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Milan/Mirage HUD system LRUs

Technical Information

Catalogue No: PM32410
Picture Type: Rochester Photo Negative
Topic: Head-Up Display [HUD]
Title: Milan/Mirage HUD system LRUs
Date: 22 Feb 1977
Width (mm): 127
Height (mm): 102
Copies: 1
Location: Negatives Cabinet PM ("54/" Negs) [RAA Office]

At the end of 1967, in response to the Swiss Air Force’s call for a tactical support aircraft even more manoeuvrable than the Mirage III. Dassault and the Fabrique fédérale d’Avions at Emmen decided to build small retractable canards into the nose cone of the Mirage. Mirage 5J n°2, christened “Asterix” for that cartoon’s character famous moustache, made its first flight at Melun-Villaroche on September 27, 1968. Various other Mirages were modified, and the aircraft was equipped with a weapons system based on the Jaguar with some new equipment elements. In 1972 the Milan was in competition with the Corsair II but in the end, Switzerland decided to prolong the life of its Hunters and buy Northrop F5. The contest nonetheless brought home the advantage of having a weapons system based on the use of an inertial computer and a HeadUp Display. Immediately on its return to France Marconi-Elliott was invited to fit the Milan with a HUD and Litton fitted their LTN-51 inertial platform. The HUDWAC was a derivative of the A-4 system with the expanded 4000-word memory in the Electronics Unit which gave a very comprehensive air to air and air to ground capability.

The success of the A-7 Corsair HUD was followed by a system for the H, M and N variants of the McDonnell Douglas A-4 SkyHawk. About 465 systems were delivered, from about 1970 to 1978 to the U.S and elsewhere. The system was distributed into the Pilot’s Display Unit (PDU), Video Signals Unit (VSU), High Voltage Power Supply (HVPSU) and the Electronics Unit (EU). It was recognised that all of the information used in the weapon aiming calculations was already being supplied to the HUD to draw the symbology format for the attack phase. A modified interface design, faster logic and expanded store in the waveform generator gave a very effective and self-contained, greatly improved, gun, bomb and missile sight and aiming system which could be installed in many different existing aircraft. Most importantly: because the unit had its own highly capable A to D interface, it could use the existing sensors, gyros, etc. in any aircraft without requiring major internal systems modifications in the aircraft.

As only one display and one weapon aiming format were required simultaneously the HUD Processor speed was found to be adequate for both tasks. An Air to Air gun aiming and a CCIP bombing mode were provided initially.

The HUD Weapon Aiming Computer HUDWAC allowed a precise calculation of Lead Angle. The wider dynamic range of the HUD also permits closer matching of the pilot and airframe kinematics for target acquisition and tracking. This was a big advantage over even the most sophisticated Gyro Gunsight. It was now possible to give displays with better visualisation to the pilot with bullet line or tracer line and these ‘line cues’ increased the probability of a snapshoot against crossing targets over the ‘point’ cue fixed reticle. The HUD system for the US Marine Corps’ A-4M Skyhawk attack jet was the first product of this new concept a HUD weapon aiming computer or HUDWAC which proved to be a world first for the Company. In later designs the Program Store was increased to 4096 words and the Data Store to 128 words the weapon aiming capability was significantly increased. Such enhanced systems were flown on the Mirage Milan, the YF-16 and the YF-17. This system finally reached an 8k instruction PROM store.

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