General Aviation Aircraft Reliability Study

Appendix A CIS Report A-1 GENERAL AVIATION AIRCRAFT COCKPIT INSTRUMENT RELIABILITY ANALYSIS March 17, 1997 Office of Safety, Environmental and Mission Assurance NASA Langley Research Center Hampton, VA 23681 A-2 TABLE OF CONTENTS EXECUTIVE SUMMARY .................................................................................... A-4 LIST OF ACRONYMS ....................................................................................... A-6 INTRODUCTION ................................................................................................ A-7 ANALYSIS RESULTS ...................................................................................... A-30 Basic Aircraft Instruments ................................................................................ A-34 LIST OF FIGURES FIGURE 1. COCKPIT INSTRUMENTATION RELIABILITY FAULT TREE ............................... A-18 FIGURE.2. INFORMATION UNRELIABILITY PERCENTAGE BREAKDOWN ......................... A-31 LIST OF TABLES TABLE 1. INTERMEDIATE EVENT TREE UNRELIABILITY .................................................... A-32 A-3 Executive Summary The Advanced General Aviation Transport Experiment (AGATE) Program is composed of a government-industry-university consortium with a goal to develop the technologies for the revitalization of the US general aviation industry. This program is designed to make the general aviation aircraft in in the US accessible to the majority of the population. This obviously requires an aircraft that is simple to operate, safe, and reliable.

To achieve the Reliability aspect of the program's goal, the baseline reliability of the instruments found in the current general aviation cockpit is needed. Those instruments provide information with which the pilot operates the aircraft. The cockpit information addressed in this report was grouped into the following six categories: • Airspeed information.

• Altitude information.

• Attitude information.

• Advisory Panel (aircraft status) information.

• Communication information.

• Navigation information.

The data presented in this report reflects the probability that the information in the six categories listed above will be provided during a typical 700 nautical mile six-hour flight. This report also contains a summary of piloting functions, a brief description of the current cockpit information, and a fault tree designed to predict the reliability of current, typical general aviation aircraft instruments. A number of sources were used in assembling the reliability data of the current instruments.

Due to proprietary concerns, those sources are not identified.

The major assumptions for this analysis are: • Human factors were not considered.

• The aircraft used was representative of general aviation aircraft population.

• External cues and information (looking out window) were not considered.

• Criticality of information was not considered.

• All ground-based navigation aids are available.

• All components will exhibit an exponential time to failure distribution.

• Environmental elements were not considered.

• Partial failures were not considered.

• Out-of-tolerance conditions were considered failures.

With the above assumptions and available reliability information, a current general aviation aircraft would have a 0.976 probability of completing the given flight profile without loss of any of the required cockpit instrumentation A-4

information. This is the baseline against which the AGATE cockpit should be

compared.

A-5

List of Acronyms

ADF Auto Director Finder AGATE Advanced General Aviation Transport Experiment ATC Air Traffic Control DI FTree Dynamic Innovative Fault Tree FAA Federal Aviation Administration FAR Federal Aviation Regulations IFR Instrument Flight Rules ILS Instrument Landing System MTBF Mean Time Between Failure Nautical Miles NM VHF Very High Frequency VOR VHF Omni Range .A,-6

Introduction

The Advanced General Aviation Transport Experiment (AGATE) is a program being pursued by a government-industry-university consortium. The experiment has as its goal to develop new technologies that will revitalize the US general aviation industry. Future aircraft and supporting technology developed through the AGATE initiative will emphasize safety, affordability, and ease of use for a single pilot. The envisioned future aircraft system will consist of a single-engine, near-all-weather transportation aircraft and related training, airspace, and ground infrastructure systems.

This report includes considerable information from the field of aviation and the basics of flying. Readers of this report who are familiar with general aviation aircraft equipment and terminology should first review Basic Aircraft Instruments, beginning on page A-34.

The AGATE program is designed to make the general aviation aircraft in the US accessible to the majority of the population, as well as make personal air transportation comparable to using private automobiles for trips between 150 nautical miles (NM) and 700 NM. Such a goal requires an aircraft that is simple to operate, safe, and reliable.

In order to establish the reliability goal of a future aircraft cockpit, a baseline of the reliability of the current general aviation cockpit must first be developed. This report is an evaluation of the reliability of the current cockpit for a single-engine, Instrument Flight Rule (IFR) 1 qualified aircraft capable of transporting four people (operator and three passengers) up to 700 NM.

The purpose of this analysis is to provide the predicted reliability of the cockpit instrumentation of a typical general aviation aircraft. This prediction is based on the available empirical data obtained for this report. This data was difficult to obtain for a number of reasons - not the least of which was proprietary concerns.

The major reason for the difficulty was, however, the fact that there is no central clearinghouse for the retention of such data. General aviation aircraft instruments are maintained and repaired by myriad maintenance and service facilities throughout the world.

1Within the US there are several layers of airspace under control of the Federal Aviation Administration (FAA) Air Traffic Control (ATC) centers. Flight into this airspace specifically requires aircraft to be operating under IFR. IFR allows for safe operation of aircraft in weather conditions that normally prevent or reduce a pilot's ability to maintain visible reference to (1) the ground for navigation and (2) the horizon for attitude control.

A-7 An aircraft cockpit's instrumentation is designed to provide the pilot operator with various elements of information required to safely fly the aircraft. Some of that information is critical to continued safe flight; while other information is often not as critical under normal flying conditions. The criticality index of the information is highly dependent on pilot experience and training, weather conditions, and location. Since the human element was not a factor in this analysis, no judgement was made regarding the criticality index of one element over another.

Federal Aviation Regulations (FAR) Part-91 specifies the minimum instrumentation required for general aviation aircraft flying under IFR conditions.

The minimum instruments are: • Airspeed indicator.

• Altimeter.

• Magnetic Direction Indicator.

• Tachometer for each engine.

• Oil pressure gauge for each engine.

• Temperature gauge for each air-cooled engine.

• Oil temperature gauge for each air-cooled engine.

• Manifold pressure gauge for each engine if a variable pitch propeller is used.

• Fuel gauge indicating the quality of fuel in each tank.

• Two-way radio communications system and navigational equipment appropriate to the ground facilities to be used.

• Gyroscopic rate-of-turn indicator.

• Slip-skid indicator.

• Altimeter adjustable for barometric pressure.

• Clock displaying hours, minutes, and seconds.

• Generator or alternator.

• Gyroscopic pitch and bank indicator (artificial horizon).

• Gyroscopic direction indicator (directional gyro or equivalent).

