Aviation Recommendation A11-01

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Assessment of the Responses to Aviation Safety Recommendation A11–01

Main Gearbox Certification Extremely Remote Provision

Background

On 12 March 2009, at 0917 Newfoundland and Labrador Daylight Time, a Cougar Helicopters' Sikorsky S-92A (registration C-GZCH, serial number 920048), operated as Cougar 91 (CH191), departed St. John's International Airport, Newfoundland and Labrador, with 16 passengers and 2 flight crew, to the Hibernia oil production platform. At approximately 0945, 13 minutes after levelling off at a flight-planned altitude of 9000 feet above sea level (asl), a main gearbox (MGB) oil pressure warning light illuminated. The helicopter was about 54 nautical miles (nm) from the St. John's International Airport. The flight crew declared an emergency, began a descent to 800 feet asl, and diverted back towards St. John's. At 0955, approximately 35 nm from St. John's, the crew reported that they were ditching. Less than 1 minute later, the helicopter struck the water in a slight right-bank, nose-high attitude, with low speed and a high rate of descent. The fuselage was severely compromised and sank quickly in 169 metres of water. One passenger survived with serious injuries and was rescued approximately 1 hour and 20 minutes after the accident. The other 17 occupants of the helicopter died of drowning.

The Board concluded its investigation and released report A09A0016 on 09 February 2011.

Board Recommendation A11-01 (09 February 2011)

The last major update of rotorcraft airworthiness standards took place in the 1980s. This update flowed from the phenomenal growth of the rotorcraft industry and the recognition by the U.S. government and industry that existing certification rules had been outdated by rapidly advancing rotorcraft technology. The rules specifically recognized the need for a high level of safety in the design requirements for rotorcraft.

The update of the design requirements for large, multiengine transport rotorcraft (Category A) recognized the need for MGB to have a significant capacity to operate following a loss of lubricant in order to optimize eventual landing opportunities. This consideration led directly to the introduction of the 30 minute requirement to operate after a loss of MGB lubricant. However the introduction of the “extremely remote” concept following the comment phase of the rule-making made it possible for a helicopter to be certified without being capable of operating for 30 minutes with only residual lubricant. Category A rotorcraft certified under the “extremely remote” criteria may not be capable of continued operation for 30 minutes with only residual lubrication. These helicopters remain vulnerable to gearbox failures stemming from unforeseen massive losses of MGB lubricant, placing passengers and crew at risk.

Therefore, the Board recommends that:

The Federal Aviation Administration, Transport Canada and the European Aviation Safety Agency remove the “extremely remote” provision from the rule requiring 30 minutes of safe operation following the loss of main gearbox lubricant for all newly constructed Category A transport helicopters and, after a phase-in period, for all existing ones.

A11-01

The Federal Aviation Administration's response to A11-01 (28 April 2011)

In its response, the Federal Aviation Administration (FAA) indicated that:

“Currently, 14 CFR 29.927(c) (effective Amendment 29-26) requires that the MGB must be tested to run satisfactorily for at least 30 minutes with a loss of lubricating oil, unless a lubrication failure resulting in a loss of lubrication is determined to be ‘extremely remote'.

All transport Category A helicopters certified (under this rule), including the Sikorsky Model S‑92A, have met the 30 minute ‘loss of lubrication' requirement. The Model S‑92A MGB used an oil cooler bypass valve to meet this requirement by eliminating the most likely sources of leakage, which are the cooler and external lines and fittings. Events that have occurred during the operational use of the Model S-92A, such as the MGB oil filter bowl failure associated with the S‑92 Cougar accident, have shown that certain failures not considered during certification testing are more likely than ‘extremely remote'. The service history therefore does not support the method of compliance that was originally accepted by the FAA at the time of the Model S‑92A type certification. Because of this very tragic and regrettable experience, the FAA will propose a rule change to either clarify or eliminate the ‘extremely remote' provision in this regulation. In the interim, the FAA will revise the guidance material associated with the rule to prevent confusion and to achieve a more robust and standardized method of compliance with the loss of lubrication requirements.”

The FAA is participating in a coordinated formal review of the rules related to the ‘extremely remote' provision and the 30 minute requirement, with Transport Canada (TC) and the European Aviation Safety Agency (EASA).

