Description

On 12 April 2019, a Boeing 717-200 (EI-EXB) being operated by Volotea on a scheduled domestic passenger flight from Montpelier to Strasbourg and a Bombardier CRJ 700 (F-GRZG) being operated by HOP! on scheduled domestic passenger flight from Strasbourg to Marseilles came into extremely close proximity in day VMC as the 717 was going around from an approach to runway 05 and the CRJ700 was climbing after takeoff from the same runway. Minimum lateral separation of 740 metres occurred as the two aircraft, without prior visual contact, came within 50 feet of each other vertically when only 740 feet apart laterally. All CRJ crew members stated that they had been aware of the near miss and the junior member of the cabin crew became unfit to continue their duties upon hearing the Captains summary account shortly after the event.

Investigation

A Serous Incident Investigation was carried out by the French Civil Aviation Accident Investigation Agency, the BEA using FDR data from both aircraft together with recorded ATC voice and radar data and statements given by those involved.

It was noted that the 717 flight crew consisted of a Captain with Spanish nationality and a First Officer with French Nationality. The First Officer was acting as PF and ATC communications with the flight were conducted in English. The CRJ700 flight crew consisted of two pilots of French nationality with the First Officer acting as PF and ATC communications conducted in French. It was also noted that the TWR controller at Strasbourg is provided with a radar display of all traffic above approximately 1500 feet and that the controller in position was an instructor who also held an APP radar rating and had 18 years’ experience including six at Strasbourg.

What Happened

The Boeing 717 was making an ILS approach to runway 05 at Strasbourg. The CRJ700 was taxiing for departure from the same runway and was transferred from GND to TWR as it taxied towards holding point ‘H’ after reporting it was ready for takeoff.

The TWR Controller asked if the departing CRJ700 could commence takeoff without delay if so cleared and on receiving confirmation issued clearance for an immediate takeoff accompanied by the advice that there was landing traffic at 3 miles without giving Boeing 717 as the aircraft type. The CRJ700 still had 30 metres to run until reaching the holding point. About 40 seconds later, the Boeing 717 reported at 2 miles as the CRJ700 lined up on the runway and the TWR Controller informed the Boeing 717 of the departure of the CRJ700 and instructed it to continue the approach. The 717 Captain responded with “unbelievable” on the frequency and five seconds later, the CRJ700 began its takeoff roll.

With just under a mile to go, the 717 crew advised that they may discontinue their approach and were again told to continue. Nine seconds later, and when just over half a mile from the runway threshold having just passed the applicable ILS DA, the 717 crew initiated a missed approach and informed ATC accordingly. At this point, the CRJ700 was still not airborne and had reached a point 780 metres from the beginning of the runway as it accelerated through approximately 115 knots. The TWR controller instructed the 717 to initially climb straight ahead in accordance with the MAP (towards the NDB ‘SE’ located 4 nm from the runway 23 threshold on its extended centreline) and received a correct readback. With the surface wind being reported as from a mean of 030° at 10 knots, the First Officer then selected a heading of 042°, rather than displaying the ‘SE’ and which was also contrary to the 047° ILS approach track in what was only likely to be a light crosswind from the left. As the CRJ700 crossed the threshold of runway 23 at an altitude of 900 feet and a speed of 160 KCAS, separation from the Boeing 717, which was maintaining a similar speed but accelerating relative to the CRJ700 ahead, was approximately 1nm horizontally and 920 feet vertically behind it.

As the 717 approached overhead the end of the runway, still slowly accelerating and now 840 feet above the CRJ700, it began to deviate to the left of the runway centreline in accordance with the selected heading at the same time as the CRJ began to deviate very slightly to the right of the extended centreline. At this point (marked 5 in the illustration below), the TWR controller instructed the much slower CRJ700, which was already cleared to continue climb to 6000 feet, to turn left and the 717 to “immediately turn right onto heading 050°”. As the CRJ700 began turning at 2,100 feet, the horizontal and vertical separation between the two aircraft was 0.6nm and 300 feet respectively with the 717 about to level at 2500 feet and the CRJ700 about to climb rapidly through the same altitude.

