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Safety Recommendation Details

Safety Recommendation A-12-002
Details
Synopsis: This letter discusses the circumstances of several survivable accidents1 that have occurred in the last 3 years in which overhead bins and passenger service units (PSU)2 on Boeing 737 airplanes became separated from their attachments during the accident sequences, likely increasing the number of reported occupant injuries, particularly injuries to the head and face. In addition to this occupant safety hazard, the negative-g strap3 attachment bracket (used as part of the flight crew five-point restraint assembly) failed in two cases, possibly contributing to back injuries to the flight crewmembers. Findings in these investigations (some of which are ongoing) suggest that current crashworthiness test requirements do not provide an adequate basis on which to evaluate how these items will withstand impact forces during survivable accidents.
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Require that the installation design for overhead bins and passenger service units (PSU) manufactured by Boeing and installed in Boeing 737NG series airplanes be modified so that the PSUs remain attached to the bins or are captured in a safe manner during survivable accidents.
Original recommendation transmittal letter: PDF
Overall Status: Open - Acceptable Response
Mode: Aviation
Location: Denver, CO, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA09MA021
Accident Reports: Runway Side Excursion During Attempted Takeoff in Strong and Gusty Crosswind Conditions Continental Airlines Flight 1404, Boeing 737-500, NN18611
Report #: AAR-10-04
Accident Date: 12/20/2008
Issue Date: 2/23/2012
Date Closed:
Addressee(s) and Addressee Status: FAA (Open - Acceptable Response)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 8/10/2018
Response: Although Safety Recommendation A-12-2 does not address Boeing 737 Classic series airplanes (models manufactured before Boeing 737-600 production started), we are pleased that you previously approved Boeing Service Bulletin (SB) 737-25-1728 and recently approved Boeing SB 737-25-1758 for design changes to the Ultem and aluminum PSU assemblies, respectively, used in Boeing 737 Classic series airplanes. We further note that you are preparing a notice of proposed rulemaking (NPRM) that will propose adopting a new airworthiness directive (AD) to mandate these SBs for 737 Classic series airplanes. On October 13, 2016, you published an NPRM that proposed adopting a new AD for the Boeing 737NG series airplanes. The proposed AD, which was based on Boeing SB 737 25 1707, would require modifications to prevent PSUs and life vest panels from detaching from the supporting airplane structure. In our November 8, 2016, comments on this NPRM, and in our June 21, 2017, letter about this recommendation, we said that the proposed AD would satisfy Safety Recommendation A-12-2. We note that after the NPRM closed, Boeing revised the SB to address parts rotability, expanded its effectivity to include additional aircraft, and modified the accomplishment instructions in response to difficulties cited by several operators. As a result, you will be issuing a supplemental NPRM (SNPRM) that will propose a new AD to mandate Boeing’s revised SB. Pending issuance of the SNPRM and an AD mandating Boeing’s revised SB, Safety Recommendation A-12-2 remains classified OPEN--ACCEPTABLE RESPONSE. Please update us at correspondence@ntsb.gov on your progress toward implementing this recommendation, and do not send both an electronic and a hard copy of the same response.

From: FAA
To: NTSB
Date: 6/29/2018
Response: -From Daniel K. Elwell, Acting Administrator: The Federal Aviation Administration (FAA) determined that the Boeing 737 Classic series airplanes are also subject to the same unsafe conditions as the 737NG series described in this recommendation. We plan to issue Airworthiness Directives (AD) for each model requiring modifications to prevent PS Us and life vest panels from detaching from the supporting airplane structure. The status of these activities are provided below. We will continue to include the status for each model in future responses to this safety recommendation until release of the final rule AD on the 737NG series, at which time we will request its closure of this recommendation. 737NG Airplanes: Boeing incorporated an FAA-approved PSU attachment design change into 737NG production on February 2, 2015. On October 13, 2016, the FAA published a notice of proposed rulemaking (NPRM) that proposed adopting a new AD to mandate Boeing Service Bulletin (SB) 737-25-1707 to address in-service 737NG airplanes. The final rule AD has not been published because SB revisions expanding the scope of the NPRM were determined necessary to address parts rotability concerns, expand the effectivity to include additional aircraft, and revise accomplishment instructions in response to difficulties cited by several operators. We reviewed Boeing's revised SB and plan to propose a new AD to mandate it in a supplemental NPRM. Depending on the complexity of comments, we expect to publish the final rule AD by April 2019. 737 Classic Airplanes: The FAA approved Boeing SBs 737-25-1728 and 737-25-1758 for design changes to the Ultem and Aluminum PSU assemblies respectively. We are in the process of initiating the NPRM AD and we estimate publication of a final rule AD by January 2019. I will keep the Board informed of the f AA's progress on this recommendation and provide an update by May 2019.

