High-speed rotorcraft such as coaxial compound helicopters have a significant degree of control redundancy that can be exploited to minimize power requirement, noise, and vibration, in various flight conditions. This lecture focuses on a new idea – how control redundancy can be leveraged to compensate for control actuation failure. Both adaptive as well as robust strategies are examined, and operation post-failure is demonstrated via simulation. Multi-copters with greater than four rotors (hexacopters, octocopters, etc.), also offer control redundancy, allowing for safe operation post-failure by using the remaining (uncompromised) rotors. The lecture will examine the kind of failures that can be compensated on classical hexacopters and octocopters, along with the changes in rotor operational speed requirements, and the associated physics, post-failure.