An Air India Boeing 787-8, registration VT-ANE performing flight AI-314 (dep Oct 19th) from Delhi (India) to Hong Kong (China) with 197 passengers and 10 crew, was on the ILS approach to Hong Kong's runway 07R at about 06:14L (22:14Z Oct 19th), ATIS had warned of possible glideslope fluctuations, when the aircraft descended to 200 feet AGL about 2.6nm short of the runway until the EGPWS issued a warning. The crew initiated a go around, positioned for another approach and landed safely on their second approach to runway 07R.
Hong Kong's Air Investigation Authority (HKAIA) released their preliminary report stating: "Before the approach to VHHH, the crew had received cautionary information from the Hong Kong arrival Automatic Terminal Information Service (ATIS) regarding the possibility of Instrument Landing System (ILS) glideslope fluctuation. At 06:08:17 hours, the Air Traffic Control (ATC) further advised the crew of the possible glide path signal fluctuation. At 06:11:00 hours, ATC cleared the aircraft for the instrument landing system (ILS) approach for Runway 07R. During the approach, the aircraft descended rapidly, triggering a Ground Proximity Warning System (GPWS) alert on board the aircraft. The crew recovered the aircraft at about 200 feet above mean sea level, approximately 2.6 nautical miles from Runway 07R before performing a go around. The aircraft landed uneventfully on Runway 07R on the second approach."
The HKAIA reported the captain (ATPL, 1750 hours on type) was pilot flying, the first officer was pilot monitoring.
On Oct 10th 2019 India's DGCA reported, based on the preliminary data from Hong Kong, that it appeared "the crew was fixated with the unreliable glide slope and followed procedure contrary to the Boeing/company procedures. The Go Around was initiated at 288 ft radio altitude. Also it was observed that had they continued the approach, aircraft would have landed short of the airport." Corrective action was recommended for the crew.
Hong Kong's AAIA released their final report concluding the probable causes of the serious incident were:
Following a glideslope signal fluctuation, which resulted in an undesired pitch down and deviation of the aircraft below the intended flight path, subsequent flight crew recovery actions were delayed with the continuation of an increasingly unstable approach from which a recovery was eventually conducted.
Contributing Factors
The aircraft prematurely captured the glideslope as a signal fluctuation occurred, which may have been caused by the B748 taxiing to take off on the same runway within the ILS sensitive area.
- The crew actions during the recovery might be attributable to reduced alertness and degraded performance during the approach.
- There was reluctance on the part of the PM to take control and execute a missed approach, which was the correct procedure, as given in the SOP and was expected to be done without any hesitancy. A steep authority gradient probably discouraged the PM from doing so.
- Although the crew were alert to possible glideslope fluctuations and had discussed challenges, they were initially startled by the actual occurrence, with the PF becoming task saturated due to the increased workload, and the PM unable to apply any effective assistance or CRM to alleviate the situation.
The AAIA analysed:
The serious incident occurred as the crew were completing a routine flight from Delhi to Hong Kong.
While the B787 was manoeuvring to intercept the ILS for Rwy 07R, a B748 was taxing into position for takeoff on Rwy 07R. Subsequently, the B787 autoflight system aggressively captured the ILS glideslope prematurely and the aircraft descended at an abnormally high rate below the normal approach path.
Correction to this departure from a normal flight profile took considerable time. The consequences of the continued descent below the ILS profile approach to Rwy 07R were mitigated, due to that there are no obstructions on the approach path compared to approaches over built up areas which may contain natural terrain and manmade obstructions.
The investigation team examined the possibility of the glideslope signal instigating the initial upset and then investigated the events following this, which resulted in a deviation from the intended flight path with the aircraft narrowly avoiding contact with the surface before the Rwy 07R threshold.
...
ILS Approach
The B787 was established on the LOC and tracking inbound to intercept the GS from below. Autopilot pitch and roll modes were engaged, with the pitch mode set to altitude hold (ALT HOLD) and the GS armed for capture.
A B748 which had been cleared to line up and then take off passed through the projected GP beam as it taxied into position to enter the runway.
As the B787 approached the GS, a GS signal fluctuation occurred which caused the B787 to capture the GS prematurely at about 6.9 NM from the runway threshold. The GS deviation data then exhibited several oscillations over the next 15 seconds.
The GS signal fluctuation then possibly initiated an early capture of the GS, which became more aggressive and which likely triggered the B787 autoflight system to pitch the aircraft down.
