Austrian DH8D at Lugano on Oct 13th 2015, GPWS warning on short ILS final

Last Update: December 21, 2017 / 17:24:49 GMT/Zulu time

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Photo of Austrian Airlines OE-LGL, De Havilland Dash 8 (400) — Austrian Airlines OE-LGL, De Havilland Dash 8 (400) (Photo credit: redlegsfan21 / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Oct 13, 2015

Classification
Incident

Airline
Austrian Airlines

Flight number
LX-2912

Departure
Zurich, Switzerland

Destination
Lugano, Switzerland

Aircraft Registration
OE-LGL

Aircraft Type
De Havilland Dash 8 (400)

ICAO Type Designator
DH8D

Airport
Lugano Airport, Lugano

Airport ICAO Code
LSZA

An Austrian Airlines de Havilland Dash 8-400 on behalf of Swiss, registration OE-LGL performing flight LX-2912 from Zurich to Lugano (Switzerland) with 55 passengers and 4 crew, was on an IGS approach to Lugano's runway 01 about 3km (1.6nm) before touchdown at about 18:11L (16:11Z) when the crew received a GPWS warning and went around climbing to and reaching 6000 feet above the aerodrome. The aircraft performed a standard missed approach, joined a hold, the crew subsequently decided to divert to Milan Malpensa due to the present weather conditions.

On Feb 1st 2016 Switzerland's SUST released notification that the occurrence was rated a serious incident and an investigation has been opened.

There is a steep rising mountain side about 500 meters/1600 feet to the right of the extended runway center line about 3km before touchdown, (unverified) ADS-B data seem to suggest the aircraft may have been to the right of the extended center line subsequently correcting to the left and overflying the runway to the left of the centerline.

The airline told Austrianwings that the crew performed a visual approach to Lugano when the GPWS warning occurred, the crew correctly executed a missed approach. The occurrence is also being investigated within Austrian Airlines.

On Dec 21st 2017 the SUST released their final report in German concluding the probable cause of the serious incident was:

a dangerous closure to terrain while on a defined visual approach in marginal weather conditions, which was the result of a combination of following causal factors:

- development and training of an unsuitable visual approach procedure by the airline
- insufficient cooperation and oversight by authorities in relation to the visual procedure
- too late initiation of go around

A contributing factor was the insufficient information exchange between BAZL and airport operator.

Editorial note: considering the analysis with respect to reaching a different understanding of BAZL's prohibition of the procedure by airline and BAZL, the contributing factor probably was meant to read: "A contributing factor was the insufficient information exchange between BAZL and airline".

The SUST reported the crew intended to perform a LOC approach runway 01. The crew was aware that the approach might not be possible due to weather and therefore intended to perform a visual procedure to break off the LOC and do a full circle around Monte Caslano (to the left of the LOC about 1.6nm before the runway threshold), which would take them into a position for landing on runway 01. The crew decided to leave the flaps at position 15 until on short final to runway 01 to permit easier maneouvering around Monte Caslano, should the circle become necessary. The crew established visual contact with the runway at 3200 feet MSL , the captain (39, ATPL, 7,700 hours total, 3,003 hours on type), pilot flying, disengaged the autopilot about 2nm before the runway threshold descending through 2770 feet MSL. The crew observed deep hanging clouds north of the aerodrome while the area around Monte Caslano appeared clear, the crew therefore decided to follow the visual approach and do the circle around Monte Caslano to reduce the height under visual flight rules and bring the aircraft into a position to approach runway 01 below the cloud. The crew initiated a left turn at 10 degrees bank angle deviating around a number of whispy clouds to avoid losing visual contact with the ground, at a heading of about 260 degrees the GPWS issued a "TERRAIN! TERRAIN" warning shortly followed by a repeated "PULL UP!", that remained active for about 12 seconds. About 5 seconds after the first "PULL UP!" the crew initiated a go around, the engines reached maximum power about 5 seconds after the initiation of the go around. The terrain closure rate increased to 2000 fpm while the aircraft climbed at 126 KCAS, 14.2 degrees nose up and 19 degrees left bank reaching a minimum radio height of 475 feet. The gear was selected up, the flaps reduced to 10 degrees and the aircraft climbed at 2150 fpm. The crew joined the standard missed approach procedure into a hold at PINIK waypoint, then decided to divert to Milan where the aircraft landed without further incident.

The SUST reported that only after levelling wings following the left turn to circle Monte Caslano the crew realized the cloud ceiling in the south was even lower.

The SUST reported that the crew recognized only after internal investigation had begun, that their flight trajectory during the left hand circle took them further west than they had assumed. The captain commented that had they remained within the track prescribed by the procedure the GPWS warning would likely not have occurred.

The SUST quoted the captain stating that hard GPWS warnings are quite usual for aerodromes like Lugano, Innsbruck or Brac, that why he regarded the warning not as critical, a view that was shared by the first officer (38, CPL, 6,049 hours total, 4,132 hours on type), pilot monitoring, who stated he might have pressed the button to disengage the GPWS warning. The SUST further stated the captain in the interviews regarded the GPWS as less critical than e.g. TCAS, the first officer disabled the GPWS warning in consent with the captain.

