On January 7, 1927, the Cierva C.6C was flying at 30 m (98 ft), when one of its blades detached from the hub.

Juan de la Cierva designed a new rotor with a second linkage on the hub to correct the overstrain to eliminate cyclic stresses.

To the existing one of abatement that eliminated the problem of lift asymmetry, a second one was added, which was designated as a drag joint, which allowed the blade to oscillate in the plane of rotation.

He could not carry out the tests with this new configuration with the prohibition against flight still in place, so de la Cierva moved to Madrid to work on the C.7; there it was fitted with a new double-jointed rotor head.

After carrying tests, including flights with Juan de la Cierva as a passenger, it was concluded that the appropriate solution had been reached.