The Smiths Flight System integrated the Smiths Electronic Pilot with four major instrument types: magnetic, pressure-induced, inertial (gyroscopic) and radio navigation indicators. It increased safety and accuracy by constantly evaluating one system against another, signalling the crew with warning lamps and flags in case of malfunction. Where it had been a separate box before, the auto-pilot could be set by adjusting markers on the main instruments, simplifying work, and reducing errors.

The Smiths Flight System was necessary to ensure a level of accuracy for an airliner covering ground at 500 miles per hour. By the mid 1950s, the SFS was specified by BOAC for all aircraft operating major routes. In 1961, Smiths Industries secured a contract to supply Boeing. Early 707 and 727 aircraft were fitted with SFS, and later the Smiths Flight Management System. This relationship has continued through to the 787.

Smiths Industries continued to work with de Havilland and the British Ministry of Aviation on advanced projects. On 10 June 1965, the Smiths Flight System, coupled to a digital computer, achieved the world’s first blind landing during a commercial flight, in a DH-121 Trident.

In the digital age, it’s easy to take for granted what engineers achieved with purely analogue signals. The principal difference is that analogue systems could only act on an input signal where the

action was proportional to the generated error. For example, an auto-pilot measures the error between the set course and actual course, and uses that value to operate the ailerons in proportion. An analogue system can do this very well. It is also able to compare the accuracy of two direction finders, and turn a light on if the values are different. What it is not able to do is to decide which direction finder is wrong, and switch it off. This still had to be done by the pilot and co-pilot. Digital computers were able to follow a programmed decision tree and take a wide range of actions.

Until the 1970s, aircraft still required a large number of people to act on warnings in the cockpit, to plan routes, and to navigate across continents. This lead to the development of digital flight management systems, into which an entire route could be fed and flown automatically. It was around 1970 that the term “avionics” became widespread. Cockpit computers took charge of more and more pre-flight checks, reducing checklists to one quarter of the time, dramatically improving turn-around. In 1982, the Boeing 767 used a “glass cockpit” computer screens to display relevant, summed information to pilots in an easily digestible way, reducing stress, and assisting decision-making in an emergency.

On 15 January 2007, Smiths Avionics was sold to General Electric for $4.8 billion.