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Remarks at the 2007 Aging Aircraft Conference, Palm Springs, CA
Mark V. Rosenker
Aging Aircraft Conference, Palm Springs, CA

Thank you very much. It is truly a pleasure and privilege to speak before such an accomplished group of aviation professionals.  I can think of no other venue where so many experts gather to collectively discuss and trade information regarding operation and the technical demands of the varied branches of flight; …… civil, military, and space.  We are gathered here today to discuss the impact of aging aircraft on the aviation and space exploration industries.  I have the honor of serving as the Chairman of the NTSB, an agency that has the responsibility to investigate transportation accidents as has been doing so for the past four decades – as a matter of fact we are celebrating our 40th anniversary this year!  We investigate all types of aviation accidents.  In fact, as you know, we are mandated by law, to establish the probable cause for all aviation accidents occurring in the United States.  Several of these investigations have involved the issue of aging aircraft.  In 1996 the Board investigated the in-flight brake-up of TWA Flight 800.  Our investigators uncovered cracked insulation on the low voltage wire installations in the center fuel tank of the Boeing 747.  This discovery led us to consult the Air Force about similar problems they were facing with aging systems on their aircraft.  Retired United States Air Force General John Loh and then NTSB Chairman Hall made a recommendation to the FAA that aging aircraft fleets and systems need to be studied in-depth.  A product of this joint safety effort is the safety recommendation that deals with protecting aircraft from the potential ignition of fuel tank vapors.  That issue still remains on the Boards Most Wanted List of Transportation Safety Improvements.

As we all know, NASA has an aging shuttle fleet that must be kept flying until the next generation of reusable space vehicle is developed, funded and built.  So the challenges facing us are serious and spread across the face of general aviation, commercial aviation, military aviation and space flight.

There is no single criteria that defines an aircraft as ‘old.’ NTSB investigations have shown over and over that the age of an aircraft depends on a number of factors that include, but is not limited to chronological age, number of flight cycles, number of flight hours and the environment in which the aircraft operates. A recent Australian examination of aircraft aging came to the same conclusions.  Determining the overall health of the aircraft is further complicated by the fact that individual aircraft components can age at different rates in different parts of an aircraft.  Given the correct inspections and maintenance, it is possible to operate an aircraft indefinitely; however, the operator needs to adjust the maintenance program accordingly.  

Some aging mechanisms, such as fatigue, occur through repetitive cycling or loading. Other factors, such as wear, deterioration and corrosion can and do occur over time.  If not identified and managed, these aging processes become significant safety concerns and can,in the worst case, lead to accidents.

Throughout the world, there have been aircraft accidents in which these aging mechanisms were at least a factor.  On April 28, 1988, 1 person was killed when the top of the fuselage of Aloha Airlines Flight 243 separated from the rest of the hull when it experienced explosive decompression due to a combination of fatigue and corrosion led to the failure of the structure.

At the time of the accident, the Aloha 737 had been in service for 19 years, .….. not an old airplane by today’s standards, however it had accumulated a disproportionately high number of flight and pressurization cycles due to the short durations of its’ flights. In fact, it was the number two fleet leader in term of flight cycles. The number one fleet leader was also owned by Aloha. At the time of the accident the number one aircraft was undergoing an extensive corrosion control and fuselage skin replacement program. I thought it was more sonic virbrations, ie. Fatigue than aging. I would leave it out. As a result of the Aloha investigation, the FAA’s Aging Airplane Program for transport airplanes was developed in 1991 to focus on regulatory initiatives related to structural fatigue and corrosion.  The program recognized that  airplanes were being used in operations beyond original design service goals.  The NTSB and FAA both noted that existing maintenance plans did not address potential age-related issues.

In 2000 and 2001, Ansett Airlines in Australia grounded their Boeing 767 aircraft fleet due to structural cracks found in the engine pylons and empennage.

In the United States, the in-flight separation of a wing from not one, but three, Forest Service firefighting aircraft occurred over relatively short period of time . Most recently the Chalks Ocean Airways accident, which occurred in Miami, in December 2005.  In that accident, the wing of a Grumman Mallard seaplane, manufactured in 1947, separated from the aircraft in flight and the resulting accident killed the 20 passengers and crew on board. These accidents and incidents have highlighted the safety implications resulting from aircraft aging and have repeatedly demonstrated the importance of continuing effective airworthiness and inspections programs. 

As late as 1991 the aging process was not considered a systems problem, because “aircraft systems were designed to be fail-safe”. Well, that assumption was proven wrong in 1996 when the center fuel tank of TWA flight 800 exploded.  The Board’s investigation found evidence of electrical problems occurring in the month preceding the accident and of short circuits immediately before the catastrophic explosion. The wiring found in the wreckage had numerous cracks in the insulation that were attributed to age, bringing to light the problem of aging systems.

We became more acutely aware of the scale of these issues over the next two years. The Safety Board began documenting numerous systems problems in fleet aircraft starting in May of 1997, with the TWA-800 investigation, and continued that documentation when SwissAir flight 111 crashed in September 1998.

In October of 1998, the FAA released the Aging Transport Non-Structural Systems Program; a concept based on the 1991 aging structures program that followed the Aloha 737 accident.

Following TWA flight 800, the FAA developed wiring initiatives to correct the problems uncovered by the Safety Board’s investigation.  The implementation of these initiatives has only been underway for slightly more than a year, so we are still attempting to measure the results.  We think that the fleet is safer, but we still lack the necessary data collection and analysis systems needed to provide the measure of safety assurance. 

