Büro für Flugunfalluntersuchungen BFU
Bureau d’enquête sur les accidents d’aviation BEAA
Ufficio d’inchiesta sugli infortuni aeronautici UIIA
Uffizi d'inquisiziun per accidents d'aviatica UIAA
Aircraft Accident Investigation Bureau AAIB
Aéropôle 1, Route de Morens, CH-1530 Payerne
Final Report No. 2088
by the Aircraft Accident
Investigation Bureau
concerning the serious incident - Airprox
involving the Airbus A318-111 aircraft, registration F-GUGK
operated by Air France under callsign AFR 989Z
and the Boeing B737-8AS aircraft, registration EI-DHK
operated by Ryanair under callsign RYR 1702
on 8 June 2009
over Trasadingen beacon, 15 NM north of Zurich airport
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 2 of 26
General information on this report
This report contains the Aircraft Accident Investigation Bureau's (AAIB) conclusions on the
circumstances and causes of the serious incident which is the subject of the investigation.
In accordance with Art 3.1 of the 9
th
edition, applicable from 1 November 2001, of Annex 13
to the Convention on International Civil Aviation (ICAO) of 7 December 1944 and Article 24
of the Federal Air Navigation Act, the sole purpose of the investigation of an aircraft accident
or serious incident is to prevent accidents or serious incidents. The legal assessment of acci-
dent/incident causes and circumstances is expressly no concern of the accident investigation.
It is therefore not the purpose of this investigation to determine blame or clarify questions of
liability.
If this report is used for purposes other than accident prevention, due consideration shall be
given to this circumstance.
The definitive version of this report is the original in the German language.
All times in this report, unless otherwise indicated, follow the coordinated universal time
(UTC) format. At the time of the incident, Central European Time (CET) applied as local time
(LT) in Switzerland. The relation between LT, CET and UTC is:
LT = CET = UTC + 2 hours
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 3 of 26
Contents
Synopsis ....................................................................................................... 5
Investigation ............................................................................................... 7
Summary ...................................................................................................... 7
Causes .......................................................................................................... 7
Safety recommendation ............................................................................... 7
1
Factual information ................................................................................ 8
1.1 History of the flight ..................................................................................... 8
1.1.1 General .................................................................................................................... 8
1.1.2 Flight preparation ...................................................................................................... 8
1.1.3 Sequence of the serious incident .............................................................................. 10
1.1.4 Location of the serious incident ................................................................................ 13
1.2 Personnel information ............................................................................... 13
1.2.1 Crew of AFR 989Z ................................................................................................... 13
1.2.1.1 Commander ..................................................................................................... 13
1.2.1.1.1 Training ...................................................................................................... 13
1.2.1.1.2 Flying experience ......................................................................................... 14
1.2.1.2 Co-pilot ........................................................................................................... 14
1.2.1.2.1 Training ...................................................................................................... 14
1.2.1.2.2 Flying experience ......................................................................................... 14
1.2.2 Crew of RYR 1702 ................................................................................................... 14
1.2.2.1 Commander ..................................................................................................... 14
1.2.2.1.1 Training ...................................................................................................... 14
1.2.2.1.2 Flying experience ......................................................................................... 15
1.2.2.2 Co-pilot ........................................................................................................... 15
1.2.2.2.1 Training ...................................................................................................... 15
1.2.2.2.2 Flying experience ......................................................................................... 16
1.2.3 Air traffic control personnel ...................................................................................... 16
1.2.3.1 Air traffic controller 1 ........................................................................................ 16
1.2.3.2 Air traffic controller 2 ........................................................................................ 16
1.2.3.3 Air traffic controller 3 ........................................................................................ 16
1.3 Aircraft information ................................................................................... 17
1.3.1 AFR 989Z aircraft .................................................................................................... 17
1.3.2 RYR 1702 aircraft .................................................................................................... 17
1.4 Meteorological information ....................................................................... 18
1.4.1 General .................................................................................................................. 18
1.4.2 General meteorological situation ............................................................................... 18
1.4.3 Weather at the time of the serious incident ............................................................... 18
1.4.4 Astronomical information ......................................................................................... 18
1.4.5 Winds at high altitude .............................................................................................. 18
1.5 Safety systems ........................................................................................... 18
1.5.1 Airborne collision avoidance system .......................................................................... 18
1.5.2 Short-term conflict alert ........................................................................................... 19
1.5.3 System for monitoring clearances ............................................................................. 19
1.6 Organisational and management information .......................................... 19
1.6.1 Procedures ............................................................................................................. 19
1.6.1.1 General ........................................................................................................... 19
1.6.1.2 Use of headsets ............................................................................................... 19
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 4 of 26
1.6.1.3 Rules concerning deployment of trainee air traffic controllers ............................... 20
2
Analysis ................................................................................................ 20
2.1 Technical aspects....................................................................................... 20