It added:

“The FAA does not believe it is practical or necessary to require that all existing and newly- manufactured transport Category A helicopters be equipped with MGBs that meet the 30-minute ‘loss of lubrication' requirement under 14 CFR 29.927(c), (Amendment 29-26). The cumulative flight hours on these helicopters are well into the millions, and their service history supports that they are operating at a satisfactory level of safety. Furthermore, modifying these helicopters to be equipped with new MGBs would have a significant economic impact on the aviation community, and the costs would outweigh any improvements in safety.”

Transport Canada's response to A11-01 (06 June 2011)

Transport Canada's response indicated that:

“Transport Canada (TC) has initiated, through a meeting in June (2011), a coordinated formal review with the Federal Aviation Administration (FAA) and 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.

While the recommendation to assess the complete loss of lubricant in Category A helicopters is not directed to TC (A11-02), it deals with the same part of the rules and will form part of the review. Any amendments to the airworthiness rules would follow the regulatory process in each jurisdiction.

TC is accelerating a review of the guidance material relating to the application of standards referred to in these recommendations to identify, by early fall of 2011, additional direction or clarification for the Canadian certification of Category A helicopters.”

In addition, the newly appointed Minister of Transport indicated that he has instructed officials to modify the consultation process to accelerate the action required as a result of the recommendations contained in this report.

The European Aviation Safety Agency's response to A11-01 (10 June 2011)

EASA's response, dated 22 March 2011 was provided to the TSB on 10 June 2011. In its response, EASA acknowledges receipt of Recommendation A11-01 and indicates that the issue is under investigation and a review of the certification guidance material is on-going with the FAA and TC. EASA will keep the recommendation open until a final opinion is published. The conclusion will be provided to the TSB.

TSB assessment of the Federal Aviation Administration's response

The FAA has indicated that it will propose a rule change to either clarify or eliminate the “extremely remote” provision in this regulation. This statement acknowledges the deficiency. In addition, one proposed course of action, eliminating the “extremely remote” provision, follows A11-01's recommended course of action. However, no timeframe to complete this process is specified. The FAA has proposed action which, if implemented in full, will substantially reduce or eliminate the deficiency for newly certified Category A helicopters.

The review of the certification guidance material initiated by the FAA, TC and EASA may result in changes in the application of the rules related to the ‘‘extremely remote'' provision and the 30 minute requirement for newly certified Category A helicopters.

However, the FAA goes on to say, it “does not believe it is practical or necessary to require that all existing and newly- manufactured transport Category A helicopters be equipped with MGBs that meet the 30-minute ‘loss of lubrication' requirement under 14 CFR 29.927(c), (Amendment 29-26)”. This suggests that Sikorsky, having already certified the S-92A under the existing “extremely remote” criteria, may not be required to redesign and refit its S-92A MGB, which would not be in keeping with the Board's recommendation. The Board will be seeking clarification from the FAA on this point.

Assessment of Transport Canada's response

In its response, TC did not indicate that it was in agreement with the recommendation. However, it indicated that, following a formal review of the rules with the FAA and EASA, there may be a need to change the rules related to the ‘‘extremely remote'' provision and the 30 minute requirement. This is a logical step considering the certification rules are harmonized between the 3 regulatory bodies.

TC has also indicated that it will accelerate the review of the guidance material relating to the application of the standards referred to in the recommendation, to identify any additional direction or clarification that might be required for the Canadian certification of Category A helicopters. TC plans on completing this review early in the fall of 2011. However, TC does not indicate that the “extremely remote” provision will be removed from the certification rules, eliminating this deficiency. Instead, it suggests that the “extremely remote” provision will remain in the meantime, with possibly additional direction and clarification being provided for its application in future certification of Category A helicopters.

There is no indication in the response as to what TC's position is on the future certification of Category A helicopters or with respect to the approximately 125 S-92A helicopters that fly today or those that will be manufactured in the coming years. Specifically, TC has not said whether it will eliminate the “extremely remote” provision nor has it said whether it will require all Category A helicopters to meet a 30 minute run dry requirement. However, TC is participating in the review of the certification requirements with the FAA and EASA which may result in changes to the rules related to the ‘‘extremely remote'' provision and the 30 minute requirement for helicopters certified in the future.

Assessment of the European Aviation Safety Agency's response

EASA's response does not indicate agreement with the identified deficiency. However, it has indicated that it is completing a review of the certification guidance material with the FAA and TC.

The review of the certification guidance material with the FAA and TC may result in changes in the application of the rules related to the ‘‘extremely remote'' provision and the 30 minute requirement.

Board assessment of the Federal Aviation Administration, Transport Canada, and the European Aviation Safety Agency's responses to A11-01 (22 June 2011)

Therefore, the responses in aggregate are assessed as Satisfactory Intent.

