14 CFR §25.901

1. (a)For the purpose of this part, the airplane powerplant installation includes each component that—
   1. (1)Is necessary for propulsion;
   2. (2)Affects the control of the major propulsive units; or
   3. (3)Affects the safety of the major propulsive units between normal inspections or overhauls.
2. (b)For each powerplant—
   1. (1)The installation must comply with—
      1. (i)The installation instructions provided under §§ 33.5 and 35.3 of this chapter; and
      2. (ii)The applicable provisions of this subpart;
   2. (2)The components of the installation must be constructed, arranged, and installed so as to ensure their continued safe operation between normal inspections or overhauls;
   3. (3)The installation must be accessible for necessary inspections and maintenance; and
   4. (4)The major components of the installation must be electrically bonded to the other parts of the airplane.
3. (c)For each powerplant and auxiliary power unit installation, the applicant must comply with the requirements of § 25.1309, except that the effects of the following failures need not comply with § 25.1309(b)—
   1. (1)Engine case burn-through or rupture,
   2. (2)Uncontained engine rotor failure, and
   3. (3)Propeller debris release.
4. (d)Each auxiliary power unit installation must meet the applicable provisions of this subpart.