2.2 Human and operational aspects ................................................................ 20
2.2.1 Air traffic control ..................................................................................................... 20
3
Conclusions .......................................................................................... 23
3.1 Findings ..................................................................................................... 23
3.1.1 Technical aspects .................................................................................................... 23
3.1.2 Crews ..................................................................................................................... 23
3.1.3 Air traffic control personnel ...................................................................................... 23
3.1.4 History of the flight.................................................................................................. 23
3.1.5 General conditions ................................................................................................... 24
3.2 Causes ........................................................................................................ 24
4
Safety recommendations and measures taken since the serious
incident ...................................................................................................... 25
4.1 Safety recommendations ........................................................................... 25
4.1.1 Safety deficit ........................................................................................................... 25
4.1.2 Safety recommendation no. 424 ............................................................................... 25
4.2 Measures taken since the serious incident ............................................... 26
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 5 of 26
Final Report
Synopsis
Aircraft 1
Owner: Société Air France, Roissy, France
Operator: Société Air France, Roissy, France
Manufacturer Airbus S.A.S., Toulouse, France
Aircraft type A318-111
Country of registration France
Registration F-GUGK
Commercial flight number AF 2989
ATC callsign AFR 989Z
Radio callsign Air France niner eight niner Zulu
Flight rules IFR
Type of operation Scheduled flight
Departure point Belgrade (LYBE)
Destination point Paris Charles de Gaulle (LFPG)
Aircraft 2
Owner: Ryanair Ltd., Dublin, Ireland
Operator: Ryanair Ltd., Dublin, Ireland
Manufacturer Boeing Commercial Airplanes, Seattle, Washington,
USA
Aircraft type B737-8AS
Country of registration Ireland
Registration EI-DHK
Commercial flight number FR 1702
ATC callsign RYR 1702
Radio callsign Ryanair one seven zero two
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 6 of 26
Flight rules IFR
Type of operation Scheduled flight
Departure point East Midlands (EGNX)
Destination point Bergamo Orio al Serio (LIME)
Location Over VOR Trasadingen
Swiss sovereign territory
Date and time 8 June 2009, 12:19 UTC
ATS unit Zurich Area Control Centre (ACC)
Sector M4
Airspace Class C
Minimum separation of the two air-
craft
1.4 NM horizontally and 725 ft vertically
Applicable minimum separation 5 NM horizontally or 1000 ft vertically
AIRPROX category of the serious
incident
ICAO category A - high risk of collision
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 7 of 26
Investigation
The serious incident occurred on 8 June 2009 at 12:19 UTC. The notification was received by
the Aircraft Accident Investigation Bureau (AAIB) on 9 June 2009 at 14:06 UTC. After pre-
liminary clarifications, which are usually necessary with this type of serious incident, the in-
vestigation was opened on 10 June 2009.
The AAIB notified the investigating authorities in France and Ireland of the serious incident.
Both states then nominated an authorised representative.
The present investigation report is published by the AAIB.
Summary
On 8 June 2009, an Airbus A318, radio callsign Air France 989Z, was flying at FL 380 on the
Kempten – Trasadingen – Hochwald route in the area of responsibility of Sector M4 of the
Zurich Area Control Centre. Flying from the north, a Boeing 737, radio callsign RYR 1702,
was flying at flight level (FL) 370 via Trasadingen to waypoint ODINA. The flight paths of the
two aircraft crossed above Trasadingen. About 12 NM east of Trasadingen, the air traffic
controller, who was under training, instructed Air France 989Z to descend to FL 360. The
supervising coach did not notice this instruction. Shortly afterwards, a short-term conflict
alert indicated the impending conflict on the radar display. The coach then took over air traf-
fic control and allowed RYR 1702 to descend to FL 360 as well. The traffic alert and collision
avoidance system generated a resolution advisory in both aircraft. The crews obeyed these
instructions. The two aircraft crossed above Trasadingen with a lateral distance of 1.4 NM
and an altitude difference of 725 ft.
Causes
The serious incident is attributable to the fact that air traffic control cleared an aircraft at
FL 380 to descend to FL 360 without taking account of an aircraft at FL 370 crossing the
flight path. The result was that an inadvertent convergence of these aircraft occurred, involv-
ing a high risk of collision.
The following factors contributed substantially to the origin of the serious incident:
An intervention by the supervising air traffic controller which was too late, because he
had not realised that the trainee air traffic controller was overwhelmed by the chal-
lenging traffic situation.
Within the Zurich air traffic control unit there was no function for monitoring clear-
ances with regard to possible conflicts.
The following factors contributed to the genesis of the serious incident:
The fact that air traffic control received no confirmation of a high rate of descent by
AFR 989Z.
The fact that the supervising air traffic controller was working without a headset.
Safety recommendation
Within the framework of the investigation, one safety recommendation was made.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 8 of 26
1 Factual information
1.1 History of the flight
1.1.1 General
For the following description of the history of the flight, the recordings of the ra-
diotelephony traffic, radar data and the statements of the crew members and air
traffic controllers were used.
At the time of the serious incident the copilot was acting as pilot flying (PF) and
the commander was acting as pilot not flying (PNF) in the cockpit of AFR 989Z.
At the time of the serious incident the commander was acting as pilot flying (PF)
and the copilot was acting as pilot not flying (PNF) in the cockpit of RYR 1702.
Both flight AFR 989Z and flight RYR 1702 were taking place under instrument
flight rules.
In air traffic control, Sector M4 of the Zurich Area Control Centre (ACC) was re-
sponsible for the airspace from FL 356 to FL 660.
Sector M4 was occupied by three persons: an air traffic controller under training
was performing the function of radar executive (RE) (RE-M4 trainee). Her work
was being monitored by a coach (RE-M4 coach). In addition, there was a third air
traffic controller in Sector M4 who was performing the function of radar planner
(RP-M4).
1.1.2 Flight preparation
The RE-M4 trainee had commenced on-the-job training in mid-February 2009
and was therefore at the beginning of the second of three practical training
phases. This took place in Sectors M1 to M4 in the range from FL 246 to FL 660.
Training on sectors FL 245 and lower was not yet a component of her training.
During her activity she wore a headset consisting of earphones and a micro-
phone.
The RE-M4 coach had more than 10 years experience of on-the-job training. He
had already worked together with the RE-M4 trainee for a few days. He was as-
signed Sector M4 together with the trainee air traffic controller. He was not ex-
pecting any extraordinary situation. No discussion of the traffic situation to be
expected or of the volume of traffic took place with the trainee air traffic control-
ler.
