The supersonic marvel called Concorde

At its peak, America and other nations became leaders of innovation and large scale industrial production of aircraft and aerospace vehicles. Soon after the war, a lot of research went into creating large, fuel-efficient and durable aircraft for passenger transportation. A lot of alloys were developed in the subsequent years with a good strength to weight and cost ratio. Although the alloys were quite expensive for homebuilding aircraft, these alloys were second to none while providing durability, safety, and efficiency. Boeing and Airbus have been using aluminium to a tune of almost 80% since decades. With the obvious advantage of being light weight and high tensile strength of the aircraft body, aluminium enables an aircraft to increase its payload and save huge quantities of fuel.

Let’s look at an engineering marvel called Concorde.

Concorde Plane

British Aircraft Corporation’s Concorde was a passenger aircraft which used to fly people above Mach 2 speeds (1,354 mph or 2,180 km/h at cruise altitude) and was built with an aluminium skin. In its 27 years of service, Concorde, the British-French turbojet-powered supersonic passenger jet airliner seated 92 to 128 passengers and was one of only two supersonic transports to have been operated commercially; the other is the Soviet-built Tupolev Tu-144, which was operated for a much shorter period.

Concorde plane through a sonic boom

There are a few interesting things to note about Concorde though.

Perhaps, one of the greatest challenges aircraft designers confront when building a supersonic plane is the effect of high temperature on the vehicle. It is a result of kinetic heating of friction between the outside air and the skin of the rapidly moving aircraft. When the aircraft approached the maximum speed of Mach 2.2 (2.2 times the speed of sound – 2615 m/s) the temperature at the nose reached roughly around 155°C (311°F). If you find these operating temperatures unbelievable, just consider the fact that the outside air temperature at the Concorde's cruise altitude of 17,000 m (56,000 ft) is a startling -57°C (-70°F)!

Temperature distribution while flying 

Now, anyone would certainly know this fact, heat expands and cold contracts most metals. Imagine if these forces act simultaneously, the whole aircraft would become brittle and distorted in shape which could be quite dangerous. According to most sources, the airframe stretched by 5 to 12 inches (12 to 30 centimeters) at Mach 2. There was yet another critical challenge – keeping the mechanical properties and functions intact at such extremes of temperatures.

Aluminium, because of its mentioned properties, became the material of choice for many conventional airliners. Improvements over traditional alloys were made to withstand the tremendous effects of the forces at play when a plane was flying.  More exotic materials like titanium could have been used, but these are very expensive and often too heavy for use on such a large plane. Today, Alcoa is developing a 3rd generation aluminum-lithium alloy which promises more weight reduction and cost savings without the need for protection against lightning strikes. Even through carbon fiber and other non-metallic materials are been used today, they still lag behind aluminum in reliability.

However, "on 10 April 2003, Air France and British Airways simultaneously announced that they would retire Concorde later that year. They cited low passenger numbers following the 25 July 2000 crash, the slump in air travel following the 11 September attacks and rising maintenance costs. Although Concorde was a technological marvel when introduced into service in the 1970s, 30 years later its cockpit, cluttered with  analogue controls and dials, looked dated, as there had been little commercial pressure or reason to upgrade Concorde due to a lack of  competing aircraft, unlike other airliners of the same vintage, for example, the Boeing 747." 

Today’s planes use aluminum in the fuselage, the wing panes, the rudder, the exhaust pipes, the door and floors, the seats, the engine turbines, and the cockpit instrumentation. The applications ensure that the airlines operate economically and place heavy emphasis on the safety of the passengers.