The ground track and vertical profile of the two aircraft involved annotated with numbered positions showing the concurrent positions of the 717 (red) and the CRJ700 (blue). [Reproduced from the Official Report]

The TWR Controller then instructed the CRJ700 to stop climb at 2000 feet which it had already exceeded with a 1300 fpm rate of climb. Seconds later, (at point 7 on the illustration above) coordinated TCAS RAs were annunciated on board both aircraft and actioned by the crews. The 717 RA received a ‘DESCEND’ RA and the CRJ700 received a ‘MAINTAIN CLIMB’ RA with the vertical separation between them just 50 feet when 740 metres apart horizontally. The CRJ700 RA changed almost immediately to ‘INCREASE CLIMB’ with the respective separations at 95 feet and 520 metres and the minimum horizontal separation of 315 metres was reached ten seconds after annunciation of the RAs with the vertical separation now increasing through 500 feet. ‘Clear of Conflict’ annunciations then occurred with the two aircraft on divergent tracks and with increasing vertical separation as the CRJ700 continued its climb. The TWR Controller then transferred both flights to the APP radar frequency.

The 717 crew stated that as they began their go around, they had been expecting an instruction to turn right in order to avoid conflict with the departing CRJ700, which they knew could be expected to turn left whilst climbing according to the applicable SID and were surprised when they were instructed to continue straight ahead to 2,500 feet. The Captain stated that he had not understood the controller’s instructions to the CRJ700 given in French and expressed surprise that “in a potential conflict situation, the exchanges were not carried out in a shared language, in English only". Neither of the pilots had visual contact with the CRJ700 until after the RA occurred and first saw the CRJ700 as it passed directly in front of them in a left hand climbing turn. They considered that “the situation was dangerous” and noted that “they had been afraid”.

The CRJ700 crew stated that although there had been “a lot of exchanges in English between the TWR controller and the 717”, they were not aware that it was on final approach and had thought that the finals traffic mentioned by the controller when he asked if they were able to take an immediate departure was a VFR light aircraft on local or circuit flight. They stated that as the Controller instructed them to “maintain 2,000 feet”, they had been climbing through 2,450 feet and as they made a slight nose-down input, the TCAS RA occurred and was followed. As this quickly changed to ‘INCREASE CLIMB’, they stated that the climb required was almost at the limit of the VSI scale and said that they had been “very surprised to have to take such a pitch attitude for the climb (and) had been afraid and had expected to strike an aircraft”. At this point, they stated that they “were not aware that the Boeing 717 had executed a missed approach” and also stated that at no time had they had visual contact with it. They also noted that “shortly after the incident and not realising how it might affect the cabin crew” they had explained to the cabin crew who had entered the flight deck what had just happened.

The TWR Controller stated that when the CRJ700 eventually became airborne, he “considered that the 717 could land”. However, he had delayed issuing a landing clearance “to check the spacing (and) confirmed that he would have been required to clear the 717 to land before the CRJ700 had crossed the end of the runway”. He stated that he had been “surprised” by the decision of the 717 crew to execute a missed approach and added that “in his opinion it was more dangerous to execute a missed approach behind the departing aeroplane than to land a bit too close behind it”. He also said that “he was convinced at this point that the crew of the CRJ700 were perfectly aware of the situation as they had been cleared for an immediate departure and had had the position information about the traffic in final approach”. He explained that he had waited until the aircraft had both appeared on his radar display which had occurred at around 1,600 feet to assess the separation but the TCAS RAs then occurred before he had time to de-conflict the flight paths of the two aircraft.

It was noted that in the absence of the designation of a 4nm approach fix for the 05 straight-in approach comparable to the one defined for runway 23, beyond which point a departing aircraft could not be lined up once an aircraft on approach was inside it, the applicable ATC requirement for runway 05 was no line up to be given once the aircraft on approach is within 3 minutes of “arrival”. It was noted that “approximately 1 minute 20 seconds” had elapsed between the takeoff clearance eventually given to the CRJ700 and the 717 crossing the runway 05 threshold.

In respect of ATC communications with the two aircraft involved being conducted in two different languages, the Investigation considered that although the use of English in both cases might have improved the situational awareness of the 717 crew and “allowed them to adapt their path accordingly” before TCAS intervened, it was “not possible” to determine if this was in fact the case.