The B787 reached a high rate of descent up to 2,800 ft/min, where the expected rate on a normal glideslope would be around 700 ft/min, which would have startled the crew. At this stage, the Master Caution activated and the PM stated that the G/S mode on the PFD had an amber line through it.
The PF then disconnected the autopilot at 1,400 ft and flew manually, applying two degrees of nose up pitch decreasing the descent rate slightly to 900 ft/min. This reduced the airspeed from a maximum of 184 kt, but the nose up pitch was insufficient to arrest the rate of descent which continued below the GS profile.
It is uncertain if the PF made the required manual flight callout when he disconnected the autopilot thus alerting the PM that a high level of monitoring was desired.
The PF then applied a nose down input on the control column possibly due to perceived flight director guidance, with the descent rate increasing again to 2,000 ft/min.
The PF requested that the flap be selected to 30, which the PM complied with, but the flaps did not extend due to the load relief protection.
Unrequested but possibly in an attempt to assist the PF, the PM then, unannounced, recycled the flight directors which changed the pitch and roll modes. ARM was then selected in an attempt to capture the APPR mode again. This would have little effect on the situation, as the B787 was now well below the GS and diverging further.
The crews continuing inaction indicated a lack of situational awareness of the aircrafts position relative to the desired glide path and of cues in the cockpit that could have alerted them to this.
Passing 1,000 ft a series of Glide Slope aural cautions commenced, but the approach was continued and between 1,000 ft and 700 ft the rate of descent was 2,200 ft/min. This rate of descent was considerably outside the maximum of 1,000 ft/min stabilised approached criteria, and the trigger for a go-around was ignored with the flight crew continuing the increasingly unstabilised approach. At that rate, the crew had approximately 18 seconds before impacting the surface.
The PF stated that as they considered they were in daylight conditions and with the approach lights in sight, they decided to continue for a visual approach and try to achieve stabilised parameters by 500 ft. The Glide Slope cautions continued with the B787 continuing to descend through 600 ft.
As the aircraft neared the runway, the PAPI lights and the visual aspect of the runway surface should have provided additional cues and the PM stated that he called Four Reds in relation to the PAPI and Go Around on two occasions.
At this stage, the cautions along with the glideslope indication and the toolow indication of four red PAPI lights along with the PMs calls of Four Reds and Go Around should have prompted an immediate go-around.
Until the PMs go-around calls, the investigation team could not find any evidence that there were any previous prompts from the PM concerning the multitude of factors indicating that an increasing deviation from the intended flight path had occurred with controlled flight into terrain imminent.
It is probable that the PFs visual attention was focused primarily outside the aircraft below 500 ft, as he was manually flying and attempting to correct the vertical deviation to establish on the glideslope.
Passing 500 ft, the aircraft did not meet any of AICs stabilised approach criteria.
The descent continued and after a Master Caution Too Low Terrain, the B787 continued in a shallow descent for another five seconds before the PF commenced a go-around at a pressure and radio altitude of approximately 280 ft, 2.6 NM before the Rwy 07R threshold, approximately 500 ft below the normal profile.
The crew reported no problems with the following ILS approach and subsequent landing.
The PF stated that as it was daylight, the cautions could be ignored. However, sunrise was at 0621 hrs, and there had been a first quarter moon two days previously with a moonset approximately four hours prior to the approach, which would indicate that there would have been minimal light.26 The PM stated that it was quite dark. Considering the possibility that the PF considered it was daylight, the compounding unstabilised approach with the rate of descent involved made a go-around mandatory in any case.
The crews decision to continue whilst not meeting stabilised approach criteria was not unusual, as industry statistics indicate about 97% of unstable approaches are continued to a landing.
Apart from the EAFR readout, the lack of any CVR information meant the investigation team had to rely on crew interviews which were some time after the event.
