TAM A320 near Rio de Janeiro on Feb 28th 2014, loss of cabin pressure

Last Update: April 16, 2019 / 22:02:22 GMT/Zulu time

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Incident Facts

Date of incident
Feb 28, 2014

Classification
Incident

Flight number
JJ-3193

Aircraft Registration
PT-MZX

Aircraft Type
Airbus A320

ICAO Type Designator
A320

A TAM Linhas Aereas Airbus A320-200, registration PT-MZX performing flight JJ-3193 from Salvador,BA to Rio de Janeiro Galeao,RJ (Brazil) with 149 passengers and 6 crew, was descending towards Rio de Janeiro when at about FL220 the crew received indication of loss of cabin pressure, donned their oxygen masks and initiated an emergency descent. The aircraft subsequently continued to Rio de Janeiro for a safe landing about 15 minutes later.

The French BEA reported in their weekly bulletin that Brazil's CENIPA have opened an investigation into the serious incident.

On Apr 16th 2019 Brazil's CENIPA released their final report concluding the probable causes of the serious incident were:

- Material handling – undetermined.

Although the tests performed by the component manufacturer have concluded that the Skin Air Outlet Valve (FIN 22HQ) was not faulty and the leakage caused by the small flap (gap) position was considered small to cause cabin depressurization, the mentioned valve malfunction was recorded during the event and this gap was the only abnormality found in the pressurization system during the Investigation. In this context, it has not been possible to rule out the possibility that an intermittent failure in the aircraft’s pressurization system components, due to handling, storage or use under inadequate conditions has caused changes in its expected design behavior.

- Aircraft maintenance – undetermined.

It was not possible to rule out the possibility that a transitory change in the functioning of the components of the pressurization system occurred due to some inadequacy of the maintenance services performed on the aircraft, preventive or corrective.

- Decision-Making Process – undetermined.

A misinterpretation of the checklist writing may have prompted crewmembers to switch the CAB PR MODE SEL to MAN position and MAN V/S CTL to FULL UP before the aircraft was below FL100/MEA, which caused the cabin pressure to be lost by manually opening Outflow Valve.

- Support Systems – undetermined.

It was not possible to discard the hypothesis that the pilots moved the CAB PR MODE SEL to the MAN position and the MAN V/S CTL to FULL UP before the aircraft was below the FL100/ MEA, due to an inadequate checklist provided for crewmembers to perform their duties, since it did not emphasize the need to reach FL100/MEA before proceeding with the next action.

CENIPA reported the aircraft was about 20 minutes prior to estimated landing when during the descent towards destination a problem with the aircraft pressurization occurred, the passenger oxygen masks were automatically released, the crew performed an emergency descent.

CENIPA analysed:

The data recorded in the PFR registered the message SKIN AIR OUTLET V 22HQ at 1748 (UTC), time of takeoff. However, this message was inhibited because the aircraft was in Phase 05-LIFT OFF. Inhibition of messages on takeoff (Phase 05-LIFT OFF) only occurs up to 1,500ft, which the plane reaches in a few minutes.

Therefore, if the failure was not intermittent (it remained manifesting), the message would appear on the pilots' display and would require a consultation procedure to checklist and carry out actions associated with the failure. However, as the failure was intermittent, the pilots proceeded on the climb normally.

The aircraft surpassed 1,500ft in height and entered Phase 06-CRUISE. No messages were recorded by PFR within 25 minutes. It is noteworthy that in this phase of the flight (Phase 06) the messages were no longer inhibited by the system.

At 1813 (UTC), the PFR recorded the message VENT SKIN VALVE FAULT. With the appearance of the message, the pilots took the pressurizing system to the OVRD condition, according to the checklist. This action caused the message to be suppressed.

A minute later, at 1814 (UTC), the message VENT BLOWER FAULT appeared. For this message, no associated actions appeared in the ECAM, since the pilots had already placed the system in OVRD.

Starting at 1907 (UTC), a series of messages associated with the system appeared and emergency descent procedures emerged in ECAM.

The pilots began an emergency descent following the procedures provided in the checklist.

The data recorded in the PFR showed that the aircraft presented intermittent problems associated with the pressurizing system from the moment of take-off. The intermittent nature of the problems in the system explains the time gap between messages recorded by the PFR.
Tests performed on Skin Air Outlet Valve found that the small flap did not close completely when the valve was electrically driven, leaving a gap of 1 to 2 millimeters. However, the leakage caused by the small flap opening was considered small.

Numerous attempts were made to try to reproduce a depressurization event, but all of them were unsuccessful. Thus, it was not possible to establish a direct relationship between the presence of the gap and the depressurization of the aircraft.

Despite this, the PFR recorded message history relates to an intermittent Skin Air Outlet Valve failure condition, which may establish an indirect relationship between the operational condition of the component and the depressurization of the aircraft.

The registration of the message CAB PR EXCESS CAB ALT, associated to the fact that the oxygen masks were activated automatically, showed that cabin altitude exceeded the 9,550ft limit. Therefore, there was depressurization of the aircraft.

The cabin depressurization occurred during the descent procedure, while the pilots performed the steps described below under the IF UNSUCCESFULL inscription of the checklist when the aircraft crossed approximately 20,000ft.

The steps of the procedure contained the following items:

IF UNSUCCESSFULL
- MAX FL 100/MEA
- CAB PR MODE SEL MAN
- MAN V/S CTL FULL UP

The aircraft is manually depressurized.

It may take 10s in manual mode before the crew notices a change of the outflow valve position.

The description of the procedure made it clear that the aircraft would be depressurized after the actions were performed.

The checklist brought the procedures in sequence but did not highlight the need to reach the MAX FL 100 / MEA before completing subsequent items. In this way, it is possible to assume that a crew, when starting a descent for the FL100, continued to perform the actions prevised in the checklist, taking the CAB PR MODE SEL to MAN and the MAN V / S CTL to FULL UP.

This action would force the Outflow Valve to the fully open position, causing the aircraft to depressurize, and if the depressurization occurred at an altitude above the threshold limit of the oxygen masks, they would automatically fall off.

All items in the checklist were performed by pilots, including moving the CAB PR MODE SEL to MAN.

However, since the CVR data were not preserved, it was not possible to retrieve the dialogues between the pilots at the time of the procedure. Therefore, it was not possible to determine if the cabin depressurization occurred at the exact moment when the crew performed the checklist actions, in particular the movement of the CAB PR MODE SEL to MAN and the MAN V / S CTL to FULL UP.

The tests performed on the Skin Air Outlet Valve failed to establish a relationship between the existing gap and the depressurization on the aircraft. However, the actions of the pilots, by performing the checklist procedures without waiting for the FL100 arrival, contributed to the loss of pressure inside the cabin.

In this context, it is possible that an intermittent failure in the components of the aircraft pressurizing system due to handling, storage or use under inadequate conditions has caused changes in its intended design behavior, contributing to the depressurization of the aircraft in flight.

Also, a misinterpretation of the wording of the checklist may have led the crew to choose to move the CAB PR MODE SEL to the MAN position and the MAN V / S CTL to FULL UP before the aircraft was below FL100 / MEA, which caused the loss of pressure of the cabin through the manual opening of Outflow Valve, characterizing a possible inadequacy of the material (checklist) available for the crew to perform their functions.
Incident Facts

Date of incident
Feb 28, 2014

Classification
Incident

Flight number
JJ-3193

Aircraft Registration
PT-MZX

Aircraft Type
Airbus A320

ICAO Type Designator
A320

This article is published under license from Avherald.com. © of text by Avherald.com.
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