Gol B738 at Brasilia on Apr 9th 2018, takeoff with landed aircraft still on runway
Last Update: May 10, 2020 / 18:00:22 GMT/Zulu time
Incident Facts
Date of incident
Apr 9, 2018
Classification
Incident
Airline
Gol Transportes Aereos
Flight number
G3-1732
Departure
Brasilia, Brazil
Destination
Sao Luis, Brazil
Aircraft Registration
PR-GTN
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
Brazil's CENIPA rated the occurrence a serious incident and opened an investigation.
On Apr 13th 2018 The Aviation Herald received additional information stating the air force Embraer C-95 Bandeirante (ICAO E110) had landed on runway 11L advising they were planning to vacate via taxiway G (1465 meters down the runway). ATC instructed to vacate the runway via G and contact ground when clear of the runway. However, the E110 continued to taxiway F (1975 meters down the runway) and reported they were clear of the runway at G and contacted ground. The controller was unable to see taxiways F and G and based on the position report cleared the Boeing for takeoff. The crew could not see the E110 due to the curvature of the runway and commenced takeoff, seeing the E110 only at the highest point of the curvature when the Boeing had already accelerated through V1. The Boeing crew rotated their aircraft ahead of the E110.
On May 10th 2020 Brazil's CENIPA released their final report dated Dec 18th 2019 concluding the probable causes of the serious incident were:
Attention – a contributor.
The attention of the Tower controller was hampered by the context in his work routine in which, due to physical obstacles, expectations were created that the aircraft would follow the instructions sent, even if they could not visually accompany them from their position, as happened in this case.
The fact that the Tower controller did not identify that the FAB, after having read back that it would clear by the TWY "G", did not do so, demonstrated that his focus of attention was not properly oriented to the situation.
In addition, the Ground controller did not identify that the aircraft, when at the first contact in his frequency, remained on the runway in use.
Attitude – undetermined.
Despite the good technical preparation, the FAB 2345 copilot still showed little familiarity with the SBBR operation at night. This may have contributed to the fact that she did not contest the instructions received from the commander regarding the taxi sequence after landing on runway 11L, as regards the selection of the TWY to clear the runway in use.
Likewise, the attitude of not following the standard phraseology prescribed in the MCA 100-16/2016, by the Tower controller, may have contributed to the FAB 2345 crew carrying out the frequency change for the Ground Control, before its exit from the runway in use.
Communication – a contributor.
Even not comprehending the request of the FAB 2345 crew after landing, the Tower controller did not urge them to repeat the message and issued instructions for the aircraft to clear the runway on TWY "G" (Golf), considering the proximity that the aircraft was from that intersection.
In this case, there was a selective listening, in which the spoken content was deduced from what was expected to be heard in that type of situation.
The message received by the FAB crew to "clear on Golf" may have been mistaken for a denial of the TWY "C" (Charlie) request.
Furthermore, the non-assimilation by the Ground controller of the verbal (future) time used by the crew of the FAB aircraft, by communicating the intersection where they would clear, contributed to the fact that he did not realize the aircraft was on the runway in use.
Physical work-conditions – a contributor.
The light interference from the North Pier apron and the TWY "H" blind spot (Hotel) constituted physical characteristics of the Tower's workplace that compromised the safe operating performance considering the nighttime operation.
Air Traffic Coordination (ATS) – a contributor.
The inadequate exchange of information between the Tower controller and the Ground Control in relation to the Air Force aircraft after its landing has contributed to the uncertainty as to the actual positioning of that traffic.
Employment of ATS means – undetermined.
Despite all difficulties identified for the visualization of the C-95M on the runway, the Tower controller did not use the resource prevised at ICA 100-37/2017, which provided an instruction for the aircraft itself to report when it had cleared the runway in use. It is possible that the employment of this means could prevent the incident.
Use of phraseology by ATS – undetermined.
It is possible that the phraseology used by the Tower controller, when he instructed the crew of the FAB 2345 to call the Ground Control, without conditioning this act to the exit of the aircraft of the runway in use, has induced the pilots to make the exchange of frequency being still on the respective runway.
With this action, the military pilots were unable to interfere when the Tower improperly authorized the 737 takeoff while the runway was still occupied.
ATS Control Ability – a contributor.
