Risk Assessment Method to Support Modification of Airfield Separation Standards (2011)

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In August 1959, the FAA issued Airport Engineering Data Sheet Item 24 as a revision to the table that appeared in the 1949 publication (see Table 1). This data sheet reduced the number of airport classes from eight to five. The data sheet stated, “In order to assure maxi- mum safety and the economical and efficient use of the air- port site, careful consideration must be given to the clearance and separation between the various aircraft operating areas” (FAA, 1959, p. 1). It states that the distances established are recommendations and further states “increases to these dis- tances may be desirable in some cases, necessary in others” (FAA, 1959, p. 1). It appears that although some classes were consolidated and renamed, only minor changes were made to the actual distances. No specific information is provided as to how these separation standards were defined. This document was issued 2 months before the “jet” age in U.S. commercial aviation began. In October 1959, nonstop transatlantic flights with Boeing 707s were initiated between New York’s Idlewild Airport (now known as John F. Kennedy International Airport) and Europe. In 1961, the FAA published the third document titled Airport Design (Federal Aviation Agency, 1961). The revised standards (see Table 2) were no longer based upon the type of service, but rather on the runway length. In the early 1960s, the FAA initiated the Advisory Circular publication series. Although the information in these publica- tions was advisory, the airport standards contained in them became mandatory when federal aid was used for airport development. As documents were updated to conform to the new publication system, there was a tendency to develop Advi- sory Circulars containing design information for a specific type of airport. For example, AC 150/5300-1, VFR Airports, applied to airports that were intended to have operations by general aviation aircraft during visual meteorological conditions (FAA, 1963). AC 150/5300-4A, Utility Airports, was issued to provide guidance and standards for airports that intended to serve air- craft weighing 12,500 lb or less (FAA, 1968). During the late 1960s and through the 1970s, there were several Advisory Circulars published on specific aspects of airport design for airports intended to serve air carriers. Sub- jects of these Advisory Circulars included such things as run- way geometry, taxiways, surface gradient and line-of-sight, and jet blast. During this period, there were no funds allocated for the research and development of design standards. The runway/ runway and runway/taxiway separation standards contained in these publications were based on the experience gained during the post-World War II period, including experience with the precision of navigational aids such as instrument landing systems (ILSs), the ability of pilots to stay on center- line, and air traffic control considerations. In the 1960s, the FAA’s Flight Standards organization and the ICAO Obstacle Clearance Panel (OCP) developed the Collision Risk Model (CRM)3 for ILS operations. The CRM was based on actual observation of 2,500 aircraft on an ILS precision approach to a runway. Four observations were made for each aircraft’s approach. This model was used to define the area that needed to be protected on an airport when an aircraft was making an ILS approach. The runway/taxiway separation also took into account the possibility of an aircraft on landing rollout or takeoff roll veering off the runway. Additional information on the CRM is provided in Appendix B. 5 Type of Service Runway Centerline to Taxiway Centerline Centerline of Parallel Runways for Contact Operations Centerline of Parallel Taxiways Taxiway Centerline to Aircraft Parking Areas Taxiway Centerline to Obstacle Secondary 150 300 125 100 75 Local 250 500 200 175 100 Trunk 350 500 275 240 150 Continental 400 700 300 260 175 Intercontinental 450 700 325 280 200 Table 1. Minimum clearance standards of airports (ft) (FAA, 1959). Runway Length Runway Centerline to Taxiway Centerline Centerline of Parallel Taxiways Taxiway Centerline to Aircraft Parking Areas Taxiway Centerline to Obstacle 1,600–3,200 150 100 100 75 3,201–4,200 250 200 175 100 4,201–6,000 400 300 250 200 6,001–7,500 400 300 250 200 7,501–10,500 400 300 250 200 Table 2. Airport design and clearance recommendations (ft) (Federal Aviation Agency, 1961). 3 FAA developed the CRM (ICAO, 1980) approach with the University of Oklahoma and input from other countries represented on ICAO’s OCP.