Auxiliary Aircraft Facility Maintenance Standards

temporary replacement with improper or missing log information, rendering calculation of “time in service” impossible. If the assumptions the investigation arrived at are correct (and an argument can be made that they are not), then this flight was in violation of Federal Aviation Regulations, irrespective of any consideration of TBO requirements. This would have made it in violation of Auxiliary regulations as well, rendering the pilot liable to disciplinary action by both the Coast Guard and FAA. This mishap resulted in a new policy statement requiring all AUXAIR aircraft to follow manufacturers’ recommended TBO (Time Between Overhaul) for engines and propellers. It is important to note that the factors behind this incident included violations of FAA regulations which AUXAIR pilots are required to follow, and so were already covered under existing policy. Despite this, a requirement was mandated that policy be modified to cover the specific facts of this incident, regardless of the existing regulations. While the policy change was initially intended to address what some perceived as a gap in Auxiliary aviation regulations, it was later viewed and debated as a being a measure to enhance safety. The current “TBO Rule”: R 042014Z OCT 06 ZUI ASN-A00277000032 ZYB FM COMDT COGARD WASHINGTON DC TO AIG 8907 BT UNCLAS //N03710// SUBJ: AUXILIARY AVIATION UPDATES REF A: COMDTINST M16798.3, AUXILIARY OPERATIONS POLICY MANUAL 1. THIS MESSAGE OUTLINES UPDATES TO THE AVIATION SECTION OF THE AUXILIARY OPERATIONS POLICY MANUAL. THE UPDATES WILL BE INCLUDED IN CHANGE 1 TO REF A AND ARE EFFECTIVE IMMEDIATELY. Page 4 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group 2. THE FIRST UPDATE IS INTENDED TO PROVIDE GUIDANCE FOR STANDARDIZED OPERATION OF AUX AIR FACILITIES IN INSTANCES WHEN CRITICAL FLIGHT SYSTEMS OR COMPONENTS ARE BEYOND THE MANUFACTURER'S RECOMMENDED TIME BETWEEN OVERHAUL (TBO). CRITICAL SYSTEMS CAN BE DEFINED AS ANY LOGGED OR TRACKED AIRCRAFT COMPONENT OR ASSEMBLY CONTAINING A CRITICAL CHARACTERISTIC WHO'S FAILURE, MALFUNCTION, OR ABSENCE MAY CAUSE CATASTROPHIC FAILURE RESULTING IN A LOSS OR SERIOUS DAMAGE TO THE AIRCRAFT. A. ALL AUX AIR FACILITIES MUST COMPLY WITH MANUFACTURERS' TBO LIMITATIONS AS THEY APPLY TO POWER PLANTS AND OTHER CRITICAL SYSTEMS IN ORDER TO BE OFFERED FOR USE, AND TO OPERATE UNDER ORDERS. EXCEPTIONS MAY BE MADE FOR THOSE AIRCRAFT WHICH ARE OPERATING UNDER AN FAA-APPROVED MAINTENANCE SCHEDULE THAT IS CONSISTANT WITH THOSE OUTLINED UNDER FAR PART 91.409 (E) AND (F). AIRCRAFT THAT ARE IN FULL COMPLIANCE WITH ALL ASPECTS OF AN FAA- APPROVED MAINTENANCE PROGRAM WILL BE ALLOWED TO BE OFFERED FOR USE, AND TO OPERATE UNDER ORDERS Although the original rule was intended to permit aircraft on progressive inspection programs to be used under the terms of those PI programs, irrespective of TBO, this exception was later reinterpreted, essentially removing it from consideration. As a result of this TBO rule, a new field was added to the 7005 form checklist, “TBO checked”. The inspector is to confirm with the aircraft owner and logs that the aircraft is in compliance with the manufacturer’s TBO recommendations. TBO and Civil Aviation For FAA regulatory purposes, Auxiliary aviation falls into the segment called General Aviation (GA). GA is defined as all civil aviation that does not provide scheduled or commuter airline operations. It is important to understand that in the world of civil aviation, and specifically in GA, overhaul of engines at recommended TBO is not required. FAR Part 91 (under which GA falls) does not require engines to be overhauled at TBO. In fact, overhauling engines at TBO is not required by the FARs, even for commercial operations. For those operating under FAR Part 135 (air taxi), overhaul at TBO may be required by their operating specifications, but this is not always the case. Many Part 135 commercial operators are permitted to operate past TBO when using PI programs and Reliability Centered Maintenance procedures. Many GA operators run their engines well past TBO without incident. TBO is established by engine manufacturers and is published in the form of a Service Bulletin. These are non-mandatory advisories. This is in contrast to Airworthiness Directives (ADs), which are approved and issued by the FAA, and with FAA-specified life-limited components, both of which require mandatory compliance. TBO is derived actuarially and is conservatively modified by arbitrary and proprietary methodology, as method of predicting the average useful life of a given class of engines. Both engine manufacturers and maintenance experts agree that TBO cannot be used as a predictor of the condition of any individual engine. The actual condition of any given engine can only be determined by inspection, testing and operational analysis of that specific engine. Accordingly, considering TBO as a maintenance tool is inappropriate. Page 5 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group One industry maintenance expert3 puts it clearly, “An engine may be long past TBO and still be legally airworthy. (An engine may also become unairworthy long before reaching TBO.) This is supported by engine manufacturer Teledyne Continental Motors4 who makes it explicitly clear in their Service Bulletin detailing TBO recommendations that: • Published TBO is strictly advisory, not compulsory. • Operation beyond recommended TBO is permitted at the operator's discretion. • Operation beyond recommended TBO does not void the manufacturer's warranty. • Engine overhaul should be performed "on condition" based on the inspecting mechanic's evaluation of engine condition, based on compression checks, spectrographic oil analysis, oil consumption, and subjective assessment of engine performance (e.g., throttle response, power, smoothness of operation). The Effect of TBO on AUXAIR When the TBO rule went into effect, a number of Auxiliarists were operating engines that were past the manufacturer’s TBO recommendations. As noted, this is very common in General Aviation. Those Auxiliarists were faced with a difficult choice; either overhaul their engines, or withdraw their aircraft as facilities, essentially leaving the AUXAIR program. Prior to 2006 there was no regulatory requirement whatsoever to overhaul a perfectly good, well-running engine. Aircraft owners will typically plan and budget for potential engine replacement at the hours manufacturers recommend for TBO. That is probably one of the most important functions of TBO: its usefulness in planning for eventual engine replacement costs. TBO may be a useful tool for planning, but the actual overhaul time is dependent on engine health. While the hours-in-service portion of TBO has this limited planning benefit, the calendar element of TBO is even less useful as it is based on presumptions that are completely unverified and unproven. The importance of budgeting is due to the fact that overhauling an engine is very expensive. Although the cost varies with the type of engine, overhaul costs for most common General Aviation engines overhaul costs run from about twenty thousand to over fifty thousand dollars. The cost of engine removal and replacement is usually in addition to the overhaul cost. Thus, an owner of a twin-engine aircraft could be faced with costs exceeding one hundred thousand dollars to overhaul both engines. It was these staggering costs, not a reluctance to comply with reasonable rules, that forced many Auxiliarists to withdraw their aircraft from service, to leave the AUXAIR program, and for many, to ultimately to leave the Auxiliary altogether. Committing this expense to replacing an otherwise airworthy engine is a very difficult proposition for most owners. In the years from 2010 to 2013 the Auxiliary aviation program lost 37 aircraft from the fleet (~20%) due to this regulation. An additional 15 are expected to be lost this year. Generally, it is the more experienced pilots that are lost, along with their aircraft, due to this TBO regulation. Since the TBO policy went into effect, we have lost almost 45% of 3 Mike Busch – The Savvy Aviator #4 – Debunking TBO, the Savvy Maintenance Corporation, Appendix 3 4 Teledyne Continental Motors, Service Bulletin M918 Page 6 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group the AUXAIR fleet and pilots over that time frame, directly due to the effects of the TBO mandate. TBO and Safety – Separating Reality from Illusion As noted earlier, the TBO rule was created to fill a perceived gap in AUXAIR regulations. It was later defended as a requirement for airworthiness and contentions were made that the regulation must be in place for the program to remain safe. But does it actually provide a measurable increase in the safety of aviation operations? It has been argued that there have been no serious mishaps attributable to engine failure in the Auxiliary since the TBO rule went into effect. While a correct statement, this is a specious argument, since, with the exception of the one arguable incident leading to this rule-making, there have been no incidents, ever, in 70 years of AUXAIR missions, which are attributable to engine operation beyond recommended TBO limits. While the TBO regulation for the Auxiliary may have been instituted in the interests of safety, as can be demonstrated, observance of TBO has had very little GA safety impact. Data from the NTSB5 shows some 11,284 GA accidents/incidents over the last 10 years. Of these 340 had engine failure listed as a cause. Of these, the total where exceeding TBO was a contributing factor: 1. Of these, the total where exceeding TBO was a probable cause: 0. The total GA accident rate continues in this time frame to be in the range of 6.5 per 100,000 hours, or approximately 1,500/year. Considering the impact of TBO on GA accidents, it falls in the range of 0.009% of total incidents over the ten year period. TBO demonstrably has a de minimis effect on GA safety under present maintenance and certification standards. Unfortunately the AUXAIR TBO regulation has had some unintended consequences. The rule, in its final iteration, did not improve safety as much as it created an illusory perception of increased safety while having a very real adverse impact on the integrity of the program. The Dark Side of Overhaul at TBO There is another significant safety concern lurking in all that NTSB data, a concern quite the opposite of the intent of the TBO rule. That concern: the chances of an engine failure significantly increase in the first few hundred hours of operation following an engine overhaul. In other words, the most likely time for a catastrophic engine failure is when the engine is young, not when it’s old. Studies6 have clearly shown that aircraft engines are far more likely to fail within the first few years and the first few hundred hours after the engine is built, rebuilt or overhauled. 