There was no ability in performing ATS procedures, such as visual scanning and phraseology usage that exhausted the possibilities of identifying an aircraft on the runway at the time of the PR-GTN takeoff.
Airport infrastructure – a contributor.
The existence of several blind spots at the aerodrome contributed to the Tower controller inferring that the FAB 2345 was in a position different from its real location after landing.
The cameras used to mitigate the risk of blind spots did not cover all areas and were not dedicated exclusively to the use of the TWR-BR.
The lighting of some aprons obfuscated the view of the TWR-BR controllers, damaging the sighting of the aircraft, especially small ones.
All these conditions, combined with the absence of a RADAR Surface Movement System, contributed to the military aircraft not being noticed on the runway in use at the time of the PR-GTN take-off was authorized.
Clearance limit – a contributor.
Involuntarily, the crew of the FAB 2345 did not comply with the Tower instruction to clear the runway by the TWY "G" (Golf).
The remaining on the runway in use by the military aircraft, in spite of a different instruction from the controller, contributed to the incident.
Perception – a contributor.
The similarity between the letters "C" and "G" associated with the conditions for their visualization at the night period contributed to the pilot's misperception.
The controller's perception was reduced by his expectation that the crew would strictly follow the guidance.
In addition, the failure to view the aircraft due to the TWY "H" (Hotel) blind spot led him to conclude that the runway was clear for another operation.
The expectation of not finding the aircraft in the runway in use reduced the controller's perception of the real location of that airplane, contributing to the ending of this occurrence.
Insufficient pilot’s experience – undetermined.
The lack of familiarity of the FAB 2345 copilot with the aerodrome may have contributed for her not questioning the commander's message, requesting to clear the runway for the TWY "C" (Charlie) when, in fact, the intersection they passed by was the TWY "G" (Golf).
It is possible that the little experience of that copilot had induced her to faithfully follow the commander's guidance.
Support systems – undetermined.
No regulation was identified that explicitly defined the position in which the aircraft should perform the frequency change for the Ground Control after landing.
The lack of prediction in standards may have contributed to the FAB 2345 crew keeping the Ground Control frequency while occupying the runway in use.
CENIPA reported the military aircraft had landed on runway 11L. CENIPA wrote:
the FAB 2345 pilot visualized the letter "C" on the taxiway's signposting plate and therefore asked the copilot (crewmember responsible for communications) to ask the TWR-BR to authorize them to clear the runway by the TWY "C" (Charlie).
In response to the crew of the military aircraft request, the TWR-BR controller directed the aircraft to clear on the TWY "G" and call the Ground control.
After receiving the message from the Tower, the FAB 2345 crew decided not to clear the runway in that position where the aircraft was already moving, switched the frequency to the GND-BR channel and remained on the main runway until the next exit intersection.
The military crew made initial contact with the GND-BR while still taxing on the main runway toward the next exit intersection and reported on that frequency that it would clear the runway through the TWY "G" (Golf).
The controller (GND-BR), in turn, only reported that he was aware and authorized the taxi of the aircraft to the military apron.
By identifying, through reading the runway vertical signaling, that the next intersection was TWY "F" (Foxtrot) and not TWY "G" (Golf), the crew rectified the message they had passed to the GND- BR, requesting to clear the runway by TWY "F" (Foxtrot).
Once again, the controller (GND-BR) authorized the departure of the aircraft from the main runway and the taxi to the military apron.
As the aircraft began to position itself toward TWY "F" (Foxtrot) to clear the runway, the occupants of that military aircraft suddenly perceived a very intense light coming from outside, accompanied by an extremely loud noise and a strong vibration.
As they looked out the window, some of the crew and passengers sighted the commercial plane that had just passed over the C-95M that still occupied the main runway.
...
After the FAB 2345 landing, the TWR-BR authorized the PR-GTN to line up and maintain threshold 11L and, about one minute and fifteen seconds later, the same controller (TWR-BR) authorized its takeoff.
The PR-GTN crew began the take-off run, and almost at the same time the Boeing reached the speed of rotation, its landing light illuminated the FAB C-95M, which was still on the runway.
Then, the PR-GTN commander advanced the power levers for the maximum thrust and immediately started the rotation, managing to take off his aircraft above the one on the runway, thus avoiding a collision.
After avoiding the accident, still in the frequency of TWR-BR, the PR-GTN crew reported to that traffic control the scenario that they had just confronted.
