14 CFR §23.2400

1. (a)For the purpose of this subpart, the airplane powerplant installation must include each component necessary for propulsion, which affects propulsion safety, or provides auxiliary power to the airplane.
2. (b)Each airplane engine and propeller must be type certificated, except for engines and propellers installed on level 1 low-speed airplanes, which may be approved under the airplane type certificate in accordance with a standard accepted by the Administrator that contains airworthiness criteria the Administrator has found appropriate and applicable to the specific design and intended use of the engine or propeller and provides a level of safety acceptable to the Administrator.
3. (c)The applicant must construct and arrange each powerplant installation to account for—
   1. (1)Likely operating conditions, including foreign object threats;
   2. (2)Sufficient clearance of moving parts to other airplane parts and their surroundings;
   3. (3)Likely hazards in operation including hazards to ground personnel; and
   4. (4)Vibration and fatigue.
4. (d)Hazardous accumulations of fluids, vapors, or gases must be isolated from the airplane and personnel compartments, and be safely contained or discharged.
5. (e)Powerplant components must comply with their component limitations and installation instructions or be shown not to create a hazard.