According to the Boeing Commercial Aircraft Company, a Boeing 747-400 aircraft has a maximum gross take-off weight (including a typical 416 passengers, 171 cubic meters of freight in the cargo hold, and over 200,000 kg of fuel) of nearly 400,000 kg. Four behemoth engines push the bird at up to 88 percent of the speed of sound for unbelievable distances, up to 13,500 km, without refueling. The length of the aircraft alone (45 m) is longer than the Wright brothers ’ entire first flight.
But these amazing statistics, after 30 years finally to be eclipsed by even larger passenger aircraft, are nothing compared to the complexity of the system of systems which makes up the Boeing 747-400. The aircraft ’ s electrical systems comprise some 274 km of wiring alone; high-strength aluminum and titanium parts are designed to work both standing still and heated by rapidly passing air. Backup systems keep navigation and life-sustaining systems running if primary systems fail; and even the in-flight entertainment system is one of the more complex systems on earth. In fact, the Boeing 747-400 comprises some 6 million parts, about half of which are simply fasteners like screws and bolts. It ’ s no wonder that a Boeing spokesman once quipped, “ We view a 777 as a collection of parts flying in close proximity. ” As a frequent flyer, I constantly and fervently hope that that proximity goal is respected!
All of these facts reflect a fact that all engineers understand: complexity is difficult to manage, and most interesting systems are complex. Worse, the compounding of systems into systems of systems—e.g., back to our airplane, the electrical, hydraulic, propulsion, lift surface, life support, navigation, and other systems of aircrafts— tends to introduce new complexities in the form of unexpected