23.621—Casting factors.
(a) General.
The factors, tests, and inspections specified in paragraphs (b) through (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) and (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) and (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 airplane or result in serious injury to occupants, the following apply:
(i)
Have a casting factor of not less than 1.25 and receive 100 percent inspection by visual, radiographic, and either magnetic particle, penetrant or other approved equivalent non-destructive inspection method; or
(ii)
Have a casting factor of not less than 2.0 and receive 100 percent visual inspection and 100 percent approved non-destructive inspection. When an approved quality control procedure is established and an acceptable statistical analysis supports reduction, non-destructive inspection may be reduced from 100 percent, and applied on a sampling basis.
(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 § 23.305 at an ultimate load corresponding to a casting factor of 1.25; and
(3)
Examples of these castings are structural attachment fittings, parts of flight control systems, control surface hinges and balance weight attachments, seat, berth, safety belt, and fuel and oil tank supports and attachments, and cabin pressure valves.
(d) Non-critical castings.
For each casting other than those specified in paragraph (c) or (e) of this section, the following apply:
(1)
Except as provided in paragraphs (d)(2) and (3) of this section, the casting factors and corresponding inspections must meet the following table:
| Casting factor | Inspection |
|---|---|
| 2.0 or more | 100 percent visual. |
| Less than 2.0 but more than 1.5 | 100 percent visual, and magnetic particle or penetrant or equivalent nondestructive inspection methods. |
| 1.25 through 1.50 | 100 percent visual, magnetic particle or penetrant, and radiographic, or approved equivalent nondestructive inspection methods. |
(2)
The percentage of castings inspected by nonvisual methods may be reduced below that specified in subparagraph (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—
(ii)
The castings must be inspected as provided in paragraph (d)(1) of this section for casting factors of “1.25 through 1.50” and tested under paragraph (c)(2) of this section.
(e) Non-structural castings.
Castings used for non-structural purposes do not require evaluation, testing or close inspection.