5 Data summarized from NTSB Aviation Accident data base, 2003-2013. Appendix 6 6 Waddington, C. H. ‘O. R. in World War 2: Operational Research against the U-boat’ , London: Paul Elek (Scientific Books) Ltd. 1973. F.S. Nowlan, Howard F. Heap, Reliability-Centered Maintenance, United Airlines, San Francisco, CA, US Department of Commerce, Dec 1978 Page 7 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group Latent defects in components, coupled with Maintenance Induced Failures (MIF), cause a high frequency of “infant mortality” failures and accidents. Accordingly, requiring that well-running engines be overhauled at an arbitrarily determined time actually increases the chances of failure, rather than decreasing it. Paradoxically, although the intent of the TBO regulation was to increase the safety of the AUXAIR program, it actually has the effect of decreasing safety. Auxiliary aviation has direct experience with these maintenance-induced failures. On at least six occasions within the past 6 years Auxiliarists have reported their Auxiliary facilities experiencing major problems with newly-overhauled engines. In each case the engine overhauls were done to comply with the TBO requirements, with engines otherwise properly performing and airworthy. This “infant mortality” is a result of data we know well from our CRM training – that most mishaps are caused by human error. Machines have become very reliable, but humans still make errors. This is why we have to keep trying to reduce errors by using sound CRM principles. Aircraft mechanics are human, and are not immune from making errors. When they make errors while maintaining our aircraft, those machines become less reliable. Sometimes aircraft fail because of errors that mechanics make; they either did something, or failed to do something that caused a failure. Some new parts will have latent defects that cause failures. These factors combine to create Maintenance Induced Failures (MIFs); the more invasive the maintenance, the greater the likelihood that MIFs will occur. Overhauling engines is as invasive a maintenance procedure as there can be. This tells us that there is little point in removing engines that are still functioning well, unless there is strong evidence that removal would result in some overall gain, such as a lower failure rate. Absent that evidence, it makes much more sense to inspect engines (and the aircraft in which they are installed), in order to detect unsatisfactory conditions, and take corrective actions before failures occur. A Fresh Approach Given the previous issues and outcomes, the Auxiliary aviation team has and continues to champion a fresh approach to engine and propeller maintenance. This fresh approach applies Operational Risk Management concepts. Risk Analysis would have us pay attention to that which provides an opportunity to prevent failures rather than hoping an arbitrary hours/time limit does so. • Overhauling at TBO, absent any physical indications to do so, arguably has no impact on safety in the air and actually may increase, rather than decrease, the chances of failure. • The AUXAIR TBO policy, albeit well intentioned, has had a debilitating effect on the AUXAIR program, all while producing no measurable benefit. We submit that it is time for a fresh approach to AUXAIR facility maintenance standards. We propose a standard based on sound risk management and Reliability Centered Maintenance principles. Page 8 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group Our proposed language: Ref (a): COMDTINST M16798.3, AUXILIARY OPERATIONS POLICY MANUAL Update to the Auxiliary Operations Policy Manual, to be included with Change 1 to REF A and is effective immediately. 1. Paragraph 2 of message R042014 OCT 06 from COMDT COGARD is cancelled. 2. Effective immediately, Auxiliary aircraft must have, within the past 100 hours of flight, completed a current 100-hour or annual inspection, to FAA standards, to be acceptable for receipt of operational orders. Ongoing oil analysis and trend monitoring is required for all such inspections. We propose that all Auxiliary aircraft facilities must have 100 hour inspections (as defined by the FAA) or an annual inspection, provided that not more than 100 hours in service has passed, to be operated under orders. In addition to that, we propose that each aircraft have ongoing oil spectrographic oil analysis and trend monitoring at those inspections.7 Such an inspection-based approach would provide an opportunity to detect issues that may lead to failure and allow them to be corrected. This is the heart of the FAA’s risk management based approach used in commercial operators’ maintenance plans and is a core concept in Reliability-Centered Maintenance. There is ample evidence of the efficacy of such an approach. Spectrographic Oil Analysis In the late 1950s and early 1960s, the US Navy was one of the largest operators of air- cooled piston aircraft engines (the same kind that AUXAIR uses) on the planet. In 1955 the Navy initiated a project to determine whether the techniques of spectrographic oil analysis could be applied to aircraft engines. The goal was to minimize inflight engine failures and to extend engine operating intervals, reducing overhauls and associated costs. The study was very successful8. “By use of spectrographic oil analysis, we are detecting engine problems earlier than they can be detected any other way. We give direction and velocity to trouble shooting and engine conditioning procedures. We can verify the effectiveness of a repair. We can and do alert the operator to many problems which if left undetected could result in inflight engine failures.” Based on the results of this study, the Navy expanded the practice of oil analysis, moved away from overhauling engines at specific TBO intervals, and toward overhauling engines on condition. 7 AV Results, Oil Analysis trend, Appendix 8 8 US Navy, AD 268-205, “Determination of Engine Condition by Spectrographic Analysis of Engine Oil Samples”, NAS Pensacola. Appendix 5. Page 9 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group 100-Hour Inspections and Expense Per FAR Part 43, 100-hour inspections must be conducted by an FAA certificated Airframe and Powerplant mechanic (A&P). Also per FAR Part 43, all other inspections, such as annual inspections, must be conducted by an A&P mechanic with Inspection Authorization (IA). The regulations surrounding the certification of mechanics and inspection authorization are found in 14 CFR Part 65. Every GA aircraft must be inspected annually in order to be found airworthy and be permitted to fly. The scope of Annual and 100 hour inspections is detailed in FAR Part 43 Appendix D. The annual and 100-hour inspections are identical in scope and detail. The only difference is in the performance and approval of the annual inspection, which must be accomplished by an A&P with IA. FAR Part 91 does not require aircraft to undergo 100- hour inspections unless they are carrying passengers for hire or conducting flight instruction. Regular inspections by FAA-certified mechanics, as described above, will minimize surprises and provides opportunity to catch problems early. This is sensible risk management and is endorsed by the FAA. Routine monitoring provides the opportunity to identify wear trends and other problems before they become problematic. Failures that cause catastrophic results rarely occur unannounced. Most component failures do not cause engine stoppages. They more often result in reduced power or other problems that are easily dealt with in flight and allow for a safe return to land. In fact, this was the case in the event that precipitated the imposition of the TBO policy. Our proposal would raise the bar set by FAR part 91 for non-commercial operators, and would hold AUXAIR to a higher standard. Private GA aircraft are generally flown by their owners between 90-200 hours per year9. An analysis of Auxiliary aviation operations for 2013 indicates that approximately 80% of aircraft facilities fly less than 125 hours per year on missions.10 For members who fly 125 hours or less per year, there would be no (or small) additional expense along with the addition of oil analysis, if not already being performed. This is typically a relatively minor expense ($20-$30 per sample inspected) with great value returned. Members who fly more than this would have to inspect some months sooner than their “annual” would otherwise require. This should be of minimal impact compared to the eventual cost of replacement of an otherwise well-operating engine. The only change to Auxiliary inspection procedures would be to have Auxiliary inspectors examine aircraft logbooks to verify that 100-hour inspections had been accomplished and that the oil analysis trend monitoring reports were on file. Auxiliary Assistant District Staff Officers for Management (ADSO-AVM), an existing position at the district level, are responsible for collecting and tracking the copies of the data as 9 AOPA Aircraft Usage data, 2013, from AOPA Web site 10 Auxiliary Facility Usage Analysis, Appendix 9 Page 10 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group provided by the inspectors. The 7005 form would be modified as needed to add these items to the check list. This process would not require any other change to the current way that Auxiliary Aircraft facilities are inspected and accepted for use. After approval and acceptance, the 7005 forms and other data would be available to the Air Stations, as they are now. Administrative changes required by this fresh approach would be minimal and at little expense: • No additional operating costs are contemplated under this proposal. In fact, recruiting, training and certification efforts and associated costs should diminish. • No additional SAMA funding or allocations are planned in regard to this proposal. Maintenance costs should be minimally impacted for most operators, especially given a comparison of overhaul costs to inspections. • CG-BSX would issue an ALAUX detailing the changes and placing it in the update list for the next issuance of the AOPM. • The R and IT Directorates would modify the online 7005 form to comply with the 100-hour and oil analysis requirements • The R Directorate would send out a bulletin to the districts detailing the new procedures required by the ALAUX and place it on the Web site. • A training point would be added to the relevant schools and Workshops. • The position of Auxiliary Branch Chief for Aviation Maintenance would assume oversight of the program to assist the districts and the ADSO- AVMs with any issues. Summary The current policy regarding compliance with manufacturer’s recommended TBO has been counter-productive. Absent other indications, risk analysis indicates that there is no demonstrable benefit to overhaul at TBO. The policy may actually increase the risk of failure by arbitrarily forcing an otherwise-healthy engine or propeller to be overhauled. Many facilities have been lost to the program and a number of members have left the program rather than overhaul an otherwise-healthy engine. Some members who have stayed have endured financial hardship in order to retain the privilege of flying missions for the Coast Guard. Recruitment efforts have suffered, as potential members have lost interest after learning about the TBO requirement. The cost to the Coast Guard and Auxiliary for replacing these lost pilots and facilities is high, both in direct training costs, recruitment efforts, and in the new members' reduced mission capability until they are seasoned. While the costs of the current policy are demonstrably high, there is no discernable benefit in safety or performance. Adoption of our proposal would mean that engines and propellers would not arbitrarily be required to be overhauled and thereby returned to a time of high risk of "infant mortality." Long-term, productive members and facilities would be retained. This fresh approach reduces risk and provides specific benefits in terms of safety and mission capability. Page 11 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group Appendices 1. 