---
kind: "range"
citation: "14 C.F.R. §§ 27.621–27.625"
title: "14"
from: "27.621"
to: "27.625"
count: 3
url: "https://uscodex.org/cfr/14/27.621..27.625"
---

# §27.621. Casting factors.

- (a) **General.** The factors, tests, and inspections specified in paragraphs [(b)](#b) and [(c)](#c) of this section must be applied in addition to those necessary to establish foundry quality control. The inspections must meet approved specifications. Paragraphs [(c)](#c) and (d) of this section apply to structural castings except castings that are pressure tested as parts of hydraulic or other fluid systems and do not support structural loads.
- (b) **Bearing stresses and surfaces.** The casting factors specified in paragraphs [(c)](#c) and [(d)](#d) of this section—
  - (1) Need not exceed 1.25 with respect to bearing stresses regardless of the method of inspection used; and
  - (2) Need not be used with respect to the bearing surfaces of a part whose bearing factor is larger than the applicable casting factor.
- (c) **Critical castings.** For each casting whose failure would preclude continued safe flight and landing of the rotorcraft or result in serious injury to any occupant, the following apply:
  - (1) **Each critical casting must—**
    - (i) Have a casting factor of not less than 1.25; and
    - (ii) Receive 100 percent inspection by visual, radiographic, and magnetic particle (for ferromagnetic materials) or penetrant (for nonferromagnetic materials) inspection methods or approved equivalent inspection methods.
  - (2) For each critical casting with a casting factor less than 1.50, three sample castings must be static tested and shown to meet—
    - (i) The strength requirements of [§ 27.305](/cfr/14/27.305.md) at an ultimate load corresponding to a casting factor of 1.25; and
    - (ii) The deformation requirements of [§ 27.305](/cfr/14/27.305.md) at a load of 1.15 times the limit load.
- (d) **Noncritical castings.** For each casting other than those specified in [paragraph (c)](#c) of this section, the following apply:
  - (1) Except as provided in paragraphs [(d)(2)](#d-2) and [(3)](#d-3) of this section, the casting factors and corresponding inspections must meet the following table:
  - (2) The percentage of castings inspected by nonvisual methods may be reduced below that specified in [paragraph (d)(1)](#d-1) of this section when an approved quality control procedure is established.
  - (3) For castings procured to a specification that guarantees the mechanical properties of the material in the casting and provides for demonstration of these properties by test of coupons cut from the castings on a sampling basis—
    - (i) A casting factor of 1.0 may be used; and
    - (ii) The castings must be inspected as provided in [paragraph (d)(1)](#d-1) of this section for casting factors of “1.25 through 1.50” and tested under [paragraph (c)(2)](#c-2) of this section.

# §27.623. Bearing factors.

- (a) Except as provided in [paragraph (b)](#b) of this section, each part that has clearance (free fit), and that is subject to pounding or vibration, must have a bearing factor large enough to provide for the effects of normal relative motion.
- (b) **No bearing factor need be used on a part for which any larger special factor is prescribed.**

# §27.625. Fitting factors.


For each fitting (part or terminal used to join one structural member to another) the following apply:

- (a) For each fitting whose strength is not proven by limit and ultimate load tests in which actual stress conditions are simulated in the fitting and surrounding structures, a fitting factor of at least 1.15 must be applied to each part of—
  - (1) The fitting;
  - (2) The means of attachment; and
  - (3) **The bearing on the joined members.**
- (b) **No fitting factor need be used—**
  - (1) For joints made under approved practices and based on comprehensive test data (such as continuous joints in metal plating, welded joints, and scarf joints in wood); and
  - (2) **With respect to any bearing surface for which a larger special factor is used.**
- (c) For each integral fitting, the part must be treated as a fitting up to the point at which the section properties become typical of the member.
- (d) Each seat, berth, litter, safety belt, and harness attachment to the structure must be shown by analysis, tests, or both, to be able to withstand the inertia forces prescribed in [§ 27.561(b)(3)](/cfr/14/27.561.md?p=b-3) multiplied by a fitting factor of 1.33.