This report presents the predicted reliability of the basic, FAA-required cockpit instruments. These instruments are considered typical of all IFR-capable, general aviation aircraft. There are a number of other instruments available to be mounted in general aviation aircraft, which are not required by the FAA (Loran, GPS, radar altimeter, etc.). This analysis does not consider these additional instruments.

Instrumentation is provided to the pilot via the instruments listed above. For this analysis, the cockpit reliability was the probability that these instruments would accurately provide the information for which they were designed. It was assumed that an instrument failed when it did not function normally or provide accurate information. It was assumed that the cockpit failed if the required information could not be determined by any one instrument or combination of instruments. The importance of the lost information on the total aircraft operation A-8

was not considered in this analysis. The analysis was concerned with the loss of

that information and its impact on cockpit reliability. Additionally, this report

disregards any information that a pilot may obtain from looking outside of the

aircraft.

The information provided by the instruments was analyzed and categorized into

the following six general groups: • Airspeed information.

• Altitude information.

• Attitude information.

• Advisory Panel2 (aircraft status) information.

• Communication information.

• Navigation information.

In order to understand how the various instruments work together to provide a

synergistic knowledge environment for the pilot, one must understand the basics

of piloting. The following is a brief description of the information supplied by

those groups of instruments. This awareness is important in order to

understanding the fault tree logic presented later in this report.

Airspeed information may be obtained by any one of three means - airspeed indicator, engine power setting, or contact with the ATC. The airspeed indication system, the primary reference for airspeed information, calculates the airspeed by measuring the difference between the total air pressure 3 and the atmospheric air pressure. The Pitot system supplies the dynamic pressure to the indicator.

There is a possibility that ice may block the Pitot tube and cause the instrument to give erroneous data; so, there is a heating element in the tube that operates from electrical power supplied from the altemator. (This is a situation where weather conditions would be important if criticality was a consideration for the different events). Another way to determine airspeed is with the tachometer, which quantifies the engine power output. If the enginepower is known, a pilot can deduce his airspeed. Pilots often set their cruising airspeed by engine power. A pilot may also determine airspeed by contacting and ATC center. The ATC can calculate and provide the pilot the aircraft's ground speed. The transponder enables the ATC to match its radar track with that particular aircraft.

The radio is used to convey the information to the pilot.

Altitude information is normally supplied by the altimeter. The altimeter measures the difference in air pressure between the aircraft's current altitude and a reference altitude (usually sea level). It then calculates the difference in feet. If the altimeter should fail in flight, altitude information can be less-accurately calculated to complete that flight by using the vertical speed indicator and the clock on the Advisory Panel.

2Advisory Panel is also known as the Annunciator Panel and the Warning/Caution Panel.

3Total air pressure consisting of the atmospheric pressure and the dynamic pressure caused by traveling through the air.

A-9

Assuming that the pilot knew the assigned (or observed) altitude before the

altimeter failed, a simple calculation of vertical airspeed (feet per minute) over

time (minutes) will provide that approximate altitude information. (While a watch

may appear to be completely satisfactory replacement for the cockpit clock, it is

not considered a cockpit instrument. The FAA does not make allowances for a

watch to substitute for the clock).

Attitude information consists of three elements - roll, yaw, and pitch. This is important information for the pilot because he may inadvertently progress into an undesirable attitude when deprived of visual references with the ground. This is a common problem when flying at night or in conditions of limited visibility. The attitude indication system (the gyroscopic pitch, bank, and direction indicators) and Turn Coordinator are the primary instruments that provide this attitude information. They allow the pilot to determine if the wings are straight and level.

The attitude indication system requires pneumatic power and the Turn Coordinator requires electrical power. Pitch information may be obtained by either direct observation of the attitude indicator or it may be deduced by observing changes in either altitude or airspeed. If an aircraft's speed is increasing, the engine power has not changed, a pilot knows that the aircraft is in a dive (pitch down). The Tum Coordinator, as its name implies, is used to make balanced turns. This is important in reducing "skid," indicating "side slip," and in improving the turn efficiency. Changes in an aircraft's yaw may be determined by the Balance Ball" in the Turn Coordinator or the Directional Gyro.

The Advisory Panel supplies information on aircraft status. The status information elements required by the FAA are fuel quantity, oil pressure/temperature, pneumatic (vacuum pressure, and ammeter s. Some cockpit layouts may not have all of these instruments located on the same panel.

For this report, the Advisory Panel refers to the instruments, which provide the status information, not the panel, itself.

Radio communications are required for entering certain airspace. They are also required by the FAA for IFR flight. The transponder is part of the communications group. It identifies the aircraft to ATC.

Navigation is composed of three elements - vector navigation (sometimes refereed to as dead-reckoning), radio navigation, and pilotage. Vector navigation is used to transverse from one point to another. It uses basic mathematics, i.e., movement at a known speed, along a known bearing, for a known amount of time. Radio navigation is used for determining current position in relation to FAA navigational aids. The Auto Direction Finder (ADF) and VHF Omni Range (VOR) are used for radio navigation. These instruments use a ground-based transmitter at a known position in order to determine bearing.

4The Turn Coordinator is composed of the Balance Ball and Turn Needle. For this analysis they are treated as one unit.

5The FAA requires a generator, not an ammeter, however its use is so universal, it is considered as a requirement for the aircraft instrumentation.

A-IO Airspeed and Attitude information are needed to maintain an aircraft's lift and control. Altitude information is very important to safe flying, especially in conditions of limited visibility. The Advisory Panel information alerts the pilot to the condition of the aircraft with information on engine status and fuel available.

Communications information helps alert the pilot to flying conditions and other air traffic. Navigation information gets the aircraft to its destination and helps to avoid obstacles en route. The information for each of these groups is obtained from individual instruments or by combining information from several instruments; and there is considerable interdependence among the groups.

This analysis also includes some components and subsystems that are not physically in the cockpit; but they are important in that they supply data or power.

Among these supporting subsystems are the Pitot tube system and electrical power supply. Current general aviation aircraft have two types of power to operate the instruments - electrical and pneumatic. Typical general aviation aircraft power all of their instruments by electrical power, except for the directional gyro and attitude indicator, which are powered by vacuum pumps.

Only one source of electrical power was considered - the alternator. If the alternator failed during flight, the aircraft would terminate its flight as soon as possible, even though all of the instruments may be able to function for a limited amount of time from power supplied by the battery. Electrical power is required by most instruments in the cockpit.

There are currently scores of different types of general aviation aircraft in service.

Additionally, there are numerous configurations of cockpit instruments with which individual owners may customize their aircraft. The only commonality is the FAA's requirement for specific instruments. This situation results in numerous instrument configurations. As such, a reliability analysis of specific configurations is impossible. The instruments used in this analysis are typical, however, of most general aviation aircraft.

