venerable Apache Attack Helicopter as an example, not only does it have at least two of everything,avionics-wise, but also a double-redundancy wiring harness throughout the aircraft. The avionics packages in the EFAB (Exterior Forward Avionics Bay) is nearly identical on each side. Instead of the wiring harnesses simply crossing from one side to the other to create a redundancy, the harnesses also go down the length of the aircraft before coming forward on the other side. Multiple splice junctions throughout the aircraft ensure that battle damage to one part of the aircraft will not affect the entire platform – making it one the most wired for survival combat aircraft on the planet.

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