14 CFR 43 Appendix D – Scope And Detail Of Items To Be Included In Annual And 100 Hour Inspections 2. 14 CFR 91.409 – Inspections 3. Busch – Debunking TBO 4. Busch Article Compilation 5. Determination of Engine Condition by Spectrographic Analysis of Engine Oil Samples, Jack F. Witten, Bureau of Naval Weapons, Bernard B. Bond, NAS Pensacola, April, 1961 6. NTSB Aviation Data and TBO Analysis, Response Directorate 7. ANSC 7005 Auxiliary Aircraft Facility Inspection and Offer For Use form 8. Sample Oil Analysis Report - AvResults - Engine Oil Sample Report 9. Auxiliary Facility Flight Hour Analysis Page 12 of 12 AUG 01, 2014 AUXAIR Facility Maintenance Standards eCFR — Code of Federal Regulations http://www.ecfr.gov/cgi-bin/text-idx?SID=80dd87b306ba334ad3ccc51f4cdeb447&node=14:1.0.1.3.21.0.363.14.56&rgn=div9 1/3 ELECTRONIC CODE OF FEDERAL REGULATIONS eCFR Data is current as of June 17, 2014 Title 14: Aeronautics and Space PART 43—MAINTENANCE, PREVENTIVE MAINTENANCE, REBUILDING, AND ALTERATION APPENDIX D TO PART 43—SCOPE AND DETAIL OF ITEMS (AS APPLICABLE TO THE PARTICULAR AIRCRAFT) TO BE INCLUDED IN ANNUAL AND 100H OUR INSPECTIONS (a) Each person performing an annual or 100hour inspection shall, before that inspection, remove or open all necessary inspection plates, access doors, fairing, and cowling. He shall thoroughly clean the aircraft and aircraft engine. (b) Each person performing an annual or 100hour inspection shall inspect (where applicable) the following components of the fuselage and hull group: (1) Fabric and skin—for deterioration, distortion, other evidence of failure, and defective or insecure attachment of fittings. (2) Systems and components—for improper installation, apparent defects, and unsatisfactory operation. (3) Envelope, gas bags, ballast tanks, and related parts—for poor condition. (c) Each person performing an annual or 100hour inspection shall inspect (where applicable) the following components of the cabin and cockpit group: (1) Generally—for uncleanliness and loose equipment that might foul the controls. (2) Seats and safety belts—for poor condition and apparent defects. (3) Windows and windshields—for deterioration and breakage. (4) Instruments—for poor condition, mounting, marking, and (where practicable) improper operation. (5) Flight and engine controls—for improper installation and improper operation. (6) Batteries—for improper installation and improper charge. (7) All systems—for improper installation, poor general condition, apparent and obvious defects, and insecurity of attachment. (d) Each person performing an annual or 100hour inspection shall inspect (where applicable) components of the engine and nacelle group as follows: (1) Engine section—for visual evidence of excessive oil, fuel, or hydraulic leaks, and sources of such leaks. (2) Studs and nuts—for improper torquing and obvious defects. APPENDIX 1 AUXAIR Facility Maintenance Standards eCFR — Code of Federal Regulations http://www.ecfr.gov/cgi-bin/text-idx?SID=80dd87b306ba334ad3ccc51f4cdeb447&node=14:1.0.1.3.21.0.363.14.56&rgn=div9 2/3 (3) Internal engine—for cylinder compression and for metal particles or foreign matter on screens and sump drain plugs. If there is weak cylinder compression, for improper internal condition and improper internal tolerances. (4) Engine mount—for cracks, looseness of mounting, and looseness of engine to mount. (5) Flexible vibration dampeners—for poor condition and deterioration. (6) Engine controls—for defects, improper travel, and improper safetying. (7) Lines, hoses, and clamps—for leaks, improper condition and looseness. (8) Exhaust stacks—for cracks, defects, and improper attachment. (9) Accessories—for apparent defects in security of mounting. (10) All systems—for improper installation, poor general condition, defects, and insecure attachment. (11) Cowling—for cracks, and defects. (e) Each person performing an annual or 100hour inspection shall inspect (where applicable) the following components of the landing gear group: (1) All units—for poor condition and insecurity of attachment. (2) Shock absorbing devices—for improper oleo fluid level. (3) Linkages, trusses, and members—for undue or excessive wear fatigue, and distortion. (4) Retracting and locking mechanism—for improper operation. (5) Hydraulic lines—for leakage. (6) Electrical system—for chafing and improper operation of switches. (7) Wheels—for cracks, defects, and condition of bearings. (8) Tires—for wear and cuts. (9) Brakes—for improper adjustment. (10) Floats and skis—for insecure attachment and obvious or apparent defects. (f) Each person performing an annual or 100hour inspection shall inspect (where applicable) all components of the wing and center section assembly for poor general condition, fabric or skin deterioration, distortion, evidence of failure, and insecurity of attachment. (g) Each person performing an annual or 100hour inspection shall inspect (where applicable) all components and systems that make up the complete empennage assembly for poor general condition, fabric or skin deterioration, distortion, evidence of failure, insecure attachment, improper component installation, and improper component operation. (h) Each person performing an annual or 100hour inspection shall inspect (where applicable) the following components of the propeller group: (1) Propeller assembly—for cracks, nicks, binds, and oil leakage. (2) Bolts—for improper torquing and lack of safetying. APPENDIX 1 6/18/2014 eCFR — Code of Federal Regulations http://www.ecfr.gov/cgi-bin/text-idx?SID=80dd87b306ba334ad3ccc51f4cdeb447&node=14:1.0.1.3.21.0.363.14.56&rgn=div9 3/3 For questions or comments regarding eCFR editorial content, features, or design, email ecfr@nara.gov. For questions concerning eCFR programming and delivery issues, email webteam@gpo.gov. (3) Antiicing devices—for improper operations and obvious defects. (4) Control mechanisms—for improper operation, insecure mounting, and restricted travel. (i) Each person performing an annual or 100hour inspection shall inspect (where applicable) the following components of the radio group: (1) Radio and electronic equipment—for improper installation and insecure mounting. (2) Wiring and conduits—for improper routing, insecure mounting, and obvious defects. (3) Bonding and shielding—for improper installation and poor condition. (4) Antenna including trailing antenna—for poor condition, insecure mounting, and improper operation. (j) Each person performing an annual or 100hour inspection shall inspect (where applicable) each installed miscellaneous item that is not otherwise covered by this listing for improper installation and improper operation. APPENDIX 1 AUXAIR Facility Mainetnance Standard eCFR — Code of Federal Regulations http://www.ecfr.gov/cgi-bin/text-idx?rgn=div8&node=14:2.0.1.3.10.5.7.5 1/3 ELECTRONIC CODE OF FEDERAL REGULATIONS eCFR Data is current as of July 9, 2014 Title 14: Aeronautics and Space PART 91—GENERAL OPERATING AND FLIGHT RULES Subpart E—Maintenance, Preventive Maintenance, and Alterations §91.409 Inspections. (a) Except as provided in paragraph (c) of this section, no person may operate an aircraft unless, within the preceding 12 calendar months, it has had— (1) An annual inspection in accordance with part 43 of this chapter and has been approved for return to service by a person authorized by §43.7 of this chapter; or (2) An inspection for the issuance of an airworthiness certificate in accordance with part 21 of this chapter. No inspection performed under paragraph (b) of this section may be substituted for any inspection required by this paragraph unless it is performed by a person authorized to perform annual inspections and is entered as an “annual” inspection in the required maintenance records. (b) Except as provided in paragraph (c) of this section, no person may operate an aircraft carrying any person (other than a crewmember) for hire, and no person may give flight instruction for hire in an aircraft which that person provides, unless within the preceding 100 hours of time in service the aircraft has received an annual or 100hour inspection and been approved for return to service in accordance with part 43 of this chapter or has received an inspection for the issuance of an airworthiness certificate in accordance with part 21 of this chapter. The 100hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done. The excess time used to reach a place where the inspection can be done must be included in computing the next 100 hours of time in service. (c) Paragraphs (a) and (b) of this section do not apply to— (1) An aircraft that carries a special flight permit, a current experimental certificate, or a lightsport or provisional airworthiness certificate; (2) An aircraft inspected in accordance with an approved aircraft inspection program under part 125 or 135 of this chapter and so identified by the registration number in the operations specifications of the certificate holder having the approved inspection program; (3) An aircraft subject to the requirements of paragraph (d) or (e) of this section; or (4) Turbinepowered rotorcraft when the operator elects to inspect that rotorcraft in accordance with paragraph (e) of this section. (d) Progressive inspection. Each registered owner or operator of an aircraft desiring to use a progressive inspection program must submit a written request to the FAA Flight Standards district office having jurisdiction over the area in which the applicant is located, and shall provide— APPENDIX 2 AUXAIR Facility Mainetnance Standard eCFR — Code of Federal Regulations http://www.ecfr.gov/cgi-bin/text-idx?rgn=div8&node=14:2.0.1.3.10.5.7.5 2/3 (1) A certificated mechanic holding an inspection authorization, a certificated airframe repair station, or the manufacturer of the aircraft to supervise or conduct the progressive inspection; (2) A current inspection procedures manual available and readily understandable to pilot and maintenance personnel containing, in detail— (i) An explanation of the progressive inspection, including the continuity of inspection responsibility, the making of reports, and the keeping of records and technical reference material; (ii) An inspection schedule, specifying the intervals in hours or days when routine and detailed inspections will be performed and including instructions for exceeding an inspection interval by not more than 10 hours while en route and for changing an inspection interval because of service experience; (iii) Sample routine and detailed inspection forms and instructions for their use; and (iv) Sample reports and records and instructions for their use; (3) Enough housing and equipment for necessary disassembly and proper inspection of the aircraft; and (4) Appropriate current technical information for the aircraft. The frequency and detail of the progressive inspection shall provide for the complete inspection of the aircraft within each 12 calendar months and be consistent with the manufacturer's recommendations, field service experience, and the kind of operation in which the aircraft is engaged. The progressive inspection schedule must ensure that the aircraft, at all times, will be airworthy and will conform to all applicable FAA aircraft specifications, type certificate data sheets, airworthiness directives, and other approved data. If