Westjet B738 at Halifax on Jan 5th 2020, overran runway on landing
Last Update: May 20, 2021 / 17:16:39 GMT/Zulu time
Incident Facts
Date of incident
Jan 5, 2019
Classification
Incident
Airline
Westjet Airlines
Flight number
WS-248
Departure
Toronto, Canada
Destination
Halifax, Canada
Aircraft Registration
C-FUJR
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
Airport ICAO Code
CYHZ
Tower advised departures on runway 05, that all emergency services were occupied and no cover was available for the departures. Tower told operations and emergency vehicles that the aircraft was at the threshold of runway 32 (at the end of runway 14).
Pictorial evidence suggests the aircraft came to a stop with all gear off the paved surface of the runway end safety area.
The Canadian TSB have dispatched a team of investigators "following a runway overrun" at Halifax.
On Jan 8th 2020 the TSB reported the aircraft came to a stop about 250 feet (76 meters) past the end of the runway. There were no injuries and no damage to the aircraft. Tyres and brakes were replaced as a precaution before the aircraft was returned to service. The investigation class is still being assessed.
On May 20th 2021 the TSB released their final report concluding the probable causes of the incident were:
Findings as to causes and contributing factors
These are conditions, acts or safety deficiencies that were found to have caused or contributed to this occurrence.
- While preparing for the runway change, the flight crew mentally assessed that the wind for Runway 05 would become a crosswind for Runway 14. As a result, they did not recalculate the effects of the wind for the approach to Runway 14, but rather considered that the landing distance and the target approach speed calculated for Runway 05 were still appropriate.
- The reported winds on the ground had backed and increased slightly as the flight progressed. This resulted in a tailwind component that exceeded the operator’s limitation of 10 knots, a lower required approach speed of Vref + 5 knots, and a landing distance that exceeded the runway length available. None of this was recognized by the flight crew and, as a result, they continued the approach to Runway 14.
- The unchanged target approach speed combined with the tailwind resulted in the aircraft crossing the threshold 10 knots faster than recommended and touching down at a faster groundspeed, thus requiring a longer stopping distance.
- The wet snow contamination on the runway resulted in a reduction in braking effectiveness, contributing to an increase in landing distance.
- The increase in the landing distance due to the fast approach, combined with the tailwind component and contaminated runway, was in excess of the remaining runway available and resulted in the overrun.
Findings as to risk
These are conditions, unsafe acts or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.
- If the cockpit voice recorder is not disabled following an occurrence, there is a risk that information valuable to the investigation may be lost.
- Without additional cues (e.g., enhanced technology or visual aids) to help flight crews determine runway suitability before landing and aircraft position once on a runway, there is a continued risk that flight crew actions based on weak or non-salient cues will result in runway overruns.
Other findings
These items could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.
- In this occurrence, the aircraft stopped within the runway end safety area.
The TSB analysed:
While in cruise, the flight crew prepared for their approach by reviewing the weather information available. At that time, the designated runway in use was Runway 05. The flight crew determined that the length of Runway 05 was sufficient given the calculated landing distance required. Based on the winds, the flight crew calculated the target approach speed of 162 knots (landing reference speed [Vref] + 15 knots).
As the aircraft approached the airport, the flight crew received new weather information, indicating a lower ceiling. Because this ceiling was below the published minima for the approach to Runway 05, the flight crew requested the Runway 14 instrument landing system (ILS) approach. The investigation determined that the winds provided by the area control centre controller at that time (020° magnetic [M] at 17 knots, gusting to 27 knots) resulted in a 15 knot tailwind component for Runway 14.
This mental model was likely a natural response by the flight crew to reduce cognitive effort during a time of high workload. Without the tailwind component being recognized when Runway 14 was selected, the wind information was not salient to the flight crew during the remainder of the approach and landing, contributing to the flight crew’s continued approach to Runway 14.
Using the winds that were reported during cruise (030°M at 16 knots, gusting to 24 knots), the landing distance required for Runway 05, calculated via the aircraft communications addressing and reporting system (ACARS), was within the 10 500 feet available. If the crew had calculated the distance required for Runway 14 using these same winds, they would have determined that the distance available was also sufficient (i.e., less than 7700 feet). However, the surface winds changed during the approach and landing.
Approach and landing
Approach and landing is a critical phase of flight. Runway changes, low visibility conditions, wet runway surfaces, and tailwinds are routine conditions that increase complexity during approach and landing. Threat and error management, as part of crew resource management practices, supports crews in managing these routine aspects of airline operations.
From the time that the flight crew requested the approach until touchdown on Runway 14, they were busy with reprogramming the approach and conducting the approach. The flight crew requested information on any braking action reports for Runway 14. They also recognized the low visibility conditions, and, although it was not required, they completed the low-visibility approach checklist to manage the threat. Furthermore, they anticipated and experienced turbulence at lower altitudes, which further increased the workload for the captain, who was the pilot flying (PF).
Situational awareness is based on perceiving, understanding and predicting information to create an awareness of the environment and unfolding events. Perception can be affected by a narrowing or focusing of attention that can occur when workload is high, and can result in some information not being processed or being missed. This can also contribute to continuing a plan when the plan is no longer viable (plan continuation). The flight crew were receiving and processing a lot of information and had many actions to perform quickly in the 14 minutes between the runway change and touchdown. The flight crew, focused on the conditions of the runway and the landing, did not detect the changes in the wind and the tailwind component. Without a salient cue to help them identify this, the flight crew continued the approach.
