I've just checked the regulations - under 3.18.1:
"The incidence of the rearmost and uppermost closed section described in Article 3.10.2 may be varied whilst the car is in motion provided :
[...]
The design is such that failure of the system will result in the uppermost closed section returning to the normal high incidence position."
"The incidence of the rearmost and uppermost closed section described in Article 3.10.2 may be varied whilst the car is in motion provided :
[...]
The design is such that failure of the system will result in the uppermost closed section returning to the normal high incidence position."