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Safety Recommendation Details

Safety Recommendation A-00-102
Details
Synopsis: .In this letter, the national transportation safety board recommends that the Federal Aviation Administration (FAA) take action to address the following safety issues: air carrier pilot training in landing techniques and bounced landing recovery, training tools and policies that promote proactive decision-making to go around if an approach is unstabilized, the use of on board computers to determine the required runway length for landing, md-11 handling characteristics and structural integrity requirements, and hard landing inspection requirements. The safety board identified these issues in its investigation of the 1997 accident involving Federal Express flight 14 in Newark, NJ. This letter summarizes the Board's rationale for issuing these recommendations
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Conduct a study to determine if landing gear vertical overload fusing offers a higher level of safety than when the gear is overdesigned. If fusing offers a higher level of safety, revise 14 Code of Federal Regulations Part 25 to require vertical overload fusing of landing gear.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Alternate Action
Mode: Aviation
Location: Newark, NJ, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA97MA055
Accident Reports: Crash During Landing Federal Express, Inc., McDonnell Douglas MD-11, N611FE
Report #: AAR-00-02
Accident Date: 7/31/1997
Issue Date: 8/25/2000
Date Closed: 5/4/2011
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Alternate Action)
Keyword(s): Landing Gear

Safety Recommendation History
From: NTSB
To: FAA
Date: 12/9/2011
Response: CC# 201100438 was closed administratively. No letter was written or mailed because A-00-102 was classified CLOSED--ACCEPTABLE ALTERNATE ACTION on May 4, 2011.

From: FAA
To: NTSB
Date: 11/16/2011
Response: -From J. Randolph Babbitt, Administrator: As noted previously, the Federal Aviation Administration (FAA) plans to revise Title 14, Code of Federal Regulations (14 CFR) § 25.72I(a) to make a number of improvements, including a requirement to address side loads in addition to upward and aft loads. The FAA is also planning to issue advisory material that specifies that the upward, aft, and side loads should be considered in any reasonable combination. In the Board's letter dated December 15,2004, it agreed with the FAA's planned approach. The FAA plans to initiate rulemaking to revise 14 CFR § 25.721(a) in early 2012 as described above. We estimate issuance of the notice of proposed rulemaking for public comment by June 2013. I will keep the Board informed of the FAA's progress on this recommendation and provide an updated response by December 30, 2012.

From: NTSB
To: FAA
Date: 5/4/2011
Response: The FAA had previously informed the NTSB that overdesigning the landing gear by increasing the strength beyond ultimate load capability would not be an acceptable means of compliance with 14 CFR Section 25.721(a), which requires that the main landing gear be designed to separate in the event of an overload condition in which the ultimate load capability is exceeded. In response, the NTSB asked the FAA whether the landing gear design for the DC-10 and MD-11 aircraft, including the airplane involved in the Federal Express flight 14 accident, were in compliance with Section 25.721(a). The FAA replied that, as built, the landing gear on these airplanes met the certification requirement as it was interpreted at the times of certification (1970 for the DC-10 and 1990 for the MD-11). The FAA further replied that the landing gear would not meet the requirements, however, if the airplanes were being certified under the present interpretation of the requirement. Although the FAA believes that current regulations are adequate, given the present interpretation of landing gear overload conditions, an Aviation Rulemaking Advisory Committee (ARAC) recommended that the FAA revise 14 CFR Section 25.721(a) and associated guidance material to require consideration of side loads in addition to upward and aft loads. The FAA plans, but has not yet begun, to make these revisions. On September 19, 2007, the European Aviation Safety Agency (EASA) incorporated the ARAC-recommended rule changes and advisory material into EASA Certification Specification (CS) 25 in Amendment 25/3. The FAA indicated that a new aircraft design that complies with CS 25 will be considered to comply equally with 14 CFR Section 25.721(a). Therefore, the FAA believes that the ARAC recommendations are already being applied on all new transport airplane programs for which joint FAA-EASA certification is sought, including the Boeing 787 and the Airbus A350. The NTSB agrees with the FAA that EASA’s incorporation of the ARAC recommendations has achieved, in an alternative manner, the intent of this recommendation to require vertical overload fusing of landing gear in new type certifications of aircraft under 14 CFR Part 25. Therefore, Safety Recommendation A-00-102 is classified CLOSED – ACCEPTABLE ALTERNATE ACTION.

