Avianca A319 at Rio de Janeiro on Jul 19th 2017, EGPWS warning on RNAV approach
Last Update: February 21, 2019 / 22:24:49 GMT/Zulu time
Brazil's CENIPA rated the occurrence a serious incident and opened an investigation.
According to radar data the aircraft went around from below 180 feet AGL (corrected for density altitude, 125 feet standard pressure) 2.41nm before the runway threshold.
On Feb 21st 2019 Brazil's CENIPA released their final report concluding the probable causes of the serious incident were:
Control skills – a contributor.
The use of the Vertical Speed guiding mode associated with the application of an excessive descent rate contributed to the destabilization of the approach.
Attention – a contributor.
During the landing procedure, pilots did not observe relevant aspects that would indicate the destabilized approach. In addition, the copilot did not pay attention to the fact that the commander had increased the rate of descent instead of reducing it after reporting that the aircraft was too low. This inattention on the part of the crew contributed to the occurrence, as it made possible the descent of the aircraft beyond the expected parameters.
Attitude – a contributor.
Failure to comply with the procedures established in the Aerodrome approach chart contributed to the occurrence of the serious incident, as it added greater risk and greater complexity to that air operation.
Crew Resource Management – a contributor.
Although it was not possible to analyze the data of the voice recorder of the aircraft, it was evident a deficiency in the coordination of the cabin by not observing several operating procedures, such as: stabilized approach parameters, procedures for EGPWS warning of "Too Low, Terrain!", compliance with DOP 28/17, among others cited in the report.
Team dynamics – a contributor.
The interaction of the pilots during the approach and landing moments was
compromised, in view of the absence of a detailed briefing on the technique used in the approach to the landing and the work overload to which they underwent by choosing a procedure divergent from the predicted, thus favoring the continuation of the flight below the established minimum limits.
Piloting judgment – a contributor.
The evaluation of performing a dive and drive approach, based on the final approach of the SBGL RNAV Y RWY 28 procedure, proved to be inadequate, as it did not bring operational advantage to that crew, yet it did not comply with parameters and restrictions of safety.
Perception – a contributor.
The lack of precision regarding the perception of the parameters of the aircraft during the final approach resulted in the surpassing of restrictions imposed on the chart profile, indicating a lowering of the level of situational awareness presented by the crew.
Decision-making process – a contributor.
The decision to proceed with the landing approach, as well as the technique chosen to carry out this procedure, showed a precipitous and imprecise assessment of the risks involved in that type of operation.
Organizational processes – undetermined.
The excess of existing communication channels in the airline, the lack of prioritization of messages of greater operational relevance, as well as the possible difficulties in communication between the different sectors may have led to the emergence of a scenario unfavorable to the proper assimilation of operational procedures and standardization of the crew.
Support systems – undetermined.
The discrete form, such as the procedure for air operations, in case of a ceiling below the minimums presented in the approach charts, was dealt with in DOP 28/17, may have contributed to a low assimilation of the crew on the guidelines defined by the airline.
CENIPA complained that they were informed about the occurrence only 29 days after the occurrence, FDR and CVR were overwritten at that time. The investigation therefore used QAR data but had no CVR data available.
CENIPA reported the crew performed the RNAV Y aproach to runway 28 and initiated the go around below the Minimum Descent Altitude (MDA), almost simultaneously with the go around two GPWS warnings ("Too Low, Terrain!") occurred. Following the go-around the crew positioned for an ILS approach to runway 15 and landed without further incident.
On 18JUL2017, the previous day of the serious incident, LOC-ILM, which marked the ILS procedure for SBGL threshold 28, presented intermittent breakdowns that culminated in the operation removal of the aid and in the issuance of a NOTAM informing about the temporary unavailability of that locator.
So, considering that the prevailing wind at Galeão in the morning of 19JUL2017 favored the landing operation on runway 28 and that the ILS procedure for that threshold was unavailable, the procedure adopted was the RNAV Y RWY 28.
According to the pilots, a complete approach briefing was carried out, considering the execution of the RNAV procedure in the FINAL APP mode, which would allow the aircraft automatism to perform lateral and vertical navigation (LNAV / VNAV) up to 417ft DA.
In this way, the pilots configured the aircraft so that it fulfilled the slope and approach axis profiles prevised in the chart for LNAV / VNAV type operation.
In this case, the autopilot would comply with all Stepdown Fixes and the aural warning system would inform the crew when the aircraft was in the DA (“Minimum” warning) and 100ft above this altitude (“Hundred above” warning), that should have been inserted in the FMGC.
Before authorizing the commencement of the procedure for the PR-AVC crew, APPRJ had to command a series of vectors and holdings, in order to provide traffic separations, since some aircraft were not able to land on Galeão (due to meteorology) and controllers needed to safely reposition all aircraft within the terminal.
CENIPA analysed that the approach charts in Brazil provide for minimas in both ceiling as well as visbility. However, a new regulation had come into effect less than a month before the occurrence requiring towers to suspend arrivals only in case of visibility dropping below limits, but no longer suspend arrivals due to ceilings dropping below minima. Tower had announced that approaches were suspended based on ceiling however, a few minutes later realized the new regulation and announced that approaches were possible again with ceilings at 300 feet (400 feet required for the RNAV Y procedure) and 2500 meters visibility. Another aircraft performed the approach and landed successfully, tower subsequently queried O6-6284 whether they wanted to perform the approach adding that one aircraft had just landed. CENIPA wrote:
When considering this context, it is possible that the information reported by the air traffic controller has influenced the pilots’ decision, leading them to choose, possibly in an impulsive way, by the attempt to approach.
