---
kind: "range"
citation: "14 C.F.R. §§ 25.621–25.625"
title: "14"
from: "25.621"
to: "25.625"
count: 3
url: "https://uscodex.org/cfr/14/25.621..25.625"
---

# §25.621. Casting factors.

- (a) **General.** For castings used in structural applications, the factors, tests, and inspections specified in [paragraphs (b) through (d)](#b..d) 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)](#d) of this section apply to any 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.** Each casting whose failure could preclude continued safe flight and landing of the airplane or could result in serious injury to occupants is a critical casting. Each critical casting must have a factor associated with it for showing compliance with strength and deformation requirements of [§ 25.305](/cfr/14/25.305.md), and must comply with the following criteria associated with that factor:
  - (1) A casting factor of 1.0 or greater may be used, provided that—
    - (i) It is demonstrated, in the form of process qualification, proof of product, and process monitoring that, for each casting design and part number, the castings produced by each foundry and process combination have coefficients of variation of the material properties that are equivalent to those of wrought alloy products of similar composition. Process monitoring must include testing of coupons cut from the prolongations of each casting (or each set of castings, if produced from a single pour into a single mold in a runner system) and, on a sampling basis, coupons cut from critical areas of production castings. The acceptance criteria for the process monitoring inspections and tests must be established and included in the process specifications to ensure the properties of the production castings are controlled to within levels used in design.
    - (ii) **Each casting receives—**
      - (A) Inspection of 100 percent of its surface, using visual inspection and liquid penetrant or equivalent inspection methods; and
      - (B) Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic or equivalent inspection methods.
    - (iii) One casting undergoes a static test and is shown to meet the strength and deformation requirements of § [25.305(a)](/cfr/14/25.305.md?p=a) and [(b)](/cfr/14/25.305.md?p=b).
  - (2) A casting factor of 1.25 or greater may be used, provided that—
    - (i) **Each casting receives—**
      - (A) Inspection of 100 percent of its surface, using visual inspection and liquid penetrant or equivalent inspection methods; and
      - (B) Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic or equivalent inspection methods.
    - (ii) **Three castings undergo static tests and are shown to meet—**
      - (A) The strength requirements of [§ 25.305(b)](/cfr/14/25.305.md?p=b) at an ultimate load corresponding to a casting factor of 1.25; and
      - (B) The deformation requirements of [§ 25.305(a)](/cfr/14/25.305.md?p=a) at a load of 1.15 times the limit load.
  - (3) A casting factor of 1.50 or greater may be used, provided that—
    - (i) **Each casting receives—**
      - (A) Inspection of 100 percent of its surface, using visual inspection and liquid penetrant or equivalent inspection methods; and
      - (B) Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic or equivalent inspection methods.
    - (ii) **One casting undergoes a static test and is shown to meet—**
      - (A) The strength requirements of [§ 25.305(b)](/cfr/14/25.305.md?p=b) at an ultimate load corresponding to a casting factor of 1.50; and
      - (B) The deformation requirements of [§ 25.305(a)](/cfr/14/25.305.md?p=a) at a load of 1.15 times the limit load.
- (d) **Non-critical castings.** For each casting other than critical castings, as specified in [paragraph (c)](#c) of this section, the following apply:
  - (1) A casting factor of 1.0 or greater may be used, provided that the requirements of (c)(1) of this section are met, or all of the following conditions are met:
    - (i) Castings are manufactured to approved specifications that specify the minimum mechanical properties of the material in the casting and provides for demonstration of these properties by testing of coupons cut from the castings on a sampling basis.
    - (ii) **Each casting receives—**
      - (A) Inspection of 100 percent of its surface, using visual inspection and liquid penetrant or equivalent inspection methods; and
      - (B) Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic or equivalent inspection methods.
    - (iii) Three sample castings undergo static tests and are shown to meet the strength and deformation requirements of § [25.305(a)](/cfr/14/25.305.md?p=a) and [(b)](/cfr/14/25.305.md?p=b).
  - (2) A casting factor of 1.25 or greater may be used, provided that each casting receives:
    - (i) Inspection of 100 percent of its surface, using visual inspection and liquid penetrant or equivalent inspection methods; and
    - (ii) Inspection of structurally significant internal areas and areas where defects are likely to occur, using radiographic or equivalent inspection methods.
  - (3) A casting factor of 1.5 or greater may be used, provided that each casting receives inspection of 100 percent of its surface using visual inspection and liquid penetrant or equivalent inspection methods.
  - (4) A casting factor of 2.0 or greater may be used, provided that each casting receives inspection of 100 percent of its surface using visual inspection methods.
  - (5) The number of castings per production batch to be inspected by non-visual methods in accordance with paragraphs [(d)(2)](#d-2) and [(3)](#d-3) of this section may be reduced when an approved quality control procedure is established.

# §25.623. 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 for a part for which any larger special factor is prescribed.**

# §25.625. Fitting factors.


For each fitting (a 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); or
  - (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) For each seat, berth, safety belt, and harness, the fitting factor specified in [§ 25.785(f)(3)](/cfr/14/25.785.md?p=f-3) applies.