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ATSB recommends mandating PW4170 engine modification after incident
6 November 2019

ATSB recommends mandating PW4170 engine modification after incident

The ATSB has issued safety recommendations to the FAA and engine manufacturer Pratt & Whitney calling for them to maximise a modification that would prevent a component failure of the PW4170 series engine which powers some Airbus A330 airliners.

The recommendations follow an ATSB investigation into a 18 January 2018 incident where a Malaysia Airlines Airbus A330-300, which was operating a scheduled passenger flight from Sydney to Kuala Lumpur, Malaysia, diverted to Alice Springs due to a malfunctioning left engine.

Subsequent disassembly and inspection of the affected engine, a Pratt & Whitney PW4170, identified that, as a result of exposure to elevated temperatures, a segment of the third stage outer transition duct (OTD) had distorted and fractured. The large fractured section caused a blockage within the engine that created turbulent airflow, partially blocking a low pressure turbine vane inlet stage and causing an increase in exhaust gas temperature. That in turn led to low pressure turbine blade failure, high vibration and compressor stall/surge events.

The ATSB investigation established that there has been a total of 16 similar events globally within the past four years, all attributed to the ‘Advantage 70’ increased thrust modification for the PW4000-100 series engine, including five involving Malaysia Airlines aircraft. The modification increased the engine outer duct gas path temperature, which led to the distortion and liberation of the outer transition duct segments.

Pratt & Whitney, which had ceased production of PW4000-100 series engines for the Airbus A330 in July 2017, has now redesigned the engine’s OTD to withstand higher temperatures. The newly designed hardware will be available for retrofit from November 2019 and service bulletins will recommend installation of the new ducts at the operator’s discretion.


International panel releases review of FAA’s Boeing 737 MAX flight control system certification process

The international team of experts convened by the FAA to review their Boeing 737 MAX Flight Control System certification process in the wake of two fatal accidents, has released its findings and recommendations.

The Joint Authorities Technical Review (JATR) consisted of technical representatives from the FAA, NASA, and civil aviation authorities from Australia, Brazil, Canada, China, Europe, Indonesia, Japan, Singapore, and the United Arab Emirates.

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NTSB issues 7 safety recommendations to FAA related to Boeing 737 MAX crash investigations

The NTSB issued seven safety recommendations to the Federal Aviation Administration (FAA) as part of their support in the investigations of two Boeing 737 MAX accidents.

The NTSB is supporting the investigation of Lion Air flight 610 that crashed in the Java Sea following a loss of control after takeoff and the crash of Ethiopian Airlines flight 302 under similar circumstances.

The seven safety recommendations issued to the FAA are derived from the NTSB’s examination of the safety assessments conducted as part of the original design of Boeing’s Maneuvering Characteristics Augmentation System (MCAS) on the 737 MAX and are issued out of the NTSB’s concern that the process needs improvement given its ongoing use in certifying current and future aircraft and system designs.

The NTSB notes in the report that it is concerned that the accident pilots’ responses to unintended MCAS operation were not consistent with the underlying assumptions about pilot recognition and response that were used for flight control system functional hazard assessments as part of the Boeing 737 MAX design.

The NTSB’s report further notes that FAA guidance allows such assumptions to be made in certification analyses without providing clear direction about the consideration of multiple, flight-deck alerts and indications in evaluating pilot recognition and response. The NTSB’s report states that more robust tools and methods need to be used for validating assumptions about pilot response to airplane failures in safety assessments developed as part of the U.S. design certification process.

The seven recommendations issued to the FAA urge action in three areas to improve flight safety:

  • Ensure system safety assessments for the 737 MAX (and other transport-category airplanes) that used certain assumptions about pilot response to uncommanded flight control inputs, consider the effect of alerts and indications on pilot response and address any gaps in design, procedures, and/or training.
  • Develop and incorporate the use of robust tools and methods for validating assumptions about pilot response to airplane failures as part of design certification.
  • Incorporate system diagnostic tools to improve the prioritization of and more clearly present failure indications to pilots to improve the timeliness and effectiveness of their response.

NTSB investigators continue to assist the KNKT and AAIB in their ongoing investigations. The NTSB has full access to information from the flight recorders, consistent with standards and recommended practices for the NTSB’s participation in foreign investigations.

The KNKT’s accident report is expected to be released in the coming months, and their analysis of the Lion Air accident may generate additional findings and recommendations.

EASA issues recommendations on explosive door openings on parked aircraft

In the wake of a fatal occurrence in Finland, the European Union Aviation Safety Agency (EASA) now issued three recommendations on explosive door openings on parked aircraft.

EASA notes that an accident involving a Gulfstream G150 in January 2018 in Finland was one of several occurrences of explosive door openings on parked aircraft, resulting in injuries, including fatalities, to persons inside or outside the aircraft. The main factor leading to these occurrences was an inadvertent development of an excessive differential pressure between the inside and the outside of the aircraft.

