TECHNICAL REPORT
ON
Propulsion System and Auxiliary Power Unit (APU)
Related Aircraft Safety Hazards
October 25, 1999
A JOINT EFFORT CONDUCTED BY THE
THE FEDERAL AVIATION ADMINISTRATION
AND
THE AEROSPACE INDUSTRIES ASSOCIATION (AIA)
1
Questions concerning distribution of this report should be addressed to: Manager, Engine and Propeller Directorate
CONTENTS
PAGE NUMBER
I. Summary1
II. Background2
III. Discussion3
IV. Appendices:
Appendix 1:CAAM Report Cover Letters5
Appendix 2:Standardized Aircraft Event Hazard Levels8
and Definitions
Appendix 3:Definitions12
Appendix 4:Propulsion System and Auxiliary16
Power Unit (APU) Related Aircraft Safety
Hazards (1982 through 1991)
Appendix 5:Turbine Engine Rotor Uncontained Events53
(1 January 1992 through 30 November 1996)
Appendix 6:Combined Turbine Engine Rotor Hazard Ratios60
(1982 through 30 November 1996)
1
I. SUMMARY
In 1991, the Aerospace Industries Association (AIA) provided the Federal Aviation Administration (FAA) with a study aimed at the development of more effective methods to identify, prioritize and resolve safety-related problems occurring on commercial aircraft engines. The activity was undertaken as a result of the rapid increase in commercial aircraft entering revenue service, leading to a corresponding increase in the exposure to flight-safety events. The AIA team that developed the study was the Continued Airworthiness Assessment Methodologies (CAAM) Committee. This initial AIA study covered a variety of propulsion system and auxiliary power unit (APU) events. Later, the AIA recognized the need to update uncontained engine events, and prepared a supplemental report.
This FAA report is a compilation of both the initial and supplemental data from the above noted reports, and provides historical safety data that document propulsion system and APU-related aircraft safety hazards. The information provided in this FAA report has been used by the Engine and Propeller Directorate since 1994 to help identify and prioritize responses to potential engine, propeller and APU unsafe conditions.
II. BACKGROUND
In 1991, the Aerospace Industries Association (AIA) produced a study to assist the Federal Aviation Administration (FAA) in developing more effective methods to identify, prioritize and resolve safety-related problems occurring on commercial aircraft engines. This activity was undertaken as a result of the rapid increase in commercial aircraft entering revenue service, leading to a corresponding increase in the exposure to flight-safety events. The AIA team that developed the study was the Continued Airworthiness Assessment Methodologies (CAAM) Committee.
Due to the availability of credible data, the CAAM committee limited the scope of its effort to engines, propellers, and auxiliary power units (APU’s) installed on transport airplanes. An event characterization system, termed the hazard level, was developed, based on the observed outcome of the event at the aircraft level (CAAM hazard levels are listed in Appendix 2 of this FAA report). Ten years of engine, propeller and APU events were analyzed and grouped by event cause (i.e., uncontainment, fire, etc.) and hazard level. Historical conditional rates of the most serious events (CAAM hazard levels 3 and 4) were also calculated for each cause.
This initial study was issued by the AIA as a report entitled “Initial Report on Propulsion System and APU Related Aircraft Safety Hazards, 1982 thru 1991” (AIA PC-342), which was released to the FAA on May 1, 1993. Several years later, the AIA reformed a new CAAM committee to update uncontained engine events for the time period of 1992 through November 30, 1996, with the intent of measuring and documenting the relative progress which had been made toward minimizing uncontained turbine engine hazardous events. The AIA issued the second report, entitled “Supplemental Report on Turbine Engine Rotor Uncontained Events, 1 January 1992 through 30 November 1996” (AIA PC-342-1), which was released to the FAA on February 5, 1997.
This FAA report is a compilation of both the initial and supplemental data from the above noted reports, and provides historical safety data that document propulsion system and APU-related aircraft safety hazards. The data provided in this FAA report have been used by the Engine and Propeller Directorate since 1994 as an important part of its efforts to prioritize responses to potential engine, propeller and APU unsafe conditions.