From: FAA
To: NTSB
Date: 3/8/2011
Response: CC# 201100103: - From J. Randolph Babbitt, Administrator: The Federal Aviation Administration has determined that overdesigning the landing gear by increasing the strength beyond ultimate load capability is not an acceptable means of compliance with Title 14 Code of Federal Regulations (14 CFR) section 25.721(a). This regulation requires that the main landing gear be designed to separate in the event of an overload condition, in which ultimate load capability is exceeded. This includes overloads that occur primarily in the vertical direction. We believe current regulations address the Board's concern. While we believe that current regulations are adequate with the present interpretation of landing gear overload conditions, we plan to revise 14 CFR 25.721(a), based on a recommendation from the Aviation Rulemaking Advisory Committee (ARAC), to require consideration of side loads in addition to upward and aft loads. The FAA is also planning to issue advisory material that specifies that the upward, aft, and side loads should be considered in any reasonable combination. The European Aviation Safety Agency (EASA) incorporated the ARAC recommended rule changes and advisory material into EASA Certification Specifications (CS) 25 in Amendment 25/3, dated September 19, 2007. Therefore, these updated criteria will be applied on all new transport airplane programs for which joint FAA-EASA certification is sought. Recent examples are the Boeing 787 and the Airbus A350. The FAA remains committed to this rulemaking activity; however, rulemaking to codify the ARAC recommendations is not as high a priority for the FAA as other rulemaking activities with more significant safety benefits. This is because the ARAC recommendations are already being applied on current certification projects. The FAA is developing the proposed revision to 14 CFR 25.721 and supporting guidance material and plans to begin the formal rulemaking process by December 2011. I will keep the Board informed of the FAA's progress on this recommendation and provide an updated response by December 2011.

From: NTSB
To: FAA
Date: 12/15/2004
Response: NMC# 102556: The Safety Board notes that the FAA reported in a November 13, 2001, letter that the Aviation Rulemaking Advisory Committee (ARAC) had recommended changes in 14 CFR Section 25.721 to specify that landing gear overloads must be assumed to act in an upward and aft direction, in effect requiring vertical overload fusing of landing gear. FAA staff confirmed in the meeting and via e-mail on September 9, 2004, that the rulemaking project is still in progress. In the same e-mail, the FAA provided information that the European Aviation Safety Agency is now applying the ARAC proposal to current certification projects, such as the Boeing 7E7. In our letter of July 23, 2002, the Safety Board asked for information regarding the FAA's position on requiring vertical fusing of the DC-10 and MD-11 landing gear. At the February 3, 2004, meeting and via e-mail on May 18, 2004, FAA staff informed Safety Board staff that, as built, the landing gear on these airplanes met the certification requirement of 14 CFR Section 25.271 as it was interpreted at the time of certification (1970 and 1990, respectively). FAA staff further reported that the landing gear would not meet the requirements if the airplanes were being certified under the present interpretation discussed above. The Safety Board appreciates the FAA's continued work in this area and is pleased to see that the more comprehensive overload combinations are being used for current certification projects before the changes are formalized in rulemaking. The Board urges the FAA to continue the rulemaking project to make the necessary changes to 14 CFR Part 25. Pending issuance of a final rule and advisory materials, Safety Recommendation A-00-102 is classified OPEN -- ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 9/9/2004
Response: UPDATE received via email 9/9/04: We are still planning to publish the NPRM and advisory material as indicated in the 11/13/01 letter. However, as you may know, our rulemaking process is quite slow, so publication may not occur for several years. For that reason, we have decided to publish "FAA policy" addressing this issue. The policy route can be much quicker, as it simply reflects our interpretation of existing requirements. This policy will clarify that 1) "Overdesigning" the landing gear (increasing the strength of the landing gear beyond ultimate load capability) is not an acceptable means of compliance with § 25.721; and 2) A comprehensive range of up and aft load combinations must be considered in demonstrating compliance with § 25.721. I would expect publication of the policy within a year, but hopefully we can get it out sooner than that. The other thing I should mention is that the European Aviation Safety Agency (EASA) is now applying the ARAC proposal on current certification projects. For example on the Boeing 7E7 program, EASA is proposing the use of the revised rule and advisory material as defined in the JAA Notice of Proposed Amendment (NPA) 25E-304, attached.

