{"data":{"id":"us/14-cfr-appendix-b-to-part-33","jurisdiction":"us","citation":"14 CFR Appendix B to Part 33","heading":"Appendix B to Part 33—Certification Standard Atmospheric Concentrations of Rain and Hail","body":"Figure B1, Table B1, Table B2, Table B3, and Table B4 specify the atmospheric concentrations and size distributions of rain and hail for establishing certification, in accordance with the requirements of § 33.78(a)(2). In conducting tests, normally by spraying liquid water to simulate rain conditions and by delivering hail fabricated from ice to simulate hail conditions, the use of water droplets and hail having shapes, sizes and distributions of sizes other than those defined in this appendix B, or the use of a single size or shape for each water droplet or hail, can be accepted, provided that applicant shows that the substitution does not reduce the severity of the test.\nTable B1—Certification Standard Atmospheric Rain Concentrations\nAltitude (feet) Rain water content (RWC) (grams water/meter 3 air)\n0 20.0\n20,000 20.0\n26,300 15.2\n32,700 10.8\n39,300 7.7\n46,000 5.2\nRWC values at other altitudes may be determined by linear interpolation.\nNote: Source of data—Results of the Aerospace Industries Association (AIA) Propulsion Committee Study, Project PC 338-1, June 1990.\nTable B2—Certification Standard Atmospheric Hail Concentrations\nAltitude (feet) Hail water content (HWC) (grams water/meter 3 air)\n0 6.0\n7,300 8.9\n8,500 9.4\n10,000 9.9\n12,000 10.0\n15,000 10.0\n16,000 8.9\n17,700 7.8\n19,300 6.6\n21,500 5.6\n24,300 4.4\n29,000 3.3\n46,000 0.2\nHWC values at other altitudes may be determined by linear interpolation. The hail threat below 7,300 feet and above 29,000 feet is based on linearly extrapolated data.\nNote: Source of data—Results of the Aerospace Industries Association (AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.\nTable B3—Certification Standard Atmospheric Rain Droplet Size Distribution\nRain droplet diameter (mm) Contribution total RWC (%)\n0-0.49 0\n0.50-0.99 2.25\n1.00-1.49 8.75\n1.50-1.99 16.25\n2.00-2.49 19.00\n2.50-2.99 17.75\n3.00-3.49 13.50\n3.50-3.99 9.50\n4.00-4.49 6.00\n4.50-4.99 3.00\n5.00-5.49 2.00\n5.50-5.99 1.25\n6.00-6.49 0.50\n6.50-7.00 0.25\nTotal 100.00\nMedian diameter of rain droplets in 2.66 mm\nNote: Source of data—Results of the Aerospace Industries Association (AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.\nTable B4—Certification Standard Atmospheric Hail Size Distribution\nHail diameter (mm) Contribution total HWC (%)\n0-4.9 0\n5.0-9.9 17.00\n10.0-14.9 25.00\n15.0-19.9 22.50\n20.0-24.9 16.00\n25.0-29.9 9.75\n30.0-34.9 4.75\n35.0-39.9 2.50\n40.0-44.9 1.50\n45.0-49.9 0.75\n50.0-55.0 0.25\nTotal 100.00\nMedian diameter of hail is 16 mm\nNote: Source of data—Results of the Aerospace Industries Association (AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.","path":["Title 14—Aeronautics and Space","CHAPTER I—FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION","SUBCHAPTER C—AIRCRAFT","PART 33—AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-14.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:24:20Z","sha256":"7fb0cf0ea8e7182eabeede764734092762a895c66c163faaf68cfeabcc47ff3e","source_id":"us-cfr","stale":true,"prev":"us/14-cfr-appendix-a-to-part-33","next":"us/14-cfr-appendix-c-to-part-33"},"notice":"GroundRules: Original legal text. Not legal advice."}