Next TSB action (22 June 2011)

The TSB will monitor the progress on actions taken by the FAA, TC and EASA to ensure the risks inherent in the “extremely remote” provision for Category A helicopter certification are reduced. The TSB is seeking prompt clarification from the FAA regarding its intentions with respect to the S-92A's MGB.

The Federal Aviation Administration's response to A11-01 (13 September 2011)

“This is our response to your letter dated July 25, 2011, requesting the FAA to clarify its response of April 28, 2011, on three specific matters relating to SR 11.035.

You requested a timeline for completing the regulatory review and proposal to change the loss of lubrication rule to either clarify or eliminate the ‘extremely remote' provision in this rule. The timeline to examine the adequacy of the “extremely remote” provision in Title 14 Code of Federal Regulations (CFR) 29.927(c) at Amendment 29-26 is as follows: The first meeting of the FAA, European Aviation Safety Agency (EASA), and Transport Canada Civil Aviation (TCCA) Joint Cooperation Team (JCT) is scheduled for October 4th and 5th , 2011. The JCT will report its final recommendations to the FAA/EASA/TCCA Certification Management Team during the summer of 2012. If a decision is made to change the rule and develop corresponding guidance material, many variables will influence the date for these activities to occur making it impractical to establish a completion date at this time.

You also requested a timeline for completing the revised guidance material associated with the loss of lubrication rule. We plan to complete the revised guidance material and publish it by March 2012. We have provided a draft copy of the proposed guidance material to our technical counterparts in TCCA and EASA for review and comment. We will provide TSB a copy of the final guidance material when it is completed.

In response to your statement that ‘the only Transport Category A helicopter that cannot operate safely for 30 minutes is the S-92A, which is the only Category A helicopter certified so far under the extremely remote provision,' we offer the following information. Specifically, the requirement for Category A helicopters to operate safely for 30 minutes following a loss of lubrication became effective on October 3, 1988, with the adoption of Amendment 29-26 to 14 CFR 29.927(c). In essence, any Transport Category A helicopter certified before that date was not required to comply with this amendment to the regulation. The Bell Model 222 and 412, Sikorsky Model S-76B, and Eurocopter Model BK 117B-l and AS 332L are examples of Transport Category A helicopters that were certified prior to this amendment and were not certified to operate safely for 30 minutes following a loss of lubrication.

We also would like to clarify that the certification approach used by Sikorsky for the S-92A did not invoke the provision of ‘extremely remote.' Sikorsky's use of a solenoid-activated bypass valve was considered a new method of maintaining an oil reserve to meet the 14 CFR 29.927(c)(1) loss of lubrication test requirement. The bypass valve, which is incorporated into production Model S-92A helicopters, is intended to shut off an oil leak in the oil cooler or hose system and to prevent further loss of oil from the Main Gearbox (MGB). With this configuration, Sikorsky was able to run the loss of lubrication test on the MGB for about 3 hours in ‘bypass mode.'

In response to your request for the FAA to be clear and to provide its official position, details on actions to be taken, and a corresponding timeline for implementing any actions about requiring

Sikorsky to redesign or refit its S-92A MGB with a supplementary lubrication system so it will be capable of operating for at least 30 minutes following a massive loss of MGB oil, we provide the following information. We have issued two airworthiness directives (ADs) that we believe have significantly improved the level of safety of the Model S-92A helicopters. One of the ADs requires replacing the MGB oil filter bowl with a more ‘robust' two-piece filter bowl design. The other AD requires changing the S‑92A flight manual emergency procedures to enable the crew to more easily identify a sudden ‘loss of lubrication' event and to complete the required flight crew actions without confusion or delay.

We are continuing discussions with Sikorsky regarding the potential for any additional Model S-92A MGB failure modes that could result in a loss of MGB oil. To support our evaluation, Sikorsky has provided us with an S-92A MGB hazard analysis that identifies MGB failures that could result in a loss of MGB oil condition. As a result of our review of the hazard analysis, we have requested that Sikorsky perform certain testing and further analysis to validate some of the assumptions made in the hazard analysis. Any decision on whether we will require future AD actions and any future MGB redesigns, such as a redesign of the MGB so that it will be capable of operating for at least 30 minutes following a massive loss of MGB oil, will not be made until we have completed our evaluation of the S-92 MGB hazard analysis and the requested information.

