Small Airplanes and Rotorcraft
U.S. civil aviation includes about 180,000 general aviation aircraft, the vast majority of which are small airplanes (with a maximum takeoff weight of less than 12,500 pounds). About 5,100 are rotorcraft. By comparison, scheduled air carriers (FAR Parts 121 and 135) operate more than 7,000 aircraft, including about 5,000 large turbojet aircraft (the rest are turboprop airplanes, piston-engine airplanes, and rotor-craft). The total fleet of general aviation aircraft accumulates about 24 million flight hours annually, compared to 14 million flight hours for large air carriers and 5 million flight hours for commuter airlines and air taxis. Similarly, the number of small airplane and rotorcraft operators in the United States (approximately 100,000) is also much larger than the number of large airplane operators (just 153 for FAR Part 121 air carriers), and the former encompass a much wider range of pilot experience and skills than the latter (GAMA, 1997; FAA, 1996a, 1996b).
Some corporate and commercial operators of small airplanes and rotorcraft use safety procedures and techniques very similar to those of large airlines. For example, the aviation departments of many Fortune 500 corporations have airplane safety records comparable to those of large airlines. Rotorcraft operators supporting offshore oil production and corporations that provide aircraft for executive transportation also tend to have relatively sophisticated operations. However, most operators of small airplanes and rotorcraft have just a few aircraft and do not have sophisticated institutional safety programs. For example, 75 percent of the operators who belong to the Helicopter Association International operate fewer than five helicopters, and 39 percent operate only one. On the other hand, the 13 largest U.S. carriers, with turbojet fleets ranging from 150 to almost 700 aircraft, have an average of more than 300 turbojet aircraft. The 62 other carriers that operate turbojets, with fleet sizes ranging from 1 to 35 aircraft, have an average of 10 turbojet aircraft (FAA, 1994).
Small airplanes and rotorcraft operate in a much broader spectrum of functional modes than most large airplanes. For example, small airplanes and rotorcraft operate as air taxis, corporate aircraft, business aircraft, personal aircraft, and instructional aircraft. Other roles include sightseeing, pipeline patrol, law enforcement, emergency rescue, scientific experimentation, transport of external loads, crop dusting, and firefighting. Operational cycles are also very different. A typical small airplane or rotorcraft is in the air many fewer hours per year than a typical large transport—an average of 140 hours for small airplanes and rotorcraft, compared to 3,000 to 3,500 hours for large transport airplanes operated by major air carriers. Small airplanes and rotorcraft also operate out of many more airports and landing areas than large airplanes, and many of these lack control towers and other landing and takeoff aids. Small aircraft, rotorcraft, and large transport airplanes do share much of the same airspace and use many of the same facilities, however. Thus, despite their differences, it is essential that systems and procedures allow them to operate together safely (GAMA, 1997; FAA, 1996a, 1996b).
The safety management process for small airplanes and rotorcraft must be flexible enough to accommodate the diverse nature of these communities, and this is likely to be a difficult challenge. Final accident investigation reports for small airplanes and rotorcraft (as with large transports) show that the majority of accidents are attributable to human error, and the small role played by aircraft system malfunctions indicates that the current aircraft certification and continued airworthiness process is working well.
This chapter deals with the differences in the safety management processes applicable to a typical transport airplane, such as a large passenger jet operated by a major airline, and a typical small airplane, such as a small general aviation aircraft or helicopter owned by an individual or business that may not own any other aircraft. The committee acknowledges, but does not specifically address, additional considerations raised by less common—but hardly unusual—
situations where small commercial air carriers operate small aircraft or a large corporation operates a fleet of business jets larger than the aircraft operated by many commuter airlines.
SAFETY AND SAFETY MANAGEMENT PROCESSES
Because of the similarities in circumstances and conditions relating to accidents involving large airplanes, small airplanes, and rotorcraft, the committee believes the recommendations that appear elsewhere in this report, which are focused on accidents and incidents involving large airplanes, are generally applicable to small airplanes and rotorcraft. The differences that do exist, however, indicate that different means should be used to carry out many of the committee's recommendations.
Causes of Accidents and Incidents
Uncertainties regarding two important factors degrade the accuracy of accident statistics for small airplanes and rotor-craft: (1) the appropriate categorization of accidents according to type of operation and (2) the accuracy of flight hour information for each type of operation.
The NTSB is unable to conduct detailed investigations into most accidents involving small airplanes and rotorcraft because of the large number of such accidents and the limited resources that the NTSB has available for this task. The NTSB conducts many of these investigations using telephone inquiries with on-scene personnel instead of dispatching field investigators to the site. If the pilot is killed and there are no other survivors (or no one else was on board), it is sometimes very difficult to accurately determine what events preceded the accident. Because of the great variety of small aircraft and small aircraft operations, little or no mechanical or system trend analyses are performed to better understand the underlying causes of small aircraft accidents.
