14 CFR § 29.901

For the purpose of this part, the powerplant installation includes each part of the rotorcraft (other than the main and auxiliary rotor structures) that—

Is necessary for propulsion;

Affects the control of the major propulsive units; or

Affects the safety of the major propulsive units between normal inspections or overhauls.

For each powerplant installation—

The installation must comply with—

The installation instructions provided under § 33.5 of this chapter; and

The applicable provisions of this subpart.

Each component of the installation must be constructed, arranged, and installed to ensure its continued safe operation between normal inspections or overhauls for the range of temperature and altitude for which approval is requested.

Accessibility must be provided to allow any inspection and maintenance necessary for continued airworthiness; and

Electrical interconnections must be provided to prevent differences of potential between major components of the installation and the rest of the rotorcraft.

Axial and radial expansion of turbine engines may not affect the safety of the installation.

Design precautions must be taken to minimize the possibility of incorrect assembly of components and equipment essential to safe operation of the rotorcraft, except where operation with the incorrect assembly can be shown to be extremely improbable.

For each powerplant and auxiliary power unit installation, it must be established that no single failure or malfunction or probable combination of failures will jeopardize the safe operation of the rotorcraft except that the failure of structural elements need not be considered if the probability of any such failure is extremely remote.

Each auxiliary power unit installation must meet the applicable provisions of this subpart.