The RE-M4 coach did not have a workstation of his own available for monitoring
the work of the RE-M4 trainee. Three workstations were envisaged for Section
M4; at the time of the serious incident one of them was not yet ready for opera-
tion. The RE-M4 coach therefore sat on the left of the RE-M4 trainee, a little to
her rear, and used the trainee’s radar screen for monitoring her work. According
to his statements, this situation restricted him somewhat in his function as a
coach. He did not wear a headset during his activity.
From 11:30 UTC the airspace to the east of airway UA9 was in use by the mili-
tary and was therefore available to civil air traffic control only subject to restric-
tions. This meant that transit traffic from waypoint SUXAN in the direction of
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 9 of 26
Figure 1: Standard route in the event of military flight operations over waypoints SUXAN
– NEGRA and the VHF beacon TRA – HOC (blue). Possible shortcut routes are shown by a
blue dotted line.
Hochwald (HOC) VHF omnidirectional radio beacon (VOR) demanded a high level
of coordination with military air traffic control. The RP-M4 was mainly occupied
with this coordination. Depending on an agreement between Sector M4 and mili-
tary air traffic control, a shortcut through the military airspace could be assigned
to civil air traffic control.
For this reason, between 11:30 and 15:00 UTC the capacity of Sector M4 had
been limited to 38 flights per hour. A traffic volume of 39 flights was predicted
for the period from 11:20 UTC to 12:40 UTC. Forty-three flights were counted
between 11:30 and 12:30 UTC.
According to the statement by the RE-M4 coach, the RE-M4 trainee was working
independently for the first 30 minutes and no assistance was necessary on his
part. He subsequently realised that the RE-M4 trainee was no longer assimilating
all the information communicated to her by the RP-M4. For this reason he inter-
mittently assumed a position between the RE-M4 trainee and the RP-M4. The
peak loading was reached about 11 minutes before the serious incident, when an
aircraft destination Lugano flew into Section M4 at FL 410. This gave rise to a
complex situation which the RE-M4 trainee was no longer able to handle inde-
pendently. The RE-M4 coach then helped her and gave her instructions for the
aircraft’s descent. This enabled separation to be maintained.
Airspace in military
use
UA9
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 10 of 26
The complexity of the traffic handling situation was additionally aggravated by
the south-westerly wind situation. Since air traffic control assesses the traffic
situation using ground speed, among other things, high wind speeds during
heading changes lead to variable speed differences between aircraft. Conse-
quently, possible crossing problems after a change in the direction of flight often
became apparent subject to some delay. Above all, this concerned flights from
the direction of SUXAN which, by agreement with military air traffic control,
sooner or later turned in the direction of the Hochwald VOR and crossed flights
on the route between waypoint BERSU and the Trasadingen VOR (TRA).
The Air France Airbus A318-111 aircraft, radio callsign AFR 989Z, had taken off
on 8 June 2009 from Belgrade (Serbia) on a flight to Paris (France). The ACC Zu-
rich area of responsibility was crossed from the Kempten VHF omnidirectional ra-
dio beacon (KPT) along airway UL856 over the Trasadingen (TRA) and Hochwald
(HOC) VOR and waypoint MOROK at FL 380.
The Ryanair Boeing 737-8AS aircraft, radio callsign RYR 1702, had taken off on 8
June 2009 from East Midlands (United Kingdom) on a flight to Bergamo (Italy).
RYR 1702 was flying from the north at FL 370 within the UAC Switzerland area of
responsibility.
According to the statements of the flight crews on both aircraft, the flights had
proceeded with no noteworthy anomalies up to the serious incident.
1.1.3 Sequence of the serious incident
At 12:07:35 UTC, the crew of AFR 989Z reported for the first time to ACC Zurich
Sector M4 on the 133.405 MHz frequency.
The RE-M4 trainee confirmed radar identification to AFR 989Z during the first
call. A little later, she requested the crew to switch the transponder code to
7527. Immediately after the confirmation by the crew of AFR 989Z, the crew of
flight RYR 1702 reported for the first time on the Sector M4 frequency. The RE-
M4 trainee cleared the crew for the route to the Trasadingen VOR and then to
waypoint ODINA.
Another flight was coming from the south east at FL 380; this would cross AFR
989Z over the HOC VHF omnidirectional radio beacon. By agreement with the
RE-M4 trainee, the RP-M4 had therefore coordinated flight level FL 360 for AFR
989Z with the neighbouring Reims UAC control unit. There was another aircraft
flying from the south-west at FL 380 into the Sector M4 area of responsibility
along route BERSU – KUDES – LOKTA. Flight level FL 320 was coordinated for
this flight with the neighbouring Rhine UAC unit. The RE-M4 trainee therefore al-
lowed this aircraft to descend to FL 360, corresponding to the lowest possible
flight level in her sector. She then handed over the aircraft to Sector M3. When
the RE-M4 trainee saw on the radar display that this aircraft had left FL 360 and
was descending, at 12:17:20 UTC she instructed the crew of the Air France 989Z
to make a descent to FL 360. This was confirmed immediately by the crew. At
this time the aircraft was some 12 NM east of the Trasadingen VOR; RYR 1702,
at FL 370, still had a distance of approximately 11 NM to fly to the TRA beacon.
In this phase, the RP-M4 was for the most part busy with military air traffic con-
trol: coordinating shortcuts for civil aircraft routed through the airspace in use by
the military. Neither he nor the RE-M4 coach had noticed the RE-M4 trainee’s
clearance to the crew of AFR 989Z for a descent to FL 360.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 11 of 26
When the RP-M4 turned back to the radar display after two coordination conver-
sations, he noticed AFR 989Z descending, shortly before the Trasadingen VOR.