Unlike most operators of transport airplanes, most operators of small aircraft are not required to report operational statistics, such as flight hours, to the FAA or any other government agency. Flying hours are presently estimated by the FAA using statistical forecasting techniques from its "General Aviation and Air Taxi Activity and Avionics Survey," which is distributed annually to a sample population of aircraft owners. Responses are not mandatory, and small operators engaged in varied operations may not have accurate records of flight hours broken down by type of operation. In addition, NTSB statistical summaries on general aviation operations and accident rates, which are derived from the same FAA survey, take nearly a year to finalize and are only available on an annual basis. The resulting lack of precision in estimated flight hours results in accident rate statistics that are equally imprecise. More precise calculations and timely dissemination of accident statistics would be helpful to understand current trends and the effectiveness of accident prevention measures.
Although there were fewer accidents in 1996 involving small airplanes and rotorcraft as a group than in the several prior years, small airplanes and rotorcraft (like large airplanes) seem to be experiencing a relatively stable fatal accident rate. With the number of flying hours projected to increase over the next decade, small airplanes and rotorcraft are expected to experience an increase in the total number of fatal accidents.
As with scheduled air carriers, final accident investigation reports for small airplanes and rotorcraft show that the majority of accidents are attributable to human error. The incomplete understanding of many human error-related accidents emphasizes the need for continued work in this area, as recommended in Chapter 5. Another similarity shared by large and small aircraft is the small role that aircraft system malfunctions play in accidents, which indicates the ongoing effectiveness of the current type certification and continued airworthiness process.
Capabilities of Manufacturers and Operators
The safety management process for the small airplane and rotorcraft communities must be flexible enough to accommodate the diverse nature of these communities, and this is likely to be a difficult challenge. Safety management processes for small airplanes and rotorcraft must overcome challenges associated with a much greater assortment of aircraft designs, more varied operational roles, and a much larger number of operators than those of large airplanes. In most cases, these differences are inherent and unavoidable. For example, large transport airplanes carry sophisticated flight management systems and safety devices, which have helped them achieve a much lower accident rate than small airplanes and rotorcraft. However, the cost of these systems exceeds the total value of many small airplanes, and the systems would be impractical to install on small airplanes or rotor-craft because of configuration limitations (weight, volume, electrical power, etc.).
Very few operators of small airplanes and rotorcraft have the resources to establish flight operations, aircraft maintenance, or data analysis comparable to those of major airlines. Many rely almost exclusively on other organizations, such as the FAA, manufacturers, repair stations, individual licensed mechanics, and/or professional organizations, to provide these resources. In particular, many small operators rely on the FAA to tell them (in the form of an AD) when special action is needed to correct unexpected safety deficiencies in their aircraft. Yet it is often difficult for the FAA to obtain comprehensive safety-related feedback upon which to base ADs because the applicable regulations (FAR Parts 61, 63, 65, 91, 133, and 137) do not require most operators of small airplanes and rotorcraft to report safety hazards.
Currently, many manufacturers of small airplanes and rotorcraft cooperate with the FAA and other aviation organizations to provide a variety of training and accident prevention
programs. However, many models of aircraft are no longer supported by manufacturers because the manufacturers have gone out of business or the aircraft are so old that manufacturers no longer produce parts for them.
Data Collection, Database Management, and Risk Analysis
AIR can fulfill its mandate to maintain the airworthiness of aircraft only if it has access to valid information about service difficulties as they develop. The data collection, database management, and risk analysis methods recommended in Chapter 4 rely heavily on manufacturers and operators to provide these services. This approach cannot be applied directly to the small airplane and rotorcraft industries because of previously noted limitations on the capabilities of most operators and manufacturers of small airplanes and rotorcraft, particularly in cases where manufacturers are no longer in the aircraft manufacturing business. In addition, AIR has much less regulatory control over most operators of small airplanes and rotorcraft than it does with a typical transport airplane operator.
Nevertheless, the small airplane and rotorcraft industries have long recognized the need to know ''what's going wrong'' before adverse situations develop into an accident. Major associations of operators and manufacturers of small airplanes and rotorcraft have tried to address this problem. For example, the Helicopter Association International (the membership of which includes manufacturers and operators) has developed, with the cooperation and support of AIR's Rotorcraft Directorate, a computerized system for collecting data on operational problems from helicopter operators. The information from this system is then made available to the respective manufacturers.