Data for this analysis was surprisingly sparse. Information on aircraft cockpit components was gathered from general aviation aircraft manufacturers and from general aviation maintenance personnel. The manufacturers tended to husband their data to its proprietary nature. Additionally, the aviation repair community (composed of thousands of small organizations) lacks the resources to collect Mean Time Between Failure (MTBF) data. (There is no FAA requirement for then to maintain such data). Data was also obtained from a commercial delivery company that operates single-engine, cargo aircraft. In addition to being similar to the aircraft under study, their aircraft had instruments and design characteristics common to all small aircraft.

This analysis did not consider mission phases. A simple mission profile of start- up to shut-down was used. Normal operating procedures call for power to all instruments throughout the flight, even though they may be used only during A-II short phases of the flight, such as landings. The mission used in this analysis was a 700-NM trip s. With a mean velocity of 120 knots 7, the flight would last approximately 5.83 hours. Taking into consideration pre-and post-flight taxing, a mission time of six-hours was used. This profile is representative of a typical cross country flight.

As single model of general aviation aircraft was used for a standard configuration. Where multiple sources of aircraft instrument reliability data was available; a non-weighted s average was used to obtain a single MTBF number.

A number of assumptions were made in order to confine this analysis to a manageable level. Some of them were: • Human factors were not considered.

• The aircraft used was representative of general aviation aircraft population.

• External cues and information (looking out window) were not considered.

• Criticality of information was not considered.

• All ground-based navigation aids are available.

• All components will exhibit an exponential time to failure distribution.

• Environmental elements were not considered.

• Partial failures were not considered.

• Out-of-tolerance conditions were considered failures.

The assumption concerning exponential time-to-failure distribution is critical.

Although this distribution is commonly used for electronic components, its application for mechanical systems could result in questionable findings. With more detailed failure data for mechanical systems, a simulation would provide improved accuracy of predicted reliability.

This analysis utilized the fault tree methodology to predict the reliability of the current general aviation cockpit's instrumentation. Fault tree analyses have gained wide acceptance and appreciation as one of the more powerful analytic tools for the study of complex systems. They enable deductive analysis to determine possible causes of an event or action; and, they provide qualitative as well as quantitative, results. A fault tree is a graphic model of the pathways within a system that can lead to a foreseeable, undesirable event. The events are not component parts of the system being analyzed; rather, they are symbols representing the logic of analysis.

6-1"hisis the maximum range AGATE requirement being considered.

7 .....

Th,s _sa typical cruising speed.

8Each MTBF number was considered as equally representative of the component's reliability.

A-12 There are three types of events used in the analysis of a cockpit instrumentation reliability fault tree: Basic Event The initiating fault not developed further. In this analysis a basic event is the failure of a hardware item.

Intermediate Event The system state produced by the preceding events.

The foreseeable undesirable event to which all Top Event fault tree logic flows.

Figure A1, Cockpit Instrumentation Reliability Fault Tree (located at the end of this section) shows the fault tree used to determine the cockpit reliability. The elements in the tree are read left to right. Its Top Event is "Loss of Cockpit Instrumentation Information." This fault tree was developed using one particular model of general aviation aircraft as a model for the basic equipment, design, and cockpit layout. To distinguish it from a second fault tree to be discussed later, this fault tree will be referred to as the "primary" fault tree.

At the second level of the fault tree, there are six intermediate events feeding into the top event. The loss of any of those intermediate events will cause the loss of the cockpit instrumentation information. The events on the second level are: 1. Loss of Airspeed Information.

2. Loss of Attitude Information.

3. Loss of Advisory Panel Information.

4. Loss of Altitude Information.

5. Loss of Navigation Information.

6. Loss of Communication Information.

Loss of Airspeed Information requires all of the three intermediate and basic events to occur.

Loss of Airspeed Indicator System: This event requires a__n_y or all of the intermediate or basic events to occur. This include failure of the: Air Speed Indicator fails, and/or Loss of Pitot Static System.

Tachometer Fails This is a basic event.

A-13 Loss of Communications Information: This event requires any or all of the intermediate events to occur. This include failure of the: Transponder System, and/or Loss of Voice Communications.

Loss of Attitude Information requires anv or all of the three intermediate events to occur.

Loss of Roll Information: This event requires both of the intermediate events to occur. This includes: Loss of Attitude Indication System, and Loss of Turn Coordination Indication.

three of the Loss of Pitch Information: This event requires all intermediate events to occur. This includes: Loss of Airspeed Information, Loss of Attitude Indication System, and Loss of Altitude Information.

Loss of Yaw Information: This event requires both of the intermediate events to occur. This includes: Loss of Directional Gyro System, and Loss of Turn Coordination System.

Loss of Advisory Panel Information requires any or all of the intermediate or basic events to occur.

Ammeter/Vacuum Pressure Gauge Fails: This is a basic event.

Oil Temperature/Pressure Gauge Fails: This is a basic event.

Loss of Clock System: This event requires any or all of the basic events to occur. This includes: Clock Fails, and/or Alternator Fails.

Loss of Fuel Quantity Indication: This event requires anv or all of the basic events to occur. This includes: Right Fuel Quantity Transducer Fails, Left Fuel Quantity Transducer Fails Fuel Quantity Indicator Fails, and/or Alternator Fails.

Loss of Altitude Information requires any or all of the intermediate or basic events to occur. This includes: A-14 Altimeter Fails: This is a basic event.

Loss of Vertical Speed Information: This event requires any or all of the basic events to occur. This includes: Vertical Speed Indicator Fails: This is a basic event.

Loss of Clock System: (See previous description).

Loss of Navigation Information requires any or all of the intermediate events to occur. This includes: Loss of Vector Navigation Information: This event requires any or all of the intermediate or basic events to occur. This includes: Loss of Airspeed information: (See previous description).

Loss of Clock System: (See previous description).

Loss of Heading Information: This occurs if al_Jl of the following intermediate and basic events to occur: Loss of Turn Coordination Indication, Magnetic Compass Fails (Basic Event), and Loss of Directional Gyro System.

Loss of Radio Navigation: This requires al_.J of the intermediate events to occur. These intermediate events are: Loss of VOR: This occurs if any or all of the following basic events occu r: VOR Antenna Fails, VOR Receiver Fails, VOR Display Fails, and/or Alternator Fails.

Loss of ADF: This occurs if any or all of the following basic events occur: ADF Antenna Fails, ADF Receiver Fails, ADF Display Fails, and/or Alternator Fails.

