TSB Recommendation A11-02

"In conjunction with the proposed rule (14 CFR 29.927(c)) change to remove or clarify the term "extremely remote" (see FAA response to Recommendation A11-02), the FAA will assess the adequacy of the 30-minute loss of lubrication requirement."

Recommendation A11-02 was not directed to Transport Canada (TC) and, as such, it was not required to respond. However, TC indicated that:

(It) has initiated...a coordinated formal review with the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) of the rules related to the extremely remote provision and the 30 minute requirements. The objective of the review is to reach an international agreement on what changes may be required to the rules... Any amendments to the airworthiness rules would follow the regulatory process in each jurisdiction.

The FAA's response indicates agreement with the course of action contained in recommendation A11-02 since, as part of the proposed rule change, the FAA will assess the adequacy of the 30-minute loss of lubrication requirement.

Therefore, the response is assessed as Satisfactory Intent.

On 02 November 2011 the TSB wrote to the FAA asking it to provide an update as to the progress of its activities taken to mitigate the residual risks associated with Recommendation A11–02. A response was requested before 02 December 2011. To date, no reply has been received.

September 2011 update

Recommendation is directed to the FAA. However, TCCA is addressing this recommendation concurrently with A11–01."

The TSB's recommendation called for the FAA to assess the adequacy of the 30 minute main gearbox run dry requirement for Category A transport helicopters that was conceived during the 1980s. Both the FAA and TC initially indicated that they would assess the adequacy of the 30–minute loss of lubrication requirement in concert with EASA. It is unclear if an assessment to consider continued improvements in technology, given the growth in the offshore helicopter industry since the last major update of certification rules, has been completed or what the results are.

While the FAA did not provide an update on the progress of its assessment of the adequacy of the 30–minute loss of lubrication requirement, the Board expects that the FAA is continuing with its assessment. The TSB also expects that the FAA will provide it with the results once the assessment is complete.

The response is considered Satisfactory Intent.

A group of technical specialists from the Federal Aviation Administration, Transport Canada and the European Aviation Safety Agency formed a Joint Cooperation Team (JCT). The JCT was chartered by a Certification Management Team (CMT) to review the current design standards and accompanying guidance material relating to the certification of helicopter gear boxes. As a part of this review, the JCT was tasked to address TSBC Recommendations A11-02 and A11-02 and their underlying safety issue, specifically with respect to loss of lubrication. The JCT has completed their task and will be presenting a report to the CMT. We have no further updates on these safety recommendations until the CMT reviews and either accepts, rejects, or modifies the JCT’ s report.

We will continue to provide periodic updates to TSBC safety recommendations A11-02 and A11-02 until final resolution.

In the last TSB assessment of the latest FAA response to A11-02 dated 07 March 2012 it was noted that both the FAA and TC indicated that they would assess the adequacy of the 30-minute loss of lubrication requirement in concert with EASA. However the response was unclear as to whether a review of the design standards for the certification of helicopter gear boxes would consider continued improvements in technology, given the growth in the offshore helicopter industry.

The current FAA response indicates that the review by the Joint Cooperation Team of the current design standards and accompanying guidance material relating to the certification of helicopter gear boxes has been completed. The FAA has declined to provide any additional details regarding the results of this review until management accepts, rejects, or modifies the JCT’s report.

The response is considered Satisfactory Intent.

In response to Safety Recommendations A11-02 and A11-02, the Federal Aviation Administration (FAA) is able to provide an update on the activities of the Joint Cooperation Team (JCT), which consisted of technical specialists from the FAA, Transport Canada, and the European Aviation Safety Agency (EASA). The JCT was chartered by a certification management team (CMT) to review the current design standards and accompanying guidance material relating to the certification of helicopter gearboxes and the underlying safety concerns, specifically with respect to loss of lubrication. The JCT has completed its task, and we have enclosed the final report that was accepted and signed by the CMT.

The final report provided by the JCT has effectively addressed the intent of Safety Recommendations All-01 and All-02. The FAA considers these recommendations closed, and no further action is planned.

Enclosure:

September 28, 2012

Report of the Joint Cooperation Team (JCT) on the Review of Helicopter Main Gearbox Certification Requirements for TCCA/FAA/EASA

Joint Cooperation Team:

Transport Canada (TCCA), the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) agreed to create a Joint Cooperation Team (JCT) to conduct a review of the current design standard and guidance material relating to the certification of helicopter MGBs, specifically with respect to loss of lubrication including AWM 529.927(c), 14 CFR § 2.9.927(c), and CS 29.927(c). In light of the above safety recommendations and in accordance with terms of reference document, this joint review was intended to review the adequacy of transport category rotorcraft standards with respect to gearbox loss of oil and consider potential areas for improvement with the intention that the certification requirements remain harmonized among TCCA, FAA, and EASA.

The terms of reference did not address any other TSB (operational) recommendations.