We would like to emphasize to the TSB that the AD requirements, along with the MGB design improvements made by Sikorsky in recent years, have resulted in a more reliable and robust MGB. We believe the responses we have provided in this letter are sufficient to address TSB recommendation A11‑01. The FAA will continue to investigate this matter and will take appropriate action to address any unsafe condition.”

Transport Canada's response to A11-01 (30 September 2011)

Transport Canada (TC) has initiated, through a meeting in June, 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 agreement by the three authorities on a response to the recommendation would be followed by changes to the airworthiness requirements in each jurisdiction.

Update request to European Aviation Safety Agency (21 October 2011)

On 21 October 2011 the TSB requested that EASA provide an update of its activities taken to mitigate the residual risks associated with Recommendation A11-01. No response was received.

Assessment of the Federal Aviation Administration's response to A11-01 (07 March 2012)

In its first response the FAA indicated that it would propose a rule change to either clarify or eliminate the “extremely remote” provision in this regulation. This statement acknowledged the deficiency and one proposed course of action, eliminating the “extremely remote” provision, followed A11-01's recommended course of action. However, no timeframe to complete this process was specified. At the time it was assessed that the proposed action, if fully implemented, would substantially reduce or eliminate the deficiency for newly certified Category A helicopters.

In response to a TSB request to provide a timeline for completing these actions the FAA has indicated the initial meetings are scheduled for October 2011 and the Joint Cooperation Team will provide its recommendations to the Certification Management Team during the summer of 2012. Its latest response indicates the decision to change the rule and develop corresponding guidance material will rest with the Certification Management Team and it would be impractical to establish a completion date at this time.

The FAA has indicated that the certification guidance material has been revised and is currently under review by TC and EASA with the intention of publishing it in March 2012. The new guidance material may result in a better application of the current rules related to the ‘‘extremely remote'' provision and the 30 minute requirement for newly certified Category A helicopters.

In its first response the FAA stated that it “does not believe it is practical or necessary to require that all existing and newly- manufactured transport Category A helicopters be equipped with MGBs that meet the 30-minute “loss of lubrication” requirement under 14 CFR 29.927(c), (Amendment 29-26)”. This suggested that the FAA, having already certified the S-92A under the existing “extremely remote” criteria, may not require the redesign and refit of the S-92A MGB, which would not be in keeping with the intent of the Board's recommendation.

The Board asked for clarification from the FAA on this point making it clear that the recommendation was only directed at the S-92A, the only Category A helicopter certified without a 30-minute continued flight capability since the “loss of lubricant” requirement was introduced. Although the FAA has introduced two new ADs which have improved the level of safety of S-92A helicopters these aircraft are still not capable of 30-minute continued flight capability if there is a total loss of lubricant in the MGB. The FAA has indicated that it is now waiting for the completion of a failure analysis and testing being conducted by Sikorsky before it makes any decisions on whether it will require a redesign of the MGB so that it will be capable of operating for at least 30 minutes following a massive loss of MGB oil.

Additional requests were made by the TSB between 02 November 2011 and 17 January 2012 to obtain further clarification from the FAA regarding its responses to A11-01 but no additional information was provided.

On 12 January 2012, the FAA issued a draft Advisory Circular (AC) with proposed changes to AC 29-2C, Section 29.927/927A, titled Additional Tests (Powerplant - Rotor Drive System). Comments from the public about the draft AC could be submitted to the FAA until 13 March 2012. This guidance is intended to change the advisory material in AC 29-2C, sections 29.927 and 29.927A by providing an explanation of the term “extremely remote” as used in the context of 14 CFR 29.927(C)(1) at Amendment 29-26. It also clarifies the explanation of the term “lubrication failure” as used in these AC sections for the 29.927(c) paragraphs.

Assessment of Transport Canada's response to A11-01 (07 March 2012)

TC has not yet indicated if it is in agreement with the recommendation. In addition, it has not indicated what TC's position is on the future certification of Category A helicopters or with respect to the S-92A helicopters that fly today or those that will be manufactured in the future. Specifically, TC has not indicated whether it will eliminate the “extremely remote” provision nor has it indicated whether it will require all Category A helicopters to meet a 30 minute run dry requirement. However, TC is participating in the review of the certification requirements with the FAA and EASA which may result in changes to the rules related to the ‘‘extremely remote'' provision and the 30 minute requirement for helicopters certified in the future.

Assessment of the European Aviation Safety Agency's response to A11‑01 (07 March 2012)

The TSB had requested that EASA provide an update as to the progress of its activities taken to mitigate the residual risks associated with Recommendation A11-01. No response was received.