Loss of Instrument Landing System (ILS): This occurs if any or all of the intermediate events occur. These intermediate events are: A-15 Loss of Localizer/Glideslope Signal: This occurs if anv or all of the following basic events occur. These intermediate events are: ILS Receiver Fails, ILS Localizer Antenna Fails, ILS Glideslope Antenna Fails, and/or Alternator Fails Loss of ILS Display: This occurs if anv or all of the following basic events occur: ILS Display Fails, and/or Alternator Fails.

Loss of Marker Beacon Signal: This occurs if any or all of the following basic events occur: Marker Beacon Receiver Fails, Marker Beacon Antenna Fails, and/or Alternator Fails Loss of Communications Information occurs if _ or all of the following intermediate events occur, Loss of Voice Communications: This occurs if any or all of the following basic events occur: Communications Radio Fails, Communications Antenna Fails, and/or Alternator Fails Loss of Tracking Signal: This occurs if any or all of the following basic events occur: Transponder Fails, Transponder Antenna Fails, and/or Alternator Fails From the primary fault tree, it can be seen that several basic and intermediate events occur multiple times. The alternator, which is the sole source of electrical power, is the most prominent. It is emphasized that there is only one alternator on the type of aircraft in this study.

In that fault tree, the loss of a particular component did not necessarily mean a loss of information; because, a pilot could cross check 9 his instrument panel and obtain the information with other instruments.

9Scanning of instrument panel to double-check instrument readings.

A-16 An alternative fault tree was developed in an excursion to establish the reliability of the cockpit instruments as a function of simple, straightforward hardware failures - independent of the information those same instruments would provide, as was done in the primary fault tree. In this alternative fault tree, every hardware item was a basic event to the top event, "Loss of Cockpit Instrumentation." Every hardware item fed to the Top Event as an "or" gate.

There were no intermediate events. Due to its simple nature and unremarkable revelations, the alternative fault tree is not included in the report.

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Analysis Results

This analysis shows that the current general aviation cockpit has little redundancy in its design. Presently, flight safety and success relies heavily on pilot training and situational awareness. Today's pilots receive extensive training in cross-checking and emergency procedures. One of the goals for the aircraft envisioned in the AGATE Program is to relieve the necessity of this comprehensive training by incorporating the cross-checking processes into the instruments, thereby greatly simplifying the piloting procedures.

This analysis predicts that a current general aviation aircraft, on a 700 NM trip taking approximately six-hours, would have a 0.976 probability of completing that trip without losing any cockpit instrumentation information. The fault tree model calculated an unreliability of 0.024. Unreliability is the probability that the system will experience a failure that will result in the loss of information during its six- hour flight. This indicates that there is a 0.024 probability that the pilot will lose some cockpit instrumentation information during a six-hour flight.

This compares with a prediction of 0.041 probability that at least one instrument will fail, as calculated by the pure hardware-failure fault tree (not included). That was the situation where every component was a basic event to the "Loss of Cockpit Instrumentation Information" event. This appears to be a significant difference in unreliability. More detailed reliability data is required in order to evaluate whether this is a statistically significant difference. The use of cross- checking for information from multiple instruments appears to improve cockpit information reliability. This is what would be expected. The 0.041 unreliability may be put into these terms - there is a 0.041 probability that at least one of the instruments required will fail. There is a 0.959 probability that a six-hour mission will be completed without a component failing.

The unreliability predictions for each of the intermediate events in the primary fault tree are tabulated in Table A1, Intermediate Event Tree Unreliability. The unreliability for each of these intermediate events was calculated independently of each other so that common, shared intermediate and basic events were not duplicated in the calculations. The "Alternator Fails," is the most common shared basic event.

Intermediate Tree Event % of Total Unreliability Unreliability 5.63 x 10 `7 0.0% Loss of Airspeed Information Loss of Altitude Information 2.26 x 10 .3 8.4% 2.97 x 10:3 11.1% Loss of Advisory Information 5.16 x 10 _ 0.1% Loss of Attitude Information Loss of Communications Information 1.05 x 10 .2 39.1% 1.11 xl0 "2 42.1% Loss of Navigation Information Table A1. Intermediate Event Tree Unreliability A - 30 The percentage that each group of information contributes to the unreliability is presented in Figure A2, Information Unreliability Percentage Breakdown. As depicted, the loss of airspeed and attitude information contribute only a miniscule amoudt - while the communications and navigation information loss combine for almost 80% of the unreliability.

There are two sources for the relative large unreliability displayed by the "Loss of Communications and Navigation" information events.

Figure A2. Information Unreliability Percentage Breakdow n Loss of Airspeed Information 0.0% Loss of Altitude .... Information 8.4% Loss of Navigation Inf ormation Loss of 42.1% Comrrunications Information 39.1% Loss of Attitude / Information J Loss of Advisory 0.1% Information 11.1% One cause of the relatively high unreliability is the low reliability of the components in the basic events. The reliability data is presented in Table A2, Component Reliability Data. Several of the components feeding into the "Loss of Communications and Navigation" intermediate events have relatively low reliability. The columns on the right side of the table indicate which "Loss of Information," intermediate event is influenced by the individual component (basic events).

The second cause of the high unreliability can be noticed from the fault tree representation. The equipment that composes the basic events in the intermediate events are all required to function in order for the event not to fail.

This is the opposite of what is experienced in the "Loss of Attitude, Airspeed, and Altitude information intermediate events. In those functions, there were multiple ways to get the information. The failure of a particular component or lower intermediate event did not automatically cause the failure of the higher intermediate event. Airspeed information would have to lose three paths in order A -31 to be lost. Although the advisory Panel relied on all of its intermediate and basic events, the components involved were relatively reliable.