the progressive inspection is discontinued, the owner or operator shall immediately notify the local FAA Flight Standards district office, in writing, of the discontinuance. After the discontinuance, the first annual inspection under §91.409(a)(1) is due within 12 calendar months after the last complete inspection of the aircraft under the progressive inspection. The 100hour inspection under §91.409(b) is due within 100 hours after that complete inspection. A complete inspection of the aircraft, for the purpose of determining when the annual and 100hour inspections are due, requires a detailed inspection of the aircraft and all its components in accordance with the progressive inspection. A routine inspection of the aircraft and a detailed inspection of several components is not considered to be a complete inspection. (e) Large airplanes (to which part 125 is not applicable), turbojet multiengine airplanes, turbopropellerpowered multiengine airplanes, and turbinepowered rotorcraft. No person may operate a large airplane, turbojet multiengine airplane, turbopropellerpowered multiengine airplane, or turbine powered rotorcraft unless the replacement times for lifelimited parts specified in the aircraft specifications, type data sheets, or other documents approved by the Administrator are complied with and the airplane or turbinepowered rotorcraft, including the airframe, engines, propellers, rotors, appliances, survival equipment, and emergency equipment, is inspected in accordance with an inspection program selected under the provisions of paragraph (f) of this section, except that, the owner or operator of a turbinepowered rotorcraft may elect to use the inspection provisions of §91.409(a), (b), (c), or (d) in lieu of an inspection option of §91.409(f). (f) Selection of inspection program under paragraph (e) of this section. The registered owner or operator of each airplane or turbinepowered rotorcraft described in paragraph (e) of this section must select, identify in the aircraft maintenance records, and use one of the following programs for the inspection of the aircraft: (1) A continuous airworthiness inspection program that is part of a continuous airworthiness maintenance program currently in use by a person holding an air carrier operating certificate or an operating certificate issued under part 121 or 135 of this chapter and operating that make and model APPENDIX 2 AUXAIR Facility Mainetnance Standard eCFR — Code of Federal Regulations http://www.ecfr.gov/cgi-bin/text-idx?rgn=div8&node=14:2.0.1.3.10.5.7.5 3/3 For questions or comments regarding eCFR editorial content, features, or design, email ecfr@nara.gov. For questions concerning eCFR programming and delivery issues, email webteam@gpo.gov. aircraft under part 121 of this chapter or operating that make and model under part 135 of this chapter and maintaining it under §135.411(a)(2) of this chapter. (2) An approved aircraft inspection program approved under §135.419 of this chapter and currently in use by a person holding an operating certificate issued under part 135 of this chapter. (3) A current inspection program recommended by the manufacturer. (4) Any other inspection program established by the registered owner or operator of that airplane or turbinepowered rotorcraft and approved by the Administrator under paragraph (g) of this section. However, the Administrator may require revision of this inspection program in accordance with the provisions of §91.415. Each operator shall include in the selected program the name and address of the person responsible for scheduling the inspections required by the program and make a copy of that program available to the person performing inspections on the aircraft and, upon request, to the Administrator. (g) Inspection program approved under paragraph (e) of this section. Each operator of an airplane or turbinepowered rotorcraft desiring to establish or change an approved inspection program under paragraph (f)(4) of this section must submit the program for approval to the local FAA Flight Standards district office having jurisdiction over the area in which the aircraft is based. The program must be in writing and include at least the following information: (1) Instructions and procedures for the conduct of inspections for the particular make and model airplane or turbinepowered rotorcraft, including necessary tests and checks. The instructions and procedures must set forth in detail the parts and areas of the airframe, engines, propellers, rotors, and appliances, including survival and emergency equipment required to be inspected. (2) A schedule for performing the inspections that must be performed under the program expressed in terms of the time in service, calendar time, number of system operations, or any combination of these. (h) Changes from one inspection program to another. When an operator changes from one inspection program under paragraph (f) of this section to another, the time in service, calendar times, or cycles of operation accumulated under the previous program must be applied in determining inspection due times under the new program. (Approved by the Office of Management and Budget under control number 21200005) [Doc. No. 18334, 54 FR 34311, Aug. 18, 1989; Amdt. 91211, 54 FR 41211, Oct. 5, 1989; Amdt. 91267, 66 FR 21066, Apr. 27, 2001; Amdt. 91282, 69 FR 44882, July 27, 2004] APPENDIX 2 USCG Auxiliary RP Group AUXAIR Facility Maintenance Standards APPENDIX 3 The Savvy Aviator on TBO Mike Busch is arguably the best-known A&P/IA in general aviation, honored by the FAA in 2008 as National Aviation Maintenance Technician of the Year. Mike began flying in 1964, and today has logged more than 7,500 hours. He is a commercial pilot with instrument, single- and multi-engine land, single-engine sea, and glider ratings; a certificated flight instructor for airplanes, instruments and multiengine; and a certificated A&P mechanic with Inspection Authorization. He has been an aircraft owner for 45 years. Mike is a mathematician by training, having earned his BA in Mathematics at Dartmouth College (Magna Cum Laude). He did graduate studies at Princeton University and Columbia University and was the recipient of a National Science Foundation fellowship. He enjoyed a long and successful career as a software entrepreneur. He is a prolific aviation author, co-founder of AVweb, and presently heads a team of world-class GA maintenance experts at Savvy Aircraft Maintenance Management, Inc., the world's largest company providing professional maintenance management services for owner-flown aircraft. Mike is on the technical staff of the Cessna Pilots Association and provides technical support to the American Bonanza Society and the Cirrus owners & Pilots Association. The following is an article that was published on AvWeb, in April of 2004. AvWeb, is an online aviation magazine and aviation news resource. Page A3 -1 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 The Savvy Aviator #4: Debunking TBO By Mike Busch Engine TBO (time between overhauls) seems to be one of the most misunderstood concepts in aviation maintenance. There are lots of TBOrelated old wives tales that are widely believed by owners and mechanic alike, and they can cost owners a great deal of money. Mike Busch endeavors to clear up these misconceptions, and explain what TBO really means. Ask any aircraft owner what the TBO is for the engine(s) on his aircraft and you'll almost always get the correct answer without hesitation: "My engine has a 1,700hour TBO." But ask that owner to explain the significance of that TBO figure and you'll get all sorts of answers, most of them flat wrong. Here are a few of the most common misapprehensions about TBO: "It's illegal to fly an airplane if the engine is past the TBO established by the manufacturer." Nonsense. The TBO figures published by Lycoming and TCM are not airworthiness limitations. An engine may be long past TBO and still be legally airworthy. (An engine may also become unairworthy long before reaching TBO.) "While it's true that manufacturer's TBO isn't compulsory for noncommercial (Part 91) operators, commercial (Part 121/135) operators are required to overhaul an engine when it reaches TBO." Not so. Both Lycoming and TCM publish engine TBOs in the form of nonmandatory Page A3 -2 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 service bulletins. Some Part 121/135 operators have Operations Specifications that require them to comply with all manufacturer's service bulletins (even nonmandatory ones), while others have Op Specs that require compliance only with mandatory service bulletins. Those in the latter group are no more obligated to comply with published TBO than are Part 91 operators. Those in the former group might theoretically be required to overhaul at published TBO, but most such operators request TBO extensions from their FSDO and these are routinely granted, often for as much as 50% over the engine manufacturer's published TBO. So, in actual practice, published TBO is hardly ever compulsory for any operators commercial or noncommercial. "Continuing to fly an engine beyond TBO could void your aircraft insurance." Poppycock. I've yet to see any aircraft insurance policy that requires compliance with nonmandatory service bulletins as a condition of coverage. Most policies only require that the aircraft be airworthy and in compliance with FAA inspection requirements. "Continuing to fly an engine beyond TBO is dangerous because doing so increases the chance of an inflight engine failure." To the contrary, an engine is much more likely to fail during the first few hundred hours after major overhaul than during the first few hundred hours after passing published TBO. If you exclude fuel starvation or exhaustion (i.e., pilot error), most engine stoppages involve mechanical failure of some "top end" engine component like a cylinder, exhaust valve, piston, magneto, turbocharger, exhaust stack, etc. Such bolt on components are routinely replaced during normal maintenance without any need to overhaul the engine. The purpose of a major engine overhaul is to inspect, recondition and or replace the engine's "bottom end" components crankshaft, camshaft, crankcase, gears, bearings, etc. that cannot be accessed without splitting the case. But these "bottom end" components are seldom implicated in catastrophic Page A3 -3 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 engine failures. Furthermore, in those rare cases when these components do fail (e.g., crankshaft fracture), the failure is almost never correlated with time since overhaul. (If a crankshaft is going to fail, it's most likely to fail during the first few hundred hours after manufacture, or after a prop strike.) "Continuing to fly an engine beyond TBO is false economy, because doing so just makes the inevitable major overhaul more expensive." This old wives tale probably originated back in the days when new cylinders were very expensive and most engines were field overhauled using reconditioned (chromed or oversized) jugs. In those days, if you pushed an engine to the point that its cylinders could not be reconditioned, you'd have to spend more at overhaul to buy new ones. Nowadays, however, the cost of new cylinders has come down to the point where most major overhauls include all new jugs as standard procedure. Consequently, there's no longer any real advantage to overhauling sooner rather than later. The only things that