Lufthansa A388 and Aeroflot A320 at Frankfurt on Dec 13th 2011, loss of separation
Last Update: December 13, 2012 / 15:14:47 GMT/Zulu time
Incident Facts
Date of incident
Dec 13, 2011
Classification
Incident
Airline
Lufthansa
Aircraft Type
Airbus A380-800
ICAO Type Designator
A388
direct causes:
- the takeoff clearance for the A320 was issued at a time, when the landing of the A380 on the parallel runway had not yet been ensured.
- there was no instruction to reject takeoff
- a flawed mental approach to resolve the conflict by the air traffic controller lead to the departing aircraft being instructed to turn towards the aircraft arriving and going around on the parallel runway.
systemic causes:
- the increased coordination between the controllers necessary due to the conditions at their work places as well as due to the organisation of operations of the various runways contributed to the reduction of separation below required minima and approach to the wake
- The procedures to disentangle departures on runway 25C and missed approaches on runway 25L provided to air traffic controllers were insufficient.
The BFU analysed that due to the low speed of both aircraft and their positions with respect to each other there was no risk of a collision despite the fact, that the minimum separation reduced to 200 feet vertically and 0.97nm horizontally, which was substantially below the required minimum of 1000 feet vertical or 7nm horizontally. However, with the weather conditions present the danger existed, that the A320 would enter the wake of the A380, which could have resulted in uncontrolled movements of the aircraft up to loss of control.
The crew of the A380 had decided to go-around when they felt the touchdown within the touch down zone of the runway was no longer assured. The decision to go-around was taken at a point when ground contact could not be avoided, the aircraft touched down before becoming airborne again.
The crew of the A320 had no possibility to hear the A380, which communicated on another tower frequency. The A320 began their takeoff run about 15 seconds after receiving takeoff clearance and 12 seconds after the A380 had initiated the go-around. The aircraft accelerated through V1 about 20 seconds later, a rejected takeoff would have been possible until then. It is unlikely however that the A320 crew would have noticed the A380 with the pilot flying focussed on the runway centerline and the pilot monitoring focussed on the instruments. The air traffic controller did not instruct to reject takeoff.
The QAR data showed that the A320 did not enter the wake of the A380, however came as close as 30 meters (100 feet) to the wake.
At the time of the incident traffic volume at Frankfurt was rather low. Both tower controllers, one responsible for 25L and the other for 25C, had been on duty for a few minutes only at that time. The BFU stated that no audio recording of the tower room was available, the intercommunication between the controllers could therefore not be replayed and was reconstructed from testimonies. The BFU complained that the availability of such a recording could have substantially helped to establish the sequence of events.
Upon detecting the go-around the controller responsible for runway 25L should have loudly exclaimed "Missed Approach 25L" to inform his collegues controlling the other runways, however, there was no testimony indicating that such a call did happen. The controller also needed to immediately coordinate with the controller controlling departure runway 18, which would be overflown shortly and terminal area control.
The controller intended to turn the A380 to the left rather than had the A380 follow the standard missed approach in order to increase the distance to the departing A320. This mental approach was suitable to resolve the conflict.
The controller of runway 25C had observed the A380 until shortly before touchdown and was convinced landing would successfully occur and therefore issued takeoff clearance for the A320 on his runway. It was more than likely that the controller looked at the A320 and thus did not detect that the A380 had initiated a go-around. No further instruction occurred during the takeoff run of the A320, when the A320 climbed through 296 feet AGL the controller issued "... proceed on runway heading, proceed on runway heading, 380 from southern runway has pulled up", the BFU believes by repetition of the instruction he wanted to underline the urgency of the instruction, however, the controller never considered to restrict the climb rate of the flight.
When the controller believed the A380 was sufficiently high he wanted to turn his A320 left in order to continue with the standard departure profile and told the south controller "I'll turn mine left". The BFU believes that this mental approach was flawed and was not suitable to resolve the conflict between the two aircraft. In addition, as the A380 was above the A320 turning the A320 left brough the aircraft closer to the wake of the A380. This conflicting instruction was corrected 26 seconds later when the A320 was instructed to turn right. This period of time to correct was too long, the BFU analysed.
At the time of the incident there were 5 to 7 octers of cloud ceiling at 2500 feet. This meant that both aircraft were not able to see each other after they had overflown runway 18, and the controllers could not observe the aircraft visually but only on their radar screens. With the winds coming out of southerly directions the wake was blown northwards towards runway 25C.
The BFU analysed that the fact, that missed approaches on runway 25L and standard departures on runway 25C crossed, establishes a systemic risk in the form of reduced fault tolerance requiring controllers to compensate by heightened levels of alertness.
The BFU analysed further that there had been no procedures developed to resolve a conflict between a go-around on 25L and a departure on 25C. In so far it was left to the controllers to develop a spontaneous procedure to resolve a possible conflict.
The BFU analysed that both TCAS systems were monitoring the threatening target, the conditions for issuing traffic or resolution advisories however were not met at any point in time.
5 safety recommendations were issued by the investigation including recommendations to develop procedures to separate missed approaches on 25L/07R and departures on 25C/07C and possible control both runways on the same frequency as well as introduce simulator training of abnormal scenarios at the aerodrome requiring controllers to deviate from normal procedures in order to maintain safe operations.
Incident Facts
Date of incident
Dec 13, 2011
Classification
Incident
Airline
Lufthansa
Aircraft Type
Airbus A380-800
ICAO Type Designator
A388
This article is published under license from Avherald.com. © of text by Avherald.com.
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