Even if the last F-104 fighter jets in active service were retired by the Italian Air Force on Oct. 31, 2004, the Starfighter legacy survived in a modern combat plane: the Eurofighter Typhoon.
As already extensively explained by Andreas Zeitler in an extensive piece for the now disappeared “Classic Aircraft”, the most advanced Starfighter ever realized anywhere in the world was a very particular German F-104 testbed.
Indeed, whereas the various G, S, ASA and ASA-M variants never featured it, there was an F-104 example fitted with fly-by-wire controls which flew about thirty years before the Italian Zippers were grounded forever.
During the 1970s, Germany understood that future fighters would need to achieve high agility as well as the ability to fly at high angles of attack. These capabilities required an unstable aircraft configuration.
In 1974, in order to address the need to test how a highly unstable supersonic jet fighter equipped with a proper redundant flight control system would fly, the German Ministry of Defense authorized MBB to proceed with the so-called Control Configured Vehicle (CCV) program.
The outcome of the CCV would be a fly-by-wire testbed: the aircraft selected for testing campaign was the F-104G, which, as Zeitler discovered, was preferred over the F-4F since the Phantom was too big and too heavy, even if its size would have offered more space for test equipment than the Starfighter.
The first phase of the trials was aimed at defining the parameters for the control algorithms of the CCV and its sensors: it lasted from Sept. 27 to Nov. 4, 1976 andwas accomplished with thirteen flights.
The second phase saw the aircraft flying in two different versions, the B (for Basic) and E (with E for Ente which means “duck”, because of the canard configuration).
Flight after flight, from a stable aircraft the F-104 became an unstable platform, a goal reached shifting the neutral point and centre of gravity of the Starfighter.
The first complete mission in CCV mode was flown on Oct. 2, 1979 by the B1 model fitted with the Control Configured Vehicle software. Another variant followed the B1: the B2 with 600 kg aft and 130 kg forward ballasts.
But the first real unstable flight took place on Nov. 20, 1980 when, along with a 240 kg nose ballast, an additional F-104 elevator was mounted behind the cockpit; a version known as E1. With this variant, the neutral point was moved forward, while the E2 configuration, adding 400 kg aft ballast, shifted back the centre of gravity.
At that point the F-104 was really unstable and 26 sorties were conducted between July and September 1981. All the flights were safely conducted and the nose trim weight was replaced with another 200 kg ballast, realizing the E3 configuration.
With this additional ballast the Starfighter could perform flights at 20 percent negative longitudinal stability.
The testing phase lasted about four years during those the F-104 CCV demonstrator was pivotal to the design and development of a delta-canard control system later adopted by the Eurofighter Typhoon.
Dario Leone for The Aviationist
Image credit: GAF via Key Publishing forum