The helicopter industry (particularly the European industry) also has been developing health and usage monitoring systems to monitor the unique characteristics of helicopters. Although the evolution of a practical system has been hindered by variations in technical expertise among users, designers, and regulatory authorities, AIR's Rotorcraft Directorate is attempting to resolve these difficulties in conjunction with JAA and industry. Meanwhile, some of the larger helicopter operators have adopted health and usage monitoring systems on their own initiative and appear to be encouraged by the results. AIR is also trying to improve its ability to manage and analyze available accident and incident data through its Aviation Safety Management Program and other programs.
Major Recommendation 6. Plans to implement the recommended safety management process within the small airplane and rotorcraft communities should be developed in cooperation with small airplane and rotorcraft operators, manufacturers, and associations of operators and manufacturers. The FAA should establish cooperative agreements that define the roles of individual operators, individual manufacturers, their associations, and AIR. These agreements should define the following:
responsibilities of operators for submitting data
responsibilities of operators, manufacturers, associations of operators and manufacturers, and AIR for data collection, database management, risk analysis, risk management/action, and monitoring effectiveness
processes for the routine exchange of data and risk analysis results between operators, manufacturers, associations, and AIR to facilitate effective risk management/action
a publicity program to inform the small airplane and rotorcraft communities of the new safety management process
ADDITIONAL SMALL AIRPLANE CONCERNS
As already noted, small airplanes include a broad spectrum of airplane designs, operators, and missions. Although small airplane accidents cause more fatalities than large aircraft accidents, individual accidents are rarely newsworthy, and accident prevention for this segment of the air transportation system receives secondary attention from the media, NTSB, and FAA. In this context, it is difficult to develop a comprehensive understanding of how and why certain kinds of accidents occur and how to prevent them.
Although human factors are clearly the leading cause of small airplane accidents, NTSB accident reports often provide only sketchy details about the human factors leading to an accident. In addition, the NTSB only performs field investigations of approximately 20 percent of general aviation accidents. As a result, the examination of aircraft systems and other physical evidence is sometimes incomplete, making it difficult to identify trends and implement broad corrective action in a timely fashion. Increasing the number of NTSB field investigations of small airplane accidents and the amount of human factors information gathered during these investigations would help address this problem.
General aviation involves many dissimilar segments, with widely differing aircraft designs, regulations, and pilot capabilities. For example, general aviation aircraft—of which small airplanes are by far the largest part—are involved in nearly 2,000 accidents per year, with an estimated accident rate of 8.06 per 100,000 flight hours and a fatal accident rate of 1.51 per 100,000 flight hours. This is 25 to 50 times higher than the corresponding values for the corporate aviation segment of the general aviation community (0.14 accidents per 100,000 flight hours and 0.06 fatal accidents per 100,000 flight hours) (NTSB, 1996). In fact, accident rates for corporate aircraft are comparable to accident rates for Part 121 air carriers (0.21 accidents per 100,000 flight hours and 0.035 fatal accidents per 100,000 flight hours) (FAA, 1994). Corporate aircraft are flown by professional pilots, and the disparity in
accident rates indicates that many small airplane accidents may result from pilots who are at risk because they lack the piloting skills or experience to identify a problem, properly evaluate the risk it poses, and take appropriate action before it is too late. An important safety challenge is to identify these pilots and improve their decision-making skills for situations in which they are likely to be at greatest risk.
Recommendation 7-1. The FAA should conduct separate safety assessments for each segment of the general aviation community to identify the continued airworthiness problems of greatest significance as a function of the type of operation, class of aircraft, and experience level of the pilots.
ADDITIONAL ROTORCRAFT CONCERNS
Rotorcraft—for which most experience to date comes from helicopters—have many of the characteristics and use many of the technical developments as fixed-wing aircraft. However, there are also important differences between rotorcraft and fixed-wing aircraft in general, and between rotorcraft and large transport airplanes in particular. Because of these differences, special efforts—including some procedural changes—will be needed to implement the recommended safety management process in a way that accommodates unique rotorcraft safety considerations and the capability of the rotorcraft industry to identify safety issues based on operator reports.
Certification of Surplus Military Helicopters
The certification of military surplus helicopters is currently an area of particular concern to the rotorcraft industry. In 1995, the U.S. Army decided to sell or give away about 3,000 surplus helicopters over the next several years (and, presumably, associated surplus spare and replacement parts). This decision caused a great deal of concern within the rotorcraft community for several reasons:
the potential economic impact that the sale of inexpensive surplus helicopters and parts could have on the market for newly manufactured equipment (an issue that is not relevant to this study)
the potential safety impact of using surplus military parts on helicopters built to civil designs
uncertainties about how accurately the certification process would assess the safety of using helicopters in civil operations that were not necessarily designed, manufactured, operated, or maintained in accordance with civil airworthiness standards
In many cases, military standards and practices would meet or exceed civil airworthiness standards. But this is not true in all cases, and defining a certification process that would protect public safety—without unduly impairing the ability of prospective purchasers to make appropriate use of their aircraft—is a complicated problem.