EASA issued a Safety Information Bulletin, recommending that:

  1. Air operators, ATOs, maintenance organisations and CAMOs identify if the risk described in this Safety Information Bulletin is present in their operations or activities, and establish procedures that reflect the associated instructions provided by the aeroplane Type Certificate Holder. Air operators ensure that all personnel involved in handling of the aeroplane (such as aircrew, aircrew instructors, maintenance, ground handling, personnel assigned to perform certain task(s) inside the cabin, etc.) are made aware of the risks and that their training and procedures include the case of explosive door opening and its prevention. Maintenance organisations and CAMOs ensure that all affected personnel are aware of the risk of explosive door opening.
  2. Aerodrome operators ensure that rescue and firefighting personnel are made aware of the risk of an explosive door opening, if their intervention is required.
  3. Other individuals that need to access the aeroplane seek the advice from the operator or the maintenance organisation in-charge before operating a door of a potentially pressurised aeroplane.

Pakistan: Maintenance lapse preceded engine failure on ATR 42 that crashed two years ago

Pakistani investigators say a maintenance lapse preceded an engine failure that led to the accident of an ATR 42 in 2016.

On December 7, 2016, Pakistan International Airlines flight 661, an ATR 42-500, was destroyed after impacting a hillside near Havelian, Pakistan. All 47 on board were killed.
The investigation board now issued two interim safety recommendations, stating that:

(a) Sequence of events was initiated with dislodging of one blade of power turbine Stage-1 (PT-1), inside engine number one (left-side engine) due to fatigue.
(b) This dislodging of one blade resulted in in-flight engine shut down and it contributed towards erratic/abnormal behavior of engine number one propeller.
(c) According to Service Bulletin these turbine blades were to be changed after completion of 10,000 hours on immediate next maintenance opportunity. The said engine was under maintenance on November 11, 2016, at that time those blades had completed 10004.1 hour (due for change). This activity should have been undertaken at that time but it was missed out by the concerned.
(d) Aircraft flew approximately ninety-three hours after the said maintenance activity before it crashed on December 7, 2016.
(e) Missing out of such an activity highlights a lapse on the part of PIA (maintenance and quality assurance) as well as a possible in-adequacy/lack of oversight by Pakistan CAA.

The following recommendations were issued:
(a) PIA is to ensure immediate implementation of said Service Bulletin in letter and spirit on the entire fleet of ATR aircraft, undertake an audit of the related areas of maintenance practices, ascertain root cause(s) for the said lapse, and adopt appropriate corrective measures to avoid recurrence.
(b) Pakistan CAA is to evaluate its oversight mechanism for its adequacy to discover lapses and intervene in a proactive manner, ascertain shortfall(s) and undertake necessary improvements.

The investigation is still ongoing.

TSB calls for adequate de-icing equipment and use at remote northern airports in Canada

The Transportation Safety Board of Canada (TSB) is making two recommendations aimed at preventing flight crews operating in remote northern areas of Canada from taking off with ice, snow and frost contamination on aircraft.

The recommendations stem from the TSB’s ongoing investigation (A17C0146) into the December 2017 collision with terrain of the West Wind Aviation ATR 42 in Fond-du-Lac, Canada.

Early in the investigation, it was determined that the crew took off from Fond-du-Lac with ice contamination on the aircraft’s critical surfaces. The operator had some de-icing equipment in the terminal building, but it was not adequate for de-icing an ATR 42.

To assess whether similar circumstances to this occurrence existed in the wider Canadian industry, the TSB sent out a questionnaire to pilots at 83 Canadian operators that fly out of remote northern airports. Over 650 responses from pilots flying a wide variety of aircraft in all northern areas were received. Preliminary analysis of the data shows that pilots frequently take off with contaminated critical surfaces. Responses also indicate that aircraft de-icing equipment is often inadequate at remote northern airports.

Many remote northern airports have an icing season of 10 months or more, and thousands of flights take off every year from these airports. The Board recommends that the Department of Transport collaborate with air operators and airport authorities to identify locations where there is inadequate de-icing and anti-icing equipment and take urgent action to ensure that the proper equipment is available to reduce the likelihood of aircraft taking off with contaminated critical surfaces. (TSB Recommendation A18-02).

The unavailability of adequate equipment increases the likelihood that pilots will conduct a takeoff in an aircraft that has ice, snow or frost adhering to any of its critical surfaces. Additionally, the questionnaire responses indicate that, in the absence of adverse consequences, taking off with contamination on critical surfaces is a deviation that has become normalized. Therefore, providing adequate de-icing and anti-icing equipment may not be sufficient to reduce the likelihood of flight crews taking off with contaminated critical surfaces. The Board recommends that the Department of Transport and air operators take action to increase compliance with Canadian Aviation Regulations subsection 602.11(2) and reduce the likelihood of aircraft taking off with contaminated critical surfaces. (TSB Recommendation A18-03).


