O AJ-37 Viggen foi um dos pioneiros na utilização de central de computação única e foi o primeiro caça do mundo
equipado com computador com circuitos integrads (CI), o Saab CK37.
In the beginning of the 1960s it was decided that the multipurpose attack/fighter
Saab 37 Viggen should be designed as a single seat aircraft. A central computer
and a head-up display made it possible to dispense with the need for a human
navigator. The computer was the central computing and integrating unit for all
electronic equipment to support the pilot. This computer, CK37 used in the Saab
AJ37, was the first airborne computer in the world to use integrated circuits
(first generation ICs). Almost 200 computers were delivered 1970 -1978. The
function was reliable and the computers were still in operation, with upgrades, at
the early beginning of 2000`s.
2. A Central Computer
2.1. Digital revolution in an aircraft
Both the Air Force and Saab discussed if the new aircraft, Viggen, should be a twin or single
seat plane. A navigator helped the pilot with navigation, radar reconnaissance and other
things in earlier military aircraft. It was decided to investigate if the functions performed by
the navigator could be replaced by electronic equipment. Analogue systems in earlier aircraft,
as in the 35 Draken, were expensive to maintain and change, and also had limited accuracy.
Reports from USA indicated similar experiences and pointed to the digital calculator as an
alternative. Evaluations at the Air Force and Saab showed that it would be quite possible to
replace the navigator’s functions with a digital computer. This resulted in a general overhaul
of all electronic equipment in the aircraft and ended in a system as shown figure 1 (página 2 do pdf abaixo).
The process was not easily achieved and several aircraft designers were very doubtful of the
concept. Several task approaches and specifications were written and discussed before a
general consensus of one central computer for the aircraft was reached. Later on it was
known that the USA-aircraft A-7D had been equipped with a computer system.
Some data
Instruction speed: 200.000 instructions per sec.
Memory: 25 kbyte, a ferrite core memory.
Communication: 64 analogue in/out signals. 450 bits of binary in/out signals.
Size: 4 units, each between 11 and 16 kg. Power 600 watts.
Reliability: MTBF min. 200 hours during flight operation.
CK37 and interacting electronic equipment to support the pilot.
Circuit unit with an aluminium beam for support of components. Several units are mounted in a frame with interwiring. One computer unit for the aircraft consists of several frames, some of them fitted with connectors to the aircraft.
The aircraft rack with the four CK37 computer units.
The interior of one of the first integrated circuits, which reached Saab in 1961, enclosed in a TO5 capsule with 7 connections. The chip is 2x2 millimetres. Fairchild, USA, was the supplier.
A CK37 frame is compared with a circuit card from the computer CD107. This computer for the aircraft Saab JA37 is a design, about 10 years later. The computer was built on a license from Singer-Kearfott. Almost 100 computers were delivery from Saab Production Unit during 1979-1985.
Fontes:
http://www.datasaab.se/Papers/Articles/Viggenck37.pdf
http://www.datasaab.se/Bildarkiv/CK37/ck37_eng.htm
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(bricadeira, ok?)
