Mr. Jir Misk
Chief, Type Approval Tests and Technical Regulations
SKODA, automobilov a.s.
Vslava Klementa 869
293 60 Mlad Boleslav
Cesk republika (Czech Republic)

Dear Mr. Misk:

This responds to your request for an interpretation of Area "A" to be wiped on motor vehicle windshields, as specified in Federal Motor Vehicle Safety Standards (FMVSS) 103, Windshield defrosting and defogging systems, and 104, Windshield wiping and washing systems. Your question is answered below.

Your letter states your understanding of two ways in which Area A is to be measured, and asks which of the two is correct:

  1. Area 'A' as described in SAE J903 and MVSS 104, may enter into the windshield perimeter zone of 25 mm from the edge of daylight opening in which case the area "A" may be reduced to keep the 25 mm perimeter zone intact for the purpose of calculating the performance of wipers or,

  2. Area 'A' as described in SAE J903 and MVSS 104, must always meet both of these requirements at the same time--

    1. specific angles 16 to 18

    2. remain (on the windshield) bounded by the perimeter zone of 25 mm from the edge of daylight opening (it can not intervene into the perimeter zone of 25 mm). Area 'A' can not be reduced.

Statement One is correct. Area A is that portion of the total area bounded by the angles in Tables I through IV of Standard No. 104 that is also within a perimeter 25 mm within the daylight opening of the windshield frame. It is not necessary that the windshield be large enough to contain the whole area bounded by the angles (of which 16 to 18 is the left border) as indicated by Statement Two.

S.4.1.2 of Standard No. 104 states the following:

Wiped area. When tested wet in accordance with SAE Recommended Practice J903a, May 1966, each passenger car windshield wiping system shall wipe the percentage of Areas A, B, and C of the windshield (established in accordance with S4.1.2.1) that (1) is specified in column 2 of the applicable table following subparagraph S4.1.2.1 and (2) is within the area bounded by a perimeter line on the glazing surface 25 millimeters from the edge of the daylight opening.

Area A of the windshield is described at S3.1 of SAE Standard J903a. S3.1 states:

[Area A] ... has been established using the angles of Table 1 applied as shown in Figs. 1 and 2. Fig. 1 (side view), the upper and lower boundary of the area is established by the intersection of two planes, tangent to the upper and lower sides of the eye range contour, with the windshield glazing surface. The planes are fixed by angles above and below the glazing surface reference line. Fig. 2 (plan view), the left and right boundaries of the area are established by the intersection of two planes tangent to the left and right sides of the eye range contour. The planes are fixed by angles to the left and right of the plan view reference line.

S3.1's description means that Area A is not a fixed, predetermined area for all windshields, but is an area that varies from windshield to windshield. The variables are the angle of measurement and the width of the car. S4.1.2 of Standard No. 104 adds another variable by describing Area A as within the area bounded by a perimeter line on the glazing surface 25 millimeters from the edge of the daylight opening.

Furthermore, not all of Area A must be wiped. In Standard No. 104, Tables I, II, III, and IV all specify that after the test is conducted, a minimum of 80% of Area A must be wiped.

Please note that since Standard No. 103 references Standard No. 104 in specifying Area A as the applicable cleared area, the above description of Area A also applies to Standard No. 103.

I hope this information is helpful. If you have any further questions, please contact Dorothy Nakama of my staff at this address or at (202) 366-2992. Our FAX number is (202) 366-3820.

Sincerely,
John Womack
Acting Chief Counsel
ref:103#104
d:5/6/97