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OCR for page 56
An Assessment of NASA’s National Aviation Operations Monitoring Service D Principal Segments of Aviation in the United States Title 14 of the Code of Federal Regulations (CFR) governs Aeronautics and Space. Within Title 14, four parts are of interest in understanding the segments of aviation addressed in this report. Those parts—91, 119, 121, and 135—are described below. Part 91 covers “General Operating and Flight Rules” and prescribes rules governing the operation of aircraft within the United States. For persons operating civil aircraft as air carriers or commercial operations, Part 119 prescribes the type of operating certificate that must be obtained, with accompanying additional regulations, specifically whether operations must be under Part 121 or Part 135. Part 121 prescribes the regulations, beyond those prescribed in Part 91, that must be followed for large aircraft operations and for scheduled operations in smaller aircraft capable of carrying 10 or more passengers. Part 135 prescribes the regulations, again beyond those prescribed in Part 91, for scheduled commuter air carriers using aircraft capable of carrying nine or fewer passengers and for on-demand, for-hire air taxi and charter operations carrying passengers and/or freight. Title 14 of the CFR has several other parts that govern specialized air operations such as agricultural aircraft operations and National Parks Air Tours, but those operations did not play a significant role in the NAOMS survey and are not described here. Flight operations are often referred to by the part of the regulations that governs them. So, large operators such as American Airlines, Delta Air Lines, Federal Express, Southwest Airlines, and United Airlines are typically referred to as Part 121 carriers. Similarly, small scheduled commuter operators, on-demand air taxis, and small charter freight operators are typically referred to as Part 135 carriers. Finally, general aviation operations by private pilots and corporate flight operations are typically referred to as Part 91 operations. As discussed in the body of the report, the committee was concerned about the aggregation of these different segments of aviation in the NAOMS survey. One of the impacts of this aggregation was the very large number of flights reported by some of the respondents in the AC survey. As can be seen in Table D.1, the number of hours that a pilot is permitted to fly during specific time periods is different in the different segments of aviation. Note that there are no limitations on pilot flight time in Part 91 operations and that the limitations are different in the scheduled and the nonscheduled segments of Part 135. In addition, other characteristics vary across the types of operations, and these variations could impact the interpretation of results if they are aggregated, such as typical frequency-of-flying and pilot-training requirements. The committee was also concerned about this aggregation because historically, the safety performance of these different segments of aviation has been notably different, as Table D.2 shows. By combining segments of aviation with disparate safety performance in the NAOMS survey, the opportunity to gain insight into the causes of the differences in safety performance was lost.
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An Assessment of NASA’s National Aviation Operations Monitoring Service TABLE D.1 Limitations on Pilot Flight Time (hours) by Category of Operation Category During 7 Consecutive Days In a Calendar Month In a Calendar Quarter or 90-Day Period In a Calendar Year Part 121 one- or two-pilot crews 32 100 1,000 Part 121 two pilots plus additional flight crew member 120 300 1,000 Part 135 scheduled 34 120 1,200 Part 135 nonscheduled 500 1,400 Part 91 No limit No limit No limit No limit SOURCE: 14 CFR 121.481, 14 CFR 121.483, 14 CFR 135.265, 14 CFR 135.267. TABLE D.2 Fatal Accident Rates, by Category of Operation, 1983-2008 Category Fatal Accidents Flight Hours Fatal Accidents per 100,000 Flight Hours Part 121 scheduled 64 357,075,443 0.018 Part 121 nonscheduled 25 16,915,795 0.148 Part 135 scheduled 78 35,201,228 0.222 Part 135 nonscheduled 575 77,989,000 0.737 Part 91 10,250 674,227,000 1.520 SOURCE: Available at http://www.ntsb.gov/aviation/Stats.htm.