In 1908 and 1909 Koechlin joined forces with de Pischoff, and built aeroplanes for other people, and their own much-modified de Pischoff et Koechlin.

   De Pischoff et Koechlin monoplane: In 1908 the team designed and built a tandem monoplane with the second wing close behind the first, and a little shorter. A horizontal tail surface brought up the rear, along with fins above and below, and rectangular rudders for each one. The thin streamlined rectangular body was supported in front by a Bleriot-style undercarriage, and behind by a large tail wheel. A separated pair of forward elevator surfaces protruded from each side of the nose, and another pair of small trapezoidal surfaces aft, forward of the tail. It is reported to have hopped once, for 500 meters, on 29 October 1908, at Villacoublay.

   (Spans: 6.3 m,5.3 m,3 m; wing area: 25 sqm; 20hp Dutheil et Chalmers)

   Either this same machine or a development appeared the same year. One of them seemed to have the same basic structure less the middle wing and the extra forward and aft surfaces: it made a very pretty conventional-looking monoplane. Another had a water-cooled flat twin engine set amidships, driving 2 tractor propellers on outriggers aft of the wing.

   Then Koechlin went off on his own and designed the monoplane which he developed steadily until 1911.