An issue the Safety Board examined in the TWA investigation and recently the subject of a report by the Government Accounting Office (GAO) is that quality of data u determine the health of the aviation fleet and the lack of a system to properly interpret that data.

The FAA has made some progress in attempting to use data-driven, risk-based safety programs since the NTSB report of August 2000.  They have recently replaced their National Safety Data Analysis Center (NASDAC) with the Aviation Safety Information Analysis and Sharing (ASIAS) program, however the FAA has made little progress in overhauling data collection and analysis initiatives.  The FAA currently delegates much of this process to individual airlines and tasks inspectors with monitoring their airline’s data analysis. Both the NTSB and GAO have opposed this approach. The GAO recently repeated a statement concerning the FAA’s efforts ……… “the agency faces data and human resource challenges that affect its ability to fully implement these programs.” A major portion of the problem is industry’s opposition to the program; this became apparent in comments made against the FAA’s proposed overhaul of the Service Difficulty Reporting system (SDRS).  The Board has remained steadfast in calling for elimination of the underlying problems that cause electrical fires, and other age-related failures, and in this regard, we need the data to understand which courses of action are working and which are not. The bottom line is that without true data collection and analysis, the concept of risk-based and data-driven programs really doesn’t exist.

It is important to note that the Board did not endorse the FAA’s wiring initiatives in the 1998 Aging Transport Non-Structural Systems program, and I would like to address why we made that decision. Two of the main FAA initiatives for aircraft systems were the Enhanced Airworthiness Program for Airplane Systems, or EAPAS; and the Enhanced Zonal Analysis Procedure, called EZAP.  The Board does not agree that visual wiring inspections by themselves are sufficient, history is proving our point:  There have been three airplanes destroyed by fuel tank explosions since TWA flight 800.  The most recent was the May 2006 loss of a relatively low-time 727 in Bangalore, India, operated by Transmile Airlines.  While assisting the Government of India, our investigators found a hole burned through the wall of an electrical conduit in a fuel tank, despite the airplane having been modified by airworthiness directives to protect against just this sort of failure.  Clearly, the AD didn’t work and though the industry thought that we had found and addressed this problem, the airplane was still vulnerable.  In this case, investigators found evidence of short circuits caused by drill shavings, which had cut the insulation of wires beneath a modification for a large cargo door.  The Transmile accident has shown that visual inspections are insufficient to protect those critical wires. The evidence of shorting was missed visually, even after the wires were removed from the airplane and closely inspected in a laboratory.  The non-destructive test that finally identified these short circuits was accomplished simply by wetting the local area with water and using a common voltmeter, an inexpensive test that used simple non-destructive test equipment. Once evidence of shorting was found, a scanning electron microscope was used to clearly confirm that power had locally melted the wire surfaces. Enhanced visual inspections will lead to improvements, but it is apparent that non-destructive tests are needed to evaluate the condition of wiring.

All of these issues can be mitigated by inerting all fuel tanks. Inerting will take care of worn wiring and FOD and other ignition sources including intentional acts  and we believe it to be the most important safety action that can be undertaken to prevent fuel tank explosions.

Aging fleet issues are being addressed on multiple levels at this conference.  There are forums for transport airplanes and light twin.  In today’s world of Feeder and Regional airlines a ticket may be sold by one air carrier for flights on a partner operators aircraft, the flying public assumes they are being afforded the same level of safety as any passenger flying on a commercially operated flight. Unfortunately that is not always the case.  The Chalks seaplane t was being operated under the same Part 121 rules as any other air carrier commercial flight in the United States. While the investigation of this accident is ongoing, it has become apparent through preliminary examination of the recovered structures that there is evidence of both multiple-element and multiple site fatigue damage in the right wing.

Unfortunately, due to the exemptions cited in the FAA’s aging aircraft final rule dealing with aging aircraft structures, this type of accident was not been completely eliminated. Structural aging issues continue to plague airplanes that entered service anywhere between the early 1940’s and the late 1950’s. Some common themes have been identified in each of these accidents, and they are:

  • Unknown service histories as is the case with military surplus aircraft,
  • Poor fatigue design details, the regulations did not require fatigue analysis for these airplanes,
  • Most older airplanes have no inspection program,
  • And just the continued operation of airplanes beyond their project economic or useful lifespan.

The Safety Board is concerned that the exemptions in the final rule excluding airplanes type-certificated before January 1, 1958, such as the Chalk’s Mallard, that was being operated under Part 121 leaves a loop hole in the one-level-of- safety initiative that the FAA espoused in the mid 1990s.  The FAA was to require all commercial aircraft in scheduled passenger service with 10 or more seats to meet Part 121 requirements. The exemptions are also contrary to the instructions sited in Congress’s 1991 Aging Aircraft Safety Act. T he FAA should require records reviews, aging airplane inspections, and supplemental inspections for all airplanes operated under Part’s 121, 129 and 135 regardless of the year they were type certificated, the number of passengers they carry or their maximum payload and we have issued related safety recommendations to that effect.   

The continued commercial operation of 50 to 60 year old airplanes to a lesser standard than those of today’s modern airplanes flies in the face of one-level-of-safety. 

Once again I would like to reiterate, there is no single criteria that defines an aircraft as ‘old,’ but if aging mechanisms are not managed properly, they can and will lead to future accidents and deaths. There can be no end in the process of learning how to address the aging of our fleets. 

Ladies and gentlemen, that is my challenge to you. ……Continue to learn what we can do today to address the safety risks to our aging aircraft fleet of tomorrow. 

Thank you again for inviting me to speak here today.