In 1905 Ferber went back to help Archdeacon and Voisin handle their glider; in the same year he was assigned to the Centre Aerostatique at Chalais-Meudon, where he built another aerodrome - by which he meant a launching device. This was a wire bridle suspended from 3 towers; initially the wire was 25 m long, but it was later lengthened to 50 m. In the last of his books he established the famous Rule of 3 Vs: a lateral V (dihedral) for roll stability; a longitudinal V (positive angle of attack on mainplanes, negative on tailplane) for pitch stability; and a horizontal V (sweepback on mainplanes) to reduce drag. He wrote that any aeroplane designed with the 3 Vs would be automatically stable.

   No 6: When Ferber arrived at Chalais Meudon in May 1904, he ordered his 6th design built in Marseille by his mechanic Marius Burdin. It was tested and modified at Chalais-Meudon. It was similar to No 5 with narrower wings and a long tailplane mounted with negative angle of attack. It was tested on the lengthened aerodrome with and without the front elevator mounted as on No 5bis between 4 struts attached to the wing leading edges. His 26-year-old daughter flew No 6 as a glider free of the wire bridle, and with the 6 hp Buchet and the contra-rotating propellers. On 27 May 1905 Ferber managed what is sometimes improperly referred to as the first powered flight in Europe - but he did not actually take off, only sliding along the wire and then gliding away. Photographs of further such flights show twisting and distorted wings and wildly waving jibs.

   The 6 hp Buchet weighed nearly 90 kg with all its equipment; in 1904 he had ordered a slightly lighter and more powerful 2-cylinder engine of 12 hp which he tested over a long period. Never satisfied with it, Ferber finally ordered a 24 hp water-cooled Levavasseur Antoinette V8, but geared it to be transverse in the airframe with the drive to be taken from the middle of the crankshaft; but unfortunately for Ferber, Colonel Renard, the Director at Chalais-Meudon, died in 1905, and his successor was not much interested in aircraft "which had not yet proved capable of flying." He saw no point in waiting for the Antoinette, thinking the Peugeot would do.

   No 7: Ferber planned to test the Peugeot on his No 7 at the start of July 1906; he was running it on a propeller test-vehicle in August, a 4-wheel frame powered by the propellers which were of wood, skinned with imitation leather and tested at Meudon. The machine was damaged.

   No 8: By the summer of 1906 Ferber was asking for a 3-year leave, and by late in the summer he joined Leon Levavasseur to work on aeroplanes at the Antoinette company. When he left Meudon, his No 8 was complete and awaiting its engine, a special V8 made with 2 V4s on either side of a vertical propeller shaft and its 2.5:1 reduction gear. Though it belonged to the Army, Ferber could have got permission to test it; perhaps he never intended to do so. In November 1906 it was taken outside from the dirigible shed where it was being kept, to make room for a dirigible; on the night of 19-20 November it was completely destroyed in a storm.

   No 7 is rarely mentioned or described, apparently confused with No 6 or No 8: it may have been the machine shown in photographs with the Peugeot V2 and odd horizontal ailerons pivoting outside and around the front tip wing struts, and captioned Ferber No 8. This machine is likely to be No 7; No 8 was a more conventional-looking biplane than his earlier designs, with a front elevator, a long triangular rudder fixed to a long fan-shaped tailplane similar to that of No 6, bicycle-style undercarriage, wingtip skids, and the same floppy construction of his earlier designs. The Antoinette drove 2 contra-rotating propellers out in front. The wings curved slightly backward (the third V) and did not warp: roll and direction were controlled by 2 jibs.