This hypothesis is reinforced by the phraseology used, in which the use of the word "then" can be considered an indication that, at that moment, the successful landing of the other aircraft consisted of one of the decision factors.
In deciding to try the procedure, the pilots no longer complied with the DOP 28/17 of the airline, which provided that, within the company, the ceiling limits still laid down in the current charters should be respected.
However, despite this guideline on the part of the company, some pilots of that airline, as identified during the investigation process did not know such information.
CENIPA continued analysis later into the approach:
As already mentioned, the pilots had previously established, in briefing, that they would carry out the procedure in the FINAL APP mode. However, shortly after passing over the final approach FIX (FAF) of the procedure, the commander selected the Vertical Speed (V/S) mode, which caused the aircraft to exit the managed/managed FINAL APP condition and operate in the managed/selected condition (in this case, with V/S connected).
When commanding the Vertical Speed mode, the commander became responsible for maintaining the aircraft slope (vertical navigation), manually controlling the desired descent rate for that approach.
The use of V/S mode was not contemplated in the company's FCOM as one of the guidelines allowed in the execution of RNAV procedures. According to the cross-reference table shown in Figure 13, the guidance modes authorized using LNAV navigation were only the FINAL APP (recommended) or NAV FPA.
When modifying the approach strategy, the crew also modified the type of procedure, which became different from the one that had been combined in a briefing, and that had already been configured in the aircraft.
With the V/S mode connected, the aircraft would no longer comply with the LNAV / VNAV approach profile to perform only the LNAV profile. Consequently, the decision altitude (DA) of 417ft would be replaced by the minimum descent altitude (MDA) of 470ft, and the crew would be responsible for meeting the intermediate descent restrictions provided in the chart (Stepdown Fixes), generating a work overload.
According to information obtained by the Investigation Team, the commander’s intention when manually commanding a descent rate using the V/S mode would be to perform the dive and drive technique, in order to achieve visual conditions in a position prior to that expected, if it kept a constant rate of descent.
However, considering the reality of the SBGL RNAV Y RWY 28 procedure, the use of the dive and drive technique would not bring any operational gain to that crew, since, firstly, the "dive" from the FAF would be restricted to altitude of 660ft in Stepdown Fix GL083.
Second, when deciding to reduce the automatism of vertical navigation, the crew consequently proceeded to perform a LNAV-only procedure. Therefore, the lowest point of the procedure was no longer a 417ft DA and became a 470ft MDA.
Thirdly, the crew caused an overload of work, by taking command of the rate of descent and compliance with the respective restrictions, whereas the same pilots could monitor the approach if the aircraft was in the managed/managed condition. Therefore, such circumstances led to a greater demand for attention and demanded high levels of situational awareness. This scenario of overloading was aggravated by the lack of a detailed briefing.
Finally, because it was a direct approach, in which the runway would be aligned with the final approach, there would be no need to establish a specific trajectory (drive) to the runway alignment.
The CENIPA analysed:
among the parameters that were not followed by the crew, it was observed in the analysis of QAR data that:
- there was a descent rate greater than 1000ft / min; and
- there was a vertical deviation (V/DEV) greater than ½ dot during the RNAV approach.
In this context, the crew should have immediately initiated a go-around procedure. However, the aircraft continued up to 295ft of barometric altitude. Thus, the decision to perform a go-around procedure, although correct, was late, since the safety limits established in the approach chart had already been exceeded.
CENIPA analysed that the crew did not initiate a GPWS escape maneouver following the two GPWS warnings "Too Low, Terrain!" and wrote:
According to what has been found, the crew reported that they did not carry out the procedures mentioned, because they interpreted it as an EGPWS caution type message and the above procedure should be used just in case of a warning message. In that context, according to the crew, the evasive maneuver should only be performed in the case of a Pull Up warning!
However, this interpretation was misleading in the light of two aspects:
1) the emergency procedure in FCOM makes clear that the maneuver should be performed in the case of EGPWS CAUTIONS and also explained the TOO LOW TERRAIN alarm, as highlighted in Figure 20; and
2) in the condition that the aircraft was, the EGPWS operated in the Terrain Clearance Floor Mode, consequently the Pull Up! warning was inhibited.
Taking into account that the go-around procedure was initiated prior to the EGPWS warning, the consequences of non-execution of the evasive maneuver provided in FCOM were not more severe.
On the other hand, the misunderstanding of the crew could have catastrophic consequences if, in another scenario, they waited for the Pull Up! warning to react according to the emergency procedure described in the manual.
CENIPA stated as last sentence of the analysis: "Failure to analyze data from voice and flight recorders may have hampered further research."
SBGL 191300Z 32005KT 7000 FEW003 SCT008 OVC013 18/15 Q1027=
SBGL 191200Z 28007KT 7000 BKN004 BKN011 17/15 Q1027 REDZ=
SBGL 191117Z 28008KT 2500 -DZ BR BKN003 OVC010 16/15 Q1027=
SBGL 191039Z 29007KT 2500 -DZ BKN008 BKN020 17/15 Q1026=
SBGL 191000Z 31005KT 7000 FEW008 BKN014 BKN020 17/15 Q1026=
SBGL 190900Z 29005KT 7000 -RA FEW005 BKN013 BKN030 17/15 Q1025=
SBGL 190800Z 29007KT 7000 -RA FEW007 BKN013 BKN030 17/15 Q1025=
This article is published under license from Avherald.com. © of text by Avherald.com.
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