Adapted from Jean Boulet's Histoire de l'hélicoptère racontée par ses pionniers – 1907-1956:
The
N 1700 was a two-seater machine with a two-blade rotor fitted with a stabilizer bar. Engineer André Bruel wanted to get over and done with cyclic pitch control, which he considered too complex. The rotor head was mounted onto an articulated parallelogram which enabled it to move sideways. In this manner, lateral control was obtained by offsetting the rotor head more or less from the center of gravity.
The 160 hp Mathis GR7 engine directly drove the axial tail propeller which blew over two sets of flaps, one horizontal and the other vertical , so as to control pitch and yaw respectively. The helicopter was first damaged after a rough clutch caused some violent vibrations in the drive shaft. Once repaired, it was able to resume tethered testing, but left in the hands of some unexperienced mechanic, it moved and hit an obstacle.
The SNCAN board thus decided to cancel the N 1700 and to focus on the small, single-seat
N 1710, built along the same principles. SNCAN requested from SNCASE that they let go of test pilot Jean Boulet to test the machine. The first flight took place on July 1, 1950. After a few difficult flights in hover mode, the first translational flight took place on July 22. The longitudinal control proved quite inefficient, and modifications had to be made. This included increasing the flexibility of the horizontal flaps. On September 29, a new translational flight was attempted , but the modifications proved to have the opposite effect of what was expected. Boulet quickly lost control of the machine, which flipped over and projected him to the ground.
The aircraft was repaired and its tail was lengthened so as to improve the efficiency of the rudders. In Spring 1951, more flights took place. Boulet was sent to work in Marignane and was therefore replaced by André Onde, who took over and performed more flights in hover mode between June 18 and July 2. Translationary flights ensued to distances between 30 and 40 kms. On July 19, when Onde tried a closed circuit flight for the first time, he lost altitude in a bend, touched the ground and flipped over. The program was cancelled after that.
Attached photos:
- The N 1700 frame on a test rig. André Bruel is the one with the cigarette in his mouth.
- The N 1710 and the team that worked on it. Bruel is now the one that is seated.
- The N 1710 in hover at Montesson airfield.
- The N 1710 after its accident.