Source: https://www.ntsb.gov/investigations/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-14-125
Timestamp: 2019-10-21 22:42:24
Document Index: 305979356

Matched Legal Cases: ['art 121', 'art 25', 'art 121', 'art 25', 'art 25', 'art 25']

Safety Recommendation A-14-125
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Evaluate whether the recording of stale data by the Boeing 787 enhanced airborne flight recorder, including whether the data are specifically identified as stale, impacts the certification of the recording system regarding the ranges, accuracies, and sampling intervals specified in 14 Code of Federal Regulations Part 121 Appendix M, and take appropriate measures to correct any problems found.
Response: On July 6, 2016, you agreed that recording stale data was not compliant with Part 25 standards, and thereby did not fulfill the requirements of Part 121, Appendix M. Your current letter states that, upon further investigation, you have determined that the EAFR acquisition and recording functions failed, and the resulting interruptions occurred due to failures to record data, rather than from recording stale data. Although you agree that this issue represents noncompliance with Part 25, you believe the noncompliance is due to a different issue than that discussed in Safety Recommendation A-14-125. You have determined that the 787 EAFR’s failure to record was caused by a design change after certification and has been corrected by a software update. You wrote that airplanes in service may experience stale data when an aircraft source stops transmitting data while a constant (“stale”) value continues to be recorded. You also said that this can occur on all model aircraft, and is not specific to the 787. For parameters with multiple sources of data, the 787 EAFR explicitly records the source used and will log if none of the sources is available. Regarding parameters for which there is only one source of data, the 787 EAFR does not explicitly identify that recorded data is stale, but does capture the last known valid value. You also said this condition occurs on all airplane models and is not unique to the 787. We note that you plan to consult with our staff members who are involved with acquiring accident data from recorders and who are familiar with stale data issues, and you will also continue working with Boeing to determine the frequency with which stale data are recorded, the parameters this affects, and the impact stale data has on the ability of accident investigators to effectively use the data in accident investigations. In our report about the Japan Airlines Boeing 787 incident at Logan Airport, we said that recording stale data impacted the early stages of our investigation because significant additional time and effort was required to identify if the data were stale. We also said that stale data could impact future investigations by potentially leading to cases in which apparently valid data continued to be recorded after a parameter source stopped providing valid values, which could result in latent faults in the recording system for mandatory parameters. These mandatory parameters would thus be unavailable because an EAFR’s source would no longer be providing the data. Recording stale data is an important issue that we believe you need to fully address and resolve. You indicated that a software revision corrected the 787 stale data issue. Please describe what steps have been taken to ensure that all 787s in service have implemented this software revision. Pending completion of your efforts to resolve stale data recording issues, Safety Recommendation A-14-125 remains classified OPEN--ACCEPTABLE RESPONSE.
Response: -From Daniel K. Elwell, Acting Administrator: This is our final response to Safety Recommendation A-14-124 and in further response to Safety Recommendations A-14-125 and -126. These recommendations were issued by the Board on December I , 2014, and this response supplements all previous letters. The Board issued these safety recommendations as a result of an incident that occurred on January 7, 2013, in which a Japan Airlines Boeing 787-8, JA8297, was parked at a gate at General Edward Lawrence Logan International Airport, Boston, Massachusetts, when maintenance personnel observed smoke coming from the lid of the auxiliary power unit battery case, as well as a fire with two distinct flames at the electrical connector on the front of the case. No passengers or crewmembers were aboard the airplane at the time, and none of the maintenance or cleaning personnel aboard the airplane were injured. In our previous letter to the Board, dated July 6, 2016, we stated that the FAA and Boeing agreed that the EAFR recording of stale data was not compliant with certain Title 14, Code of Federal Regulations (14 CFR) Part 25 standards. Upon further investigation, however, we determined that the EAFR acquisition and recording functions failed, and the resulting interruptions actually occurred due to failures to record data, rather than recording stale data. While this issue represents a non-compliance with part 25 standards, as noted in our previous letter, it is not the same issue identified by the safety recommendation. The 787 EAFR's failure to record was caused by a design change after certification and was corrected by a software update. Regarding the safety issue identified by the Board's recommendation, we note that EAFRs are intended to record all specified parameters. However, our evaluation determined that airplanes in service may experience stale data when an aircraft source stops transmitting data while a constant (i.e .. , "stale") value continues to be recorded. This can occur with flight data acquisition and recording systems on all model aircraft and is not specific to the 787. For parameters with multiple sources of data, the 787 EAFR explicitly records the source used. It will also log if none of the sources are available. For a limited set of parameters in which there is only one source of data (i.e. miscellaneous analog signals), we found that the 787 EAFR does not explicitly identify if recorded data is stale, but does capture the last known valid value, as is the case with flight recorders used on other airplane models. We will continue to communicate with the Board's specialists regarding the impact of stale data. We will also continue working with Boeing to determine the frequency with which stale data are recorded, the parameters this affects, and the impact stale data has on the ability of accident investigators to effectively use these data systems in their investigations.