BA2011-120-4P-1 A Investigations revealed that the emergency procedure (air conditioning smoke) did not direct the flight crew's decision making on how to remove smoke from the cockpit and cabin if smoke persisted. Comparing to similar aircraft types (Saab 340, Fokker 50 and Dash 8), differences were noted and it was found that the ATR smoke emergency procedures seemed not to be sufficient if smoke was persisting and cockpit/passenger cabin ventilation was required.

Although in the serious incidents on subject this finding was not considered as a contributing factor, however, whether or not a similar incident takes place shortly after takeoff or at any altitude, no ATR smoke removal emergency procedure seemed to be at the disposal of a flight crew. For that reason, the signing investigation authorities regarded this finding as a flight safety issue, which needed further consideration.

TSB recommends to EASA to review the emergency procedures on ATR aircraft in order to ensure efficient removal of persisting smoke and appropriate cockpit/passenger cabin ventilation.
The IC believes that the acceptance and implementation of the recommendation would enable the ATR crews to react to future cases more effectively – following proper guidance and training - when smoke is persisting and cockpit/passenger cabin ventilation is required.

BA2011-120-4P-2 A Fatigue failure of PT1 rotor blade was found a recurrent failure on this engine, with a total of at least 28 events already due to this root cause in the timeframe 2005-2011, with a peak in 2008-2009. As a consequence, in April 2008 the engine manufacturer improved the X-Ray inspection on the new blades by introducing an additional view specifically to be taken in the area of interest (core pocket). In addition, all retained X-Ray films were reviewed and 68 blades were limited in terms of service life in accordance with SB 21766.

Furthermore, a previous recommendation was issued in 2010 by ASC-Taiwan as a result of a similar event occurred during take-off at Magong airport on 11 Feb 2009, requiring "to incorporate measures to efficiently detect the shrinkage porosity which beyond maximum allowable limits".

However, the recurrence of the failure in a wide range of accumulated cycles/flight hours shows that time to rupture cannot be predicted and it is mainly dependant on the size of the original shrinkage porosity. So, all other blades currently in service could be potentially affected by the same kind of deferred fatigue failure when a defect, not revealed at the first and only check for blades manufactured before 2007 or not detected at the second check in case of blades manufactured between 2007 and 2008, is big enough to propagate a crack.

TSB recommends to Transport Canada to consider the need to early withdraw from service the PT1 rotor blades manufactured before the introduction of NDT improvement or, alternatively, to urgently introduce a one shot X-Ray inspection on all those blades having accumulated a number of cycles beyond a limit to be established (e.g. 2000), specifically focused on the pocket area to exclude the presence of a fatigue crack.
The IC believes that the acceptance and implementation of the recommendation would reduce the risk of similar or more serious occurrences caused by turbine blades that carry hidden core pocket area deficiencies large enough to allow for crack development.

BA2011-120-4P-3A One more fatigue breakage was observed on new PT1 blades manufactured after implementing the improved X-Ray inspection, although at the moment they only have accumulated a limited number of cycles. In effect, in absence of a robust POD (Probability of Detection) study and with no knowledge of the minimum casting defect able to promote the crack growth, it seems there is still some uncertainty on the effective improvement achieved in terms of reliability of the parts.

The significant increase in rejection rate at production, being only limited to 2011, at the moment cannot be considered as a proof of the effectiveness of the modifications introduced since 2008.

Taking into account the high volume of PT1 rotor blade production, TSB recommends to Transport Canada to consider the opportunity to introduce in production, at least as a temporary measure, an additional Computed Tomography check on a representative sample of blades in order to gain confidence on the effective improvement achieved through the review of the X-Ray methodology implemented in 2008.
The IC believes that the acceptance and implementation of the recommendation would allow for a statistical proof for (or against) the effectivity of the improved X-ray procedure.

BA2011-120-4P-4 A All events were due to a severe mechanical damage and occurred at initial climb, although not necessarily immediately recognized as such by the crews and treated as an in-flight fire at a following stage.
The investigation highlighted an uncertainty on the emergency procedure in force at the time of the event, considering the several amendments issued and ongoing on this subject.
Examination of the existing documentation, namely the EU-OPS 1.130, seems not able to clarify in mandatory terms the timeframe and the procedures to achieve the effective operator compliance on this item when the AFM modification is not accompanied by a dedicated AD.

TSB recommends to EASA to consider the need to harmonize the procedures, or to review the existing documentation as necessary, in order to establish in all cases a time limit within which to make effective in the AFM owned by operators the amendments approved by EASA.

The IC believes that the acceptance and implementation of the recommendation would make it easier for the operators to track changes in air operating manuals.

BA2011-120-4P-5A ATR AFM Temporary Revision of the "engine fire at take-off" emergency procedure approved in Nov. 2011 introduced a large number of further memory items.
The increasing number of memory items seems to reflect a general trend in the implementation or review of the emergency procedures; however, it seems highly desirable that a careful consideration take place on the potential negative effects of the consequent build-up of the crew workload.
In this case, in addition to a delay of the shutoff action on the affected engine, it may potentially cause an area of hazard taking into consideration the criticality of the phase of flight.

TSB recommends to EASA to promote an internal debate (e.g.: dedicated working group, workshop, etc.) to carefully evaluate the pros and cons of a continuously increasing of memory items introduced in the implementation or review of the emergency procedure, mainly when to be applied in a critical phase of flight.

The IC believes that the acceptance and implementation of the recommendation would result in emergency procedures with optimized „memory items” as far as their number and complexity are concerned, especially in chapters relevant for the critical phases of flight.

BA2011-120-4P-6 The IC determined during the investigation that the cabin crew was not able to use the Passenger Address (PA) system during the preparation to emergency landing, the landing and the evacuation while it would have been necessary to calm down the passengers and to pass instructions. The PA system was blocked when a cabin crew member tried to call the cockpit by pressing the „EMER” button but received no reply. The blocking could have been released by replacing the handset back to its holder.
TSB recommends to EASA to consider a modification of the Passenger Address system on ATR aircraft and all other aircraft equipped with similar passenger address systems that it allows release of „EMER” blocking with the PA button (situated next to the „EMER” button) or in other suitable way.

As a temporary measure until the above recommendation is implemented, TSB recommends to EASA to apply changes in the Cabin Crew Operating Manuals of the affected aircraft types in order to direct the attention of cabin crew members with more emphasis to the possibility of PA blocking release by replacing the handset back to its holder.

The IC believes that the acceptance and implementation of the recommendation would ensure enhanced robustness of PA system fuctioning on ATR cabin and, as a result, cabin crews would be able to handle emergency situations more effectively.