Sterna A30B at Recife on Oct 21st 2016, nose gear collapse and runway excursion on landing, right engine in reverse, left at maximum takeoff on landing
Last Update: September 25, 2021 / 18:10:09 GMT/Zulu time
Incident Facts
Date of incident
Oct 21, 2016
Classification
Accident
Airline
Sterna Linhas Aereas
Departure
Sao Paulo Guarulhos, Brazil
Destination
Recife, Brazil
Aircraft Registration
PR-STN
Aircraft Type
Airbus A300
ICAO Type Designator
A30B
Airport ICAO Code
SBRF
The crew deployed the L1 slide, the slide inflated but detached from the aircraft before the crew could vacate the aircraft, the crew subsequently left the aircraft via ladders.
The runway was closed for about 2 hours as result of the occurrence.
On Oct 27th 2016 Brazil's CENIPA reported the crew lost control of the aircraft during the landing roll, the aircraft veered off the right side of the runway as result. An investigation is underway.
In 2021 Brazil's CENIPA released their final report concluding the probable causes of the accident were:
- Control skills – undetermined.
Inadequate use of aircraft controls, particularly as regards the mode of operation of the Autothrottle in use and the non-reduction of the IDLE power levers at touch down, may have led to a conflict between pilots when performing the landing and the automation logic active during approach. In addition, the use of only one reverse (on the right engine) and placing the left throttle lever at maximum takeoff power resulted in an asymmetric thrust that contributed to the loss of control on the ground.
- Attitude – undetermined.
The adoption of practices different from the aircraft manual denoted an attitude of noncompliance with the procedures provided, which contributed to put the equipment in an unexpected condition: non-automatic opening of ground spoilers and asymmetric thrust of the engines. These factors required additional pilot intervention (hand control), which may have made it difficult to manage the circumstances that followed the touch and led to the runway excursion.
- Crew Resource Management – a contributor.
The involvement of the PM in commanding the aircraft during the events leading up to the runway excursion to the detriment of its primary responsibility, which would be to monitor systems and assist the PF in conducting the flight, characterized an inefficiency in harnessing the human resources available for the airplane operation. Thus, the improper management of the tasks assigned to each crewmember and the non-observance of the CRM principles delayed the identification of the root cause of the aircraft abnormal behavior.
- Organizational culture – a contributor.
The reliance on the crew's technical capacity, based on their previous aviation experience, has fostered an informal organizational environment. This informality contributed to the adoption of practices that differed from the anticipated procedures regarding the management and operation of the aircraft. This not compliance with the procedures highlights a lack of safety culture, as lessons learnt from previous similar accidents (such as those in Irkutsk and Congonhas involving landing using only one reverse and pushing the thrust levers forward), have apparently not been taken into account at the airline level.
- Piloting judgment – undetermined.
The habit of not reducing the throttle lever to the IDLE position when passing at 20ft diverged from the procedures contained in the aircraft-operating manual and prevented the automatic opening of ground spoilers. It is possible that the consequences of this adaptation of the procedure related to the operation of the airplane were not adequately evaluated, which made it difficult to understand and manage the condition experienced.
- Perception – a contributor.
Failure to perceive the position of the left lever denoted a lowering of the crew's situational awareness, as it apparently only realized the real cause of the aircraft yaw when the runway excursion was already underway.
- Decision-making process – a contributor.
An inaccurate assessment of the causes that would justify the behavior of the aircraft during the landing resulted in a delay in the application of the necessary power reduction procedure, that is, repositioning the left engine power lever.
The CENIPA analysed:
Under these circumstances, although this fact apparently did not contribute to the accident in question, the lack of record of the plane's irregularities in the logbook indicated a failure in the company's technical maintenance management processes, which prevented effective control about the airworthiness condition of the aircraft.
According to data recorded by the FDR, at 500 feet, indicated by the Radio Altimeter (RA), the aircraft was in stabilized approach, with the autopilot engaged and set for landing.