Intermediate Event Influenced Communications Altitude Attitude Advisory Navigation Component MTBF _(/hr) Airspeed X ADF Antenna* 4000 2.50E-04 X ADF Display* 19900 5.03E-05 ADF Receiver* 4200 2.38E-04 X X X Airspeed Indicator 18100 5.52E-05 X X X Altimeter 5500 1.82E-04 k x x x Alternator 7600 1.32E-04 X X Attitude Indicator 2500 4.00E-04 X Clock 17600 5.68E-05 X X X X X X Directional Gyro 3400 2.94E-04 X Fuel Quantity 16500 6.06E-05 Indicator X Fuel Quantity 51400 1.95E-05 Transducer* ILS Antenna* 900 1.11 E-03 X X ILS Display* 10000 1.00E-04 X ILS Receiver* 900 1.11E-03 X Magnetic 19900 5.03E-05 Compass Marker Beacon 14800 6.76E-05 X Antenna* Marker Beacon 5300 1.89E-04 X Receiver* X Oil 6200 1.61 E-04 PressurefTempera ture Gauge Pitot Tube* 73600 1.36E-05 X X X X Radio (Comm) 1200 8.33E-04 X Antenna* X Radio (Comm) 900 1.11E-03 X Radio * X X Vacuum Gauge* 21500 4.65E-05 Tachometer 8400 1.19E-04 X X X X X Transponder* 1700 5.88E-04 X X X Transponder 9500 1.05E-04 X Antenna* Turn Coordinator 2100 4.76E-04 X X X X Vacuum Gauge* 21500 4.65E-05 X Vacuum Pump* 4000 2.50E-04 X X Vertical Speed 14500 6.90E-06 Indicator 0 VOR Antenna* 9600 1.04E-04 X X VOR Display* 10000 1.00E-04 VOR Receiver 900 1.11E-03 X Table A1. Intermediate Event Tree Unreliability This analysis indicates that system which incorporate mechanical components experience very high reliability - particularly the airspeed and attitude. This runs counter to the expectations that electronic parts are more reliable than mechanical parts. There are several major factors, however, that effects this result. First, there are several crosschecks for the information. This is similar to having built-in redundancy (redundancy being the fundamental method for improving reliability in any design). Secondly, the reliability data may not A - 32 accurately reflect the true reliability. The limited data available may not represent a significant sample size. Also, there may be some bias in the data. Data collected on aircraft currently in mass production (for quality control objectives) may be different from data collected from developmental projects (for design validation and verification).

Another considerable factor is that most of the mechanical instruments do not fail in a catastrophic manner. There most common failure mode is to gradually go out of specified tolerances. As the item starts to gradually fail, operators will notice this and preventive maintenance is performed before actual failure of the instrument. These tolerances are also checked during scheduled inspections.

This analysis did not consider failure modes, only the basic good/failed condition.

Lastly, the assumption that mechanical parts display an exponential time to failure distribution may distort the prediction. The data collected gave no indication of their time-to-failure distribution. Without more information from the manufacturers on matters such as quality control or environmental control factors, it cannot be determined if any distortion of the data may have occurred.

The exponential time-to-failure distribution assumptions are used to simplify the models to a point where an analytical solution exists.

The results of this analysis indicate that there is approximately a one-in-forty chance of losing some portion of the cockpit instrumentation information during a six-hour flight.

Further analysis of the cockpit reliability will require additional data. The limited availability, of the data needed for this analysis suggests that a new, cohesive effort is necessary to collect instrumentation reliability data.

A-33 Basic Aircraft Instruments There are many names used for instruments found in a general aviation cockpit. The following instruments are used throughout this report. These descriptions presented here are meant only for familiarization.

There are numerous manufacturers of these instruments and their appearance may differ from one manufacturer to another: however, their basic functions are the same.

Some models may combine several of these primary instruments into one unit.

Airspeed Indicator This instrument tells the pilot the speed at which the airplane is flying through the air. This value is different from the ground speed because the air surrounding the aircraft is affected by the currents aloft.

Attitude Indicator Also called the Artificial Horizon, this gyroscopic instrument tells the pilot if the airplane is in a nose-high or a nose-low attitude; or, if the airplane is banked to the left or to the right.

This is the basic instrument used to fly in the clouds.

Altimeter The altimeter indicated at what height the airplane flies compared to sea level. It can be adjusted for changes in barometric pressure.

The Vertical Speed Indicator This instrument tells the pilot if the airplane is climbing or descending, and if so, at what speed (in feet per minute).

A - 34 Headinq Indicator This is a gyroscopic instrument that is used like a compass, only it is more precise and more stable during climbs, descents, and turns. It is also called a directional gyro.

Turn Coordinator In a turn, this instrument gives the pilot an indication of the rate of turn (how long it will take to turn 180 ° for example).

It also includes the ball, that shows if the flight is coordinated (symmetrical) or not.

Tachometer This instrument allows the pilot to precisely set the engine RPM.

Engine Gauges These gauges are used to monitor engine performance. They include oil temperature, oil pressure fuel quantity, engine power, and engine temperature. The fuel quantity and oil temperature are among the most important ones.

VOR The VHF Omni Range (VOR) is a radio navigation instrument. Its Course Deviation Indicator (CDI) gives the pilot an indication on the position of the airplane in relation to a ground station. The VOR is the primary system used to define airways.

A -35

IL_SS

The instrument Landing System is a very sensitive VOR that also includes vertical information. It is used for precision approaches and landing in bad weather conditions.

ADF The needle of the Automatic Direction Finder always points towards the ground station on which frequency the receiver is operating (acting like an "artificial North pole"). This radio- navigation instrument is also called a radio-compass.

Radios There are two kinds of aircraft radios - voice transceivers that are used by the pilot to talk with Air Traffic Controllers, and radio-navigation equipment which are the VOR or ADF receivers.

Transponder Whenever it is interrogated by a RADAR, the transponder sends back a 4-digit code along with altitude information. This allows Air Traffic Controllers to identify the aircraft displayed as echoes on their RADAR screens.

A - 36

Appendix B Exponential Distribution Properties B- 1 In reliability engineering the mean time to failure (MTTF) is defined by: MTTF= E(T)= itf(t)dt = iR(t)dt Eq. 1 0 0 which is the mean, or expected value of the probability distribution defined by f(t).

0. 2 Variance, or , is the average squared distance a failure time will be from the MTTF.

It is a measure of spread or dispersion about the mean defined by: 0.2= i(t-M77"F)2 f(t)dt= i t2f(t)dt-(MTTF) 2 Eq. 2 0 0 The standard deviation, 0., has the same units as the mean and is defined by: 0.= _-0.2 Eq. 3 For the exponential distribution, reliability R(t) is defined as: t R(t) = exp [ Iadt'] = exp(-2t) Eq. 4 and the probability density function is defined as: f (t) - dR(t) _ X exp (-at) Eq. 5 dt Therefore, to define MTTF for the exponential distribution using equations 1 and 4, it is found that: MTTF=E(T)= R(t)dt=fexp(-Rt)- -A, 1o_- Eq. 6 0 0 Similarly, using equation 2, integration by parts and the results for MTTF, the variance for the exponential distribution can be determined: 0.2= t,f(t)dt_(MTTF):=yt2exp(_at)dt_( )2=( )2 Eq. 7 0 0 Using the results from equations 6 and 7, along with equation 3, it can now be seen that for the exponential distribution, MTTF = 0. = -- B-2

Appendix C

Control System

Probability Plots

C- 1

Longitudinal Probability Plot

99.00

'_' 1Weibull

90.00

. P=2, A=RRX

' F=31 I

........... CB/FM: 95%

...... 2 Sided-B

• ;_ , : C-Ty pe 1

50.00

• ' " "" t ;_ " @ / ................ i . .. Q/ , _ .....

