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Component Removal Reduction

Most operators have reliability programs to identify which airplanes experience the highest number of delays or which groups of components most frequently experience unscheduled removal. However, many operators do not have a plan to optimally use the data gathered through these programs. As an alternative to reliability programs, the component removal reduction process has recently been developed to enable operators to use information about component failure to implement timely, effective corrective actions. Following the process can produce considerable cost savings for the operator.

Based on an operator’s complaint about excessive short-life units (SLU) on a fleet of four 737 airplanes, Boeing investigated the possible causes for this problem. As a result, Boeing established a process that has proved to be beneficial and cost effective in reducing the quantity of unscheduled removals of line replaceable units (LRU). By following this process, the 737 operator was able to reduce the number of replacements for line replaceable units from 32 to 18 per month. Based on an assumption that each shop visit would cost the operator $1,000, the monthly cost savings would be $14,000. The component removal reduction (CRR) process was later introduced to another operator with similar results (see “Results of Component Removal Reduction”).

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The CRR process consists of five steps that can be tailored for individual operators:

  1. Obtain and categorize LRU list.
  2. Analyze removal reasons and patterns.
  3. Determine corrective action.
  4. Implement corrective action.
  5. Follow up after corrective action.

1. OBTAIN AND CATEGORIZE LRU LIST
The first step of the process requires operators to obtain a list of all LRUs replaced in the previous month with less than 2,000 hr since last overhaul or repair (time since overhaul [TSO]). If possible, this list should be sorted according to TSO to ensure that the primary focus is on units with the shortest service life; this is where the greatest potential cost savings can be found. The listing should include the part number (P/N), serial number (S/N), name or description, TSO, and airplane tail number (ATN) (fig. 1).

Short-Life Units Listing

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If the list is not sorted by TSO, it should be color coded to classify these times. For example, all LRUs that failed in 200 hr or less could be marked in red, those that failed in 201 to 1,000 hr in orange, and those that failed in 1,001 to 2,000 hr in yellow.

2. ANALYZE REMOVAL REASONS AND PATTERNS The list from step one should then be reviewed for common characteristics. These can include multiple failures of a particular P/N or repeated reports of failures related to the same ATN or S/N.

Shop repair reports should also be reviewed to find the causes of component failure. For example, do the reports often say “No Fault Found” (NFF) or show the same repair being done (the same component replaced) to all LRUs of a particular P/N? This can indicate some controllable action, such as incorrect handling of electrostatic discharge-sensitive (ESDS) LRUs, that is causing the failure. It can also indicate an uncontrolled environment (e.g., heat, cold, or humidity) on the airplane or in a storeroom. If more than one shop is performing repairs, the shop reports should be reviewed to determine whether the SLUs are all from the same shop. (One operator concluded that a cheaper shop was actually more expensive because the service-hour per dollar cost was higher.)

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3. DETERMINE CORRECTIVE ACTION
After identifying the causes of early failures, the next step is to determine the appropriate corrective action. This can include asking such questions as the following:

  • Is an airplane or component modification available to eliminate that failure mode?
  • If the shop reports show excessive NFFs, are the troubleshooting instructions inadequate, are they too time consuming, or do they require special equipment that is not available on the line?
  • Do the troubleshooting instructions produce inconclusive results or contain faulty logic?
  • Is the shop using correct processes and equipment? On one job, the shop was testing the LRU without grounding the LRU case, but in the airplane the case was grounded. The unit was repeatedly returned as NFF.
  • Do the shop reports or other evidence indicate ESDS abuse? This type of abuse often shows up as LRU failure around 200 to 300 hr TSO. If so, are increased training, other equipment, or improved processes required to stop ESDS abuse to LRUs? This could apply to the repair shop, line maintenance, or shipping (including customs), storage, and handling.

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4. IMPLEMENT CORRECTIVE ACTION
After corrective action is identified, the next decision is whether to apply it. This decision must be made based on the operator’s particular situation. For example, one operator discovered a situation involving LRUs that were supplied on a flat-rate basis. As a result, the operator saw no need to be concerned. However, after considering that their airplanes often flew into isolated airports where an LRU failure could have serious financial consequences, the operator decided to investigate the situation and resolved the SLU issue.

Resolution of vendor and contract shop problems may require a visit from the operator’s quality assurance manager, but these problems can usually be resolved by consulting with the shop sales representative.

By using the CRR process, the operator can collect the necessary data to make the best decisions about additional training and equipment. In some cases, additional training or equipment can reduce the SLU problem, but the operator still may not be able to justify those expenses.

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Shipping and handling is suspect from the time an LRU is removed from its position in the airplane until it is reinstalled in another airplane. Although ESDS damage is high on the list of concealed damage, other damage, such as bearing damage, can also occur when instruments are transported without adequate padding. This applies to the transport of both serviceable and unserviceable units. Training, revised processes, or both usually eliminate this problem.

Finally, the CRR process provides valuable feedback to the engineers who must decide whether to apply a service life improvement modification.

5. FOLLOW UP AFTER CORRECTIVE ACTION
After corrective action is implemented, SLU problems can still exist, but repeating the CRR process will show whether the cause is the same, a new cause, or a cause created by the corrective action for the original cause. Repeating the cycle will eliminate the causes of SLUs.

After several months of applying the CRR process, operators should re-evaluate whether using it is continuing to provide cost savings.

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SUMMARY

The CRR process helps operators solve delay problems and reduce the unscheduled removal of components. Any operator, regardless of fleet size, can reduce the occurrence of these problems by following the process. The chief benefit of using the CRR process is that it allows operators to focus on the specific areas that will result in the highest possible cost savings.

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RESULTS OF COMPONENT REMOVAL REDUCTION

The following items are examples of the benefits operators have achieved by using the component removal reduction (CRR) process.

Line Replaceable Unit (LRU) Removals Reduced by Nearly 50 Percent
Within six months of implementing the CRR process, one operator reduced LRU removals from 32 per month to 18 per month.

Rogue Units Found
An inertial reference unit (IRU) was removed after less than 1,000 hr in service. A check of the records for this unit showed that it had been installed five times in four years and had never lasted more than two weeks in service after each installation. The vendor exchanged the rogue unit for a new one. Another operator using the CRR process encountered a similar situation with an IRU from another vendor.

Life-Improvement Modification Applied
Investigation of multiple failures of one part number LRU revealed that a free life-improvement modification had not been performed. After the modification was implemented, the LRU no longer showed up on the short-life unit list.

Maintenance Practices Revised
A repair shop reported that an electromechanical indicator failed because of dry grease on the gear train. Inspection of an airplane, which was parked at the maintenance ramp, revealed that technicians had checked the lights in the cockpit and had left the light controls on full bright. As a result, the instrument panel was too hot to touch, and the extremely high temperature caused the grease in the instruments to dry out. The technicians were instructed to turn off the lights after checking them, and the problem did not reoccur.

Shop Practices Revised
Several computers were found to have a short life (200 to 300 hr) after shop repair. Investigation revealed that the vendor shop was not using correct electrostatic discharge-sensitive protection on repaired units. After being alerted to this issue, the vendor revised its shop practices and the life of the computers returned to normal.

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