The speed brake doesn't lock without hydro/elec pwr and the switch in hold. It's a pretty heavy control surface so between gravity and air pressure it's not going to come up in flight without 3000 psi extending the actuator. Essentially with the switch in up, side "A" let's pressure through to raise the speed bk, with the switch in down side "B" gets pressure to retract and with hold selected they both get pressure to fluid lock the actuator. So with the absence of hydro or electrical power the speed brake will just fall down. I hope that answers your question.