/ ,' v It.

• ,' , ................................................................................

................ /.f.. • . / .......... Legend: / • /' ..Q , , P = 2-Parameter (Weibull) °_ RRX = Rank Regression on X / F = # of Failures c- /_ . /' ....

10.00

/ , . _ • ,' ...... CB =Confidence Bounds FM = Fisher Matrix (Meth(_l of ' ' CB Calculalion ' _ / .... ..... ) ......... I / • / ! 2-Sided B = 2-Sided Bounds

5.00 Plotted

, " . /" ,' , C-Type I = Confidence Type - / / Percentile , Time, (t) - hours / / / ........... I. ................ i I L/- / /

1.00

100.00 1000.00 10000.00

Time, (t)

13=1.57, 13---4718.22, p--0.98

C-2

Lateral Probability Plot

99.00

Weibull

90.00

P=2, A=RRX

F=351

CB/FM: 95%

2 Sided-B

C-Type 1

50.00

v Ii r ................................................................................ • Legend: .m m .m P = 2-Parameter (Weibull) RRX = Rank Regression on X (D F = # of Failures r- CB = Confidence Bounds

10.00

FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted

5.00

C-Type I = Confidence Type - Percentile Time. (t) - hours

1.00

I

1000.00

10000.00

Time, (t)

_=2.25, q=5843.58, p--0.99

C-3

Flap Probability Plot

99.00

* Weibull

P=2, A=R RX

F=451

CB/FM: 95%

2 Sided-B

C-Type 1

50.00

v ii Legend: P = 2-Parameter (Weibull) t_ RRX = Rank Regression on X F = # of Failures t- CB = Confidence Bounds

10.00

.... FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted

5.00

C-Type 1 = Confidence Type - Percentile ......... i Time, (t) - hours i ............................................................................

t = / I

1.00

10000.00

10.00 100.00 1000.00

Time, (t)

_---0.95, q=3956.09, p=0.97

C-4 Trim Probability Plot 99.00 Weibull P=2, A=RRX F=491 CB/FM: 95% 2 Sided-B C-Ty pe 1 50.00 v Ii Legend: >,, P = 2-Parameter (Weibull) RRX = Rank Regression on X c'_ F = # of Failures .m Q) CB = Confidence Bounds t"-- FM = Fisher Matrix (Melhod of 10.00 CB Calculation 2-Sided B = 2-Sided Bounds Plolted C-Type I = Confidence Type - 5.00 Percentile Time, (t) - hours 1.00 10.00 100 00 1000.00 10000 00 Time, (t) [3--0.73, I"1=2672.10, 9---0.98 C-5

Directional Probability Plot

99.00

Weibull

90.00

P=2, A=RRX

F=291

CB/FM: 95%

2 Sided-B

C-Ty pe 1

50.00

V LI_ Legend: om P = 2-Parameter (Weibull) c_ RRX = Rank Regression on X F = # of Failures IL_ CB = Confidence Bounds ¢- FM = Fisher Matrix (Method of

10.00

CB Calculation 2-Sided B = 2-Sided Bounds Plotted C-Type 1 = Confidence Type -

5.00

Percentile Time, (t) - hours

1.00

i

100.00 1000.00 10000.00

Time, (t)

13=1.85, 11---4728.93, p=0.97

C-6

Hydraulic Probability Plot

99.90

, Weibull

90.00

P=2, A=RRX

F=81 I

J CB/FM: 95%

2 Sided-B

50.00

C-Ty pe 1

v 1.1_ Legend:

10.00

°k P = 2-Parameter (Weibull) RRX = Rank Regression on X .... F = # of Failures

5.00

c- ....... CB = Confidence Bounds . : FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted C-Type I = Confidence Type -

1.00

...... _ ............. Percentile i " J Time. It) - hours

0.50

/

0.10

10.00 100.00 1000.00 10000.00

Time, (t)

13=1.14, q=3977.39, 9=0.98

C-7

Landing Gear Probability Plot

99.90

" Weibull

90.00

P=2, A=RRX

F=318 I

CB/FM: 95%

..... 2 Sided-B

50.00

C-Ty pe 1

V I.I.

Legend: /

_, 10.00

/ P = 2-Parameter (Weibull) J ..................

RRX --- Rank Regression on X a_ 7" ...............

F = # of Failures

_.-m5.00

O CB = Confidence Bounds (..- FM = Fisher Matrix (Method of CB Calculation 2-Sided B -- 2-Sided Bounds Plotted C-Type 1 = Confidence Type -

1.00

Percentile Time, (t) - hours

0.50

0.10

1.00 10.00 100.00 1000.00 10000. O0

Time, (t)

13--0.92, q=2895.62, 9--0.99

C-8

Steering Probability Plot

Weibull

i

90.00

P=2, A=RRX

F=12 I

CB/FM: 95%

2 Sided-B

C-Ty pe 1

" II LI_ Legend: P = 2-Parameter (Weibull) RRX = Rank Regression on X F = # of Failures CB = Confidence Bounds t'- FM = Fisher Matrix (Method of

10.00

CB Calculation 2-Sided B = 2-Sided Bounds Plotted C-Type I = Confidence Type -

5.00

Percentile Time. II) - hours

1.00

10000.00

1000. O0

Time, (t)

13=1.65, q=3994.78, p--0.94

C-9

Appendix D

Airframe System

Probability Plots

D-1

Electrostatic Devices Probability Plot

99.00

Weibull

I

90.00

P=2, A=RRX

/

F=23 I

I CB/FM: 95%

2 Sided-B

C-Ty pe 1

50.00

I1 / i Legend: i P = 2-Parameter (Weibull) °_ RRX = Rank Regression on X F = # of Failures °i i CB = Confidence Bounds FM = Fisher Matrix (Method o" ¢-

10.00

CB Calculauon 2-Sided B = 2-Sided Bounds Plotted C-Type I = Confidence Type -

5.00

Percentile Time, (t) - hours

1.00 -_

10000.00

1000.00

lqme, (t)

[3=2.53, 11=5887.53, p=0.97

D-2

Empennage Probability Plot

99.00

Weibull

90.00

P=2, A=R RX

F=251

CB/FM: 95%

2 Sided-B

C-Ty pe 1

50.00

v i.l_ Legend: P = 2-Parameter (Weibull) RRX = Rank Regression on X e_ F = # of Failures CB = Confidence Bounds t--

10.00

F'M = Fisher Matrix (Method of CB Calculation i 2-Sided B = 2-Sided Bounds Plotted

5.00

C-Type I = Confidence Type - Percemile i Tirne, _t) - hours

1.00

10000.00

100.00 1000.00

Time, (t)

[3=1.16, q=5025.35, 9-----0.94

D-3

Engine Box and Cabin Fuselage Probability Plot 99.90 ° Weibull 90.00 P=2, A=RRX F=123 I CB/FM: 95% 2 Sided-B 50.00 C-Ty pe 1 .,I,-..

v Ii ...... .......................................................................... Legend: >, 10.00 i i P = 2-Parameter (Weibull) i _ RRX = Rank Regression on X i F = # of Failures _.-_ 5.00 CB = Confidence Bounds C FM = Fisher Matrix (Method o' CB Calculation 2-Sided B = 2-Sided Bounds Plotted 1.00 .............. C-Type I = Confidence Type - • " / ' Time, (t) - hours 0.50 ...... • .......................................................................