will impact the overhaul cost are an unserviceable crankshaft or a cracked crankcase, and neither of those items are any more probable for an engine operated beyond TBO. By the way, it's not just owners who hold these misconceptions. Plenty of A&P mechanics believe these things, too. TBO From The Horse's Mouth The definitive word on the subject of TBO for engines manufactured by Teledyne Continental Motors is TCM Service Bulletin M918 "Recommended Overhaul Periods for All Teledyne Continental Motors Aircraft Engines" dated July 10, 1991. This is the document in which TCM publishes a table of recommended TBOs for all TCM engine models. TCM service bulletins come in three different grades: recommended, mandatory, and critical. Critical service bulletins are typically reserved for items that are considered so urgent that TCM asks the FAA to issue an Airworthiness Directive to mandate Page A3 -4 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 compliance. Mandatory service bulletins are less urgent, normally not accompanied by an AD, and normally "mandatory" only for commercial operators. Recommended service bulletins are used for conveying helpful hints to owners and mechanics, but they are merely suggestions and compliance is strictly up to the individual operator. M918 is one of these lowest priority service bulletins. It offers recommendations, but they are not intended by TCM to be obligatory for any operator. To underscore this point, let's take a look at exactly what TCM says in M918 (emphasis mine): The wording of TCM's service bulletin M918 makes it explicitly clear that: • Published TBO is strictly advisory, not compulsory. • Operation beyond recommended TBO is permitted at the operator's discretion. Thousands of hours of operating experience indicate that Teledyne Continental Motors (TCM) aircraft engines, when operated within prescribed limitations, instructions and recommendations, can be operated between overhauls for the number of hours listed in the following table. The overhaul periods listed are recommendations only. They are predicated on the use of genuine TCM parts, compliance with all applicable Service Bulletins and ADs, as well as all required preventive maintenance, periodic inspections, manufacturer's specifications, and the determination by a qualified mechanic that the engine is operating normally and is airworthy. The accomplishment of cylinder leakage checks and spectrographic oil analysis may be helpful in making this determination. Any operation beyond these periods is at the operator's discretion and should be based on the inspecting mechanic's evaluation of engine condition and operating environment. Calendar time also affects this condition and should be taken into account. Particular attention should be paid to throttle response, power, smoothness of operation, oil consumption, to the proper use and maintenance of oil and air filters, and adherence to the recommended oil change periods. Emphasis should also be placed on recommended fuel management. These recommended overhaul periods in no way alter TCM's warranty policies. Page A3 -5 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 • Operation beyond recommended TBO does not void the manufacturer's warranty. • Engine overhaul should be performed "on condition" based on the inspecting mechanic's evaluation of engine condition, based on compression checks, spectrographic oil analysis, oil consumption, and subjective assessment of engine performance (e.g., throttle response, power, smoothness of operation). Bottom line is that if an engine is still going strong when it reaches TBO, there's absolutely no reason to consider removing it from service for major overhaul, and every reason to continue flying until it starts showing signs that overhaul is warranted. So What Good Is TBO? Does this mean that the manufacturer's TBO is a worthless figure that should be ignored? No, not at all. In my view, the best way to think about published TBO is the way we think about human life expectancy statistics. According to the National Vital Statistics Report (http://www.cdc.gov/nchs/data/nvsr/nvsr52/nvsr52_14.pdf) published by the Centers for Disease Control, the current life expectancy at birth for a white male in the United States is 75 years. This statistic might be quite useful in figuring out what premium to charge for a life insurance policy, or how to plan for retirement. Does this mean that white U.S. males should be euthanized (removed from service) when they reach age 75? I certainly hope not! In fact, the same CDC figures show that the current life expectancy for a 75-year-old white male in the U.S. is 11 years. In other words, if you're still kicking at age 75, you can expect on average to live until age 86. Furthermore, if you are still alive at age 86, your life expectancy is 6 years so on average you can be expected to live until age 92. Page A3 -6 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 Similarly, according to TCM Service Bulletin M918, the "life expectancy at birth" (recommended TBO) of TSIO520BB engines (like the ones in my 1979 Cessna T310R) is 1,400 hours. This statistic might be quite useful in figuring out a suitable dollar amount for amortizing overhaul expense. Since it costs about $30,000 to overhaul one of these engines, a reasonable "reserve for overhaul" would be $21.43 per hour (i.e., $30,000 divided by 1,400 hours). This figure would also be appropriate for adjusting the "blue book" value of my airplane to account for higher or lower than average engine time. Does this mean that I should have euthanized my engines when they reached 1,400 hours SMOH (since major overhaul), despite the fact that they were running great, had excellent compressions, low oil consumption, no metal in the oil filters, and excellent oil analysis reports? No, I don't think so. Although TCM doesn't publish figures for "life expectancy at 1,400 hours" for these engines, it only stands to reason that TSIO520BB engines that are in good shape at 1,400 hours surely have a good deal of useful life left in them. (As previously noted, many commercial operators routinely run their engines to 150% of manufacturer's TBO with the FAA's official blessing.) Some Real World Experience When I purchased my T310R in 1987, it had 1,300 hours total time on the airframe and engines. Since TCM's published TBO for its TSIO520BB engines is 1400 hours, those engines were pretty much "run out" when I acquired the airplane (and the price I paid was adjusted downward accordingly). At 1,400 hours those engines were still running superbly, and all signs pointed to them being in great shape. I wound up flying those engines trouble free to 1,900 hours (500 hours past published TBO), at which time I started getting nervous and pulled the engines for major overhaul. Page A3 -7 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 As it turned out, my nervousness about flying those engines 500 hours past published TBO were completely unfounded. The overhaul shop reported that all 12 cylinders were still within new limits, as was pretty much everything else. It was clear from the results of the teardown inspection that those engines could have gone considerably longer at least another 500 hours with no problem. Those engines received minimalist (i.e., el cheapo) major overhauls in 1990. The cylinders had their valves replaced, their barrels lightly honed, new pistons and rings installed, and were bolted back on for another run. I saved about $12,000 by not replacing the cylinders at overhaul, but I figured that there was probably no way these jugs would survive another 1,400 hours. I figured wrong. Those engines and cylinders now have accumulated another 1,600 hours since the overhaul, and so those cylinders have 3,500 hours on them. I am just wrapping up my 2004 annual inspection as I write this. The compressions are all 75/80 or better, the oil consumption remains about a quart in 15 hours, the oil filters are clean, the oil analysis is excellent, and the engines are running as well as they ever have. I imagine I'll be flying behind them for a while longer (knock on wood). This time around, I'm not even the slightest bit nervous about continuing to fly past TBO. I know that so long as I continue to keep a watchful eye on compression, oil consumption, oil filter inspection, oil analysis, temperatures and performance, I'll know when the engines are getting tired and it's time to overhaul them. That could be next year, or it might be five years from now. I'm not even going to try to predict how much more useful life those engines have left, but when the time comes to major them, they'll tell me. I haven't yet decided exactly what I'll do when that time comes. Will I have the engines field overhauled again, or exchange them for factory rebuilt engines? Will I recondition the cylinders or install new ones? Install TCM factory cylinders, Superior Page A3 -8 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 3 Milleniums, or ECI Titans? These are complex decisions that I discuss at considerable length in my Savvy Owner Seminar (/sponsors/savvy/). In my own case, I'll make those decisions when the time comes, based on the best information available at the time. But I can tell you one thing for sure: When those freshly overhauled or rebuilt engines are installed back in the airplane and it's time for me to get back in the air, that's when I'll be nervous! Page A3 -9 of 9 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Mike Busch on TBO Mike Busch is arguably the best-known A&P/IA in general aviation, honored by the FAA in 2008 as National Aviation Maintenance Technician of the Year. Mike began flying in 1964, and today has logged more than 7,500 hours. He is a commercial pilot with instrument, single- and multi-engine land, single-engine sea, and glider ratings; a certificated flight instructor for airplanes, instruments and multiengine; and a certificated A&P mechanic with Inspection Authorization. He has been an aircraft owner for 45 years. Mike is a mathematician by training, having earned his BA in Mathematics at Dartmouth College (Magna Cum Laude). He did graduate studies at Princeton University and Columbia University and was the recipient of a National Science Foundation fellowship. He enjoyed a long and successful career as a software entrepreneur. He is a prolific aviation author, co-founder of AVweb, and presently heads a team of world-class GA maintenance experts at Savvy Aircraft Maintenance Management, Inc., the world's largest company providing professional maintenance management services for owner-flown aircraft. Mike is on the technical staff of the Cessna Pilots Association and provides technical support to the American Bonanza Society and the Cirrus owners & Pilots Association. This collection includes a series of articles published by the Aircraft Owners and Pilots Association. The AOPA is the largest aviation association in the world. The dates of publication range from January to June of 2014. Page A4 -1 of 36 USCG Auxiliary RP Group AUXAIR Facility Maintenance Standards APPENDIX 4 The Waddington Effect January 14th, 2014 by Mike Busch In 1943, a British scientist named Conrad Hal (C.H.) Waddington made a remarkable discovery about aircraft maintenance. He was a most unlikely person to make this discovery, because he wasn’t an aeronautical engineer or an aircraft mechanic or even a pilot. Actually, he was a gifted developmental