FAA certification regulations define requirements for converting surplus military aircraft to civil use. Procedures for fixed-wing aircraft were first developed immediately after the end of World War II, when there was a flood of surplus military aircraft, many ex-military pilots were searching for ways to stay in the aviation business, and most manufacturers were configured to produce military aircraft. At that time, the Civil Aeronautics Administration (the predecessor to the FAA) established a test program to quickly assess the characteristics of available military aircraft. Some of these aircraft—particularly aircraft that had been purchased off-the-shelf by the military—were, in fact, built to civil designs, and they were promptly absorbed into the airline fleets. Other aircraft were required to undergo a more lengthy certification process. These procedures have been modified many times over the years and now provide for civil certification of ex-military helicopters.
Current FAA regulations identify two methods by which aircraft manufactured in accordance with the requirements of, and accepted for use by, the armed forces of the United States can be certificated for civil use:
Certification in the restricted category is possible for military surplus aircraft that have been modified for a limited number of specifically identified special purposes, will be operated only for those special purposes, and will not carry persons or property for compensation or hire (except for helicopters, which may be certificated to transport for hire objects carried as an external load).
Certification in the normal or transport category is possible for aircraft that were designed and constructed in the United States and can be shown to comply with the standard FARs in force at the time the aircraft were accepted by the armed forces.
The current civil fleet of military surplus helicopters being operated today in the United States is composed primarily—if not entirely—of helicopters in the restricted category. Safety concerns for helicopters certificated in the restricted category relate to the following factors:
the physical condition of the aircraft
the degree to which military safety directives have been implemented
the completeness and accuracy of the aircraft's operation and maintenance records
military limits of operation and whether they will apply to civil operation
More than fixed-wing aircraft, the service life of many helicopter systems and components is strongly influenced by a history of severe use, such as frequent consecutive carriage
of heavy loads, and it can be difficult to accurately assess the severity of use of an individual military helicopter. Thus, complete and accurate records of operation and maintenance are especially important for every ex-military helicopter being considered for civil certification.
Many military helicopters are variants of designs certificated for civil use and, because they generally look the same as their civil counterparts, the model designations can be easily confused. Even though the military and civil variants were designed and built by the same manufacturer, they may have been constructed under different quality control standards and to different design criteria and operational limits.
In 1976, the FAA, with the agreement of the Department of Defense, initiated a program to determine the feasibility of certification surplus military aircraft through FAA Order 8130.6, which has since lapsed and been replaced by Order 8130.2C. As requested by the military, FAA inspectors examine each aircraft being released and validate its potential for civil certification. Chief among the conditions surveyed are items (1), (2), and (3), above, and the presence of the name plate from the original manufacturer. Many aircraft that undergo this examination are found to be unworthy of civil certification, although they may be suitable as a source of spare parts. Procedures and criteria for the release of spare parts by the military and guidelines for handling those parts are being negotiated by the FAA and the Department of Defense, and the FAA intends to issue an advisory circular on this topic.
Unfortunately, FAA certification offices have little specific guidance for evaluating applications for restricted category type certificates involving military surplus helicopters. Different aircraft of the same military model have received different restricted category type certificates from different FAA offices. In addition, applications for restricted certificates may receive less attention than standard certification programs because the aircraft are probably going to be used only for industrial work, which reduces the risk to the general public. The safety of the crew and third parties remains a valid concern, however.
Recommendation 7-2. AIR, in conjunction with the original equipment manufacturers of military surplus helicopters, should take timely action to define specific guidance for ACOs (aircraft certification offices) and industry to use in evaluating the airworthiness of military surplus helicopters in accordance with current regulatory standards.
FAA (Federal Aviation Administration). 1994. 1994 Statistical Handbook of Aviation. Washington, D.C.: FAA.
FAA. 1996a. Aviation System Indicators 1996 Annual Report. Washington, D.C.: FAA.
FAA. 1996b. Aviation Safety Statistical Handbook. Washington, D.C.: FAA.
GAMA (General Aviation Manufacturers Association). 1997. General Aviation 1997 Statistical Handbook. Washington, D.C.: GAMA.
NTSB (National Transportation Safety Board). 1996. Annual Review of Aircraft Accident Data. U.S. General Aviation Calendar Year 1994. Washington, D.C.: NTSB.