However both the FAA and TC have indicated in their latest responses that EASA is working with them to review the rules related to the extremely remote provision and the 30 minute requirements. The review of these certification rules with the FAA and TC may result in changes in the application of the rules related to the ‘‘extremely remote'' provision and the 30 minute requirement.

Board assessment of the Federal Aviation Administration, Transport Canada, and the European Aviation Safety Agency's responses to A11-01 (07 March 2012)

The three separate regulatory bodies (FAA, TC, EASA) must work together to achieve certification harmonization. If the planned actions result in Category A helicopters being capable of 30 minutes of safe operation following a massive loss of main gearbox lubricant, then this will eliminate or substantially reduce the safety deficiency. However, the action has not been sufficiently advanced to reduce the risks to transportation safety.

Therefore, the responses in aggregate are assessed as Satisfactory Intent.

Next TSB action (07 March 2012)

The TSB will monitor the progress on actions taken by the FAA, TC and EASA to ensure the risks inherent in the “extremely remote” provision for Category A helicopter certification are reduced.

The deficiency file is assigned an Active status.

Transport Canada's response to A11-01 (04 December 2012)

“In June 2011, Transport Canada (TCCA) initiated a coordinated Joint Cooperation Team (JCT) with the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) to formally review the rules related to the ‘extremely remote' provision and the 30 minute requirements. The objective of the review was to reach agreement on what changes may be required to the rules. The JCT met twice (October 2011 and February 2012) and has drafted a set of recommendations that are being currently circulated within the respective authorities for final review and approval.

This TSB recommendation asserts that the design standard may be deficient. However, subsequent investigation has revealed that it was not a deficiency of the standard that led to the accident, but rather that the accidented (sic) rotorcraft possessed a design defect that invalidated one of the design assumptions for the main gearbox lubrication system. An airworthiness directive was issued to address the unsafe condition and restore the rotorcraft design to the level of safety implicit in its certification basis.

In parallel and in advance of approval of the JCT report, changes have been made to the related advisory circular (AC) 29-2C, specifically to clarify the application of ‘extremely remote' and the failure conditions that must be considered when performing loss-of-lubrication tests (e.g. oil lines, fittings, seal plugs, sealing gaskets, valves, pumps, oil filters, oil coolers, accessory pads, etc.). Revision pages to AC 29-2C, dated 07/06/2012, have been posted on the FAA's Regulatory Guidance Library (RGL) internet website. These changes to the AC are believed to substantially address the immediate concern raised by the TSB recommendation.

Finally, as part of an anticipated future FAA Part 27/29 ARC, a second phase of review on the design standards of 14 CFR 29.927(c) may be expected. Areas of review may include the drafting of a more prescriptive test requirement, the consideration of operating environment (e.g. availability of landing opportunities) and/or other factors in determining the appropriate information to furnish in the rotorcraft flight manual.”

FAA's response to A11-01 (27 November 2012)

“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 A11-01 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 A11-01 and A11-02 until final resolution.”

European Aviation Safety Agency's response to A11-01 (14 March 2013)

“EASA accepts that the interpretation of ‘extremely remote' in paragraph 29.927 of the rotorcraft certification specifications is ambiguous and has caused confusion in demonstrating compliance. EASA together with the Federal Aviation Administration (FAA) and Transport Canada (TCCA), are considering methods to clarify the intent.

In addition, a Joint Cooperation Team (JCT) between EASA, FAA and TCCA is being initiated under the leadership of TCCA, to undertake a detailed review of current certification standards and guidance material (Advisory Circular) relating to the certification of helicopter main gear box lubrication systems. This will include issues such as loss of lubrication, the reliability of lubrication systems, and the adequacy of the 30 minute Cat A capability. The JCT aims to be completed within 1 year and any recommendations will be considered for future rulemaking. Open.”

Board assessment of the Federal Aviation Administration, Transport Canada, and the European Aviation Safety Agency's responses to A11–01 (17 April 2013)

The Joint Cooperation Team (JCT) has completed its task of reviewing the current design standards and accompanying guidance material relating to the certification of helicopter gear boxes and its report is awaiting review and approval. It is unknown whether this review will result in the elimination of the “extremely remote” concept from the certification standard. At this time, the actions taken to date have not been sufficiently advanced to reduce the risks to transportation safety.

Therefore, the responses in aggregate are assessed as Unable to Assess.

Next TSB action (17 April 2013)

The deficiency file is assigned an Active status.