After repeating his question in this regard he received the RE-M4 trainee’s an-
swer, to the effect that this aircraft was descending.
Figure 2: Schematic representation of the flight paths of the aircraft from the south-
west, direction waypoint BERSU and the aircraft from the south-east over waypoint
SUXAN, direction NEGRA, with a shortcut through the airspace in military use (both
shown in blue, both at FL 380). Flight AFR 989Z is approaching the TRA VHF omnidirec-
tional radio beacon from the east at FL 380 and flight RYR 1702 from the north (both
shown in red).
At 12:17:54 UTC a short-term conflict alert (STCA) appeared on the Sector M4
radar display which made the controllers aware of the dangerous situation be-
tween AFR 989Z and RYR 1702. The RE-M4 coach immediately made his way be-
tween the RE-M4 trainee and the RP-M4 and gave the RE-M4 trainee the instruc-
tion to get AFR 989Z to descend at a rate of descent of at least 3000 ft/min. This
instruction was transferred immediately by the RE-M4 trainee.
BERSU – KUDES – LOKTA
FL 380 descending FL 360
later descending FL 320
AFR 989Z FL 380 descending
FL
360
SUXAN – HOC
FL 380
RYR 1702
FL 370
NEGRA
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 12 of 26
Figure 3: Radar recording of the crossing of AFR 989Z (red) and RYR 1702 (blue). The
Trasadingen beacon (TRA) is shown in brown and the national frontiers are shown in yel-
low.
According to the RE-M4 coach’s statement, the RE-M4 trainee requested him to
take over traffic control when there was no confirmation from the crew of AFR
989Z. The RE-M4 coach took over traffic control and repeated the order to the
crew of AFR 989Z. To do this he used the hand-held microphone to the right of
the RE-M4 trainee’s workstation, as he was not wearing a headset. When there
was still no answer, he instructed the crew of RYR 1702 to descend to FL 360.
According to his statements, the RE-M4 coach assumed that the crew of AFR
989Z had not heard the instructions and were descending at a low rate of de-
scent. His intention was to have RYR 1702 pass below AFR 989Z.
The RP-M4 was of the opinion that the impending conflict between AFR 989Z and
RYR 1702 was already known to all those involved in the sector when the STCA
was triggered.
The autopilot on AFR 989Z was switched on.
According to his statements, the
copilot had heard all the ATC instructions and had operated the aircraft accord-
ingly. On the first instruction from the RE-M4 trainee to descend to FL 360, he
initiated the descent using the vertical speed (VS) flight mode. He initially se-
lected a rate of descent of 1000 ft/min. When he received the instruction to de-
scend at a rate of descent of 3000 ft/min, he switched off the autopilot in order
to be able to make the descent more quickly. At this time he was aware that
there was a risk of collision. Both pilots were surprised at this high rate of de-
scent and judged it to be inappropriate for this situation.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 13 of 26
Shortly afterwards the traffic alert and collision avoidance system (TCAS) on AFR
989Z generated the resolution advisory (RA) ‘
descend, descend’
. The copilot
obeyed the descent instruction according to the displays on the primary flight
display (PFD). At 12:18:38 UTC the crew reported the TCAS descent. The RE-M4
coach gave the following reply:
"Air France nine eight nine zulu, traffic twelve
o’clock, turn right by twenty degrees"
. This instruction was confirmed immedi-
ately by AFR 989Z. At this time the aircraft was some 2.5 NM east of the TRA
VOR. The commander saw the other aircraft when the copilot initiated the right
turn.
When RYR 1702 received the instruction at 12:18:23 UTC to descend to FL 360,
it was approximately 4 NM north of the Trasadingen VOR. After the crew had ac-
knowledged the clearance, the coach gave the following traffic information:
"...Traffic on your left hand side, same level, five miles".
At almost the same time
the crew received a TCAS traffic advisory (TA), followed immediately by an RA
with the instruction “climb, climb now”. The crew’s answer to Sector M4 was in-
terrupted by the report by AFR 989Z that they had initiated a TCAS descent. The
RE-M4 coach’s repeated question to RYR 1702 as to whether they had visual
contact with the aircraft on their left also produced no result, as two simultane-
ous reports overlapped and the answer was not comprehensible.
The radar recording shows that RYR 1702 first descended to FL 367 and then
climbed back to FL 369. The two aircraft crossed above Trasadingen with a lat-
eral distance of 1.4 NM and an altitude difference of 725 ft. Both crews continued
their flights to their destinations.
1.1.4 Location of the serious incident
Geographical position Over the Trasadingen VOR
Date and time 8 June 2009, 12:19 UTC
Lighting conditions Daylight
Height above sea level or flight level AFR 989Z: FL 368
RYR 1702: FL 361
1.2 Personnel information
1.2.1 Crew of AFR 989Z
1.2.1.1 Commander
1.2.1.1.1 Training
Person French citizen, born 1962
Licence Airline transport pilot licence aeroplane –
ATPL(A)) according to joint aviation re-
quirements (JAR), issued by the French
supervisory authority on 18 May 2009.
Ratings Type rating Airbus A320 as pilot in com-
mand
Instrument flying multi-engined aircraft
IR ME(A)
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 14 of 26
Instrument flying rating
Last proficiency check Simulator check
Medical fitness certificate Class 1 with the following restriction:
VDL – shall wear corrective lenses
Valid till 31 January 2010
Last medical examination 28 January 2009
1.2.1.1.2 Flying experience
Total 11 370 hours
on the type involved in the incident 3500 hours
1.2.1.2 Co-pilot
1.2.1.2.1 Training
Person French citizen, born 1972
Licence Airline transport pilot licence aeroplane –
ATPL(A)) according to joint aviation re-
quirements (JAR), issued by the French
supervisory authority on 4 April 2007.