From: NTSB
To: FAA
Date: 6/21/2017
Response: We note that, on February 2, 2015, Boeing incorporated an approved PSU attachment design change into production for Boeing 737NG (next generation) series airplanes (the Boeing 737NG series includes 737-600, -700, -700C, -800, -900, and -900ER airplanes). We further note that, on October 13, 2016, you published a notice of proposed rulemaking (NPRM) that proposed adopting a new airworthiness directive (AD) for this series. The proposed AD, which was based on Boeing Service Bulletin (SB) 737-25-1707, would require modifications to prevent PSUs and life vest panels from detaching from the supporting airplane structure. In our November 8, 2016, comments on this NPRM, we said that issuance of the proposed AD would satisfy Safety Recommendation A-12-2. We recently discovered, however, that the proposed AD has not yet been issued. Although Safety Recommendation A-12-2 does not address Boeing 737 Classic series airplanes (models manufactured before Boeing 737-600 production started), we were pleased to learn that you approved Boeing SB 737-25-1728, which addresses the Ultem PSU assemblies used in Boeing 737 Classic series airplanes, and that Boeing is developing a separate SB to address the aluminum PSU configurations in these airplanes. We note that, once the aluminum PSU SB is approved, you plan to issue an AD for Boeing 737 Classic series airplanes that will mandate that improved PSU assemblies be installed. Pending issuance of the AD proposed in your October 13, 2016, NPRM, Safety Recommendation A-12-2 remains classified OPEN—ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 4/14/2017
Response: -From Michael P. Huerta, Administrator: As noted in the Federal Aviation Administration’s (FAA) letter dated July 6, 2016, Boeing incorporated an approved PSU attachment design change into production for the 737NG on February 2, 201 5, and continues to make progress developing a design improvement for the 737 Classic models. We note that for the 737NG aircraft, Boeing re leased Service Bulletin (SB) 737-25-1 707 on September 24. 2015. Furthermore, the FAA released an Airworthiness Directive (AD), titled “Airworthiness Directives; The Boeing Company Airplanes.'' effective on March 17, 2017. This AD is available at: https://www.federalregister.gov/documents/2017/02/J0/2017-01778/airworthiness-directives-theboeing-company-airplanes. For the 737 Classic mode ls. the FAA has approved Boeing SB 737-25- 1728, which only addresses the Ultem PSU assemblies. A separate SB is being drafted by Boeing to address the aluminum PSU configurations. The FAA anticipates receipt of the related service information for approval by the end of 2017. Once the aluminum PSU SB is approved, the FAA intends to issue an AD for the 737 Classic aircraft to mandate installation. I will keep the Board informed of the FAA·s progress on this recommendation and provide an update by May 2018.

From: NTSB
To: FAA
Date: 11/18/2016
Response: The National Transportation Safety Board (NTSB) has reviewed the Federal Aviation Administration’s (FAA) notice of proposed rulemaking (NPRM), titled “Airworthiness Directives; The Boeing Company Airplanes,” which was published at 81 Federal Register 70647 on October 13, 2016. The NPRM proposes to adopt a new airworthiness directive (AD) for certain Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This proposed AD was prompted by reports of passenger service units (PSUs) becoming detached from the supporting airplane structure in the applicable model 737 airplanes during several survivable accidents that exceeded the design emergency load requirements for the PSUs. The proposed AD, which is based on Boeing Service Bulletin 737-25-1707 (dated September 24, 2015), would require replacing the existing inboard lanyard of the PSUs and life vest panels with two new lanyards on the outboard edge of these structures. The FAA is proposing this AD to prevent PSUs and life vest panels from detaching from the supporting airplane structure, which could lead to passenger injuries and impede passenger and crew egress during evacuation. The NTSB investigated several survivable accidents that occurred from 2008 through 2011 in which overhead bin and PSUs on Boeing 737 airplanes became separated from their attachments during the accident sequences, likely increasing the number of reported occupant injuries, particularly to the head and face. Among the six safety recommendations we issued as a result of our findings is Safety Recommendation A-12-002, which asked the FAA to do the following: Require that the installation design for overhead bins and passenger service units (PSU) manufactured by Boeing and installed in Boeing 737NG series airplanes be modified so that the PSUs remain attached to the bins or are captured in a safe manner during survivable accidents. On August 23, 2016, the NTSB classified Safety Recommendation A-12-002 “Open—Acceptable Response,” pending ADs for all Boeing 737 fleets to mandate the PSU attachment design changes. If the proposed AD is issued, it will satisfy Safety Recommendation A-12-002. The NTSB concurs with the proposed AD and appreciates the opportunity to comment.

