Applying SAAAR

By Frank Alexander | February 1, 2008
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In December 2005, FAA published Advisory Circular 90-101, "Approval Guidance for RNP Procedures with SAAAR (Special Aircraft and Aircrew Approval Required)." This AC provides guidance material for approvals to take advantage of the Required Navigation Performance (RNP) procedure design criteria in FAA Order 8260.52.

SAAAR is an important element in the continuing evolution from traditional, ground-based navigation to a system that gives credit for aircraft performance based on its RNP capability.

RNP SAAAR procedures provide the opportunity to design instrument approach procedures that can be tailored to the geographic situation through the use of curved segments, including curved legs on the final approach, something that is impossible with conventional procedures. They also allow for more precise vertical paths, a key element in obtaining lower landing minima using barometric vertical navigation.

FAA at this writing had published more than 20 SAAAR procedures, with plans to continue developing them at a rate of about 25 per year.

Today, there are a growing number of air carrier and general aviation aircraft capable of navigation performance to RNP values of less than 0.3 nautical miles, equipped with navigation system features that enable them to take greater advantage of the flexibility of approach procedures based on area navigation (RNAV) principles. Alaska Airlines pioneered these approaches when it developed a RNP approach at Juneau, Alaska, in the late 1990s.

Delta’s Experience

To help gain a better understanding of the SAAAR application process, I spoke to Capt. Mark Bradley, chief technical pilot for Delta Air Lines. He gave me his airline’s perspective on the benefits of SAAAR and the process Delta is going through for approval.

Bradley said he felt Delta could gain operational benefits by gaining access to airports where conventional procedures either did not exist or did not provide adequate service in terms of approach minima. He said he believes it would not be extremely costly to make the transition from RNAV procedures to SAAAR and views the benefits from SAAAR as being primarily applied to Delta’s fleet of Boeing 737NGs, which Boeing has certified as meeting a RNP value of.11. The main challenge for the 737 fleet will be in the training development for flight crews.

Delta also is seeking SAAAR approval for its Boeing 757, 767 and 777 fleets and envisions the benefits to those aircraft for operations in South America, including destinations such as Quito, Ecuador. Delta is presently engaged in an equipment upgrade for the B757/767 fleets that will include GPS and the Honeywell Pegasus flight management computer (FMC) software package. Bradley expects the 757/767 fleet will be approved for RNP.16 operations.

Part of the reason for the higher RNP value is the inability of the FMC software to display course deviation in values of less than one-tenth of a mile. Delta also is proposing certain operational mitigations to offset that and other SAAAR equipment requirements. The airline expects to complete the avionics upgrades by 2013.

As with any new process, there were some issues that were encountered during the application. Bradley’s overall observation of working with FAA on this process was favorable. He said there was an overall willingness to help resolve outstanding issues and that everyone wanted to do the right thing. He said he also was pleased FAA’s All Weather Operations Branch division manager, John McGraw, and Jeff Williams, manager of the Air Traffic Organization’s RNAV/RNP group, were engaged in the process. He believes as long as they stay involved and airline senior management continues to support the effort, there will be a continued incentive to move forward.

Bradley said he did feel, however, that FAA was resource limited and there was a lack of communication between FAA headquarters and the certificate management office at the local level. There were occasions when problems that were solved at the headquarters level were not communicated to the local level, he related.

Advisory Circulars

There is an industry concern that the movement toward a performance-based navigation system is being promulgated by Advisory Circular rather than regulatory change. I asked Bradley his thoughts on this. He said that in spite of some of the challenges Delta faced in working through the approval process, he believes use of ACs is a better choice. He believes this approach allows greater flexibility for operators and local certificate management offices in interpreting the guidance.

Bradley also said that changes can be made to AC 90-101 and Order 8260.52 to improve the process.

To facilitate these changes, the FAA-designated Performance Based Aviation Rulemaking Committee created an Action Team to address the documents and was nearing completion of a set of recommendations to accomplish the task.

SAAAR exemplifies the opportunities and advantages of performance-based area navigation, and in doing so provides greater access and safety margins than conventional non-precision approach procedures. In some instances, it may even provide lower landing minimums than ILS approach procedures where obstacles in the missed approach segment cannot be avoided by headings or courses based on ground-based navigation aids. As we continue to evolve in this direction, SAAAR procedures will play an important role in defining the benefits of RNP.

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