0.10 10. O0 100. O0 1000. O0 10000. O0 lqme, (t) [5=1.42, q=6278.95, p=0.96 D-4

Paint Probability Plot

99.00

Weibull

90.00

P=2, A=R RX

F=14 I

CB/FM: 95%

2 Sided-B

C-Type 1

50.00

v LI..

Legend: >..

i P = 2-Parameter (Weibulll °m .c} RRX = Rank Regression on X F = # of Failures (1) CB = Confidence Bounds c-

10.00

FM = Fisher Matrix (Melhod of Z) CB Calculation 2-Sided B = 2-Sided Bounds Plolted

5.00

C-Type I = Confidence Type - Percentile Time, (t) - hours

1.00

100.00 1000.00 10000.00

"lqme, (t)

13=1.45, q=2985.38, p=0.98

D-5

Seats Probability Plot

99.90

• [ Weibull

• Seats

90.00

P=2, A=R R X

F=105 I

" CB/FM: 95%

..... 1 2 Sided-B

50.00

C-Ty pe 1

v Ii 1_ 0 _ ° ...............................................................................

10.00

.... . ....... Z ............... . - ] Legend: .i . - _ _ , P = 2-Parameler (Weibull) I .......

......... ] RRX = Rank Regression on X

•-_ 5.00

O " ....... - t F = # of Failures ¢- "0 CB = Confidence Bounds • FM = Fisher Matrix (Method of • f CB Calculation ./ / 2-Sided B = 2-Sided Bounds Plotted

1.00

/ C-Type 1 = Confidence Type - Percentile

0.50 / Time, (t) - hours

/ I f" " ..................... • ........................................................................

0.10

10000.00

1000.00

-time, (t)

_=2.66, r1=6767.87, 9=0.98

D-6

Upholstery Probability Plot

99.00

Weibull

90.00

P=2, A=RRX

F=8 I

CB/FM: 95%

2 Sided-B

_ _ .

C-Type 1

50.00

V It Legend: i I .Q P = 2-Parameter (Weibull) RRX = Rank Regression on X (D F = # of Failures C CB = Confidence Bounds _D

10.00

FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted

5.00

C-Type I = Confidence Type - Percentile Time, (t) - hours

1.00

10000.00

1000.00

Time, (t)

_=1.79, q--4291.74, 9=0.96

D-7

Wing Probability Plot

99.00

Weibull

90.00

P=2, A=RRX

F=16 I

CB/FM: 95%

7- - , 2 Sided-B

C-Ty pe 1

50.00

V It.

Legend: °_ P = 2-Parameter (Weibull) °_ RRX = Rank Regression on X F = # of Failures t-

10.00

I CB = Confidence Bounds FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted

5.00

C-Type I = Confidence Type - Percentile Time, (t) - hour_ ............... i /

1.00

100.00 1000.00 10000.00

"iqme, (t)

13=1.79, q=4247.38, p=0.98

D-8

Appendix E Powerplant System Probability Plots E- 1 Engine Probability Plot 99.99 Weibull P=2, A=RRX F=864 I CB/FM: 95% 50.00 2 Sided-B C-Type 1 "- 10.00 !1 5.00 Legend: ,.(3 P = 2-Parameter (Weibull) RRX = Rank Regression on X F = # of Failures :3 1.00 CB = Confidence Bounds FM = Fisher Matrix (Method of 0.50 CB Calculation 0.10 0.05 0.01 10.00 100.00 1000.00 10000.00 lqme, (t) 13=1.58, q=4821.49, 9=0.99 E-2 Fuel Probability Plot 99.90 • We°bull 90.00 P=2, A=RRX F=143 I CB/FM: 95% T 2 Sided-B 50.00 C-Ty pe 1 v ii 10.00 .... Legend: .m ./. " , o'O P = 2-Parameter (We°bull) 5.00 ..... : ..... "-- : 'ti ....... RRX = Rank Regression on X t- ......... _ ./ /..,_ ........ F = # of Failures / /,;o ......

., , • CB = Confidence Bounds ...... t i_ _" '_' '-'_ FM = Fisher Matrix ,Method of ......... CB Calculation " ' 2-Sided B = 2-Sided Bounds Plotted • /. /,.

1.00 // "' r; C-Type I = Confidence Type - i " Percentile 0.50 ....... : I " "' ............... Time.(t)- hours / t • .................................................................................

0.10 10.00 100.00 1000.00 10000.00 Time, (t) 9=1.44, 11=5131.56, 19=0.95 E-3 Heating and Ventilation Probability Plot 99.00 '- Weibull 90.00 P=2, A=RRX F=321 ........ CB/FM: 95% -L ................

-. 2 Sided-B 50.00 IJ_ ,.Q 10.00 5.00 1.00 10000.00 100. O0 1000.00 -time, (t) 13=1.60, q--4187.26, 9=0.96 E-4 Propeller Probability Plot 99.90 Weibull 90.00 P=2, A=RRX F=991 .... CB/FM: 95% 2 Sided-B 50.00 C-Type 1 v It.

Legend: 10.00 P = 2-Parameter (Weibull) t_ . RRX = Rank Regression on X ...... F = # of Failures (D 5.00 k.,.

t- CB = Confidence Bounds FM = Fisher Matrix (Melhod of CB Calculation 2-Sided B = 2-Sided Bounds Plotted 1.00 C-Type I = Confidence Type - Percenlile Time. I'1) - hours 0.50 0.10 100.00 1000.00 10000.00 rime, (t) [3=1.63, 11=3742.01, 9---0.98 E-5

Appendix F Electrical System Probability Plots F- 1 Lighting Probability Plot 99.90 [ i Weibull 90.00 P=2, A=RRX F=821 CB/FM: 95% 2 Sided-B 50.00 C-Type 1 I1.