Metars:
VHHH 200000Z 09017KT 9999 FEW022 26/19 Q1019 NOSIG=
VHHH 192330Z 08013KT 9999 FEW022 SCT035 25/19 Q1019 NOSIG=
VHHH 192300Z 08011KT 9999 FEW022 SCT035 24/19 Q1019 NOSIG=
VHHH 192230Z 09012KT 9999 FEW022 SCT035 24/19 Q1019 NOSIG=
VHHH 192200Z 09010KT 9999 FEW020 SCT030 24/19 Q1018 NOSIG=
VHHH 192130Z 08014KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 192100Z 09012KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 192030Z 08011KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 192000Z 08013KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 191930Z 08013KT 9999 FEW020 SCT032 24/20 Q1018 NOSIG=
VHHH 191900Z 09013KT 9999 FEW022 SCT035 24/20 Q1018 NOSIG=
VHHH 191830Z 08012KT 9999 FEW022 SCT032 24/19 Q1018 NOSIG=
VHHH 191800Z 09015KT 9999 FEW022 SCT030 25/20 Q1018 NOSIG=
Hong Kong's Air Investigation Authority (HKAIA) released their preliminary report stating: "Before the approach to VHHH, the crew had received cautionary information from the Hong Kong arrival Automatic Terminal Information Service (ATIS) regarding the possibility of Instrument Landing System (ILS) glideslope fluctuation. At 06:08:17 hours, the Air Traffic Control (ATC) further advised the crew of the possible glide path signal fluctuation. At 06:11:00 hours, ATC cleared the aircraft for the instrument landing system (ILS) approach for Runway 07R. During the approach, the aircraft descended rapidly, triggering a Ground Proximity Warning System (GPWS) alert on board the aircraft. The crew recovered the aircraft at about 200 feet above mean sea level, approximately 2.6 nautical miles from Runway 07R before performing a go around. The aircraft landed uneventfully on Runway 07R on the second approach."
The HKAIA reported the captain (ATPL, 1750 hours on type) was pilot flying, the first officer was pilot monitoring.
On Oct 10th 2019 India's DGCA reported, based on the preliminary data from Hong Kong, that it appeared "the crew was fixated with the unreliable glide slope and followed procedure contrary to the Boeing/company procedures. The Go Around was initiated at 288 ft radio altitude. Also it was observed that had they continued the approach, aircraft would have landed short of the airport." Corrective action was recommended for the crew.
Hong Kong's AAIA released their final report concluding the probable causes of the serious incident were:
Following a glideslope signal fluctuation, which resulted in an undesired pitch down and deviation of the aircraft below the intended flight path, subsequent flight crew recovery actions were delayed with the continuation of an increasingly unstable approach from which a recovery was eventually conducted.
Contributing Factors
The aircraft prematurely captured the glideslope as a signal fluctuation occurred, which may have been caused by the B748 taxiing to take off on the same runway within the ILS sensitive area.
- The crew actions during the recovery might be attributable to reduced alertness and degraded performance during the approach.
- There was reluctance on the part of the PM to take control and execute a missed approach, which was the correct procedure, as given in the SOP and was expected to be done without any hesitancy. A steep authority gradient probably discouraged the PM from doing so.
- Although the crew were alert to possible glideslope fluctuations and had discussed challenges, they were initially startled by the actual occurrence, with the PF becoming task saturated due to the increased workload, and the PM unable to apply any effective assistance or CRM to alleviate the situation.
The AAIA analysed:
The serious incident occurred as the crew were completing a routine flight from Delhi to Hong Kong.
While the B787 was manoeuvring to intercept the ILS for Rwy 07R, a B748 was taxing into position for takeoff on Rwy 07R. Subsequently, the B787 autoflight system aggressively captured the ILS glideslope prematurely and the aircraft descended at an abnormally high rate below the normal approach path.
Correction to this departure from a normal flight profile took considerable time. The consequences of the continued descent below the ILS profile approach to Rwy 07R were mitigated, due to that there are no obstructions on the approach path compared to approaches over built up areas which may contain natural terrain and manmade obstructions.
The investigation team examined the possibility of the glideslope signal instigating the initial upset and then investigated the events following this, which resulted in a deviation from the intended flight path with the aircraft narrowly avoiding contact with the surface before the Rwy 07R threshold.
...
ILS Approach
The B787 was established on the LOC and tracking inbound to intercept the GS from below. Autopilot pitch and roll modes were engaged, with the pitch mode set to altitude hold (ALT HOLD) and the GS armed for capture.
A B748 which had been cleared to line up and then take off passed through the projected GP beam as it taxied into position to enter the runway.
As the B787 approached the GS, a GS signal fluctuation occurred which caused the B787 to capture the GS prematurely at about 6.9 NM from the runway threshold. The GS deviation data then exhibited several oscillations over the next 15 seconds.
The GS signal fluctuation then possibly initiated an early capture of the GS, which became more aggressive and which likely triggered the B787 autoflight system to pitch the aircraft down.
The B787 reached a high rate of descent up to 2,800 ft/min, where the expected rate on a normal glideslope would be around 700 ft/min, which would have startled the crew. At this stage, the Master Caution activated and the PM stated that the G/S mode on the PFD had an amber line through it.
The PF then disconnected the autopilot at 1,400 ft and flew manually, applying two degrees of nose up pitch decreasing the descent rate slightly to 900 ft/min. This reduced the airspeed from a maximum of 184 kt, but the nose up pitch was insufficient to arrest the rate of descent which continued below the GS profile.