CENIPA analysed:
During the approach and landing briefing by the FAB aircraft commander, while still on a cruise flight, he stated that after the touchdown, he would control the deceleration of the aircraft, in order to clear the main runway through TWY "F" (Foxtrot).
This decision was based on the arguments that TWY "F", by virtue of its angulation in relation to the direction of landing, would be a quick exit intersection (for landings on runway 11L) and also because that taxiway would allow a more direct access to the Brasilia military apron.
Considering the landing performance of the military aircraft and the runway length from the touch zone (from threshold 11L) to TWY "F", the pilot could plan a fairly smooth deceleration as it would have a great distance to degrade the speed which was not very high (low performance aircraft).
However, it was found that during the landing, the pilot used the reverse and brake controls at an intensity higher than that, which would be required for the aircraft to be at a controlled speed in a position close to TWY "F".
After controlling the aircraft, in an earlier position than previously planned, the pilot tried to identify, by reading the vertical signs of the aerodrome, what would be the new intersection that he would use to clear the runway.
However, when he glanced quickly at the identification plate of the intersection he would be able to use, he confused the letter "G" with the letter "C" and therefore asked the copilot to request TWR-BR the authorization to clear the runway by the intersection that he believed to be TWY "C" (Charlie).
It should be noted that this type of distorted perception is plausible, considering the similarity of the letters and the conditions of visualization, which, in this case, were aggravated by the fact that it was a night period.
In this case, in theory, the pilot would not have failed to comply with item 6.7.1.5.2 of the ICA 100-37/2017, which dealt with the procedures to be adopted for situations of "Uncertainty about position in the maneuvering area", because when he saw (even if incorrectly) the vertical signaling for the taxiway that he wished to enter, there was no uncertainty in his judgment.
Some conditions may have contributed to the copilot not responding to the
commander's misguided request, such as her lack of familiarity with the aerodrome, the actual existence of a TWY "C" (Charlie) connected to that runway and her attention which was aimed at performing the after-landing check, rather than assisting in following the aircraft roll.
It was not possible to clarify whether the SBBR ADC chart consultation was fully explored at the time of the approach and landing briefing performed by the FAB 2345 pilot, as well as its use during the taxi. In this context, the lack of real-time monitoring of this chart by the copilot, may have contributed to the incorrect perception of the aircraft position on the ground after landing.
Allied to these conditions, it is possible that the little familiarity of the copilot with the operation in SBBR at night has contributed for her to exert little interference on the actions of the pilot.
Thus, the copilot followed strictly what was requested by the commander and questioned the Tower about the possibility of clearing the runway by TWY "C" (Charlie).
In turn, the Tower controller was not expecting to receive any message from the aircraft that had just landed, because at controlled aerodromes, normally the first post-landing message is sent by the Tower rather than by the aircraft.
In addition, in the controller’s perception, the copilot had sent the message (of a request to clear on the TWY "C") with a rapid pace of speech, which made it impossible to understand the information.
Despite not being able to understand the content of the message sent by the military aircraft’s copilot, the controller did not request that the crew repeat the phraseology, because it inferred that the pilots should only be informing that the aircraft was controlled.
The correct attitude in this situation would be a Tower controller request to have the message repeated by the crew, in order to avoid communication conflicts.
In the real context, the controller disregarded the crew message, which was erroneously requesting to clear the runway through TWY "C" (Charlie) and simply sent the standard message it would already use, even if it had not been surprised by the initial call of the aircraft on the ground.
When verbalizing: "Pioneer 45, clear on the Golf and call Ground on frequency 121.8.", the controller experienced the following context:
- visualized a fully controlled aircraft, having a compatible speed to immediately clear the runway;
- inferred that the aircraft had reported that it was already controlled;
- the exit intersection next to that already controlled aircraft was TWY "G" (Golf);
- had observed the trajectory of the aircraft, moving to enter in TWY "G" (Golf); and - after his post-landing instruction, there was the correctly read back by the crew, reporting that they would clear the runway by the TWY "G" (Golf).
However, from the crew's perspective, the message conveyed by the controller represented a totally different context.
In fact, the aircraft was controlled and the crew would clear the runway through TWY "G" (Golf), as the controller could observe from the Tower.