The crew was aware that, on previous flights, the left reverser had presented problems and, as a result, chose to perform the landing using only the one on the right. This is a nonrespect of the Standard Operating Procedures, which should have been monitored and detected by the Flight Data Analysis department.
Although the SBRF METAR indicated that the landing would be made with a left crosswind, its intensity was of only 7kt, which would not imply extreme difficulty in controlling the aircraft.
Tests conducted on the brake components and directional systems led to the conclusion that they did not show any evidence of abnormalities that could have contributed to the loss of control in the landing run.
Based on the laboratory tests performed, it was concluded that the fractures observed on the nose landing gear occurred due to overload. Thus, its collapse probably occurred because of the effort due to misalignment in relation to the displacement of the aircraft, aggravated by the entry of the plane on soft ground. The breaking of this component possibly resulted in the pitch being reduced to -9.6°.
Thus, the hypothesis that a mechanical failure has contributed to this accident has been ruled out.
On the other hand, movements in opposite directions of the left and right power throttles, recorded by the FDR shortly after the touch, explained the difficulty encountered by pilots in keeping the aircraft within runway limits.
Since the thrusters reacted appropriately to the position of the throttle, the thrust asymmetry produced a resultant right-turn moment that was initially countered by using the full-scale rudder, differential braking, and left steering command.
However, 24 seconds after the touchdown, as the speed decreased, which reduced the rudder's aerodynamic efficiency, and thrust asymmetry reaching its maximum value, maintaining the aircraft on the runway axis became difficult and it began a steeper turn to the right and out of the paved area.
Thus, the data recorded by the FDR led to the conclusion that the thrust asymmetry observed during almost the entire ground run was the root cause of the runway excursion.
From this finding, the investigation sought to explain how the aircraft could have come to this situation. It was initially assumed that such a discrepant condition of normal aircraft operation would probably not have been intentionally commanded by the pilots. Thus, the possibility that the Autothrottle System has accelerated the left engine has been considered.
One of the hypotheses studied was that, by activating the reverse on the right engine, the PF had inadvertently commanded one of the go levers, which would result in the Autothrottle entering in the go-around procedure mode.
However, considering the information provided by Airbus that during a go-around procedure commanded by the go levers activation, the throttle progress rate would be in the order of + 8°/sec, this hypothesis was ruled out, since the speed of the left throttle movement recorded was about + 2°/sec.
A second possibility studied was that the ATS increased power to maintain a selected speed. However, since the PF was commanding the right engine to reverse, this action would have surpassed the Autothrottle command with respect to that engine, as described in FCOM 7.03.04. According to the recorded data, the aircraft approached for landing with 132kt of speed.
Assuming the crew was using the autothrottle to maintain that speed during the final and had not disengaged it, the Speed Select Mode could still be running the engines during flare and landing, as the conditions for automatic cancellation had not been met in full, since:
- initially only the right main landing gear damper was recorded compressed;
- the AP was disengaged; and
- the power levers have not been reduced to IDLE at the 20ft (RA) intersection.
This hypothesis seemed to corroborate the fact that the left engine started to accelerate when the aircraft was with 128kt, which would be exactly the tolerance limit of the Speed Select Mode, as reported by FCOM 7.03.04.
In this scenario, it would be possible that the Autothrottle had accelerated the left engine, surprising the pilots who apparently only realized their performance when the runway excursion was already underway.
In this case, an inadequate use of the aircraft controls, particularly as regards the mode of operation of the Autothrottle in use and the non-reduction of power levers at the time of the touch down, would have led to a conflict between the pilots' intent to perform the landing and the automation logic active during the approach.
Although this was considered the strongest hypothesis to explain the sequence of events of this accident, it could not be proven, as the condition of the Autothrottle was not recorded by the FDR.
Regarding crew procedures during the landing, the habit of not reducing the throttle to the IDLE position when passing by 20ft height diverged from the procedures contained in the aircraft operation manual and prevented the automatic opening of ground spoilers, characterizing an inadequate evaluation of parameters related to aircraft operation.