Legend: >2 10.00 P = 2-Parameter {Weibull} -/ • RRX = Rank Regression on X

5.00

F = # of Failures Q} / t- / • CB = Confidence Bounds FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted C-Type I = Confidence Type - 1.00 I Percentile L 0.50 ...... Time. (t} - hours 0.10 10000.00 100.00 1000.00 "l]me, (t) _=1.66, q=5613.87, p=0.98 F- 2 Source and Distribution Probability Plot 99.90 • Weibull 90.00 P=2, A=RRX F=262 I J-CB/FM: 95% 2 Sided-B 50.00 C-Ty pe 1 v I1 Legend: 10.00 P = 2-Parameter (Weibull) RRX = Rank Regression on X F = # of Failures 5.00 ,L CB = Conlidence Bounds t,- FM = Fisher Matrix (Method of CB Calculation 2-Sided B = 2-Sided Bounds Plotted 1.00 C-Type I = Confidence Type - Percentile i Time, (t) - hours 0.50 0.10 100. O0 1000.00 10000.00 Time, (t) _=1.67, q=4945.24, 9=0.99 F- 3

Appendix G

Weibull Failure Law G-1 The failure rate or hazard rate function is another probability function that is used in reliability. It provides instantaneous (at time t) rate of failure and is defined as follows, h(t)- f(t) R(t) Eq. 1 dR(t) where f(t) = probability density function (PDF) = Eq. 2 dt Eq. 3 and R(t) = reliability function = if(t')dt' For the Weibull distribution, Eq. 4

R(t) =e

and dR(t) _113 yt I n-' .e- (_1/_ Eq. 5 f(t)= _-_ ( a )(,a) therefore,

h(t) = (a X a )

Eq. 6

e-(" )

For a system comprised of many components, serial and parallel configurations can be used to describe how they relate to each other. If components are in series, they must each function for the system to function. If they are in parallel, or redundant, configuration, at least one component must function for the system to function.

Using reliability block diagram for components in series, The reliability of the series system following the exponential failure law is defined as: H /:_ n Eq. 7

Rs (t) : H Ri (t) : I'I e-z't = e___ - _it =e -z''

i=1 i=1 i=1 G-2 Where,by usingEquation1,theconstantfailure ratemodelcanbederived,

- e _:_ • - _i t

i=1

h_(t) = "

,_ =L 2x, Eq. 8 -E ,71./t i:1 e i=l For components governed by the Weibull failtire law, the reliability of a system comprised of components in series is,

f,/_' _(,]_

Rs(t)= l-'IR_(t): l"[e (_' ) =e :'_ )

Eq. 9 i=1 i=1 and from Equation 1 above, the system hazard rate function as governed by the Weibull failure law is,.

hs(t ) =

Eq. lO -_( t-f--] !3i i=1_0_ i e i=lk°_i ) G-3

Appendix H

Weibull Parameter

Bounds

H-I ° ,.

'=,_E ¢o =0 _ o i ¢_ .Q ! ILl uJ ¢u m =07_ • ¢" _ '- " O,I 03 O_ I'_ I.g IlL/ 14.1 ILl 111 • , !¢'_ 9 9 9 9 U.I _ W _ W =0E = o _.

(0 _.1 O,J "_'- ,,, w wlw w w ,,', u_, ,,,,,',',,',',,',',_, w w w '_o_, h- ¢0 i,r- _) i i_m o _'_'_'_'_7_'d !o .........

tO I I W__ O00J U") '_1" _. " __

I_ o

_ _ _'_'_ ......... _ d'_'_'o'_ _,_ rn _.- i

I_ _=

_._._._._._._ o o_ o .....,, d'_l_Td'_ d _:d om O _E oc _, cc ,.- "_ • _ 0 o

-a-o _ _ ®o =o

__!_. __ __ '_, ¢= o i =-

o ) _8 ,o

I.Ig H-2 REPORT DOCUMENTATION PAGE Form Approved OMB No o7o4-ot_ Pubhc reporting borOan for this collection of information is estimated to average 1 hour per response, including the rime for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of inlormation Send comments regarding this borden eslimate or any other aspect of 1his collection ol information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate 1or Intormation Operalions and Reports, 1215 Jefferson Davis H_ghway, Suite 1204, Artinglon, VA 22202-4302 and to the Office ot Management and Budget, Paperwork Redu_ion Pro_.ect (0704-0t88), Washington, DC 20503 / 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3 REPORT TYPE AND DATES COVERED February, 2001 Contractor Report 4 TITLE AND SUBTITLE 5. FUNDING NUMBERS General Aviation Aircraft Reliability Study C HAS 1-96013 Task AF05 6. AUTHOR(S) WU 323-71-01-05 Duane Pettit and Andrew Turnbull 8. PERFORMING ORGANIZATION 7. PERFORMING ORGANIZATION NAME(S) ANDADDRESS(ES) REPORT NUMBER FDC/NYMA, Inc.

Aerospace Sector NASA Langley' Research Center Hampton, VA 23681-000 I 9 SPONSORING/MONITORING AGENCY NAME(S) ANDADDRESSEES) 10. SPONSORING/MONITORING AGENCY REPORT NUMBER National Aeronautics and Space Administration NASA/CR-2001-210647 Langley Research Center Hampton, VA 2368 !-2199 11. SUPPLEMENTARY NOTES Langley Technical Monitor: Henk A. Roelant 12a.DISTRIBUTIOWAVAILABILn'Y STATEMENT 12b. DISTRIBUTION CODE Unclassified-Unlimited Subject Category' 03 Distribution: Standard Availability: NASA CASi (301) 621-0390 13. ABSTRACT (Maximum 200 words) This reliability, study estimates Complex General Aviation (GA) Aircraft System reliability. As part of an effort to successfully improve the safety and reliability of the next generation of GA aircraft, a benchmarking of the current reliability, of GA Aircraft Systems was performed. Specifically, Complex GA Aircraft System reliability was estimated using data obtained from the logbooks of a random sample of the Complex GA Aircraft population. The results of this analysis provide insight into the current reliability of Complex GA Aircraft Systems (i.e., Airframe, Electrical, Powerplant, Flight Control and Ground Control Systems). In addition, an estimate of Cockpit Instrumentation reliability, performed in an earlier report, is also presented.

14. SUBJECT TERMS 15. NUMBER OF PAGES General Aviation; Reliability 16. PRICE CODE A06 19. SECURITY CLASSIFICATION 20. LIMITATION 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION OF REPORT OF THIS PAGE OF ABSTRACT OF ABSTRACT Unclassified Unclassified Unclassified UL NSN 7540-01-280-5500 Standard Form 298 (Ray. 2-89) Prescribed by ANSI Std. Z-39-18 298-102