III. DISCUSSION
1. The data contained in this FAA report have been used by the FAA’s Engine and Propeller Directorate since 1994, and have become an important part of the safety management process. This report serves as a compilation of the initial and supplemental CAAM data, and includes the relevant definitions and descriptions integral to the analyses. The cover letters of the initial and supplemental reports are also included; ellipses (i.e., “...”) indicate the removal of appendix/attachment number references within those AIA reports.
2. The conclusions/recommendations developed in the initial report were as follows:
a. The data may be used to prioritize safety-related industry studies, research and regulatory development activities.
b. The data demonstrate the importance of human factors in propulsion/APU-related flight-safety and the need for early industry consideration of how these issues can best be addressed. Additionally, reduction of multiple-engine powerloss events deserves early industry attention.
c. The data will be beneficial to safety professionals within industry in placing the various powerplant and APU-related flight-safety issues into proper context and in guiding decision making related to potential hazards associated with the defined powerplant and APU malfunctions.
d. Further refinement and development of this initial report should continue and user comments and recommendations for enhancements should be solicited.
e. The process developed under CAAM should be considered for other propulsion applications (i.e., turboshaft engines) and, more importantly, the entire aircraft.
3. The conclusion/recommendation developed in the supplemental report was as follows:
a. The 1992-1996 (5-year) time period uncontained event data indicate a reduced rate for uncontained events when considered against the data from the 1982 through 1991 time period. The reduction in uncontained event rates is approximately 50 percent for "All" events and approximately 66 percent for "Serious" and "Severe” events.
4. The data in this report are organized into the following categories:
a. turboprop,
b. low bypass ratio (LBPR) turbofan engines, and
c. high bypass ratio (HBPR) turbofan engines.
IV. APPENDICES
Appendix 1
CAAM Report Cover Letters
AIA PC-342
COMMITTEE ON CONTINUED AIRWORTHINESS ASSESSMENT
METHODOLOGY
INITIAL REPORT
ON
PROPULSION SYSTEM AND APU RELATED AIRCRAFT SAFETY HAZARDS
1982 THRU 1991
1 May 1993
FOREWORD
The material presented in this “Initial Report” has been developed by experts from industry and the FAA under the auspices of the Aerospace Industries Association (AIA) Propulsion Committee (PC). At the request of the FAA, the AIA PC formed the Continued Airworthiness Assessment Methodology (CAAM) Committee “…to work together with the FAA to develop guidance and common methods to be used by the FAA and Industry to identify, prioritize and resolve safety related issues occurring on aircraft propulsion systems and APUs.”
This “Initial Report” contains the following material:
1)standardized definitions of safety significant propulsion system and auxiliary power unit (APU) malfunctions,
2)standardized definitions of propulsion system and APU related aircraft hazard levels based on the consequences to the aircraft, passengers and crew,
3)data on safety significant event quantities, hazard ratios, rates and generic summaries for severe and serious events during the period 1982 thru 1991; and
4)Pareto prioritization of safety significant propulsion system and APU malfunctions.
The material presented is not separable and should be considered in its entirety. The safety significant events were gathered and analyzed based on the malfunction and aircraft hazard level definitions. These definitions are fundamental keys to understanding the data presented and they are unique to this activity. The material presented is the first comprehensive propulsion system and APU related safety assessment undertaken by Industry (AIA/FAA) and deserves careful consideration.
The CAAM Committee believed that an early release of an “Initial Report” would be justified based on the need for early Industry consideration of this new material. The CAAM Committee fully expects that review and use of this “Initial Report” will lead to clearly defined needs for clarification, expansion or other enhancements. The CAAM Committee intends to continue developing the material presented and reserves the right to modify or otherwise supersede the current “Initial Report” with an improved version.
CONCLUSIONS/RECOMMENDATIONS
The conclusions/recommendations drawn by the CAAM Committee and which are appropriate to an “Initial Report” are as follows:
1)The data may be used to prioritize safety related Industry studies, research and regulatory development activities.
2)The data demonstrates the importance of “Human Factors” in propulsion/APU related flight-safety and the need for early Industry consideration of how these issues can best be addressed. Additionally, reduction of multiple-engine power loss events deserves early Industry attention.
3)The “data” will be beneficial to safety professionals within Industry in placing the various powerplant and APU-related flight-safety issues into proper context and in guiding decision making related to potential hazards associated with the defined powerplant and APU malfunctions.
