Description

On 13 January 2017, a Boeing 747-8F (VQ-BLR) being operated by ABC Cargo Airlines on an international cargo flight from Novosibirsk to Amsterdam made an initial main gear touchdown just prior to the beginning of the landing runway at destination in night VMC. The crew stated that they were unaware of this until maintenance personnel who attended the aircraft on stand reported multiple scratches and dents on the wings and fuselage.

Investigation

The event was classified as a Serious Incident and an Investigation was carried out by the Dutch Safety Board. Relevant data were downloaded from the aircraft FDR and the information on activations of the EGPWS on short final was available. It was noted that the operating crew had been passengers on the previous 6 hour sector from Hong Kong to Novosibirsk where the aircraft had been on the ground for 1¼ hours and had been on duty for more than 14 hours by the time the aircraft landed at Amsterdam. However, no reference was made by either pilot to any fatigue.

It was established that the aircraft landing weight was well within the maximum permitted - 318 tonnes against the maximum permitted 346 tonnes - and the centre of gravity was within the permitted flight envelope. At the time of the approach, the surface wind being reported on the ATIS was from a mean of 320° and variable from 290° to 360° at a mean speed of 26 knots gusting to a maximum of 38 knots. The flight crew reported having been fully aware of this and confident that the conditions were within applicable operational limits. FDR data showed that the ILS approach to runway 36R had been normal until 700 feet aal, at which point the Captain had disconnected the AP and flown the aircraft manually. Almost immediately, the flight path began to deviate below the ILS GS.

It was noted that the prevailing procedures at the aircraft operator required that a go-around must be flown if the annunciated GS deviation exceeds 1 dot when the aircraft is below 500 feet in VMC. During this approach under investigation, the deviation below the ILS GS remained within 1 dot until passing 100 feet agl after which it exceeded this and the rate of descent reached 1070 fpm resulting in the successive activations of EGPWS Modes 5 (Glideslope) and 1 (Sink Rate) just a few seconds away from touchdown.

The Captain subsequently stated that “he was unable to execute a go-around because the touchdown followed almost immediately”. Initiation of the flare reduced the rate of descent to 500 fpm and the initial main gear touchdown just prior to the beginning of the runway was made with a recorded 1.76g and three elevated runway threshold lights were hit and destroyed. The aircraft briefly bounced before a second and final ground contact just within the runway but well short of the TDZ (Touch Down Zone) occurred at 1.84g. There were no control problems and the aircraft normally decelerated before exiting the runway and taxiing to its assigned parking position.

After the landing the flight crew heard on the ATC frequency that another aircraft on approach to the same runway had made a go-around after receiving a windshear warning. On interview, the Captain stated he suspected that windshear shortly before the landing had been the cause of the undershoot. It was noted that the 2825 metre runway 36R LDA is “relatively short for a loaded 747-8” and that the crew had calculated a landing distance required of 2549 metres.

It was noted that the aircraft operator’s definition of a stable (ILS) approach required that the following conditions should be met:

• Only small control inputs are necessary to remain on the glideslope and localiser course.
• Indicated airspeed shall not be below the reference speed for the given landing configuration.
• Indicated airspeed shall not deviate more than +10 knots or -5 knots.
• Glideslope deviation shall be within 1 dot.
• The rate of descent shall be within 1000 feet/minute unless more is operationally necessary.
• The landing can be made within the touchdown zone.

If any one of these is no longer met, the approach is considered unstable and a go-around must be made. In addition, if the PM calls that the approach has become unstable, the PF must make a go-around regardless of his own judgement. The Investigation was unable to determine at interview if the First Officer, as PM had communicated to the Captain that the approach was unstable or called for a go-around.

The Investigation found that as well as the windshear warning mentioned by the Captain at interview, two other such warnings had been reported by aircraft on approach to runway 36R that night. It noted that the ANSP, LVNL, had “not been able to demonstrate” that these reports led to updating of the ATIS in accordance with its own operating procedures. However, there was no on-aircraft windshear warning during the approach under investigation.

It was noted that the FDR record of wind velocity during the approach matched that recorded by the on-ground wind measurement system located near the beginning of runway 36R and that shortly before landing, ATC had transmitted to the aircraft a spot wind derived from this ground equipment.

Boeing were invited to analyse the FDR data relating to the event and concluded the flight conditions during the approach could be described as turbulent. It was also noted that the control inputs made by the Captain during the manual control phase had been insufficient to recapture the glideslope and that “shortly before landing the aircraft mainly experienced updrafts and to a lesser degree downdrafts which decreased in magnitude while approaching the runway”. It was evident that once below 200 feet, deviation below the glideslope continuously increased. After the EGPWS ‘sink rate’ was annunciated, the data showed that the Captain had pulled back on the control column and reduced the rate of descent to 500 fpm but this was not enough to avoid a hard landing. It was concluded that the data did not allow the increase in sink rate shortly before landing to be attributed to windshear.

Safety Action taken by the Operator as a result of the investigated event was understood to have included the provision of additional training for both the Captain and the First Officer which consisted of eight hours of simulator training with prior self-study on the causes of hard landings, the importance of landing in the TDZ and visual illusions. This was followed by eight sectors’ line training and completion of a line check. Also, all the Operator’s pilots were alerted to the importance of following the ILS GS until landing and of initiating a go-around at any time an approach becomes unstable.

The Conclusion of the Investigation was formally documented as follows:

The hard landing was caused by a high rate of descent. The flare manoeuvre was insufficient to reduce the sink rate satisfactorily. The fact that the aircraft hit the runway threshold lights was a combination of the continued flight below the glideslope, from the moment the Captain disconnected the autopilot at 700 feet and took over the controls manually, and a high sink rate shortly before the touchdown. The approach was stable until just before the landing, but then two automatic EGPWS alerts were generated (“glideslope” and “sink rate”) whereby the stable approach criteria were exceeded. This should have been followed by a go-around but this did not happen even though the procedures required it.

According to the Operations Manual of the ANSP, ATIS messages should include any reported windshear conditions. Flight crews are thereby made more aware of sudden wind changes and the necessity to make a go-around in case the approach becomes unstable. The ANSP, LVNL, has not been able to demonstrate that the windshear conditions reported by aircraft crews resulted in the ATIS being modified.

The measures taken by the aircraft operator after the event are necessary to avoid occurrences like hard landings as well as landing short. Those measures underline the importance of adhering to international established guidelines concerning stabilised approach criteria and the importance of making a go-around when the approach becomes unstable.

The Final Report was published in 17 July 2018.

Related Articles

• Controlled Flight Into Terrain (CFIT)
• Stabilised Approach
• Missed Approach
• Go Around
• Crew Resource Management
• Cross-checking Process