Reading this article (on the Boeing 737 MAX saga; irrelevant), I found the following excerpt:
Boeing ultimately accepted Davies recommendation and, we understand, halted production of the 707 for 10-11 months, whilst a new fin was designed and installed. All existing 707s were then retrospectively modified. A ventral fin was also installed on some variants to prevent ‘fully stalled take-offs’ which the Comet was also susceptible to.
I tried to search, but I found nothing on "fully stalled take-offs", whether about the Comet or any other aircraft.
So, what is a "fully-stalled take-off"? Are some aerodynamic designs (or aircraft models) more susceptible to it?