Two varieties of flight simulator exist, of which only one type is built today. Analogue simulators were superceded by sequential digital simulation.

Analogue Flight Simulation

In America¹ Ed Link produced a blind-flying trainer that was widely deployed, becoming known colloquially as the Link Blue Box, a miniature aeroplane cockpit with a canopy, smaller than the cockpit of a sports car; mounted on a crude motion system made of bellows controlled by vacuum pumps—Ed Link was the son of a musical organ manufacturer.

Once seated inside the Blue Box, with the lid closed, the pilot had the usual flying controls under hands and feet, with an instrument panel containing compass, attitude indicator, engine instruments, direction finding displays, and wireless communication controls. Outside, seated at a desk, the instructor observed the pilot's motions by watching movement of a kind of electronic pantograph across a large scale map of the airfield and surrounding local area. Action of the pantograph is controlled by the pilot flying the Blue Box, guided by the instructor acting as a ground controller and by the simulated environment represented on the instruments in the cockpit.

As technology developed, analogue simulators increased in complexity with the addition of hydraulic motion systems and visual displays of the view outside the cockpit.

Analogue simulators make extensive use of standard amplifiers that can be configured to add, subtract, multiply, and divide, differentiate and integrate. Servo motors and synchronous transmitters and receivers connect the cockpit instruments to the repeaters and controls of the instructor's station. Equations of motion and other formulæ are solved directly by the electronic circuitry, constructed from standard building blocks. Solution of an equation can be followed as you progress through the wiring diagrams of the simulator.

Eventually, in the 1950s and 1960s, the sequential digital computer replaced the analogue machinery. Key difference between an analogue and digital simulator is that the analogue machine works instantaneously massive parallel computations whereas the digital simulation solves parts of the simulation model sequentially; even though digital computers are fast, they have a critical latency between inputs at the controls and outputs from the instruments, the motion, and visual system.

Digital Flight Simulation

Unlike analogue simulators that break the problem into functional parts then solve the equations simultaneously, digital simulators first relied upon a single computer to solve the equations sequentially, albeit very fast so as to fool the pilot into thinking that everything is happening at once as in a real aircraft.

Also unlike an analogue simulator in which the solution to the equations is inherent to the design, digital computers must be instructed how to solve the equations. How these instructions are stored defines the character of the digital computer used. Instruction storage types in digital computers are listed below in increasing order of modernity.

• Magnetic Drum.
• Magnetic Core Memory.
• Magnetic Disc.

Simulator Structure

A flight simulator is composed of several basic systems, be it analogue or digital.

• Cockpit.
• Primary Controls.
• Secondary Controls.
• Visual System.
• Motion System.
• Radio Aids System.
• Navigation System.
• Aircraft Systems.
• Control Loading System.
• Instructor's Operating System.
• Flight Dynamics.
• Powerplant.
• Patch Panel.
• Equipment Cabinets.

Additional systems peculiar to digital simulation are:

• Scheduler.
• Computer Systems.
• Input & Output System.