From: FAA
To: NTSB
Date: 5/18/2004
Response: This is in response to your question regarding NTSB SR A-00-102. You requested clarification of the following information, which we provided as part of the SWAT review. The FAA stated that "We believe the DC-10 and MD-11 met the intent of FAR 25.721 at the time of certification (1971 and 1990, respectively), and are in compliance with the interpretation of the requirement at that time. The DC-10 and MD-11 main landing gears were designed to safely fail and break away from the airplane due to an overload condition. This overload condition was assumed to occur as a result of striking an obstruction (pure drag load), combined with a range of vertical loads from 0 to 2 g's. In current accepted practice, a more comprehensive range of up and aft load combinations is considered, in effect requiring vertical overload fusing of landing gear." What you're asking is, would the MD-11 design be certified to § 25.721, if that design were submitted today (for new type certification). The simple answer is no. The rationale for my answer is that industry and the authorities have learned from the past, and a more comprehensive range of up and aft load combinations would be required to comply with § 25.721 today. This is reflected in the ARAC proposal, as outlined in the FAA's previous response to the recommendation, and is also reflected in recent certification programs. Additionally, it is FAA policy that overdesigning the landing gear by increasing the strength of the landing gear beyond ultimate load capability is not an acceptable means of compliance with § 25.721. I believe that this is where it gets confusing. While the MD-11 and DC-10 landing gear are "overdesigned" in the vertical direction, this was not done in order to comply with § 25.721, but occurred as a secondary result of other regulatory requirements and company design objectives, (for example, the 10 foot per second sink rate landing condition and other design and fatigue load requirements). Meanwhile, § 25.721 was met by considering overloads occurring largely in the aft direction. Again, we believe the MD-11 and DC-10 landing gear are in strict compliance with § 25.721 at the time of certification. However, a more comprehensive range of failure conditions is required to comply with § 25.721 on current certification programs. I hope this helps. If there is anything further I can provide, please let me know.

From: FAA
To: NTSB
Date: 2/3/2004
Response: 2/3/04 SWAT meeting response: : In its previous response, the FAA stated that over-designing the landing gear by increasing its strength beyond ultimate load capability is not an acceptable means of complying with applicable regulations. The NTSB noted that this would seem to indicate that the DC?10 and MD?11 main landing gear designs are not in compliance with applicable regulations because their vertical load strength is greater than the ultimate load capability of the wing. We believe the DC-10 and MD-11 met the intent of FAR 25.721 at the time of certification (1971 and 1990, respectively), and are in compliance with the interpretation of the requirement at that time. The DC-10 and MD-11 main landing gears were designed to safely fail and break away from the airplane due to an overload condition. This overload condition was assumed to occur as a result of striking an obstruction (pure drag load), combined with a range of vertical loads from 0 to 2 g's. In current accepted practice, a more comprehensive range of up and aft load combinations is considered, in effect requiring vertical overload fusing of landing gear. In addition to the FedEx accident that prompted this recommendation, the NTSB letter references several other accidents in which structural failure occurred and there was fuel spillage: · On December 21, 1992, a Martinair DC-10 crashed on landing at Faro, Portugal. The right main gear touched down at a sink rate above 17 ft/sec. · On August 22, 1999, a Mandarin China Airlines MD-11 crashed on landing at Hong Kong. The right main gear touched down at a sink rate above 16 ft/sec. These above events, as well as the most recent FedEx accident, represent extreme sink rate conditions that are well beyond the design ultimate load requirements established by the FAR.

From: NTSB
To: FAA
Date: 7/29/2002
Response: The Safety Board appreciates the FAA's and ARAC's action on this issue and looks forward to the final rule and advisory material. However, the FAA's response indicates that the DC-10 and MD-11 main landing gear designs are not acceptable means of compliance with applicable regulations because their vertical load strength is greater than the ultimate load capability of the wing. Various combinations of roll angle and vertical speed at touchdown can cause the DC-10 and MD-11 wing spar to fail before the landing gear fails. In this situation, fuel spills and fuel fires are likely as evidenced by the December 21, 1992, DC-10 accident at Faro, Portugal, and the July 31, 1997, and August 22, 1999, MD-11 accidents at Newark, New Jersey, and Hong Kong, respectively. The FAA's response to Safety Recommendation A-00-102 does not specifically explain how the FAA will handle the apparent noncompliance of the DC-10 and MD-11 main landing gear designs. Based on the FAA's response, it seems appropriate that the FAA should require vertical overload fusing of the DC-10 and MD-11 landing gear. Further, the FAA should review all 14 CFR Part 25 landing gear designs to ensure compliance. Safety Recommendation A-00-102 asked the FAA to determine whether landing gear vertical overload fusing offers a higher level of safety than that offered when the gear is overdesigned. The FAA has not conducted this study, but has clarified that overdesigning the landing gear is not an acceptable means of compliance. The FAA's actions to clarify the regulations and advisory material on this subject represent an acceptable alternative means of addressing the recommendation. Pending receipt of further information regarding the FAA's position on requiring vertical overload fusing of the DC-10 and MD-11 landing gear, and issuance of a final rule and advisory material, Safety Recommendation A-00-102 is classified OPEN -- ACCEPTABLE ALTERNATE RESPONSE.

