When the A4D-1 Skyhawk first entered service with the US Navy and Marine Corps, it was simple almost to the point of crudity. For instance, to pare down the weight, it didn’t even have a battery. External power carts were needed to start the aircraft. The only “sophisticated” avionics on board was the AJB-3 computer used for the delivery of nuclear weapons. A combination of an attitude indicator and crude analog computer, it guided a Skyhawk pilot through an “idiot loop” over the shoulder toss. It was good enough for nukes, but nowhere near precise enough for conventional weapons. Regular bombs and rockets were delivered using essentially the same aiming technology as a World War II dive bomber or fighter.
Later models of the Skyhawk introduced air-to-ground radar, but even that was more an aid to navigation than anything else, and weapons delivery was still contingent upon clear skies and an ability to actually see the target. And again, the actual delivery was made using the same techniques as in World War II.
This lack of precision delivery avionics explains why Argentinian A-4B and A-4C aircraft had to press their attacks on British warships in the Falklands to insanely close ranges, to the point where their fuses didn’t have enough time to arm.
Eventually, digital computers would find their way into modern avionics. One nifty tool that quickly gained popularity was the Continuously Computed Impact Point mode. A digital computer would assess the attitude of the aircraft, its airspeed, known winds, type of ordnance selected, and altitude, and predict the impact point. As the mode implies, that process is updated continuously. It made visual dive bombing much, much easier, and much more accurate.
Updating older aircraft to take advantage of these new systems, and new smart weapons such as the Maverick missile, became a very popular option, especially for smaller air forces. And one of the smallest air forces was the Royal New Zealand Air Force. The RNZAF had operated 10 A-4K Skyhawks (essentially an A-4F with minor changes) since the 1970s. In 1986, they began an upgrade program that included the installation of the APG-66 radar (used in the F-16A) and other modern avionics, including the ability to fire the Maverick missile, the 1000 pound GBU-16 laser guided bomb,* and the AIM-9L Sidewinder missile. Known as Project KAHU, the upgraded Skyhawk was a formidable little jet, and the success of the project is evident by the subsequent upgrade of surplus A-4Ms to A-4AR standard for Argentina.
In 1998, the New Zealand government finally decided to replace the A-4 with the F-16, but in 2001 a newly installed liberal Labour government cancelled that plan, and instead decided to drop the combat mission from the RNZAF, leaving it with just transport and maritime patrol capabilities.
The KAHU Skyhawks were retired into long term storage until 2011, when they were bought by Draken International. Today they serve as contract adversary aircraft supporting US Navy and Air Force training.
*It could carry and drop the bomb, but had no designation capability. That laser designation would have to be provided by a controller on the ground, or an allied aircraft.