Ratings Type rating Airbus A320 as copilot
Instrument flying rating Instrument flying multi-engined aircraft
IR ME(A)
Last proficiency check Simulator check
Training on ACAS During the last proficiency check on 16
May 2009 a TCAS situation was trained
for on the simulator.
Medical fitness certificate Class 1 with the following restriction:
VDL – shall wear corrective lenses
Valid till 31 August 2009
1.2.1.2.2 Flying experience
Total 2720 hours
on the type involved in the incident 286 hours
1.2.2 Crew of RYR 1702
1.2.2.1 Commander
1.2.2.1.1 Training
Person French citizen, born 1950
Licence Airline transport pilot licence aeroplane –
ATPL(A)) according to joint aviation re-
quirements (JAR), issued by the United
Kingdom supervisory authority on 16 July
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 15 of 26
2008.
Relevant ratings
Type rating B737 300-900, valid till 7
October 2009.
Instrument flying rating Instrument flight aircraft IR(A)
Instrument approaches on B737 300-
900, last extended on 8 October 2008,
valid till 7 October 2009.
Last proficiency check Simulator check
on 7 October 2008
Training on ACAS During the last proficiency check on 7
October 2008, a TCAS situation was
trained for on the simulator.
Medical fitness certificate Class 1
VDL – shall wear corrective lenses
Valid till 29 May 2010
Last medical examination 28 May 2009
1.2.2.1.2 Flying experience
Total 17 121:42 hours
on the type involved in the incident 2287:31 hours
1.2.2.2 Co-pilot
1.2.2.2.1 Training
Person British citizen, born 1980
Licence Commercial pilot licence – CPL(A) issued
by the Irish aviation supervisory author-
ity on 4 November 2008.
Ratings
Type rating B737 300/900, valid till 30
September 2009.
Instrument flying rating Instrument flight aircraft IR(A)
Instrument approaches on B737
300/900, last extended on 16 September
2008, valid till 30 September 2009.
Last proficiency check Operational proficiency check
Training on ACAS During the last proficiency check on 28
March 2009, a TCAS situation was
trained for on the simulator.
Medical fitness certificate Class 1 without restrictions
Valid till 20 December 2009
Last medical examination 3 December 2008
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 16 of 26
1.2.2.2.2 Flying experience
Total 572 hours
on the type involved in the incident 357 hours
1.2.3 Air traffic control personnel
1.2.3.1 Air traffic controller 1
Function Radar executive Sector M4 (RE-M4)
coach
Person Swiss citizen, born 1968
Work days before the day of the inci-
dent
2 days
Duty times in the 48 hours before the
serious incident
06/06/09 03:20 UTC – 10:20 UTC
07/06/09 05:10 UTC – 12:10 UTC
Start of duty on the day of the incident 11:10 UTC
Licence Air traffic controller licence based on
European Community Directive
2006/23, first issued by the FOCA on
2 November 1995, valid till 22 March
2010
Relevant ratings Area control surveillance, valid till 22
March 2010
On-the-job training instructor valid till
22 March 2010
1.2.3.2 Air traffic controller 2
Function Radar planner Sector M4 (RP-M4)
Person Swiss citizen, born 1971
Work days before the day of the inci-
dent
1 day
Duty times in the 48 hours before the
serious incident
06/06/09 Rest day
07/06/09 14:50 UTC – 21:50 UTC
Start of duty on the day of the incident 11:20 UTC
Licence Air traffic controller licence based on
European Community Directive
2006/23, first issued by the FOCA on
15 November 1996, valid till 26 April
2010
Relevant ratings Area control surveillance, valid till 26
April 2010
1.2.3.3 Air traffic controller 3
Function Radar executive Sector M4 (RE-M4)
trainee
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 17 of 26
Person German citizen, born 1984
Work days before the day of the inci-
dent
2 days
Duty times in the 48 hours before the
serious incident
06/06/09 03:20 UTC – 10:20 UTC
07/06/09 14:00 UTC – 21:00 UTC
Start of duty on the day of the incident 11:10 UTC
Licence Student air traffic controller licence
based on European Community Direc-
tive 2006/23, first issued by the FOCA
on 11 September 2008, valid till 16
October 2010
Relevant ratings Area control surveillance, valid till 16
October 2010
1.3 Aircraft information
1.3.1 AFR 989Z aircraft
Registration F-GUGK
Aircraft type A318-111
Characteristics Twin-jet short-haul and medium-haul commercial
aircraft
Manufacturer Airbus S.A.S, Toulouse, France
Year of manufacture 2005
Serial number 2601
Owner: Société Air France, Roissy, France
Operator: Société Air France, Roissy, France
1.3.2 RYR 1702 aircraft
Registration EI-DHK
Aircraft type B737-8AS
Characteristics Twin-jet short-haul and medium-haul commercial
aircraft
Manufacturer Boeing Commercial Airplanes, Seattle, Washington
United States of America
Year of manufacture 2005
Serial number 33820
Owner: Ryanair Ltd., Dublin, Ireland
Operator: Ryanair Ltd., Dublin, Ireland
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 18 of 26
1.4 Meteorological information
1.4.1 General
The information in sections 1.4.2 to 1.4.5 was provided by MeteoSwiss.
1.4.2 General meteorological situation
A low-pressure zone was moving from the eastern Atlantic in the direction of the
Bay of Biscay. It was pushing humid, warm air from southern France into Swit-
zerland.
