Core Plane Module.

Ling-Temco-Vought responded to the VA(L) competition which was for a new fighter to replace the US Navy A-4s. In March 1964 the company received a contract for the initial batch of aircraft, designated A-7. In 1965 the aircraft received the popular name Corsair II. It was the first US aircraft to have a modern HUD which displayed information such as dive angle, airspeed, altitude, drift, and aiming reticle. In 1967 it was announced from Dallas in Texas U.S.A that Elliott Flight Automation had been awarded a four year contract to supply LTV with Head Up Displays for the A-7. The initial contract was worth £14million for 1,200 displays and was the largest ever awarded to a British firm.

The highly innovative optics was manufactured by Pilkington in North Wales. It had a 5" exit lens giving a 20° TFoV and had a two position combiner. The optics incorporated a clever split prism with dichroic coatings to allow the injection of a red Standby Sight from each side which was coupled to small lamps by fibre-optics. The A-7 Electronics Unit had a flexible symbol repertoire and the more complex symbols necessitated a faster writing rate. A key new requirement was the specification for a high level of built-in test. The HUD was part of the sophisticated ILAAS weapon system and this introduced predominantly digital serial data links for the aircraft data.

By 1970 the A-7D and A-7E began to move to squadron service and pilots were reported to say that "they like it better all the time". It was doubling the weapon delivery accuracy. Also in 1970 Elliott Flight Automation was awarded a Double Queen’s Award for both Export of all products and Technology of the Digital Head Up Display. In 1971 Vought Aeronautics Corporation donated a silver cup to be known as the Corsair Trophy in recognition of the Division’s achievements in designing, developing and manufacturing the A-7 Head Up Display. Much later in 1978 the Corsair Building was opened at Rochester again to note this very important programme.

The A-7 HUD was the breakthrough into the US market and was the start of a golden era for HUDs; 2534 to of this design were made and build rates exceeded 30/month at one time.

Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or rope core memory and also core plane.

Core uses tiny magnetic toroids (rings), the cores, through which wires are threaded to write and read information. Each core represents one bitof information. The cores can be magnetized in two different ways (clockwise or counterclockwise) and the bit stored in a core is zero or one depending on that core's magnetization direction. The wires are arranged to allow for an individual core to be set to either a one or a zero and for its magnetization to be changed by sending appropriate electric current pulses through selected wires. The process of reading the core causes the core to be reset to a zero, thus erasing it. This is called destructive readout. When not being read or written, the cores maintain the last value they had, even when power is turned off. This makes them nonvolatile.

     
 There was a development programme preceding the A-7 project called 'Integrated Light Attack Avionic System'  (ILAAS) and for this the Team Leader Jim Machin and the team  developed a 2K rope core memory Read Only Memory (ROM) from scratch as it was necessary to ensure non volatility and a very wide temperature range (in fact he achieved about -70C to around +120C).  The approach used large ferromagnetic cores threaded with a number of copper wires, threading or bypassing the ferrite cores. The design gave a store cycle time of around 1 microsecond. and avoided the ½ current drives of a conventional core stack. (For the subsequent A-7 HUD production a manufacturing source was established in Portugal drawing on their lace making skills.) The provision of reliable storage was a problem and a magnetic core store, of 2048 words, was used for the main program store. The new 16bit bipolar RAM was used for the data memory but to keep costs down this was limited to 64 words. In the A-7 the weapon aiming calculations were performed in a central computer and although such data as airspeed, height, aircraft velocity vector and altitude were provided to the HUD for generation of the symbology this design was not used  to carry out the weapon aiming itself. The original 18/12 processor used a programmable memory of 2K read only rope core memory. There was  a story that hese were assembled at one time  by the lace maker ladies of Portugal; following a workers revolution this was then shifted to the lace makers of Malta  and finally to Hong Kong. The production derivative extended the memory to 4k to allow for weapon aiming computation.