This option to perform engine landings may also have been responsible for not automatically triggering the ground spoilers on a previous flight, as known to the PM, which may have led him to interpret that it was a failure and to control this equipment manually.
Thus, failure to comply with the procedures provided in the aircraft manual, contributed to placing the equipment in a condition that confused the crew, which expected the automatic trigger of the ground spoilers, which required additional pilot intervention (manual control) and may have made it difficult managing the circumstances that followed the touch.
It was not possible to record cabin crew interaction; however, it is possible that the reverser usage checklist provided in the A300 FCOM was not performed, as the left lever position was not realized until the runway excursion was imminent.
According to the statements gathered, the PM, realizing that the aircraft did not slow down and tended to exit to the right, became involved in his command and acted on the brakes and steering, leaving aside his main responsibility that would be to monitor systems and assist the PF in conducting the flight.
Such initiatives characterized an inefficiency in harnessing the human resources available to operate the airplane, particularly in relation to the management of tasks assigned to each crewmember and compliance with the principles of Crew Resource Management (CRM), and delayed the identification of the root cause of the behavior abnormality presented by the aircraft.
According to data recorded by the FDR, three seconds after the touch down, engine 1 lever was brought to maximum takeoff power and only after 34sec, during runway excursion, this lever was positioned at REV.
Given this scenario, it was possible to infer that the crew only became aware of what could be happening to the aircraft at that time. Thus, the time lapse between the airplane abnormal behavior and the action taken, indicated that there was an inaccurate assessment of the situation, in which the adverse condition was not immediately recognized by the crew.
In addition, the informality characteristic of that organizational context, as well as possible performance without the use of the checklist, may have favored a lowering of the crew's situational awareness level, which contributed to an inaccurate perception of the events experienced at that time of the flight.
Finally, the triggering of the CONFIG audio message that the crew claimed to have heard as soon as the nose landing gear hit the ground, probably occurred due to inconsistencies in the aircraft configuration at that time, as the TL1 had been advanced to MAX TAKE-OFF POWER while the flaps were at 25°, a position used for landing.
Related NOTAMs:
I0570/16 - RWY 36 FST 1200M CLSD DUE TO ACCIDENT ACFT. 21 OCT 12:47 2016 UNTIL 21 OCT 23:59 2016. CREATED: 21 OCT 12:49 2016
I0569/16 - DECLARED DIST RWY 18/36 CHANGED
TORA TODA ASDA LDA
RWY 18 1807M 1807M 1807M 1807M
RWY 36 1807M 1807M 2107M 1807M.
21 OCT 12:12 2016 UNTIL 21 OCT 23:59 2016. CREATED: 21 OCT 12:16 2016
I0568/16 - RWY 36 FST 1200M CLSD. 21 OCT 12:05 2016 UNTIL 21 OCT 23:59 2016. CREATED: 21 OCT 12:07 2016
Metars:
SBRF 211100Z 07008KT 9999 SCT022 SCT070 28/23 Q1014
SBRF 211000Z 08008KT 9999 SCT020 BKN060 28/23 Q1013
SBRF 210900Z 07007KT 9999 BKN020 SCT050 26/23 Q1012
SBRF 210800Z 07005KT 9999 SCT020 SCT050 26/23 Q1012
SBRF 210700Z 07005KT 9999 SCT020 26/23 Q1011
SBRF 210600Z 07006KT 9999 BKN020 26/22 Q1011
SBRF 210500Z 10006KT 9999 SCT020 25/23 Q1011
SBRF 210400Z 07005KT 9999 SCT020 26/23 Q1011
Incident Facts
Date of incident
Oct 21, 2016
Classification
Accident
Airline
Sterna Linhas Aereas
Departure
Sao Paulo Guarulhos, Brazil
Destination
Recife, Brazil
Aircraft Registration
PR-STN
Aircraft Type
Airbus A300
ICAO Type Designator
A30B
Airport ICAO Code
SBRF
This article is published under license from Avherald.com. © of text by Avherald.com.
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