At the same time the southerly air current was increasing on the face of
the Alpine area. The intensity of
precipitation was low on the north side of the
Alps.
1.4.3 Weather at the time of the serious incident
The following information on the weather at the time of the serious incident in
the Trasadingen region is based on a spatial and chronological interpolation of
the observations of different weather stations.
Quotation from MeteoSwiss report
Weather/cloud Outside of cloud
Cloud ceiling at approximately FL 240
Visibility
Over 10 km
Wind
FL 360, 240 degrees at 75 kt
Temperature/Dewpoint
FL 360, -58 °C / -66 °C
Hazards:
None detectable
1.4.4 Astronomical information
Position of the sun: Azimuth:
208°
Elevation:
63°
Lighting conditions Daylight
1.4.5 Winds at high altitude
On wind chart FL 340, west south-westerly winds at 70 kt and a temperature of
minus 55 ˚C were forecast for this region; on wind chart FL 390 the forecast was
also for west south-westerly winds at 70 kt and minus 59 ˚C.
The Payerne and Stuttgart radio probes (12:00 UTC) indicated south-westerly
winds at 75 to 80 knots at the altitude of the airprox. The temperature at FL 360
was minus 58 °C and the dewpoint was minus 66 °C.
1.5 Safety systems
1.5.1 Airborne collision avoidance system
1
Functioning collision avoidance systems (traffic alert and collision avoidance sys-
tem - TCAS) were fitted to both aircraft; they provided traffic information (traffic
advisories
-
TA) and instructions for conflict resolution (resolution advisories
-
1
Airborne collision avoidance system (ACAS) is the designation of the basic concept. The International Civil Avia-
tion Organization (ICAO) uses this term when drawing up the standards with which the system must comply. The
traffic alert and collision avoidance system (TCAS) is a concrete implementation of this concept.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 19 of 26
RA). Both crews reacted to the system commands without delay. AFR 989Z de-
scended to FL 360, whilst RYR 1702 climbed back to FL 370.
1.5.2 Short-term conflict alert
The Skyguide radar system included a convergence warning system (short-term
conflict alert – STCA). In the present case, in accordance with its design, it made
the air traffic controllers aware of the impending conflict.
1.5.3 System for monitoring clearances
Since 22 December 2005, Skyguide’s flight plan processing system (stripless en-
vironment) has included a function in the Geneva Area Control Centre which
monitors whether altitude clearances entered into the system will lead to a con-
flict between the aircraft involved. This stripless environment was not available in
the Zurich Area Control Centre at the time of the serious incident.
1.6 Organisational and management information
1.6.1 Procedures
1.6.1.1 General
The relevant basis for air traffic control procedures is defined in the air traffic
management manual (ATMM) for the Zurich Area Control Centre (ACC). At the
time of the serious incident, the following regulations, among others, applied.
1.6.1.2 Use of headsets
“3
HEADSET OBLIGATION
RE, and other operators at ATC sectors and FIS positions, shall normally work
with headsets. While working with headsets, the loudspeakers shall be switched
on at an appropriate volume level.
RP, RC and DOM are not required to work with headsets.
In the following situations it is not necessary to work with headsets:
- For ACC sectors/DELTA/FIC: When the adjacent sector is not active
- For APP/ARFA/DEP: When only one of these working positions is active
Note: Headsets shall be used during visits, periods of maintenance or cleaning
work in the immediate vicinity of the relevant sector, or during other noise gen-
erating activities.
The correct operation of the headset shall be verified when taking over a working
position
(....)”
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 20 of 26
1.6.1.3 Rules concerning deployment of trainee air traffic controllers
“
4 PERSONNEL UNDER TRAINING
Personnel under training, having passed neither a licensing or final test, nor an
appropriate intermediate test, shall only work in positions that permit permanent
supervision of their actions. After having passed an appropriate intermediate
test, they work without supervision, taking into account the workload at the posi-
tion concerned.
Persons holding an appropriate entry in their licence (Special authorisation for
the supervision of training at working positions) only are allowed to supervise
personnel under training. If the supervising person must leave the working posi-
tion, the supervision task must be transferred to another authorised person, or
the position must be occupied by an appropriately trained person.
The responsibility for the safety and efficiency of ATM services provided by a
trainee lies with the OJT instructor to the same extent as if he were providing the
services himself, except that he will not be held responsible for the consequences
of any action taken by the trainee which disregard his instructions
.”
2 Analysis
2.1 Technical aspects
Both for the aircraft involved and for the air traffic control systems concerned,
there are no indications of any pre-existing technical defects which might have
caused or influenced the serious incident.
At the time of the serious incident, unlike in the area control centre Geneva, in
the area control centre Zurich there was no function available which monitored
whether planned altitude clearances would lead to a conflict with other aircraft.
This function would have detected the impending conflict, so it would very
probably not have been possible for the serious incident to have occurred.
The fact that the RE-M4 coach had no workstation of his own available does not
constitute a shortcoming, but it may have restricted him somewhat in his activity.
2.2 Human and operational aspects
2.2.1 Air traffic control
Between 11:30 and 12:30 UTC the workload in Sector M4, at 43 flights, was
above the sector capacity of 38 flights. The circumstance of the strong westerly
wind flow current also increased the complexity of traffic management. Further-
more, there was the additional factor that the military airspace of airway UA9
was available only subject to restrictions.
In view of these general conditions it can be concluded that the RE-M4 trainee
had to work for a fairly long period at the limits of her personal performance.
This also corresponds to the statement of the RE-M4 coach to the effect that the
RE-M4 trainee, after a presence of about 30 minutes in sector M4 was no longer
able to assimilate and process all the coordination conversations with the RP-M4.