From: NTSB
To: FAA
Date: 8/23/2016
Response: We note that Boeing incorporated an approved PSU attachment design change into production for Boeing 737NG series airplanes on February 2, 2015, and you are currently developing a design change for Boeing 737 Classic series airplanes. Once the service information is available and approved for each model and configuration, you plan to issue airworthiness directives (ADs) for both the Boeing 737NG and 737 Classic fleets to mandate the design change. Pending issuance of these ADs, Safety Recommendation A-12-002 remains classified OPEN--ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 7/6/2016
Response: -From Michael P. Huerta, Administrator: Boeing incorporated an approved PSU attachment design change into production for the 737 Next-Generation (NG) model on February 2, 2015, and continues to make progress developing a design improvement for the 73 7 Classic models. Once the service information is available and approved for each model and configuration, the Federal Aviation Administration (FAA) intends to issue airworthiness directives for both the 737NG and 737 Classic fleets to mandate installation. We expect to receive the related service information for approval within the next 6 months. I will keep the Board informed of the FAA's progress on this recommendation and provide an update by May 31, 2017.

From: NTSB
To: FAA
Date: 11/20/2014
Response: We note that Boeing developed a design change to the PSU attachment method that addresses this recommendation, and that the company is incorporating this change in its new 737 airplanes. We further note that your analysis showed that PSU drops in survivable crash landings occur more frequently on Boeing 737 airplanes than on other similar airplanes. We are encouraged that you plan to issue an airworthiness directive (AD) to bring the 737 to the same level of PSU integrity as that of other airplane models. Pending issuance of such an AD, Safety Recommendation A-12-2 remains classified OPEN—ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 9/23/2014
Response: -From Michael P. Huerta, Administrator: We determined that the existing Boeing 737NG series PSU design is compliant with the regulatory standards. As a product improvement, Boeing developed a design change to the PSU attachment method that is being incorporated into production of new 737NG airplanes. The change is designed to restrict the movement of the PSU and prevent it from falling or striking passengers during emergency landing conditions. As previously noted in our response to A-12-1 and -3, our quantitative risk analysis determined that the risk is well below the risk guideline for mandatory action, due to the absence of any direct link between the PSUs and fatalities or impeded egress. However, our qualitative assessment of the number of PSU drops and associated non-fatal injuries that occurred in survivable 737 accidents demonstrates that the number of PSU drops on the 737 is higher than many other airplane models (significant numbers ofPSU drops were not observed on other airplane models' survivable crash landing events). The 737 PSUs, though similar in design to wide-body aircraft, have shown to be more susceptible to falling in a survivable crash. Wide-bodies do not appear to have this issue as more of the crash loads are absorbed by the fuselage such that loads imparted on the bins is not as high. Therefore we are pursuing an airworthiness directive to bring the 737 to the same level of PSU integrity as other airplane models. I will keep the Board informed of our progress on this recommendation and provide an update by August 31, 2015.

From: NTSB
To: FAA
Date: 11/6/2012
Response: Thank you for the Federal Aviation Administration’s (FAA) May 18, 2012, letter to the National Transportation Safety Board (NTSB) regarding Safety Recommendations A-12-1 through -6, stated below. We issued these recommendations to the FAA on February 23, 2012, as a result of our investigations of several survivable accidents that have occurred over the past 3 years in which overhead bins and passenger service units (PSU) on Boeing 737 airplanes have separated from their attachments during the accidents and the negative-g strap attachment bracket (used as part of the flight crew five-point restraint assembly) failed. In its letter, the FAA indicated that it had reviewed the related accident data and found no data to indicate that the PSUs or the negative-g strap bracket failure had contributed to serious injury of either passengers or crewmembers. On the basis of its review, the FAA planned not to take the recommended actions; however, the FAA suggested that representatives of both our agencies meet to discuss additional data that could indicate these issues had contributed to passenger or crewmember injury. That meeting took place on August 31, 2012. In its letter, the FAA indicated that it is currently working with Boeing to review the PSU attachment method to evaluate potential improvements. During the August 31, 2012, meeting, the FAA confirmed that this work with Boeing continues. Accordingly, pending completion of this review and implementation of the recommended requirement, Safety Recommendation A 12-2 is classified OPEN—ACCEPTABLE RESPONSE.

From: NTSB
To: FAA
Date: 6/20/2012
Response: The FAA indicated that it had reviewed the related accident data and found that the bins and PSUs that separated from their attachments had been subject to loads that greatly exceeded their certification standards. The FAA’s review found no data to indicate that the PSUs or the negative-g strap bracket failure had contributed to serious injury of either passengers or crewmembers. On the basis of this review, the FAA does not plan to take the recommended actions; however, the FAA suggested that representatives of both our agencies meet to discuss additional data that could indicate PSUs or overhead bins had contributed to passenger or crewmember injury. We agree that such a meeting would be beneficial, and this meeting is currently being scheduled. Accordingly, the NTSB will classify these recommendations after we have had an opportunity to evaluate the results of the meeting.

From: FAA
To: NTSB
Date: 5/18/2012
Response: -From Michael P. Huerta, Acting Administrator: The existing Boeing 737NG series design is compliant with the regulatory standards. We are working with Boeing to review the PSU attachment method to evaluate potential improvements. I will keep the Board informed of the FAA's progress on this safety recommendation and provide an update by May 31 , 2013.