ROOT CAUSES OF SBO EVENTS
SBO events were analyzed to determine the root cause for each event. Root cause was identified (when possible) down to the component level. Available potential corrective or preventive actions were correlated to the root causes and included in the service letters. Only the top root causes that account for approximately 30 percent of all the reported SBO events are correlated to corrective or preventive action. The results of the studies were provided to operators in service letters that graphically show the predominant root causes (identified by root cause code [RCC] and description), as well as the occurence count of the SBO event (see fig. 2).
Root cause codes (RCCs) and operational impacts of SBO events reported for the 757, July 2004 – August 2008.
Minimal Interruption
Delay
Cancellation/Out of Service
Air Turnback
Diversion
Airplane on Ground
RCC 212.001
Recirculation Fan
RCC 790.001
Engine Oil — Over-Servicing
RCC 215.005
Equipment Cooling Fan
RCC 720.001
Engine Fault —
Air Supply Contamination
RCC 561.001
Window Anti-Ice Circuit
RCC 490.001
APU Fault — Air Supply Contamination
RCC 710.001
External Element Ingestion —
Air Supply Contamination
RCC 233.001
Overhead Video Monitor Unit
RCC 243.004
Static Inverter
RCC 253.004
Galley Oven
RCC 215.002
Air Cycle Machine
Because not all SBO events are reported to Boeing, the number of occurrences in figure 2 should be treated on a relative basis. Each root cause is further broken down by an operational impact category, such as delay, diversion, or airplane on ground. Only the predominant root causes are shown in the chart. As a result, not all operational impact categories appear in figure 2. Also, events of undetermined root causes are excluded.
SUGGESTED OPERATOR ACTION
Operators can use the data provided in the associated service letters to initiate action at their discretion to reduce the occurrences of SBO events. The information provided in the service letters is intended for maintenance operations. Flight crew response to in-flight smoke, fire, and fumes is addressed separately in the accompanying article "Flight Crew Response to In-Flight Smoke, Fire, or Fumes."
IDENTIFICATION OF ODOR SOURCE
Most operators would like to locate and stop the cause of the odor, which is often reported as an oil smell or aerosol odor. It can be difficult to identify the odor source, and troubleshooting can result in long airplane downtime and unnecessary engine or auxiliary power unit (APU) changes.
In response, Boeing has developed an oil detection kit that can be used to quickly identify the source of oil leaks or aerosol odors. The kit includes a bleed air sampler and portable infrared spectrometer. Ground crews connect the air sampler to the 3-inch pneumatic ground cart connector and run engine or APU bleed air through the sampler for 10 minutes. The spectrometer and a laptop computer are used to analyze the sample. The kit’s software alerts the user when the sample matches a known contaminant, such as oil or hydraulic fluid.
The oil detection kit works for all Boeing models except the 787 and on all McDonnell-Douglas airplanes. The kit may be ordered online at the Web portal MyBoeingFleet.com by requesting part number J21009.
SUMMARY
SBO events can result in expensive operational interruptions. Boeing publishes the most significant root causes for SBO events and correlates these to potential corrective or preventive action in model-specific service letters.
For more information, please contact James Holley at james.a.holley@boeing.com.