When the peak loading was reached some eleven minutes before the serious in-
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 21 of 26
cident, the RE-M4 coach had to support the RE-M4 trainee in resolving a separa-
tion problem. During this intensive phase, the RE-M4 coach did not realise that
the RE-M4 trainee was overwhelmed. This meant that the RE-M4 coach allowed
the RE-M4 trainee to continue working independently and did not subsequently
take over traffic control.
There followed a phase of decreasing traffic volume which lightened the burden
on the RE-M4 trainee somewhat. The RE-M4 coach did not notice the clearance
for AFR 989Z to descend to FL 360 given in this phase by the RE-M4 trainee. This
is quite probably attributable to the fact that the RE-M4 coach was not wearing a
headset. Headsets attenuate ambient noise and therefore facilitate complete and
accurate perception of radiocommunications. It is also conceivable that the con-
centration of the RE-M4 coach had lapsed a little after the demanding phase or
that he was distracted by other activities.
The traffic situation in connection with the serious incident involved three aircraft
which were flying at FL 380 into Sector M4 from different directions. In addition,
RYR 1702 was flying from the north at FL 370 in the direction of Trasadingen.
The attention of the RE-M4 trainee was directed at the three flights at FL 380
which had to be separated from each other. For two of these flights, including
flight AFR 989Z, a descent to lower flight levels was envisaged. The RE-M4
trainee initially allowed the flight from the south-west to descend. After this flight
had started descending from FL 360 and after she had noted this on the radar
display, she allowed AFR 989Z to descend to FL 360; this was not noticed by the
RE-M4 coach. RYR 1702, at FL 370, was at this time not part of the RE-M4
trainee’s traffic concept. The fact that she did not include this flight in her traffic
concept might be attributable on the one hand to her lack of experience. On the
other hand, the lapse in concentration could be attributable to the previous high
workload. This would explain why her attention was directed primarily at the
three flights at FL 380.
After the STCA alert was triggered, the RE-M4 coach tried to resolve the problem
by instructing AFR 989Z to maintain a rate of descent of at least 3000 ft/min.
This instruction was issued by the RE-M4 trainee at the behest of the RE-M4
coach. This high rate of descent was not appropriate for a descent of 2000 ft. It
constituted an emergency air traffic control measure to prevent a collision. For
the pilots, it was an astonishing instruction. However, in order to comply with it
as far as possible they were obliged to switch off the autopilot and increase the
rate of descent without delay. Such a manual intervention while cruising is ex-
traordinary and demands greater concentration from the flight crew as well as
regulated application of the controls, because at high altitudes in particular there
are only narrow margins relating to the aircraft’s aerodynamic limits. In addition,
for a descent with a comparatively small difference in altitude and a high rate of
descent there is the problem that this rate can only be maintained for a short
time and the descent must be levelled off after only a few seconds in order not
to drop below the assigned flight level. It is therefore understandable that under
these circumstances the crew of AFR 989Z was concentrating on the challenging
implementation of the instruction in accordance with the generally recognised
aviate – navigate – communicate
principle and that confirmation of the instruc-
tion was omitted as a less important task.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 22 of 26
In the present case, the RE-M4 coach interpreted the absence of a response
from AFR9892 and the initially low rate of descent as non-compliance with the
instruction to descend at a rate of at least 3000 ft/min. In this situation he took
over traffic control and repeated the descent instruction, with no acknowledge-
ment. The RE-M4 coach therefore sought a different solution. He instructed the
crew of RYR 1702 to initiate a descent to FL 360, with the intention of allowing it
to pass below AFR 989Z. This decision to clear two aircraft on a conflicting head-
ing at the same flight level is difficult to justify and has to be attributed to the
stressful situation which had arisen within a very short time.
The TCAS then made the two flight crews aware of the danger of collision and is-
sued evasive manoeuvres. These were carried out by the crews without delay. At
12:18:38 UTC the crew of AFR 989Z were able to inform air traffic control that
they were in a TCAS descent. The RE-M4 coach answered this statement with
“
Air France nine eight nine zulu, traffic
twelve
o’clock, turn right by twenty de-
grees
”
.
The internationally valid rules at the time of the serious incident for dealing with
a TCAS evasive manoeuvre specify that after receipt of a TCAS RA message, air
traffic control must not transfer any further instructions to flight crews relating to
the flight path until they report “
clear of conflict
”. The air traffic controller's reac-
tion did in fact deviate from this principle, but did not increase the risk. It is ex-
plicable in that on the one hand he was trying by any means to avoid a collision
and on the other hand he may possibly have been in a reaction pattern applied
earlier.
In retrospect, the reactions of the RE-M4 coach, which were not adequate to re-
solve the situation, show that he allowed the RE-M4 trainee to work independ-
ently for too long and waited too long before taking over traffic control himself.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 23 of 26
3 Conclusions
3.1 Findings
3.1.1 Technical aspects
The investigation produced no indications of any pre-existing technical
faults which might have caused the incident.
The TCAS generated a resolution advisory on both aircraft, the instructions
of which were obeyed immediately and correctly by the crews.
The Sector M4 STCA was triggered at 12:17:54 UTC.
Since 22 December 2005, Skyguide’s flight plan processing system (stri-
pless environment) has included a function in the Geneva Area Control
Centre which monitors whether planned clearances lead to a conflict be-
tween the aircraft involved.
This stripless environment was not available in the Zurich Area Control Cen-
tre at the time of the serious incident.
3.1.2 Crews
The crews of the two aircraft involved in the serious incident were in pos-
session of the licences necessary to exercise their activities.
3.1.3 Air traffic control personnel
The air traffic controllers and the trainee controller were in possession of
the licences necessary to exercise their activities.
