FAA Federal Aviation Regulations (FARS, 14 CFR)

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.

 

     Table B1_Certification Standard Atmospheric Rain Concentrations
------------------------------------------------------------------------
Rain
water
content
(RWC)
Altitude (feet)                           (grams
water/
meter \3\
air)
------------------------------------------------------------------------
0............................................................       20.0
20,000.......................................................       20.0
26,300.......................................................       15.2
32,700.......................................................       10.8
39,300.......................................................        7.7
46,000.......................................................        5.2
------------------------------------------------------------------------
RWC values at other altitudes may be determined by linear interpolation.
Note: Source of data_Results of the Aerospace Industries Association
(AIA) Propulsion Committee Study, Project PC 338-1, June 1990.

     Table B2_Certification Standard Atmospheric Hail Concentrations
------------------------------------------------------------------------
Hail
water
content
(HWC)
Altitude (feet)                           (grams
water/
meter \3\
air)
------------------------------------------------------------------------
0............................................................        6.0
7,300........................................................        8.9
8,500........................................................        9.4
10,000.......................................................        9.9
12,000.......................................................       10.0
15,000.......................................................       10.0
16,000.......................................................        8.9
17,700.......................................................        7.8
19,300.......................................................        6.6
21,500.......................................................        5.6
24,300.......................................................        4.4
29,000.......................................................        3.3
46,000.......................................................        0.2
------------------------------------------------------------------------
HWC 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.
Note: Source of data_Results of the Aerospace Industries Association
(AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.

      Table B3_Certification Standard Atmospheric Rain Droplet Size
Distribution
------------------------------------------------------------------------
Contribution
Rain droplet diameter (mm)                    total RWC
(%)
------------------------------------------------------------------------
0-0.49....................................................            0
0.50-0.99.................................................         2.25
1.00-1.49.................................................         8.75
1.50-1.99.................................................        16.25
2.00-2.49.................................................        19.00
2.50-2.99.................................................        17.75
3.00-3.49.................................................        13.50
3.50-3.99.................................................         9.50
4.00-4.49.................................................         6.00
4.50-4.99.................................................         3.00
5.00-5.49.................................................         2.00
5.50-5.99.................................................         1.25
6.00-6.49.................................................         0.50
6.50-7.00.................................................         0.25
-------------
Total.................................................       100.00
------------------------------------------------------------------------
Median diameter of rain droplets in 2.66 mm
Note: Source of data_Results of the Aerospace Industries Association
(AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.

   Table B4_Certification Standard Atmospheric Hail Size Distribution
------------------------------------------------------------------------
Contribution
Hail diameter (mm)                        total HWC
(%)
------------------------------------------------------------------------
0-4.9.....................................................            0
5.0-9.9...................................................        17.00
10.0-14.9.................................................        25.00
15.0-19.9.................................................        22.50
20.0-24.9.................................................        16.00
25.0-29.9.................................................         9.75
30.0-34.9.................................................         4.75
35.0-39.9.................................................         2.50
40.0-44.9.................................................         1.50
45.0-49.9.................................................         0.75
50.0-55.0.................................................         0.25
-------------
Total.................................................       100.00
------------------------------------------------------------------------
Median diameter of hail is 16 mm
Note: Source of data_Results of the Aerospace Industries Association
(AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.

[Doc. No. 28652, 63 FR 14799, Mar. 26, 1998]