The PF flew a stable approach. When the tower controller provided the flight crew with a final wind check of 010°M at 19 knots, the flight crew still did not recognize this as significant, concentrating on the crosswind, turbulence, low visibility and runway surface condition. The PF continued using the briefed approach speed of Vref + 15 knots calculated for the original runway, and maintained it until the flare. The extra speed was in excess of the company’s procedure of using Vref + 5 knots for tailwinds.
Touchdown and runway overrun
The aircraft touched down at 164 knots and at a groundspeed of 173 knots. It landed within the touchdown zone, and the deceleration devices, such as the speedbrakes and thrust reversers, deployed as designed. The PF, recognizing the faster speed on the rollout, applied manual braking. By using manual braking, the autobrake 3 selection disengaged.
The antiskid system activated immediately upon use of manual braking and likely remained active for the remainder of the rollout. Regardless of whether autobrake 3 selection had remained on or the PF had maintained maximum braking and maximum reverse throughout, the aircraft’s antiskid system was likely active, already providing the maximum deceleration available for the runway conditions.
The runway surface condition was reported as trace of wet snow, which equates to a “good” braking action, according to the runway condition equivalency table. However, the deceleration obtained during the rollout represents a braking action more akin to “medium to poor.” In terms of wet snow, the difference between good braking and medium to poor braking is predicated on whether there is a trace or greater than a trace.
The investigation could not determine the actual condition of the runway. The braking action expected (good to medium) based on the reported runway surface condition was not equivalent to the braking action encountered (medium to poor). The degraded runway condition decreased the braking action. Even if the braking action had been good to medium, the investigation calculated that the required landing distance would have exceeded the distance available.
The TSB further analysed that the CVR was not preserved due to a typing error in an ACARS message maintenance transmitted to the flight crew: "In this case, the maintenance controller typed the circuit breaker numbers in the ACARS message. However, the ACARS message was typed incorrectly, likely because of a slip of attention, stating circuit breaker C7 and repeating C8 when it needed to state D6 and D7. As a result of the flight crew following the ACARS instructions, the appropriate CVR circuit breaker was not pulled."
Related NOTAM:
E0041/20 NOTAMN
Q) CZQM/QMRLC/IV/NBO/A/000/999/4453N06331W005
A) CYHZ B) 2001051623 C) 2001051900
E) RWY 14/32 CLSD.
Metars:
CYHZ 051735Z 36022G33KT 3/4SM R14/5000VP6000FT/U -SN DRSN OVC004 M01/M01 A2910 RMK ST8 /S10/ SLP860=
CYHZ 051700Z 36020G29KT 3/4SM R14/5500VP6000FT/N -SN DRSN OVC002 M01/M01 A2911 RMK ST8 /S09/ SLP864=
CYHZ 051618Z 36018G25KT 1/2SM R14/4000FT/N SN OVC003 M01/M01 A2912 RMK ST8 SLP869=
CYHZ 051600Z 36015G23KT 1/2SM R14/4000V5500FT/D SN OVC002 M00/M00 A2912 RMK ST8 /S07/ SLP869=
CYHZ 051549Z 01016G27KT 1/2SM R14/5000FT/N SN OVC002 M00/M00 A2912 RMK ST8 SLP869=
CYHZ 051530Z 01016G23KT 5/8SM R14/P6000FT/D -SN OVC002 M00/M00 A2914 RMK ST8 /S05/ SLP874=
CYHZ 051500Z 01016G24KT 1 1/4SM -SN OVC003 M00/M00 A2915 RMK ST8 SLP879=
CYHZ 051417Z 01018G23KT 1 1/2SM -SN OVC004 M00/M00 A2918 RMK ST8 SLP889=
CYHZ 051402Z 02017G23KT 1SM R14/6000FT/U -SN OVC002 M00/M00 A2919 RMK ST8 PRESFR SLP893=
CYHZ 051400Z 02015G21KT 3/4SM R14/6000FT/U -SN OVC003 M00/M00 A2919 RMK ST8 /S04/ PRESFR SLP893=
CYHZ 051300Z 02012KT 5/8SM R14/P6000FT/N -SN OVC003 M00/M00 A2925 RMK ST8 /S01/ SLP913=
CYHZ 051218Z 02010KT 3/4SM R14/P6000FT/D -SN OVC003 M00/M00 A2929 RMK ST8 PRESRR SLP924=
CYHZ 051200Z 02009G16KT 1SM R14/P6000FT/N -SN OVC002 M00/M00 A2925 RMK ST8 PRESRR SLP913=
Aircraft Registration Data
Aircraft registration data reproduced and distributed with the permission of the Government of Canada.
Incident Facts
Date of incident
Jan 5, 2019
Classification
Incident
Airline
Westjet Airlines
Flight number
WS-248
Departure
Toronto, Canada
Destination
Halifax, Canada
Aircraft Registration
C-FUJR
Aircraft Type
Boeing 737-800
ICAO Type Designator
B738
Airport ICAO Code
CYHZ
This article is published under license from Avherald.com. © of text by Avherald.com.
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