Approach and Scope of the JCT:

Technical specialists from TCCA, FAA and EASA formed a JCT to review the current design standards and accompanying guidance material that address loss of lubrication from pressure lubricated gearboxes and are the subject of TSB recommendations A11-02 and A11-02.

Specialists from all three national civil airworthiness authorities (CAAs) have arrived at a common recommendation maintaining a harmonized airworthiness framework. This report states the findings of the JCT which are to be provided to the FAA, EASA and TCCA management for their consideration.

Regarding loss of oil endurance capability, the current loss-of-lubrication test requirement for MGB of a transport category rotorcraft sets a minimum objective for the applicant to demonstrate a minimum of 30 minutes of safe operation for Category A rotorcraft. FAA Advisory Circular (AC) AC29-2C provides guidance on failures of interest in the oil system sub-components (see section AC29.927A). This AC is referenced by all three CAAs as acceptable guidance; however, it does not provide guidance on application of the “extremely remote” failure criteria.

The JCT have examined the adequacy of these regulations, including the provision of the “extremely remote” criteria in the standard, and provided recommendations for revising 14 CFR § 29.927(c) and the related AC material. These recommendations identify the need to clarify the application of “extremely remote” and the failure conditions that must be considered when performing loss-of-lubrication tests.

JCT Recommendations:

This report to the FAA, EASA and TCCA management presents recommendations for harmonized action to improve the design standards and guidance material, or elsewhere, which address the safety risk associated with loss of oil from pressure lubricated gearboxes. These recommendations address gaps identified between the existing requirements, clarification of the intent of the rule and redefinition of test requirements to meet the safety standard. This final report also provides technical justification to support those recommendations.

General Recommendation:

An FAA Advisory Rulemaking Committee (ARC), or European equivalent should be formed with multi-lateral CAA participation and/or a multi-lateral CAA working group (WG) which will consider the subject of loss of oil as follows:

1. Consider further technical detail in requirements
2. Include helicopter design and manufacturing industry representation
3. Consider rule changes at the 14 CFR part 29/CS-29/ AWM 529 level
4. Consider impact on other categories
5. Consider impact on operating rules and emergency procedures

The JCT is of the opinion that the scope of this rulemaking activity should only be applicable to new Part 29 Cat A helicopter types (i.e. not applicable to variants unless considered to be a “significant change”). Though TSB recommendation A11-02 applies to “all newly constructed Category A transport helicopters and, after a phase-in period for all existing ones”, the JCT believe that once the certification basis for an aircraft type is set, and the type approval has been granted the certification basis should remain fixed. If subsequently an unsafe condition is found to exist this should be addressed using the continued operational safety or continued airworthiness procedures of the NAA of the state of design. These procedures usually require any unsafe condition to be managed using one or more Airworthiness Directives (ADs). Accordingly an AD will not change the design standards applied to the aircraft, but can mandate a design change to restore the level of safety to that envisioned by the requirements defined in the certification basis.

The specific recommendations made below are the current opinion of the JCT but may be subject to change after review by an ARC.

Note 1: Near-term action (pre-ARC review) - AC stand-alone changes have already been pursued, independent of 14 CFR part. (FAA AC was published and posted in the FAA Regulatory Guidance Library (RGL) internet website in July2012.)

Note 2: ARC review will include an initial feasibility study.

Recommendations Relating to Title 14 Code of Federal Regulations Part 29.927(c) and Advisory Circular

Recommendation 1: All part 29 Cat A new types (i.e. not applicable to variants unless 21.101 significant change) should comply with a loss of oil test and "extremely remote" should be removed from the requirement.

Recommendation 1.1: Interim position to issue revised AC to clarify intent of 29.927(c) Amdt 26. Accordingly, FAA, TC and EASA should continue to progress the draft revision of the loss of lubrication guidance material that is currently in work for AC 29.927 and publication of the material prior to the end of calendar year 2012.

Note: Since drafting this recommendation FAA AC has been published and posted in the FAA RGL internet website in July 2012.

Supporting Rationale: The AC revision provides an explanation of the phrase “unless such failures are extremely remote” as used in the context of 14 CFA § 29.927(c)(1 ). The explanation brings to attention that unforeseen variables and complexity associated with predicting potential failure modes and their associated criticality and frequency of occurrence make it challenging to employ the “extremely remote” concept.

