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I. GENERAL DISCUSSION This addendum is to expand on the earlier report submitted on November 10, 2004 showing that the Geneva Commons Building project will not adversely effect the instrument procedures at SNA. It is to address some concerns that have been expressed about buildings in the location of the Geneva Commons project. Part 77 surfaces are advisory in nature and provide the requirements for submission of Notices of Proposed Construction or Alteration, Form 7460-1. If the object exceeds a height or surface defined in Subpart C of FAR Part 77, it would be an obstruction and would be the subject of an aeronautical study by the FAA to determine its effect on navigable airspace. If the object is concluded to have a substantial adverse effect upon the safe and efficient utilization of such airspace, it would be determined to be a hazard to air navigation. In the Obstacle Analysis and Determination of No Hazard1 of the Geneva Commons site, the FAA determined that the building would not constitute a substantial adverse effect upon the safe and efficient utilization of such airspace. Our independent analysis concluded the same. As part of the FAA's aeronautical determination an analysis is made as to any impact to Instrument procedures at the effected airport. The reason for this analysis is that the United States Standard for Terminal Instrument Procedures (TERPS) surfaces is more restrictive than Part 77, and TERPS surfaces are regulatory. Therefore, any penetrations of the applicable TERPS surfaces would adversely impact the instrument procedure and require a modification or nullification of the procedure if such object were allowed to be built depending on the amount of penetration and any mitigating factors. In the present case, there is neither any impact to any of the instrument procedures at John Wayne Airport from the Geneva Commons building site nor does the building penetrate any of the regulatory TERPS obstacle clearance surfaces. II. ILS ANALYSIS There appears to be some concern from the ALCU staff on potential impacts of the Geneva building on the ILS to Runway 19R at John Wayne Airport. As pointed out in the above discussion, and readily viewable in diagrams A and B, the proposed building site is located well outside the ILS TERPS surfaces. The proposed Geneva Commons building sits approximately 1300 feet outside the nearest edge of the ILS trapezoid. Precision (ILS) Final Approach obstruction clearance surfaces are as depicted in Diagram B. The "Y", "X" and 'W" obstacle clearance surface (OCS) dimensions are as specified in diagram B. There are many additional formulae utilized but this page provides the basics. The 'W" OCS is an inclined plane at SNA at a 1 :34 slope beginning 200' from the landing threshold point (L TP) and extending along the approach course centerline to the final approach fix. The "X" obstacle surface begins at the height of the 'W" surface and rises at a slope of 1 :4 perpendicular to the final approach course. 1 2003 - A WP - 2870 - OE issued 9/23/2003 2 75C-107