biologist, paleontologist, geneticist, embryologist, philosopher, poet and painter who wasn’t particularly interested in aviation. But like many other British scientists at that time, his career was interrupted by the outbreak of the Second World War and he found himself pressed into service with the Royal Air Force (RAF). C.H. Waddington (1905-1975) Waddington wound up reporting to the RAF Coastal Command, heading up a group of fellow scientists in the Coastal Command Operational Research Section. Its job was to advise the British military on how it could more effectively combat the threat from German submarines. In that capacity, Waddington and his colleagues developed a series of astonishing recommendations that defied military conventional wisdom of the time. For example, the bombers used to hunt and kill U-boats were mostly painted black in order to make them difficult to see. But Waddington’s group ran a series of experiments that proved that bombers painted white were not spotted by the U-boats until they were 20% closer, resulting in a 30% increase in successful sinkings. Waddington’s group also recommended that the depth charges dropped by the bombers be set to explode at a depth of 25 feet instead of 100 feet. This recommendation—initially resisted strongly by RAF commanders—ultimately resulted in a sevenfold increase in the number of U-boats destroyed. Consolidated B-24 “Liberator” bomber Page A4 -2 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Waddington subsequently turned his attention to the problem of “force readiness” of the bombers. The Coastal Command’s B-24 “Liberator” bombers were spending an inordinate amount of time in the maintenance shop instead of hunting U-boats. In July 1943, the two British Liberator squadrons located at Ballykelly, Northern Ireland, consisted of 40 aircraft, but at any given time only about 20 were flight-ready. The other aircraft were down for any number of reasons, but mostly undergoing or awaiting maintenance—either scheduled or unscheduled— or waiting for replacement parts. At that time, conventional wisdom held that if more preventive maintenance were performed on each aircraft, fewer problems would arise and more incipient problems would be caught and fixed—and thus fleet readiness would surely improve. It turned out that conventional wisdom was wrong. It would take C.H. Waddington and his Operational Research team to prove just how wrong. Waddington and his team started gathering data about the scheduled and unscheduled maintenance of these aircraft, and began crunching and analyzing the numbers. When he plotted the number of unscheduled aircraft repairs as a function of flight time, Waddington discovered something both unexpected and significant: The number of unscheduled repairs spiked sharply right after each aircraft underwent its regular 50-hour scheduled maintenance, and then declined steadily over time until the next scheduled 50-hour maintenance, at which time they spiked up once again. When Waddington examined the plot of this repair data, he concluded that the scheduled maintenance (in Waddington’s own words) “tends to INCREASE breakdowns, and this can only be because it is doing positive harm by disturbing a relatively satisfactory state of affairs. There is no sign that the rate of breakdowns is starting to increase again after 40-50 flying hours when the aircraft is coming due for its next scheduled maintenance.” In other words, the observed Page A4 -3 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 pattern of unscheduled repairs demonstrated that the scheduled preventive maintenance was actually doing more harm than good, and that the 50-hour preventive maintenance interval was inappropriately short. The solution proposed by Waddington’s team—and ultimately accepted by the RAF commanders over the howls of the maintenance personnel—was to increase the time interval between scheduled maintenance cycles, and to eliminate all preventive maintenance tasks that couldn’t be demonstrably proven to be beneficial. Once these recommendations were implemented, the number of effective flying hours of the RAF Coastal Command bomber fleet increased by 60 percent! Fast forward two decades to the 1960s, when a pair of gifted scientists who worked for United Airlines—aeronautical engineer Stanley Nowlan and mathematician Howard Heap— independently rediscovered these principles in their pioneering research on optimizing maintenance that revolutionized the way maintenance is done in air transport, military aviation, high-end bizjets and many non-aviation industrial applications. They were almost certainly unaware of the work of C.H. Waddington and his colleagues in Britain in the 1940s because that work remained classified until 1973, when Waddington’s meticulously-kept diary of his wartime research activities was declassified and published. Next time, I’ll discuss the fascinating work of Nowlan and Heap on what came to be known as “Reliability Centered Maintenance.” But for now, I will leave you with the major takeaway from Waddington’s research during World War II: Maintenance isn’t an inherently good thing (like exercise); it’s a necessary evil (like surgery). We have to do it from time to time, but we sure don’t want to do more than absolutely necessary to keep our aircraft safe and reliable. Doing more maintenance than necessary actually degrades safety and reliability. Page A4 -4 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Roots of Reliability-Centered Maintenance February 11th, 2014 by Mike Busch Last month, I discussed the pioneering WWII-era work of the eminent British scientist C.H. Waddington, who discovered that the scheduled preventive maintenance (PM) being performed on RAF B-24 bombers was actually doing more harm than good, and that drastically cutting back on such PM resulted in spectacular improvement in dispatch reliability of those aircraft. Two decades later, a pair of brilliant American engineers at United Airlines—Stan Nowlan and Howard Heap—independently rediscovered the utter wrongheadedness of traditional scheduled PM, and took things to the next level by formulating a rigorous engineering methodology for creating an optimal maintenance program to maximize safety and dispatch reliability while minimizing cost and downtime. Their approach became known as “Reliability-Centered Maintenance” (RCM), and revolutionized the way maintenance is done in the airline industry, military aviation, high-end bizjets, space flight, and numerous non- aviation applications from nuclear power plants to auto factories. The traditional approach to PM assumes that most components start out reliable, and then at some point start becoming unreliable as they age The “useful life” fallacy Nowlan and Heap1 showed the fallacy of two fundamental principles underlying traditional scheduled PM: o Components start off being reliable, but their reliability deteriorates with age. o The useful life of components can be established statistically, so components can be retired or overhauled before they fail. It turns out that both of these principles are wrong. To quote Nowlan and Heap: 1 [F. Stanley Nowlan and Howard F. Heap, “Reliability-Centered Maintenance” 1978, DoD Report Number AD-A066579.] Page A4 -5 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 “One of the underlying assumptions of maintenance theory has always been that there is a fundamental cause-and-effect relationship between scheduled maintenance and operating reliability. This assumption was based on the intuitive belief that because mechanical parts wear out, the reliability of any equipment is directly related to operating age. It therefore followed that the more frequently equipment was overhauled, the better protected it was against the likelihood of failure. The only problem was in determining what age limit was necessary to assure reliable operation. “In the case of aircraft it was also commonly assumed that all reliability problems were directly related to operating safety. Over the years, however, it was found that many types of failures could not be prevented no matter how intensive the maintenance activities. [Aircraft] designers were able to cope with this problem, not by preventing failures, but by preventing such failures from affecting safety. In most aircraft essential functions are protected by redundancy features which ensure that, in the event of a failure, the necessary function will still be available from some other source. RCM researchers found that only 2% of aircraft components have failures that are predominantly age-related (curve B), and that 68% have failures that are primarily infant mortality (curve F). “Despite the time-honored belief that reliability was directly related to the intervals between scheduled overhauls, searching studies based on actuarial analysis of failure data suggested that the traditional hard-time policies were, apart from their expense, ineffective in controlling failure rates. This was not because the intervals were not short enough, and surely not because the tear down inspections were not sufficiently thorough. Rather, it was because, contrary to expectations, for many items the likelihood of failure did not in fact increase with increasing age. Consequently a maintenance policy based exclusively on some maximum operating age would, no matter what the age limit, have little or no effect on the failure rate.” Page A4 -6 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Winning the war by picking our battles Another traditional maintenance fallacy was the intuitive notion that aircraft component failures are dangerous and need to be prevented through PM. A major focus of RCM was to identify the ways that various components fail, and then evaluate the frequency and consequences of those failures. This is known as “Failure Modes and Effects Analysis” (FMEA). Researchers found that while certain failure modes have serious consequences that can compromise safety (e.g., a cracked wing spar), the overwhelming majority of component failures have no safety impact and have consequences that are quite acceptable (e.g., a failed #2 comm radio or #3 hydraulic pump). Under the RCM philosophy, it makes no sense whatsoever to perform PM on components whose failure has acceptable consequences; the optimal maintenance approach for such components is simply to leave them alone, wait until they fail, and then replace or repair them when they do. This strategy is known as “run to failure” and is a major tenet of RCM. A maintenance revolution… The 747, DC-10 and L-1011 were the first airliners that had RCM-based maintenance programs. As a direct result of this research, airline maintenance practices changed radically. RCM- inspired maintenance programs were developed for the Boeing 747, Douglas DC-10 and Lockheed L-1011, and for all subsequent airliners. The contrast with the traditional (pre-RCM) maintenance programs for the Boeing 707 and 727 and Douglas DC-8 was astonishing. The vast Page A4 -7 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 majority of component TBOs and life-limits were abandoned in favor of an on-condition approach based on monitoring the actual condition of engines and other components and keeping them in service until their condition demonstrably deteriorated to an unacceptable degree. For example, DC-8 had 339 components with TBOs or life limits, whereas the DC-10 had only seven—and none of them were engines. (Research