From: FAA
To: NTSB
Date: 11/13/2001
Response: Letter Mail Controlled 11/19/2001 10:56:51 AM MC# 2010909: - From Jane F. Garvey, Administrator: In its letter dated August 25, 2000, the Board raises a specific concern regarding the fire hazard following overload and failure of the landing gear. Overload is considered to mean exceeding ultimate load capacity. The FAA's review indicates that the current regulations address the Board's concern. The FAA has determined that overdesigning the landing gear by increasing the strength of the landing gear beyond ultimate load capability is not an acceptable means of compliance with applicable regulations. Current regulations are intended to ensure that the main landing gear is designed to separate in the event of an overload condition. For airplanes with 10 or more seats, 14 CFR 25.721(a), Amendment 25-32, states, in part, that "the main landing gear system must be designed so that if it fails due to overloads during takeoff and landing (assuming the overloads to act in the upward and aft directions), the failure mode is not likely to cause…the spillage of enough fuel from any part of the fuel system to constitute a fire hazard." In designing the landing gear to comply with 14 CFR 25.721(a), different manufacturers have assumed different combinations of "upward and aft" loads. Some landing gear was designed considering every possible combination of vertical and drag load, including pure vertical load. The MD-11 main landing gear, however, was designed for an overload condition in which the drag load was the primary component. This landing gear was not designed to separate for a purely vertical overload. The FAA is currently revising 14 CFR 25.721 and publishing related advisory material in cooperation with the Aviation Rulemaking Advisory Committee (ARAC). The ARAC has forwarded the following recommendations for revising 14 CFR 25.721 to the FAA: * The landing gear system must be designed so that when it fails due to overloads during takeoff and landing, the failure mode is not likely to cause spillage of enough fuel to constitute a fire hazard. The overloads must be assumed to act in the upward and aft directions--in combination with side loads acting inboard and outboard up to 20 percent of the vertical load or 20 percent of the drag load, whichever is greater. The ARAC's proposed requirement applies to all landing gear as opposed to the main landing gear, uses the phrase "when it fails" as opposed to "if it fails," and includes additional consideration for side loads. The ARAC also proposes the following advisory material to clarify the intent of the rule: * Landing gear separation (Compliance with 14 CFR 25.721(a) and 25.963(d)(4)). Failure of the landing gear under overload should be considered, assuming the overloads to act in any reasonable combination of vertical and drag loads, in combination with side loads acting both inboard and outboard up to 20 percent of the vertical load or 20 percent of the drag load, whichever is greater. It should be shown that, at the time of separation, the fuel tank itself is not ruptured at or near the landing gear attachments. The assessment of secondary impacts of the airframe with the ground following landing gear separation is not required. If the subsequent trajectory of a separated landing gear would likely puncture an adjacent fuel tank, design precautions should be taken to minimize the risk of fuel leakage. The advisory material will clarify the intent of the rule by indicating that the overloads are assumed to "act in any reasonable combination of vertical and drag loads." The FAA is developing a notice of proposed rulemaking and advisory material in accordance with the ARAC recommendations. The FAA believes that the proposed changes to the applicable regulations and the new advisory material will clarify the rule's intent and will ensure that all landing gear are designed to separate safely in the event of an overload condition. I will keep the Board informed of the FAA's progress on these efforts.

From: NTSB
To: FAA
Date: 6/13/2001
Response: The Safety Board reiterates the point it made in the safety recommendation letter that several major landing accidents have now occurred as a result of pilots allowing their airplanes to land with more adverse combinations of lift, roll angle, and sink rate than those specified in the regulations. In each accident, a wing broke and a fuel fire erupted. Each of these accidents involved aircraft whose landing gear were not fused for upward (vertical) acting loads. Pending completion of the review and notification of the Board of the FAA's planned actions, Safety Recommendation A-00-102 is classified OPEN -- ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 11/13/2000
Response: Letter Mail Controlled 11/15/2000 3:27:59 PM MC# 2001695 - From Jane F. Garvey, Administrator: The Board raises a specific concern regarding the fire hazard following overload and failure of the landing gear in its letter dated August 25, 2000. The FAA's review indicates that the current regulations address the Board's concern. For airplanes with 10 or more seats, 14 CFR 25.721(a), Amendment 25-32, states, in part, that "the main landing gear system must be designed so that if it fails due to overloads during takeoff and landing (assuming the overloads to act in the upward and aft directions), the failure mode is not likely to cause…the spillage of enough fuel from any part of the fuel system to constitute a fire hazard." The FAA will review past compliance findings to determine if further action is warranted. It is anticipated that this effort will be completed by March 2001. I will inform the Board of the FAA's course of action as soon as the review is completed.