Appendix 5.1 — FAA Airworthiness Requirements for Airframes
- Standards Branch
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1. Transport Category Aircraft — FAR 25
1.1. Part 25.571 Damage — Tolerance and Fatigue Evaluation of Structure
(a) General. An evaluation of strength, detailed design, and fabrication must show that catastrophic failure due to fatigue, corrosion, or accidental damage, will be avoided throughout the operational life of the airplane. This evaluation must be conducted in accordance with the provisions of paragraphs (b) and (e) of this section, except as specified in paragraph (c) of this section, for each part of the structure which could contribute to a catastrophic failure (such as wing, empennage, control surfaces and their systems, the fuselage, engine mounting, landing gear, and their related primary attachments).
(e) Damage — tolerance (discrete source) evaluation. The airplane must be capable of successfully completing a flight during which likely structural damage occurs as a result of:
- Impact with a 4-pound bird when the velocity of the airplane relative to the bird along the airplane's flight path is equal to Vc at sea level or 0.85Vc at 8,000 feet, whichever is more critical;
- Uncontained fan blade impact;
- Uncontained engine failure; or
- Uncontained high energy rotating machinery failure.
1.2 Part 25.631 Bird Strike Damage — Empennage
The empennage structure must be designed to assure capability of continued safe flight and landing of the airplane after impact with an 8-pound bird when the velocity of the airplane (relative to the bird along the airplane's flight path) is equal to Vc at sea level, selected under Part 25.335(a). Compliance with this section by provision of redundant structure and protected location of control system elements or protective devices such as splitter plates or energy absorbing material is acceptable. Where analysis, tests, or both show compliance, use of data on airplanes having similar structural design is acceptable.
1.3. Part 25.775 Windshields and Windows
(a) Internal panes must be made of non-splintering material.
(b) Windshield panes directly in front of the pilots in the normal conduct of their duties, and the supporting structures for these panes, must withstand, without penetration, the impact of a 4-pound bird when the velocity of the airplane (relative to the bird along the airplane's flight path) is equal to the value of Vc, at sea level, selected under Part 225.335(a).
1.4. Part 25.1323 Airspeed Indicating System
(f) Where duplicate airspeed indicators are required, their respective pitot tubes must be far enough apart to avoid damage to both tubes in a collision with a bird.
2. Normal, Utility, Acrobatic and Commuter Aircraft — FAR 23
2.1 Part 23.775 Windshield and Windows
(h) In addition, for commuter category airplanes, the following applies:
Windshield panes directly in front of the pilots in the normal conduct of their duties, and the supporting structures for these panes, must withstand, without penetration, the impact of a 2-pound bird when the velocity of the airplane (relative to the bird along the airplane's flight path) is equal to the airplane's maximum approach flap speed.
- The windshield panels in front of the pilots must be arranged so that, assuming the loss of vision through any one panel, one or more panels remain available for use by a pilot seated at a pilot station to permit continued safe flight and landing.
2.2. Part 23.1323 Airspeed Indicating System
(f) For commuter category airplanes, where duplicate airspeed indicators are required, their respective pitot tubes must be far enough apart to avoid damage to both tubes in a collision with a bird.
3. Normal Category Rotorcraft — FAR 27
There are no specific requirements for bird proofing within these standards.
4. Transport Category Rotorcraft — FAR 29
Part 29.631 Bird Strike
The rotorcraft must be designed to ensure capability of continued safe flight and landing (for Category A) or safe landing (for Category B) after impact with a 2.2-lb. bird when the velocity of the rotorcraft (relative to the bird along the flight path of the rotorcraft) is equal to VNE or VH (whichever is less) at altitudes up to 8,000 feet. Compliance must be shown by tests or by analysis based on tests carried out on sufficiently representative structures of a similar design.
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