The very-high-speed tests carried out by SNCF between the end of 1989 and May 1990, are an extension of the investigations which have been made for many years in order to acquire the control of high speeds. The high-speed run which ended the tests is well known [1], [2], [3]. In order to place the final test campaign in its context, we can recall progression made during the last decade. In February 1981, the maximal speed of 380 km/h was reached with a TGV-PSE1 train set, having the same configuration as the series, but only seven trailers instead of eight. During the following years, until 1986, the pneumatic suspension and the new Y 231 carrying bogies designed for TGV-ATL train sets were developed, with numerous test runnings in the speed range from 300 to 350 km/h, in order to obtain certitudes as regards the stability of the bogies and the appropriate choice of anti-hunting devices for commercial speeds of 270 km/h (LGV-PSE) or 300 km/h (LGV-ATL). These tests allowed the definition of the TGV equipment design principles, which are applied today as regards the critical speed of the bogies. Between 1985 and 1988, the development of the prototype train set equipped with self-controlled synchronous motors (March 1988) led once more to numerous runnings at high speed, in December 1988 with the so-called "operation TGV 88". During this operation, the speed range from 350 to 400 km/h was investigated (maximal speed 408,4 km/h on December 12th 1988). Apart from the capability of the synchronous traction equipment to develop the required power and the performance consisting in the realization of such tests on a line kept in operation (LGV-PSE), the teachings gathered together during this test campaign were decisive for the pursuit of the operation. On this occasion, we discovered that: - with the single-phase GPU pantograph mounted on this train set, we could get the current collection under control without difficulties inside the studied speed range, - the bogies presented a stability margin distinctly higher than that which had been estimated, according to the results of former experiences. Consequently, the test campaign of the TGV 117 could be engaged with a great confidence in the capabilities of the TGV equipment to achieve markedly higher speeds with full safety. The preparation of this test campaign had begun in 1986 and was conducted in a parallel direction to the above mentioned experimentation. The campaign was preceded by a preliminary test campaign with the train set TGV-ATL n-degrees 308, with a reduced train composition, including eight trailers. The goal was the validation, until 390 km/h, of the test field consisting in the TGV-ATL Aquitaine branch, as well for the track as for the overhead contact line, the achievement of which was just ended. The operation TGV 117 was then carried out in two phases: - in December 1989 the train set TGV-ATL 325 with a reduced train composition consisting in four trailers between two motor cars reached the maximal speed of 482,4 km/h on December 5th, - in May 1990 the same train set, but with only three trailers, improved the performance unto the final record: the speed of 515,3 km/h was reached on May 18th.