3.1.4 History of the flight
Flight RYR 1702 was flying from the north in the direction of the Trasadin-
gen VOR at FL 370.
Flight AFR 989Z was flying from the east in the direction of the Trasadin-
gen VOR at FL 380.
At 12:17:20 UTC the RE-M4 trainee instructed the crew of AFR 989Z to de-
scend from FL 380 to FL 360.
The instruction from the RE-M4 trainee to AFR 989Z to descend to FL 360
was not noticed by the RE-M4 coach.
The RE-M4 coach gave the RE-M4 trainee the instruction to get AFR 989Z
to descend at a rate of descent of at least 3000 ft/min.
The crew of AFR 989Z switched off the autopilot in order to be able to
achieve the rate of descent of 3000 ft/min for the 2000 ft reduction in alti-
tude.
After the STCA occurred, the RE-M4 coach took over traffic control.
Since the crew of AFR 989Z had not confirmed the 3000 ft/min rate of de-
scent, the RE-M4 coach repeated the instruction.
When the crew of AFR 989Z still gave no answer, he instructed the crew of
RYR 1702 to also descend to FL 360.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 24 of 26
The two aircraft crossed above the Trasadingen VOR with a lateral distance
of 1.4 NM and an altitude difference of 725 ft.
3.1.5 General conditions
The M4 workstation was occupied by an RE-M4 coach, an RE-M4 trainee
and the RP-M4.
The RE-M4 trainee was at the beginning of the second of three training
phases.
When working, the RE-M4 trainee wore a headset consisting of head-
phones and a microphone.
The RE-M4 coach monitored the RE-M4 trainee without wearing a headset.
A separate workstation was not available for the RE-M4 coach.
The military airspace was available only to a limited extent and only after
coordination had taken place.
Between 11:30 and 15:00 UTC, the capacity of Sector M4 was limited to 38
flights per hour.
Forty-three flights were counted in sector M4 between 11:30 and 12:30
UTC.
The complexity of the traffic handling situation was additionally aggravated
by the south-westerly wind situation.
3.2 Causes
The serious incident is attributable to the fact that air traffic control cleared an
aircraft at FL 380 to descend to FL 360 without taking account of an aircraft at
FL 370 crossing the flight path. The result was that an inadvertent convergence
of these aircraft occurred, involving a high risk of collision.
The following factors contributed substantially to the origin of the serious inci-
dent:
An intervention by the supervising air traffic controller which was too late,
because he had not realised that the trainee air traffic controller was over-
whelmed by the challenging traffic situation.
Within the Zurich air traffic control unit there was no function for monitor-
ing clearances with regard to possible conflicts.
The following factors contributed to the genesis of the serious incident:
The fact that air traffic control received no confirmation of a high rate of
descent by AFR 989Z.
The fact that the supervising air traffic controller was working without a
headset.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 25 of 26
4 Safety recommendations and measures taken since the serious incident
4.1 Safety recommendations
4.1.1 Safety deficit
On 8 June 2009, an Airbus A318, radio callsign Air France 989Z, was flying at
FL 380 on the Kempten – Trasadingen – Hochwald route in the area of responsi-
bility of Sector M4 of Zurich Area Control Centre. Coming from the north, a Boe-
ing 737, radio callsign RYR 1702, was flying at flight level (FL) 370 via Trasadin-
gen to waypoint ODINA. The flight paths of the two aircraft crossed above
Trasadingen. About 12 NM east of Trasadingen, the air traffic controller, who
was under training, instructed Air France 989Z to descend to FL 360. The super-
vising coach did not notice this instruction. Shortly afterwards, a short-term con-
flict alert indicated the impending conflict on the radar display. The coach then
took over air traffic control and allowed RYR 1702 to descent to FL 360 as well.
The
traffic alert and collision avoidance system generated a resolution advisory in
both aircraft. The crews obeyed these instructions. The two aircraft crossed
above Trasadingen with a lateral distance of 1.4 NM and an altitude difference of
725 ft.
Within the framework of the investigation it was established that since 22 De-
cember 2005, Skyguide’s flight plan processing system (stripless environment) in
the Geneva Area Control Centre has included a function which monitors whether
planned clearances will lead to a conflict between the aircraft involved.
This stripless
environment was not available in the Zurich Area Control Centre at
the time of the serious incident. Such a function would have detected the im-
pending conflict, so it would very probably not have been possible for the serious
incident to have occurred.
4.1.2 Safety recommendation no. 424
The Federal Office of Civil Aviation (FOCA) should ensure that the Zurich Area
Control Centre is equipped in such a way that planned clearances are monitored
for possible conflicts.
Final report AFR 989Z / RYR 1702
Aircraft Accident Investigation Bureau Page 26 of 26
4.2 Measures taken since the serious incident
In the area control centre Zurich, in all work sectors, a third workstation for a ra-
dar coordinator was put into service. Among other things, these workstations are
also available to supervising coaches.
Payerne, 30 November 2010 Aircraft Accident Investigation Bureau
This report contains the AAIB’s conclusions on the circumstances and causes of the accident/serious
incident which is the subject of the investigation.
In accordance with Art 3.1 of the 9th edition, applicable from 1 November 2001, of Annex 13 to the
Convention on International Civil Aviation (ICAO) of 7 December 1944 and Article 24 of the Federal Air
Navigation Act, the sole purpose of the investigation of an aircraft accident or serious incident is to
prevent accidents or serious incidents. The legal assessment of accident/incident causes and circum-
stances is expressly no concern of the accident investigation. It is therefore not the purpose of this
investigation to determine blame or clarify questions of liability.
If this report is used for purposes other than accident prevention, due consideration shall be given to
this circumstance.