The SUST analysed that the slightly climbing runway 01 offering 150 meters additional landing distance was the preferred runway in Lugano. However, the Dash 8-400 was not capable of the IGS approach, hence only the visual approach was available, which however posed a high workload onto the crew to establish a stabilized final approach without triggered GPWS warnings related to the high sinkrates required to achieve that approach.

The idea to introduce a visual approach procedure as guideline to flight crews in the sense of best practise intended to reduce the number of proliferated visual approaches to runway 01. No rules for a visual approach with prescribed track (PRT) had yet been established by ICAO, the operator assumed a minimum obstacle clearance of 1800 meters at 400 feet AGL, which is only half of the later introduced guidelines by ICAO. The procedure required a maximum IAS of 130 knots and a bank angle of 25 degrees to not exceed the radius of the turn required. In unfavourable conditions it is possible to leave this corridor within seconds.

The SUST further analysed that the visual approach procedure and its chart did not make clear that it was just an aid (guidance) to flight crews, the remark "strict following of tracks required" makes clear however, that is was not meant as usual visual approach procedure.

Austria's Austrocontrol acting as Civil Aviation Authority knew about that visual procedure, participated in the sim session to explore the procedure, however, did not approach the BAZL as responsible Civil Aviation Authority for Lugano. When the BAZL learned about the approach procedure in 2014 they immediately decided that this approach was invalid and must not be followed, there were severe doubts whether this procedure could be safely conducted. However, airline and BAZL did not reach the same understanding - the airline regarded the approach plate as invalid, while the BAZL regarded the procedure itself as invalid and prohibited the procedure to be flown in marginal visibility. The BAZL however did not further intervene following a meeting and protocols of that meeting that still contained the procedure in writing.

With respect to the actual approach flown the SUST analysed that the chosen flap setting (15 degrees) and the deviation around whispy clouds meant a larger turn radius, in addition an early levelling of wings contributed to the aircraft being in a position northwest of the desired position. In addition, a 500 feet lower alitude resulted in an almost instant "Pull Up!". The SUST wrote: "as situational awareness had been lost for a brief period of time, the crew did not recognize the severity of the GPWS warning." Despite briefing of this approach procedure prior to the approach the crew left the prescribed track as well as went below the minimum safe altitude and recognized too late that a continuation of the approach was not possible.

Believing the EGPWS warning was triggered by Monte Mondini ahead the crew initiated a go around and left turn instead of the EGPWS escape procedure. Shortly after initiating the go around the aircraft was in instrument meteorologic conditions, intercept the LOC beam and proceeded to waypoint PINIK and entered the hold.

The SUST analysed that both crew members did not exhibit any deficits in their airmanship, that would have influenced the serious incident. Also there was no problem with crew resource management. The captain however exhibited an interpretation of the EGPWS which was oriented by experience gathered in practise. He knew from collegues that the GPWS sounds occasionally on approach to Lugano without any signficance.

Neither captain nor first officer recognized their flight track had taken them too far to the west.

The SUST analysed that following the airline internal investigation the airline recognized that the flight had narrowly escaped a controlled flight into terrain. A following report to the Austrian flight safety investigation unit (FUS) did not make sufficiently clear that a terrain warning had occurred. The FUS therefore did not recognize the severity of the occurrence.

The SUST learned of the severity of the occurrence therefore only on Jan 25th 2016. The investigation therefore could not access the flight data recorder or hold prompt interviews with the flight crew, which did not help the efficiency of the investigation.

Metars:
LSZA 131820Z VRB01KT 5000 DZ FEW007 SCT018 OVC025 14/13 Q1010 NOSIG=
LSZA 131750Z VRB01KT 4000 -RA FEW007 SCT010 OVC020 14/13 Q1011 NOSIG=
LSZA 131720Z 15002KT 5000 DZ FEW007 SCT012 OVC025 14/13 Q1011 NOSIG=
LSZA 131650Z 00000KT 5000 -RA FEW005 SCT011 OVC025 13/13 Q1011 NOSIG=
LSZA 131620Z 18002KT 5000 -DZ FEW005 SCT011 OVC025 14/13 Q1011 NOSIG=
LSZA 131550Z VRB02KT 5000 +DZ FEW007 SCT020 OVC030 13/13 Q1011 NOSIG=
LSZA 131520Z VRB01KT 5000 DZ FEW007 SCT020 OVC030 14/13 Q1011 NOSIG=
LSZA 131450Z 20003KT 5000 -RA FEW010 SCT020 OVC040 14/13 Q1011 NOSIG=
LSZA 131420Z 19002KT 8000 FEW010 SCT020 OVC040 14/13 Q1012 NOSIG=
LSZA 131350Z VRB02KT 8000 FEW005 SCT020 OVC040 15/13 Q1012 NOSIG=
LSZA 131320Z VRB01KT 7000 FEW005 SCT020 OVC040 14/13 Q1012 NOSIG=
LSZA 131250Z 18003KT 5000 BR FEW005 SCT020 OVC040 14/13 Q1012 NOSIG=