Recommendation 1.2: Propose a new amendment to AWM 29.927(c), 14 CFR § 29.927(c), and CS 29.927(c) as a test requirement, similar in format to that of 29.923 and 29.927(b). This will require the creation of an aviation authorities and industry working group (ARC). This group should consider removal of the term “extremely remote” and rewriting the requirement to become a prescriptive “oil out” durability test of the rotor drive system gearboxes used on Category A rotorcraft. The JCT recommends that this test be of a duration to be agreed by the ARC group but in any case not less than 30 minutes. The test should prescribe the torque(s) and rotational speed(s) that must be applied to the rotor drive system. The type of operation, such as search and rescue, human external cargo, emergency medical systems, and the operating environment, i.e., hostile terrain, over water, etc., should also be considered when determining the appropriate test duration, torque(s), and rotational speed(s). At a minimum, the torque and rotational speed-should not be less than that required to maintain continued level flight at maximum takeoff gross weight (applicant may elect to consider some adjustment to gross weight as a result of fuel burn). On completion of the test, the test results and the duration of the test should be taken into consideration when developing the appropriate emergency procedures in the rotorcraft flight manual for loss of lubrication.

Supporting Rationale: The 29.927(c) 30 minute loss of lubrication regulatory requirement was always intended as a test requirement to ensure that the rotor drive gearbox designs used on Category A rotorcraft are capable of operating safely for an extended period of time under various operating conditions following a loss of lubrication to the rotor drive gearboxes. The opportunity to extend the period of operation following a loss of lubrication was deemed essential in order to increase the eventual landing opportunities that are available to the flight crew.

Recommendation 2: Ideally a new 29.927(c) requirement should define a test which can justify confidence that 30 minutes of continued flight would be probable. This test data could be used to allow emergency operation up to 30 minutes in flight manual emergency procedures. This will be a subject for review by the ARC group and any determination on this subject should be made in association with each Authority's flight test department. The JCT believe that this would be consistent with the intention of 29.927(c) amendment 26 text which requires 30 minutes of continued safe operation in service to be shown by test.

Note: The JCT consider that operation of an independent auxiliary lubrication system to achieve this duration would be acceptable.

Recommendation 3: Propose a change to AC 29.927(c) to state the method for draining oil from the gearbox.

Note: Since drafting this recommendation FAA AC has been published and posted in the FAA RGL internet website in July 2012. This describes that the method for draining oil should be determined by identifying and simulating the worst-case oil leak.

Recommendations Relating to AC Sections 29.917

Recommendation 4: In conjunction with the JCT's review of the current 29;927(c} regulatory requirements and associated guidance material, the team found it necessary to review the rotor drive system related guidance material in AC 29 . 917 and, as a result, makes the following additional recommendation to the CMT:

Lubrication system design should be subject to a drive system design assessment to assess failures in the lubrication system. Accordingly, JCT recommends revising the guidance material in AC 29.917 to include the rotor drive lubrication system as part of the rotor drive system and therefore include lubrication system failures in the rotor drive system design assessment. Under the 29.917(b) rotor drive system design assessment requirement, a failure analysis would be required to identify all lubrication failures that will prevent continued safe flight or safe landing. Consideration should be given to extending the AC to provide specific advice for the assessment of lubrication system reliability in addition to minimizing the likelihood of individual lubrication system failure modes;

Supporting Rationale: The lubrication system is an integral part of the rotor drive system and is necessary to achieve continued safe operation of the rotor drive system.

Current Status:

The JCT recommendations fit into near and far term strategies. Some of the near-term strategies, such as revising AC 29.927 have already been accomplished. Further revisions will be required as other changes are implemented; however, these initial steps begin to address some of the weaknesses identified by the JCT.

Next Steps:

The JCT members recommend to the FAA, EASA and TCCA management that these recommendations be endorsed and initiated in a timely fashion.

Respectfully,

Joint Cooperation Team

For Recommendation A11-02, the TSB requested that “The Federal Aviation Administration assess the adequacy of the 30 minute main gearbox run dry requirement for Category A transport helicopters.” In the Report of the Joint Cooperation Team (JCT) on the Review of Helicopter Main Gearbox Certification Requirements for TCCA/FAA/EASA, the JCT recommends rewriting the requirement to become a prescriptive “oil out” durability test of the rotor drive system gearboxes used on Category A rotorcraft. This test should be of a duration to be agreed by the Advisory Rulemaking Committee (ARC) group, but in any case, not less than 30 minutes.

Notwithstanding the FAA's position that this recommendation is closed, the TSB will require confirmation of actions the FAA will take in response to the JCT recommendations regarding the rotor drive system gearboxes used on Category A rotorcraft.

Therefore, the response is considered Satisfactory Intent.

On 19 November 2014, in response to the annual TSB request for information update regarding the status of Recommendation A11-02, the FAA forwarded the following message with a copy of the FAA's response from the previous year (dated 14 November 2013) attached.

“Thank you for providing us with the Transport Safety Board of Canada's Annual Reassessment of Active Aviation Recommendations for year 2014/2015. Your recommendations in question A11-02, A11-01, A06-10 and A06-09 have been addressed in last year's FAA response to your annual reassessment and were considered closed, with no further action planned by the FAA.

Please let me know if you have any new information regarding recommendations A11-02, A11-01, A06-10 and A-06-09, that would require reconsideration.”