It is uncertain if the PF made the required manual flight callout when he disconnected the autopilot thus alerting the PM that a high level of monitoring was desired.
The PF then applied a nose down input on the control column possibly due to perceived flight director guidance, with the descent rate increasing again to 2,000 ft/min.
The PF requested that the flap be selected to 30, which the PM complied with, but the flaps did not extend due to the load relief protection.
Unrequested but possibly in an attempt to assist the PF, the PM then, unannounced, recycled the flight directors which changed the pitch and roll modes. ARM was then selected in an attempt to capture the APPR mode again. This would have little effect on the situation, as the B787 was now well below the GS and diverging further.
The crews continuing inaction indicated a lack of situational awareness of the aircrafts position relative to the desired glide path and of cues in the cockpit that could have alerted them to this.
Passing 1,000 ft a series of Glide Slope aural cautions commenced, but the approach was continued and between 1,000 ft and 700 ft the rate of descent was 2,200 ft/min. This rate of descent was considerably outside the maximum of 1,000 ft/min stabilised approached criteria, and the trigger for a go-around was ignored with the flight crew continuing the increasingly unstabilised approach. At that rate, the crew had approximately 18 seconds before impacting the surface.
The PF stated that as they considered they were in daylight conditions and with the approach lights in sight, they decided to continue for a visual approach and try to achieve stabilised parameters by 500 ft. The Glide Slope cautions continued with the B787 continuing to descend through 600 ft.
As the aircraft neared the runway, the PAPI lights and the visual aspect of the runway surface should have provided additional cues and the PM stated that he called Four Reds in relation to the PAPI and Go Around on two occasions.
At this stage, the cautions along with the glideslope indication and the toolow indication of four red PAPI lights along with the PMs calls of Four Reds and Go Around should have prompted an immediate go-around.
Until the PMs go-around calls, the investigation team could not find any evidence that there were any previous prompts from the PM concerning the multitude of factors indicating that an increasing deviation from the intended flight path had occurred with controlled flight into terrain imminent.
It is probable that the PFs visual attention was focused primarily outside the aircraft below 500 ft, as he was manually flying and attempting to correct the vertical deviation to establish on the glideslope.
Passing 500 ft, the aircraft did not meet any of AICs stabilised approach criteria.
The descent continued and after a Master Caution Too Low Terrain, the B787 continued in a shallow descent for another five seconds before the PF commenced a go-around at a pressure and radio altitude of approximately 280 ft, 2.6 NM before the Rwy 07R threshold, approximately 500 ft below the normal profile.
The crew reported no problems with the following ILS approach and subsequent landing.
The PF stated that as it was daylight, the cautions could be ignored. However, sunrise was at 0621 hrs, and there had been a first quarter moon two days previously with a moonset approximately four hours prior to the approach, which would indicate that there would have been minimal light.26 The PM stated that it was quite dark. Considering the possibility that the PF considered it was daylight, the compounding unstabilised approach with the rate of descent involved made a go-around mandatory in any case.
The crews decision to continue whilst not meeting stabilised approach criteria was not unusual, as industry statistics indicate about 97% of unstable approaches are continued to a landing.
Apart from the EAFR readout, the lack of any CVR information meant the investigation team had to rely on crew interviews which were some time after the event.
Metars:
VHHH 200000Z 09017KT 9999 FEW022 26/19 Q1019 NOSIG=
VHHH 192330Z 08013KT 9999 FEW022 SCT035 25/19 Q1019 NOSIG=
VHHH 192300Z 08011KT 9999 FEW022 SCT035 24/19 Q1019 NOSIG=
VHHH 192230Z 09012KT 9999 FEW022 SCT035 24/19 Q1019 NOSIG=
VHHH 192200Z 09010KT 9999 FEW020 SCT030 24/19 Q1018 NOSIG=
VHHH 192130Z 08014KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 192100Z 09012KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 192030Z 08011KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 192000Z 08013KT 9999 FEW020 SCT030 24/20 Q1018 NOSIG=
VHHH 191930Z 08013KT 9999 FEW020 SCT032 24/20 Q1018 NOSIG=
VHHH 191900Z 09013KT 9999 FEW022 SCT035 24/20 Q1018 NOSIG=
VHHH 191830Z 08012KT 9999 FEW022 SCT032 24/19 Q1018 NOSIG=
VHHH 191800Z 09015KT 9999 FEW022 SCT030 25/20 Q1018 NOSIG=
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