Figure 1.14 illustrates another example. Here, the design capability is an MAWP of 650 psi and the required performance is 500 psi. Is this scenario acceptable? Yes, because what the organization requires (500 psi) fits within the design capability of the asset.
Figure 1.13 Organizational requirements exceed design capability
Figure 1.14 Organizational requirements fit within the design capability of the asset
This may seem to be an incredibly simple concept—so basic and fundamental that it doesn’t even warrant being mentioned. It appears that way. However, this concept is a very serious issue. If an organization gets it wrong, it can turn deadly. In fact, it has turned deadly.
Three Air Tanker Crashes
The National Transportation Safety Board (NTSB) investigated three air tanker crashes. The following information was reported in the NTSB Safety Recommendation dated April 23, 2004.
On August 13, 1994, a Lockheed C-130A Hercules experienced an in-flight separation of the right wing near Pearblossom, California, while responding to a forest fire near the Tahachapi Mountains. All three crewmembers were killed and the airplane was completely destroyed. (An aircraft similar to the C-130A can be seen in Figure 1.15.)
Figure 1.15 C-130 Aircraft, similar to the C-130A Tanker that crashed on August 13, 1994 and June 17, 2002 (Photo from Photo NSA online; http://www.nsa.gov/about/photo_gallery/index.shtml.)
Figure 1.16 C130A June 17, 2002, crash site from the NTSB report (Photo from NTSB, September 24, 2002, NTSB Advisory, Update on Investigations of Firefighting Airplane Crashes in Walker, California and Estes Park, Colorado; http://www.ntsb.gov/pressrel/2002/020924.htm )
On June 17, 2002, another Lockheed C-130A Hercules experienced an in-flight breakup that was initiated by separation of the right wing, followed by separation of the left wing, while executing a fire retardant drop over a forest fire near Walker, California. Both wings detached from the fuselage at their respective center wing box-to-fuselage attachment locations. All three flight crewmembers were killed, and the airplane was completely destroyed. Figure 1.16 depicts the June 2002 crash site.
On July 18, 2002, a Consolidated Vultee P4Y Privateer experienced an in-flight separation of the left wing while maneuvering to deliver fire retardant over a forest fire near Estes Park, Colorado. Both crewmembers were killed and the airplane was destroyed. (A similar aircraft is shown in Figure 1.17.)
Figure 1.17 P4Y Privateer similar to the one that crashed on July 18, 2002 (Library of Congress, Prints & Photographs Division, FSA/OWI Collection, [LC-USE6- D-009930])
All three aircraft were leased by the U.S. Department of Agriculture’s Forest Service for public firefighting flights. However, the aircraft detailed above were originally designed to transport cargo for the U.S. military—not to fight forest fires.
Air Tanker Crashes: Design Capability versus Required Performance
The operational environment and the loads experienced by an aircraft transporting cargo are vastly different from those experienced by an aircraft fighting forest fires. The NTSB report explains that during a fire-fighting mission, an aircraft experiences “frequent and aggressive low-level maneuvers with high acceleration loads and high levels of atmospheric turbulence.” The NTSB report further details that the maintenance programs used for the aircraft were the same that were derived for the aircraft when their mission was transporting cargo for the military. The report states that the aircraft were likely “operating outside the manufacturers’ original design intent.”
In the context of RCM, the required performance of the organization using the air tankers far exceeded the design capability of the aircraft. The structural lives of the aircraft were shortened because of the harsh operating environment and the far more aggressive loads applied to the aircraft during fire-fighting versus transporting cargo. The increased loading accelerated fatigue crack initiation and sped up the crack propagation time. Therefore, the structural inspections that were in place were not accomplished often enough to identify the crack before it caused catastrophic failure. The simple concept of ensuring that an asset is capable of doing what the organization requires was completely overlooked.
Aloha Airlines, Flight 243
On April 28, 1988, Aloha Airlines, Flight 243 took off from Hilo, Hawaii, at 1:25 p.m. Shortly after the aircraft leveled off at 24,000 feet, the aircraft experienced explosive decompression and structural failure that ripped away a large section of the fuselage, as shown in Figure 1.18. One of the flight attendants, Clarabelle Lansing was immediately wrenched from the airplane. The aircraft made an emergency landing at Kahului Airport. The 89 passengers onboard and the remaining 4 crewmembers survived.
This tragedy is another example of required performance being allowed to exceed design capability.
Aloha Airlines: Design Capability versus Required Performance
Aloha Airlines was using its 737s for inter-island Hawaiian flights. According to the NTSB Aircraft Accident Report, those aircraft were accumulating three flight cycles (take-off and landing) for every hour in service. However, Boeing designed the structural inspections for the 737 assuming that the aircraft would accumulate about one and a half cycles per flight hour. Therefore, the aircraft were accumulating flight cycles at twice the rate for which the Boeing Maintenance Planning Data (MPD) was designed. Similar to the air tanker crashes described previously, this use accelerated fatigue crack initiation and increased the crack propagation time. The structural inspections and associated intervals in place were inadequate; they were not accomplished frequently enough to detect the crack before catastrophic failure occurred.
Figure 1.18 Aloha Airlines, Flight 243, April 28, 1988 after landing (Associated Press /Robert Nichols)
The air tanker fatal crashes and the Aloha Airlines’ accident are only two examples that underscore the critical importance of ensuring that an asset’s design capability is capable of meeting organizational requirements. It is a simple concept that is too often overlooked. During an RCM analysis, asset design capability and required performance are carefully analyzed.
The application of True RCM consists of preparing an Operating Context and carrying out the 7 steps of RCM.
1.9 Introduction to the RCM Process
The application of True RCM consists of preparing an Operating Context and carrying out the 7 steps of RCM.