However, mistakenly believing that TWY "G" (Golf) was TWY "C" (Charlie), upon hearing the controller's "Clear on the Golf" message, after the request to clear on Charlie, the crew interpreted the phraseology as negative to their request, which may have sounded like: do not clear on TWY "C" (Charlie), but on TWY "G" (Golf).
Considering that TWY "G" (Golf) was located on the next exit on the right, after TWY "C" (in the direction of aircraft landing), the pilots interpreted that they should clear the runway by the next exit on the right and not by the one which was already in its side.
Soon, in fact, the crew stopped joining TWY "G" (Golf) and headed towards TWY "F" (Foxtrot).
Another communication problem occurred due to the same message sent by the Tower, but referring to the moment of the frequency change for the Ground Control.
From the point of view of the Tower controller, as the aircraft was already on the verge of clearing the runway by the TWY "G" (Golf), the pilots could already listen to the Ground Control.
Thus, using the additive conjunction "and" in the phrase "clear on the Golf and call Ground at frequency 121.8", the controller was inferring that the aircraft was already clearing the runway in use, and consequently, could change the frequency as soon as passing the stop bar of the intersection in question.
In this context, the Tower controller did not use the standard phraseology prevised in item 3.4.3.4 of the MCA 100-16/2016 Phraseology, which presented in its model an example of instruction after landing, conditioning the frequency change at the exit of the aircraft from the runway in use, as already presented in section 1.19 (Additional information) of this Final Report.
Nevertheless, from the perspective of the FAB aircraft pilots, upon receiving the determination of the Tower controller to clear on the Golf and call Ground Control on the 121.8MHz frequency, they may have internalized that, from that moment, they would be authorized to perform the two actions (clear the runway and change the frequency to call the Ground Control) without one being necessarily conditioned to the other.
However, because of the aforementioned FAB 2345 crew's misunderstanding regarding TWY positioning, the additive conjunction used in the controller's message, rather than a conditional one, may have contributed to the copilot carrying out the frequency change for the Ground Control with the aircraft still occupying the main runway.
By switching the frequency to the Ground Control, still occupying the main runway, the military aircraft stopped listening to the Boeing 737's flight, controller's authorization to take off, and thus were unable to interfere with that inadequate clearance given by the Tower.
Such a situation would not occur if the controller had conditioned the call at the new frequency to clear the main runway, using phraseologies such as: "When cleared on Golf, call Ground on frequency 121.8"; or, "After clearing on Golf, call Ground on frequency 121.8"; or "When you clear on Golf, call the Ground on frequency 121.8".
From this moment on, it is necessary to go back a bit in the chronology of the event, in order to understand the factors that contributed (or may have contributed) to the failure of the Tower controller when authorizing the takeoff of an aircraft, with the runway still occupied by other traffic.
There was that moment in which the controller visualized the FAB controlled aircraft, after the landing, next to TWY "G" (Golf) and therefore sent the message so that the crew cleared the runway by that intersection, even without having understood that the crew had requested to clear on TWY "C" (Charlie).
However, when the controller received the correct read back of the instruction, even though it was sent in a synthesized manner by the military crew, he temporarily stopped focusing his attention to C-95M, considering that his orientation (which was "repeated" by the FAB’s copilot) would be strictly enforced.
It turns out that the Tower controllers were already accustomed to working with a marginal operating scenario, where a grove on the side of TWY "H" (Hotel) prevented the visualization of a controlled stretch of this taxiway as already shown in Figures 3 and 4.
When attempting to see the FAB 2345 near TWY "G" (Golf) and not see it, the controller immediately inferred that the aircraft should be hidden in the blind spot of TWY "H" (Hotel), since it would be moving to the military apron.
Therefore, in the context experienced by the controller, not having seen the aircraft on the taxiway meant that plane should be hidden behind the grove, not that the aircraft could still be on the main runway.
However, according to the Tower controller himself, even believing that the aircraft was already in TWY "H" (Hotel), he made a visual check of the main runway before authorizing the PR-GTN for takeoff, since according to item 6.13 .2.1 of ICA 100-37/2017, take-off could only be authorized with the runway totally clear.
In this context, some factors may have contributed to the fact that the controller had not sighted the C-95M, considering the hypothesis that a visual scan was actually performed on the main runway prior to the commercial aircraft takeoff.
