What is the smallest aircraft under 14 CFR Part 135 required to have a cockpit voice recorder?

The requirement for cockpit voice recorders (CVRs) under 14 CFR Part 135 is specifically targeted at multiengine turbine-powered airplanes that can carry 6 or more passengers. This regulation is in place to enhance safety and provide a record of cockpit conversations and ambient sounds that could be relevant during investigations of incidents or accidents.

Multiengine turbine-powered airplanes are seen as higher risk due to their operational complexity and the potential for significant passenger loads. These aircraft typically operate in commercial air transport and the additional layer of recording cockpit interactions serves to improve safety and accountability in flight operations.

In contrast, single-engine turbine-powered airplanes, regardless of the number of passengers, do not fall under the same requirement as they are generally perceived to have a lower operational complexity and different risk profile. Likewise, while multiengine turbine-powered helicopters could also operate with 6 or more passengers, their requirements differ from those of multiengine turbine-powered airplanes under the same aviation regulations.

Thus, the smallest aircraft under 14 CFR Part 135 required to have a cockpit voice recorder is indeed the multiengine turbine-powered airplane with 6 or more passengers.