showed clearly that overhauling engines at a specific TBO didn’t make them safer, and actually did the opposite.) In addition, the amount of scheduled maintenance was drastically reduced. For example, the DC-8 maintenance program required 4,000,000 labor hours of major structural inspections during the aircraft’s first 20,000 hours in service, while the 747 maintenance program called for only 66,000 labor hours, a reduction of nearly two orders of magnitude. Owner-flown GA, particularly piston GA, is the only remaining segment of aviation that does things the bad old-fashioned way. Of course, these changes saved the airlines a king’s ransom in reduced maintenance costs and scheduled downtime. At the same time, the airplanes had far fewer maintenance squawks and much better dispatch reliability. (This was the same phenomenon that the RAF experienced during WWII when they followed Waddington’s advice to slash scheduled PM.) …that hasn’t yet reached piston GA Today, there’s only one segment of aviation that has NOT adopted the enlightened RCM approach to maintenance, and still does scheduled PM the bad old-fashioned way. Sadly, that segment is owner-flown GA—particularly piston GA—at the bottom of the aviation food chain where a lot of us hang out. I’ll offer some thoughts about that next month. Page A4 -8 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Do Piston Engine TBOs Make Sense? March 13th, 2014 by Mike Busch Last month, I discussed the pioneering work on Reliability-Centered Maintenance (RCM) done by United Airlines scientists Stan Nowlan and Howard Heap in the 1960s, and I bemoaned the fact that RCM has not trickled down the aviation food chain to piston GA. Even in the 21st century, maintenance of piston aircraft remains largely time-based rather than condition-based. Most owners of piston GA aircraft dutifully overhaul their engines at TBO, overhaul their propellers every 5 to 7 years, and replace their alternators and vacuum pumps every 500 hours just as Continental, Lycoming, Hartzell, McCauley, HET and Parker Aerospace call for. Many Bonanza and Baron owners have their wing bolts pulled every five years, and most Cirrus owners have their batteries replaced every two years for no good reason (other than that it’s in the manufacturer’s maintenance manual). Despite an overwhelming body of scientific research demonstrating that this sort of 1950s-vintage time-based preventive maintenance is counterproductive, worthless, unnecessary, wasteful and incredibly costly, we’re still doing it. Why? Mostly, I think, because of fear of litigation. The manufacturers are afraid to change anything for fear of being sued (because if they change anything, that could be construed to mean that what they were doing before was wrong). Our shops and mechanics are afraid to deviate from what the manufacturers recommend for fear of being sued (because they deviated from manufacturers’ guidance). Let’s face it: Neither the manufacturers nor the maintainers have any real incentive to change. The cost of doing all this counterproductive, worthless, unnecessary and wasteful preventive maintenance (that actually doesn’t prevent anything) is not coming out of their pockets. Actually, it’s going into their pockets. If we’re going to drag piston GA maintenance kicking and screaming into the 21st century (or at least out of the 1950s and into the 1960s), it’s going to have to be aircraft owners who force the change. Owners are the ones with the incentive to change the way things are being done. Owners are the ones who can exert power over the manufacturers and maintainers by voting with their feet and their credit cards. For this to happen, owners of piston GA aircraft need to understand the right way to do maintenance—the RCM way. Then they need to direct their shops and mechanics to maintain their aircraft that way, or take their maintenance business to someone who will. This means that owners need both knowledge and courage. Providing aircraft owners both of these things is precisely why I’m contributing to this AOPA Opinion Leaders Blog. Page A4 -9 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 When are piston aircraft engines most likely to hurt you? Fifty years ago, RCM researches proved conclusively that overhauling turbine engines at a fixed TBO is counterproductive, and that engine overhauls should be done strictly on-condition. But how can we be sure that his also applies to piston aircraft engines? In a perfect world, Continental and Lycoming would study this issue and publish their findings. But for reasons mentioned earlier, this ain’t gonna happen. Continental and Lycoming have consistently refused to release any data on engine failure history of their engines, and likewise have consistently refused to explain how they arrive at the TBOs that they publish. For years, one aggressive plaintiff lawyer after another have tried to compel Continental and Lycoming to answer these questions in court. All have failed miserably. So if we’re going to get answers to these critical questions, we’re going to have to rely on engine failure data that we can get our hands on. The most obvious source of such data is the NTSB accident database. That’s precisely what brilliant mechanical engineer Nathan T. Ulrich Ph.D. of Lee NH did in 2007. (Dr. Ulrich also was a US Coast Guard Auxiliary pilot who was unhappy that USCGA policy forbade him from flying volunteer search-and-rescue missions if his Bonanza’s engine was past TBO.) Dr. Ulrich analyzed five years’ worth of NTSB accident data for the period 2001-2005 inclusive, examining all accidents involving small piston-powered airplanes (under 12,500 lbs. gross weight) for which the NTSB identified “engine failure” as either the probable cause or a contributing factor. From this population of accidents, Dr. Ulrich eliminated those involving air- race and agricultural-application aircraft. Then he analyzed the relationship between the frequency of engine-failure accidents and the number of hours on the engine since it was last built, rebuilt or overhauled. He did a similar analysis based on the calendar age of the engine since it was last built, rebuilt or overhauled. The following histograms show the results of his study: Page A4 -10 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 If these histograms have a vaguely familiar look, it might be because they look an awful lot like the histograms generated by British scientist C.H. Waddington in 1943. Now, we have to be careful about how we interpret Dr. Ulrich’s findings. Ulrich would be the first to agree that NTSB accident data can’t tell us much about the risk of engine failures beyond TBO, simply because most piston aircraft engines are voluntarily euthanized at or near TBO. So it shouldn’t be surprising that we don’t see very many engine failure accidents involving engines significantly past TBO, since there are so few of them flying. (The engines on my Cessna 310 are at more than 205% of TBO, but there just aren’t a lot of RCM true believers like me in the piston GA community…yet.) Page A4 -11 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 What Dr. Ulrich’s research demonstrates unequivocally is striking and disturbing frequency of “infant-mortality” engine-failure accidents during the first few years and first few hundred hours after an engine is built, rebuilt or overhauled. Ulrich’s findings makes it indisputably clear that by far the most likely time for you to fall out of the sky due to a catastrophic engine failure is when the engine is young, not when it’s old. (The next most likely time for you to fall out of the sky is shortly after invasive engine maintenance in the field, particularly cylinder replacement, but that’s a subject for a future blog post…stay tuned!) So…Is there a good reason to overhaul your engine at TBO? It doesn’t take a rocket scientist (or a Ph.D. in mechanical engineering) to figure out what all this means. If your engine reaches TBO and still gives every indication of being healthy (good performance, not making metal, healthy- looking oil analysis and borescope results, etc.), overhauling it will clearly degrade safety, not improve it. That’s simply because it will convert your low-risk old engine into a high-risk young engine. I don’t know about you, but that certainly strikes me as a remarkably dumb thing to do. So why is overhauling on-condition such a tough sell to our mechanics and the engine manufacturers? The counter- argument goes something like this: “Since we have so little data about the reliability of past-TBO engines (because most engines are arbitrarily euthanized at TBO), how can we be sure that it’s safe to operate them beyond TBO?” RCM researchers refer to this as “the Resnikoff Conundrum” (after mathematician H.L. Resnikoff). To me, it looks an awful lot like the same circular argument that was used for decades to justify arbitrarily euthanizing airline pilots at age 60, despite the fact that aeromedical experts were unanimous that this policy made no sense whatsoever. Think about it… Page A4 -12 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 How Do Piston Aircraft Engines Fail? April 9th, 2014 by Mike Busch Last month, I tried to make the case that piston aircraft engines should be overhauled strictly on- condition, not at some fixed TBO. If we’re going to do that, we need to understand how these engines fail and how we can protect ourselves against such failures. The RCM way of doing that is called Failure Modes and Effects Analysis (FMEA), and involves examining each critical component of these engines and looking at how they fail, what consequences those failures have, and what practical and cost-efficient maintenance actions we can take to prevent or mitigate those failures. Here’s my quick back-of-the-envelope attempt at doing that… Crankshaft There’s no more serious failure mode than crankshaft failure. If it fails, the engine quits. Yet crankshafts are rarely replaced at overhaul. Lycoming did a study that showed their crankshafts often remain in service for more than 14,000 hours (that’s 7+ TBOs) and 50 years. Continental hasn’t published any data on this, but their crankshafts probably have similar longevity. Crankshafts fail in three ways: (1) infant-mortality failures due to improper materials or manufacture; (2) failures following unreported prop strikes; and (3) failures secondary to oil starvation and/or bearing failure. Over the past 15 years, we’ve seen a rash of infant-mortality failures of crankshafts. Both Cnntinental and Lycoming have had major recalls of crankshafts that were either forged from bad steel or were damaged during manufacture. These failures invariably occurred within the first 200 hours after the new crankshaft entered service. If the crankshaft survived its first 200 hours, we can be confident that it was manufactured correctly and should perform reliably for numerous TBOs. Unreported prop strikes seem to be getting rare because owners and mechanics are becoming smarter about the high risk of operating an engine after a prop strike. There’s now an AD mandating a post-prop-strike engine teardown for Lycoming engines, and a strongly worded Page A4 -13 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 service bulletin for Continental engines. Insurance will always pay for the teardown and any necessary repairs, so it’s a no-brainer. That leaves failures due to oil starvation and/or bearing failure. I’ll address that