4)Further refinement and development of this “Initial Report” should continue and user comments and recommendations for enhancements should be solicited.
5)The process developed under CAAM should be considered for other propulsion applications (i.e., turboshaft engines) and, more importantly, the entire aircraft.
CAAM MEMBER SIGNATURES
G. P. Sallee / Alan T. WeaverD. W. Allard / David Lotterer
J. J. Nolan / R. S. Crandall
Matthew A. Heuss / R. Tavenner
Jean Dubreuil / Philip Hensley
Thomas A. Boudreau / C. A. Freck
Nasos Karras / Carol Martineau
J. Johnston / Joseph W. Grdenick
Richard L. Edinger
AIA PC-342-1
COMMITTEE ON CONTINUED AIRWORTHINESS ASSESSMENT
METHODOLOGY
SUPPLEMENTAL REPORT
ON
TURBINE ENGINE ROTOR UNCONTAINED EVENTS
1 JANUARY 1992 THROUGH 30 NOVEMBER 1996
5 February 1997
FOREWORD
The material presented in this supplemental report has been developed by experts from the Aerospace Industries Association (AIA) Propulsion Committee (PC). The AIA-PC directed that the PC-342 Committee be recalled for the specific task of updating the uncontained turbine engine rotor event data provided in the Initial Report of 1 May 1993. This action was undertaken based on the Industry need for a measurement of the relative progress made toward minimizing uncontained turbine engine hazardous events.
The material presented in this report is consistent with the definition for "Uncontained" in the Major Propulsion System Malfunction Definitions and the Standardized Aircraft Hazard Levels presented in the earlier report...(t)he data on uncontained turbine engine events and aircraft flights cover the vast majority, but not all, of the turbine engines in commercial transport and commuter airline service, and manufactured in other than the Commonwealth of Independent States (CIS), Eastern Europe, or China. This report covers all multi-engine turbine powered civil/commercial aircraft, i.e.,
*All FAR25 commercial transports;
*All other FAR25 - business jets;
*Small business jets - FAR25 or FAR23 < 12,500 lbs.;
*Commuters - FAR23, SFAR23, 41, etc., up to 19 passenger or 6000 lbs. payload.
Turbine engines for rotorcraft are not included. Specifically, the events which may have occurred on early turboprop, jet, and low bypass turbofan engines (i.e., JT3C, JT4, JT3D, CJ610, CF700, C1805-3, CJ805-23, CT64, Avon, Conway, Proteus, and Tyne) are not included due to absence of reliable reporting. This update continues the same exclusions and maintains consistency with the earlier report.
Appendix 2
Standardized Aircraft Event Hazard Levels and Definitions
This appendix outlines propulsion system and auxiliary power unit (APU) malfunctions or related incidents, in certain cases coupled with crew error or other aircraft system malfunctions, resulting in the following consequences to the aircraft or its passengers/crew.
1. LEVEL 1 - MINOR CONSEQUENCES.
a. Uncontained nacelle damage confined to affected nacelle/APU area.
b. Uncommanded power increase, or decrease, at an airspeed above V1 and occurring at an altitude below 3,000 feet (includes in-flight shutdowns (IFSD) below 3,000 feet).
c. Multiple propulsion system malfunctions or related events, temporary in nature, where normal functioning is restored on all propulsion systems and the propulsion systems function normally for the rest of the flight. Includes common cause environmental hazard-induced events.
d. Separation of propeller/components which cause no other damage.
e. Uncommanded propeller feather.
f. Propulsion system (engine or propeller) malfunctions resulting in a load and frequency spectrum which exceeds the level demonstrated for compliance with §§ 33.23, 25.361, or 25.903(c) or their equivalent (e.g., engine malfunctions resulting in an imbalance exceeding the level of imbalance demonstrated under § 33.94 or its equivalent).