The first factor is related to a psychological aspect called expectation, which occurs when an individual projects in a given situation what he or she really expected to encounter at first.
Therefore, the controller may have been encouraged to believe that the runway was clear since it was expected that the FAB aircraft would have left the site, thus leading to its non-sighting, due to the TWY "H" (Hotel) blind spot.
CENIPA further analysed that the spotlights at the apron as well as the camouflage paint scheme as well as lack of strobe lights (only the red position light present) of the small military aircraft impaired the controllers' ability to identify the aircraft.
CENIPA continued analysis:
To trigger the analysis of the event, now from the viewpoint of the Ground controller, it is necessary to go back to the moment when the crew of the FAB 2345 made the initial call on the frequency 121.8 MHz, sending the following message:
"Brasilia Ground, good evening! Pioneer 45 landed on 11L. It will clear on the "Golf" to the military apron."(our emphasis).
Although the crew used the verb tense in the future, when they said they would clear the runway through TWY "G" (Golf), the Ground Controller probably did not realize that the message implied in essence the information that the aircraft would still be on the runway in use.
Otherwise, if the aircraft was already off the runway, the verbal time employed by the crew would be in the past with a message containing something like: "... cleared on "Golf"...".
Therefore, it is possible to establish the hypothesis that the Ground Controller probably did not visually follow the C-95M movement after the initial call made on his frequency, because if he had done so, he would have realized that, at the moment the pilots reported they would clear the runway through the TWY "G" (Golf), the aircraft had already passed through that intersection.
It is inferred that, at the moment the initial call was made in the Ground Control frequency, the FAB aircraft was already in the process of displacing to TWY "F" (Foxtrot), since there was a lapse of about twenty seconds from the Tower's message (00h30min33s UTC) until that first contact with the Ground Control (00h30min53s UTC).
Considering that the crew of FAB 2345 believed that TWY "G" was the next to its right, in theory, any trajectory of that military aircraft, from that moment on, he would already be characterized as a displacement for TWY "F" (Foxtrot).
Therefore, if the Ground controller had noticed that the aircraft had already passed the TWY "G", would be able to rectify the message sent by the military crew and warn the Tower controller about the presence of the aircraft on the runway and with these actions, perhaps even avoiding the incident.
It should be noted that the interferences related to the work environment, experienced by the Ground Controller, were the same as those of the Tower controller, since both operated from the same tower.
With respect to PR-GTN CENIPA analysed:
In turn, the scenario experienced by the PR-GTN crew involved in the occurrence also contained some influencing conditions for the serious incident.
The first of them was the receipt of the takeoff authorization from the Tower controller, because in aviation, there is the common understanding that a controller would only authorize a takeoff with the runway totally cleared.
Even so, the authorization of a controller does not inhibit the commander's responsibility to ensure the safety of the flight.
Therefore, if in this case the presence of the FAB aircraft still in the runway was noticed, the pilot should not takeoff, in spite of the instruction of the controller authorizing the takeoff.
However, because of the runway slope, it would not be possible for a crew to see a small aircraft at a position close to the intersection of TWY "F" (Foxtrot), with its aircraft lined up over threshold 11L, as was the case.
That way, when authorized for takeoff, the PR-GTN pilots did not spot any obstacles that could prevent the start of their run.
During the take-off run, after passing the runway slope, the FAB 2345 early viewing by the PR-GTN crew may have been hampered by the following factors:
- the lack of stroboscopic lights on the military aircraft may have reduced the possibility to notice the presence of this aircraft on the runway;
- the aircraft camouflaged painting may have attenuated the visual contrast, hindering its sighting; and
- the red lights of the FAB 2345 collision system could easily be mistaken for the red signal lights at the end of the runway in use.
Therefore, the combination of all these conditions may have contributed to the sighting to occur only at the time when the 737 headlights fully lit the military aircraft.
In this scenario, where the traffic conflict visualization occurred in marginal conditions, the dexterity of the PR-GTN crew was essential to avoid collision and thus prevent a catastrophe.
Incident Facts
Date of incident
Apr 9, 2018
Classification
Incident
Airline
Gol Transportes Aereos
Flight number
G3-1732
Departure
Brasilia, Brazil
Destination
Sao Luis, Brazil
Aircraft Registration
PR-GTN
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
This article is published under license from Avherald.com. © of text by Avherald.com.
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