shortly. Crankcase Crankcases are also rarely replaced at major overhaul. They are typically repaired as necessary, align-bored to restore critical fits and limits, and often provide reliable service for many TBOs. If the case remains in service long enough, it will eventually crack. The good news is that case cracks propagate slowly enough that a detailed visual inspection once a year is sufficient to detect such cracks before they pose a threat to safety. Engine failures caused by case cracks are extremely rare—so rare that I don’t think I ever remember hearing or reading about one. Page A4 -14 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Camshaft and Lifters The cam/lifter interface endures more pressure and friction than any other moving parts n the engine. The cam lobes and lifter faces must be hard and smooth in order to function and survive. Even tiny corrosion pits (caused by disuse or acid buildup in the oil) can lead to rapid destruction (spalling) of the surfaces and dictate the need for a premature engine teardown. Cam and lifter spalling is the number one reason that engines fail to make TBO, and it’s becoming an epidemic in the owner-flown fleet where aircraft tend to fly irregularly and sit unflown for weeks at a time. The good news is that cam and lifter problems almost never cause catastrophic engine failures. Even with a badly spalled cam lobe (like the one pictured at right), the engine continues to run and make good power. Typically, a problem like this is discovered at a routine oil change when the oil filter is cut open and found to contain a substantial quantity of ferrous metal, or else a cylinder is removed for some reason and the worn cam lobe can be inspected visually. If the engine is flown regularly, the cam and lifters can remain in pristine condition for thousands of hours. At overhaul, the cam and lifters are often replaced with new ones, although a reground cam and reground lifters are sometimes used and can be just as reliable. Gears The engine has lots of gears: crankshaft and camshaft gears, oil pump gears, accessory drive gears for fuel pump, magnetos, prop governor, and sometimes alternator. These gears are made of case-hardened steel and typically have a very long useful life. They are not usually replaced at overhaul unless obvious damage is found. Engine gears rarely cause catastrophic engine failures. Page A4 -15 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Oil Pump Failure of the oil pump is rarely responsible for catastrophic engine failures. If oil pressure is lost, the engine will seize quickly. But the oil pump is dead-simple, consisting of two steel gears inside a close-tolerance aluminum housing, and usually operates trouble free. The pump housing can get scored if a chunk of metal passes through the oil pump—although the oil pickup tube has a suction screen to make sure that doesn’t happen—but even if the pump housing is damaged, the pump normally has ample output to maintain adequate oil pressure in flight, and the problem is mainly noticeable during idle and taxi. If the pump output seems deficient at idle, the oil pump housing can be removed and replaced without tearing down the engine. Bearings Bearing failure is responsible for a significant number of catastrophic engine failures. Under normal circumstances, bearings have a long useful life. They are always replaced at major overhaul, but it’s not unusual for bearings removed at overhaul to be in pristine condition with little detectable wear. Bearings fail prematurely for three reasons: (1) they become contaminated with metal from some other failure; (2) they become oil-starved when oil pressure is lost; or (3) main bearings become oil-starved because they shift in their crankcase supports to the point where their oil supply holes become misaligned (as with the “spun bearing” pictured at right). Contamination failures can generally be prevented by using a full-flow oil filter and inspecting the filter for metal at every oil change. So long as the filter is changed before its filtering capacity is exceeded, metal particles will be caught by the filter and won’t get into the engine’s oil galleries and contaminate the bearings. If a significant quantity of metal is found in the filter, Page A4 -16 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 the aircraft should be grounded until the source of the metal is found and corrected. Oil-starvation failures are fairly rare. Pilots tend to be well-trained to respond to decreasing oil pressure by reducing power and landing at the first opportunity. Bearings will continue to function properly at partial power even with fairly low oil pressure. Spun bearings are usually infant-mortality failures that occur either shortly after an engine is overhauled (due to an assembly error) or shortly after cylinder replacement (due to lack of preload on the through bolts). Failures occasionally occur after a long period of crankcase fretting, but such fretting is usually detectable through oil filter inspection and oil analysis).They can also occur after extreme unpreheated cold starts, but that is quite rare. Connecting Rods Connecting rod failure is responsible for a significant number of catastrophic engine failures. When a rod fails in flight, it often punches a hole in the crankcase (“thrown rod”) and causes loss of engine oil and subsequent oil starvation. Rod failure have also been known to cause camshaft breakage. The result is invariably a rapid and often total loss of engine power. Connecting rods usually have a long useful life and are not normally replaced at overhaul. (Rod bearings, like all bearings, are always replaced at overhaul.) Many rod failures are infant- Page A4 -17 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 mortality failures caused by improper tightening of the rod cap bolts during engine assembly. Rod failures can also be caused by the failure of the rod bearings, often due to oil starvation. Such failures are usually random failures unrelated to time since overhaul. Pistons and Rings Piston and ring failures usually cause only partial power loss, but in rare cases can cause complete power loss. Piston and ring failures are of two types: (1) infant-mortality failures due to improper manufacturer or assembly; and (2) heat-distress failures caused by pre-ignition or destructive detonation events. Heat-distress failures can be caused by contaminated fuel (e.g., 100LL laced with Jet A), or by improper engine operation. They are generally unrelated to hours or years since overhaul. A digital engine monitor can alert the pilot to pre-ignition or destructive detonation events in time for the pilot to take corrective action before heat-distress damage is done. Cylinders Cylinder failures usually cause only partial power loss, but occasionaly can cause complete power loss. A cylinder consists of a forged steel barrel mated to an aluminum alloy head casting. Cylinder barrels typically wear slowly, and excessive wear is detected at annual inspection by means of compression tests and borescope inspections. Cylinder heads can suffer fatigue failures, and occasionally the head can separate from the barrel. As dramatic as it sounds, a head separation causes only a partial loss of power; a six-cylinder engine with a head-to-barrel Page A4 -18 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 separation can still make better than 80% power. Cylinder failures can be infant-mortality failures (due to improper manufacture) or age-related failures (especially if the cylinder head remains in service for more than two or three TBOs). Nowadays, most major overhauls include new cylinders, so age-related cylinder failures have become quite rare. Valves and Valve Guides It is quite common for exhaust valves and valve guides to develop problems well short of TBO. Actual valve failures are becoming much less common nowadays because incipient problems can usually be detected by means of borescope inspections and digital engine monitor surveillance. Even if a valve fails completely, the result is usually only partial power loss and an on-airport emergency landing. Rocker Arms and Pushrods Rocker arms and pushrods (which operate the valves) typically have a long useful life and are not normally replaced at overhaul. (Rocker bushings, like all bearings, are always replaced at overhaul.) Rocker arm failure is quite rare. Pushrod failures are caused by stuck valves, and can almost always be avoided through regular borescope inspections. Even when they happen, such failures usually result in only partial power loss. Page A4 -19 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Magnetos and Other Ignition Components Magneto failure is uncomfortably commonplace. Mags are full of plastic components that are less than robust; plastic is used because it’s non-conductive. Fortunately, our aircraft engines are equipped with dual magnetos for redundancy, and the probability of both magnetos failing simultaneously is extremely remote. Mag checks during preflight runup can detect gross ignition system failures, but in-flight mag checks are far better at detecting subtle or incipient failures. Digital engine monitors can reliably detect ignition system malfunctions in real time if the pilot is trained to interpret the data. Magnetos should religiously be disassembled, inspected and serviced every 500 hours; doing so drastically reduces the likelihood of an in-flight magneto failure. The Bottom Line The bottom-end components of our piston aircraft engines—crankcase, crankshaft, camshaft, bearings, gears, oil pump, etc.—are very robust. They normally exhibit long useful life that are many multiples of published TBOs. Most of these bottom-end components (with the notable exception of bearings) are routinely reused at major overhaul and not replaced on a routine basis. When these items do fail prematurely, the failures are mostly infant-mortality failures that occur shortly after the engine is built, rebuilt or overhauled, or they are random failures unrelated to hours or years in service. The vast majority of random failures can be detected long before they get bad enough to cause an in-flight engine failure simply by means of routine oil-filter inspection and laboratory oil analysis. The top-end components—pistons, cylinders, valves, etc.—are considerably less robust. It is not at all unusual for top-end components to fail prior to TBO. However, most of these failures can be prevented by regular borescope inspections and by use of modern digital engine monitors. Even whey they happen, top-end failures usually result in only partial power loss and a successful on-airport landing, and they usually can be resolved without having to remove the engine from the aircraft and sending it to an engine shop. Most top-end failures are infant- mortality or random failures that do not correlate with time since overhaul. The bottom line is that a detailed FMEA of piston aircraft engines strongly suggests that the traditional practice of fixed-interval engine overhaul or replacement is unwarranted and counterproductive. A conscientiously applied program of condition monitoring that includes regular oil filter inspection, oil analysis, borescope inspections and digital engine monitor data analysis can yield improved reliability and much reduced expense and downtime. Page A4 -20 of 36 AUXAIR Facility Maintenance Standards USCG Auxiliary RP Group APPENDIX 4 Quest for a TBO-Free Engine M