Pitot probe covers focus of safety advisory notice for operators at Brisbane Airport, Australia

The ATSB has issued a safety advisory notice to all operators flying to Brisbane Airport, Australia, to consider the use of pitot probe covers there and to have rigorous processes in place to confirm the covers are removed before flight.

The release of the safety advisory notice comes after the publication of the ATSB’s preliminary report into an airspeed indication failure on take-off involving a Malaysia Airlines Airbus A330-300 at Brisbane Airport on 18 July 2018.

The ATSB found that local engineering support crew placed covers on the pitot probes soon after the previous landing. Inspections during the aircraft’s turnaround did not identify their fitment and they remained on the aircraft for its departure. This resulted in unusable airspeed information being displayed to the flight crew. The flight crew continued the take-off and carried out several checklists before returning to Brisbane Airport.

Several high-capacity aircraft have departed from Brisbane with one of the pitot probes blocked by insect nests in recent years, including two that resulted in rejected take-offs investigated by the ATSB.

The airport has had a wasp eradication program since 2006 and the Civil Aviation Safety Authority and Airservices Australia have issued advice about the risk they pose, with some operators now using pitot probe covers for short turnarounds.

Aircraft about to be pushed back with pitot covers in place (two of three visible)


EASA issues safety bulletin on proper ground de-icing of aircraft following several incidents

The European Aviation Safety Agency (EASA) issued a safety bulletin to remind authorities and operators that personnel involved in the process of ground de-icing of aircraft should be aware of the importance of conducting effective de-icing procedures.

The bulletin was issued in response to several incidents where improper ground de-icing of the incident aircraft was a factor. One of those incidents occurred in November 2016 when a Swedish Avro RJ100 returned to land at Gothenburg Airport after encountering severe control issues after takeoff. It was concluded that the aircraft suffered vibrations due to the unbalance of the elevator system that arose due to ice contamination. As the report states: “It is apparent from the investigation that the personnel who were to inspect the aircraft prior to the flight did not detect all ice contamination, which meant the de-icing order did not cover all of the ice contamination, and that there were shortcomings in the de-icing actually carried out.
The incident was partly caused by the fact that the operator lacked enough detailed procedures for performing a complete contamination inspection, and that the existing routine’s was not fully applied, partly by the fact that the operator had not properly checked, evaluated and controlled the subcontractor’s working methods.
A contributing factor was that the de-icing operation had insufficient organisational support to help the staff to resist requests of departure on time and to ensure that the de-icing was properly executed despite actual or experienced time shortage.”

Consequently, EASA issued four recommendations to authorities and operators:

  1. EASA recommends that air operators take note of this SIB, ensure that training of the involved personnel is conducted in accordance with the applicable procedures, and check their competency.
  2. EASA recommends that air operators allow suitable time and ensure adequate visibility conditions for the de-icing personnel to properly conduct the de-icing of the aircraft, including the post de-icing checks.
  3. EASA recommends that air operators disseminate the SIB to their contracted ground de-/anti-icing service providers and pay particular attention to the above-mentioned recommendations during their audits by checking compliance of the ground de-icing service providers with their training syllabi and operations manuals. This process should be captured through the operator’s management system.
  4. EASA recommends that NAAs pay particular attention to the above-mentioned recommendations in their oversight programmes.


EASA warns airports after incidents: dark coloured aircraft may not be recognised by parking systems

The European Aviation Safety Agency (EASA) issued a bulletin, recommending airport operators to determine if the docking systems may encounter problems in identifying aircraft due to their colour.

This recommendation was issued in the light of an incident in Lisbon, Portugal in May 2015. An Airbus A320 operated by Brussels Airlines arrived at the parking stand at Lisbon Airport but was not identified by the automatic guidance system. The Aircraft Positioning and Information System (APIS) is a laser-based technology, which identifies and guides the aircraft to stop at the correct point corresponding to the aircraft type. The APIS system did not identify the aircraft and failed to give information to the pilot to stop at the position corresponding to the type of aircraft (A320).
The aircraft stopped a few meters ahead having struck the jetbridge with the nacelle of engine # 1.

An investigation showed that the APIS system did not recognize the aircraft because of the dark color of its painting. The aircraft carried a special Tintin colour scheme.

EASA states that Brussels Airlines after this occurrence, found that similar occurrences have happened around the world.



FAA issues safety alert on procedures for addressing odors, smoke and/or fumes in flight

The U.S. Federal Aviation Administration (FAA) issued a Safety Alert for Operators (SAFO) bulletin on procedures for addressing odors, smoke and/or fumes in flight.

The SAFO highlights the need to enhance flight crew procedures that mitigate the risk to passengers and crew in the event of odors, smoke and/or fumes.

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