The narrative Conclusions in respect of the scenario which led to the unsafe proximity between the two aircraft included the following points:

• The TWR Controller’s confidence, despite contrary indications, that it was appropriate to offer an immediate takeoff clearance to the crew of the CRJ700 despite the position of the inbound 717 on final approach.
• The decision of the 717 crew to discontinue their approach when they realised that the departing CRJ700 would not have crossed the far end of the runway by the time they touched down.
• The reliance of the TWR Controller on the capability of the CRJ700 crew to immediately follow his instructions when in dynamic flight phases with a high workload and a difference in acceleration between the two aircraft, it was difficult for the crews to perceive, analyse and follow those instructions, especially as they were given in different languages.
• The fact that the TWR Controller had difficulty in following the progress of each flight from his position and the late appearance of relevant information on his radar display did not allow him to adapt his initial strategy.
• The fact that the 717 deviated to the left during its go around after its crew had selected a heading which was different to the runway magnetic heading and which accentuated the horizontal closure of the two aircraft after the CRJ700 also turned to the left.
• The conflict was only resolved after compliance with the resulting TCAS RAs by the crews of both aircraft.

Six Potential Contributory Factors were identified as follows:

1. In respect of the CRJ700 being issued with an immediate take-off clearance although the Boeing 717 was at 3nm on final approach:
   • The TWR Controller’s wish to optimise the use of the runway, without any particular reason and without anticipating the risks in the event of something unexpected happening, meant that the prescribed separations between the arriving and departing aircraft were not complied with.
   • The absence at the time of the incident of means, practices or systematic procedures at Strasbourg airport, such as the setting up of an approach fix for runway 05.
   • The (inbound) aircraft type not being mentioned by the TWR Controller when giving traffic information to the crew of the CRJ700 with a view to an immediate take-off which meant that the crew did not have all the information to allow them to judge whether they could guarantee the immediate take-off conditions (given that) they did not share the same situational awareness as the controller and the crew of the Boeing 717.
2. In respect of the activation of the TCAS RA between the CRJ700 which was taking off and the Boeing 717 which was (making) a go-around:
   • The TWR Controller not anticipating and developing action plans in the event of a potential conflict following a low-level missed approach or a delay with the immediate take-off.
   • The situational awareness between the TWR controller and the two crews not being shared.
   • The initial paths for the departure and missed approach towards the NDB 'SE' at 2,500 feet not guaranteeing sufficient separation between the aircraft.

Safety Action taken by the ANSP as a result of the investigated event whilst the Investigation was still in progress was noted to have been the designation of an “approach fix” for runway 05 at 4nm, the same range as the existing fix for approaches to runway 23. This new fix, like the existing one for runway 23 defined a point beyond which if any inbound aircraft has passed, a departing aircraft may not be instructed to line up.

One Safety Recommendation was made as a result of the Investigation as follows:

• that the DNSA (the French ANSP), in the absence of means or procedures such as runway approach fixes, which means that management of aircraft line-up and landing sequences mainly relies on the experience, assessment and judgement of the position controller despite the criteria specified by the regulations and whereas this absence of means or procedures creates a difference between the initial training for the Aerodrome Control Instrument (ADI) rating which relies on the use of such means and continuation training or conversion training, take into account the specific aspects at each aerodrome where there is commercial traffic in order to define all measures which will improve separation management of arriving and departing aircraft so that landing clearances are given sufficiently early and the risk of a low-level go around is limited. [FRAN 2020-013]

The Investigation also identified Two ‘Safety Lessons’ as follows:

• One of the tasks of the airport controller is to “expedite and maintain an orderly flow of air traffic”. He may do this by approaching the regulatory minima when this is necessary, but this should not be done systematically due to the ensuing risk of exceeding them. Thus, the optimisation of the use of the runway and the search for operational efficiency must not take precedence over the prevention of collisions which requires the controller to continuously carry out a strategic analysis of the risks.
• After an in-flight (Serious) Incident, it is particularly complex for a Captain to synthesise the (available) information to explain it and continue the flight. The emotional load (may) make it difficult for both the flight crew and the cabin crew to be objective about (what) has occurred, even if there are no more consequences for the rest of the flight. Sharing information with the crew can, however, affect certain crew members according to their sensitivity and their experience.

The Final Report in English translation was published on 20 November 2020 simultaneously with the definitive French language version.

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• Loss of Separation
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• Separation Standards
• Multi-language ATC Operations
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