2. LEVEL 2 - SIGNIFICANT CONSEQUENCES.
a. Nicks, dents and small penetrations in aircraft primary structure.
b. Slow depressurization.
c. Controlled fires (i.e., extinguished by on-board aircraft systems).
d. Fuel leaks beyond normal extinguishing capabilities, if fire had resulted. (Note: "All fuel leaks resulting from aircraft fuel cell or fuel line penetrations.")
e. Minor injuries.
f. Multiple propulsion system/APU malfunctions, or related events, where one engine remains shutdown but continued safe flight at an altitude 1,000 feet above terrain along the intended route is possible.
g. Any high-speed takeoff abort (usually 100 knots or greater).
h. Separation of propulsion system, inlet, reverser blocker door, translating sleeve in-flight without level 3 damage consequences to the aircraft structure or systems (separations on the ground are excluded.
i. Partial in-flight reverser deployment or propeller pitch change malfunction(s) which does not result in loss of aircraft control or damage to aircraft primary structure.
3. LEVEL 3 - SERIOUS CONSEQUENCES.
A serious incident as defined by the International Civil Aviation Organization (ICAO) is “any event involving the operation of an aircraft other than an accident where the event, or the event coupled with any other reasonably probable second event, has the direct potential to result in an accident.”
a. Substantial damage to the aircraft or second unrelated system.
(1) The National Transportation Safety Board (NTSB) definition of "substantial damage" means damage or structural failure that adversely affects the structural strength, performance or flight characteristics of the aircraft, and that would normally require major repair or replacement of the affected components. (Not considered “substantial damage” are engine failure damage limited to the engine, bent fairings or cowlings, dented skin, small puncture holes in the skin or fabric, or damage to landing gear, wheel, tires, flaps, engine accessories, brakes or wing tips).
(2) Damage to a second unrelated system must impact the ability to continue safe flight and landing. Coordination and agreement between the engine/propeller/APU manufacturer and the airframe manufacturer may be required to properly categorize events related to second system damage. In general, aircraft are designed to be dispatched with one part of a redundant system inoperative with no effect on flight-safety. Therefore, an uncontained rotor event which severed an unrelated hydraulic system line without significantly degrading the ability to continue safe flight should not be considered a level 3.a. event.
(3) Small penetrations of aircraft fuel lines or aircraft fuel tanks, where the combined penetration areas exceed two square inches, is a level 3.a. classification. Assistance of the airframe manufacturer should be sought when questions arise.
(4) Damage to a second engine (cross-engine debris) which results in a significant loss of thrust or an operational problem requiring pilot action to reduce power is a level 3.a. event. Minor damage which was not observed by the crew during flight and which did not affect the ability of the engine to continue safe operation for the rest of the flight is a level 2 event.
b. Uncontrolled fires - not extinguished by on-board aircraft systems. Note: internal tailpipe fires that hazard the aircraft are considered uncontrolled fires.
c. Rapid depressurization of the cabin.
d. Permanent loss of thrust or power greater than one propulsion system.
e. Temporary or permanent inability to climb and fly 1000 feet above terrain (increased threat from terrain, inclement weather, etc.) along the intended route which results in restricted capability (i.e., multiple propulsion system malfunctions or single propulsion system malfunctions and/or other aircraft system malfunction or crew error).
f. Any temporary or permanent impairment of aircraft controllability caused by propulsion system malfunction, thrust reverser in-flight deployment, propeller control malfunction, or propulsion system malfunction coupled with aircraft control system malfunction, abnormal aircraft vibration, or crew error.
4. LEVEL 4 - SEVERE CONSEQUENCES.
a. Forced landing. Forced landing is defined as the inability to continue flight due to the consequences of damage, uncontrolled fire or thrust loss where imminent landing is obvious but aircraft controllability is not necessarily lost (i.e., total powerloss due to fuel exhaustion will result in a "forced landing”). The term "emergency landing" may also be used to mean a forced landing if there is an urgent requirement to land. An air turn back or diversion due to a malfunction is not a forced landing, since there is a lack of urgency and the crew has the ability to select where they will perform the landing. However, off-airport landings are almost always forced landings.
b. Loss of aircraft (hull loss).
c. Serious injuries or fatalities. The National Transportation Safety Board (NTSB) definition of "serious injury" means any injury that:
(1) Requires hospitalization for more than 48 hours, commencing within seven days from the date the injury was received;
(2) results in the fracture of any bone (except simple fractures of fingers, toes or nose);
(3) involves lacerations that cause severe hemorrhages, nerve, muscle or tendon damage;
(4) involves injury to any internal organ; or
(5) involves second- or third-degree burns or any burns affecting more than 5 percent of the body surface, and