Air Canada A333 at Montreal on Oct 7th 2014, temporary runway excursion on landing
Last Update: March 28, 2017 / 15:17:56 GMT/Zulu time
Date of incident
Oct 7, 2014
ICAO Type Designator
Airport ICAO Code
The Canadian TSB reported 4 runway edge lights were damaged, the damage to the aircraft is being assessed. A go team has been dispatched to Montreal to investigate the serious incident.
NAV Canada reported that two approaches in the minutes following the occurrence went around due to the presence of a storm cell in the final approach path to runway 24R. The runway was subsequently closed for about one hour until repairs were completed.
On Mar 28th 2017 the Canadian TSB released their final report concluding the probable causes of the serious incident were:
Findings as to causes and contributing factors
- During an approach in the presence of a thunderstorm, pilot-induced oscillation led to the aircraft being in a left bank as it crossed the runway threshold which, combined with a strong right crosswind, resulted in a rapid drift to the left very close to the ground.
- Once the aircraft crossed the runway threshold, the intensity of the precipitation increased suddenly, such that the pilot flying (PF) had reduced visual references. Under these conditions, the PF did not detect the lateral movement of the aircraft in time to correct the drift before the outboard tires of the left bogie landed in the grass.
- Given the absence of runway lighting in reduced visibility conditions, it was difficult for the pilot flying to detect the lateral movement of the aircraft over the runway and therefore to prevent the runway excursion.
- A lateral wind shear generated by a downburst to the north of the runway suddenly increased the aircraft’s drift to the left during the landing flare.
- Runway 24R was not closed in instrument meteorological conditions, even though the runway lighting was not working. As a result, the runway was not equipped with the lights required to enable crews to clearly distinguish the lateral confines of the runway.
Findings as to risk
- If airports are not equipped with a low-level wind shear alert system, crews landing there may not be aware of the presence of downbursts or microbursts, and therefore may be exposed to the risk of approach-and-landing accidents.
- If a crew is unable to verify landing performance in heavy rain conditions involving a risk of hydroplaning, there is an increased risk of runway excursion.
- If the “landing” response to the “minimum” calls reinforces the notion that landing is assured, there is a possibility that preparation for, and the decision to, go-around could be affected, increasing the risk of a landing incident or accident.
- If the rain repellent system is unavailable or not used, there is an increased risk, in heavy rain conditions, that crews will lose the visual references necessary to avoid a runway excursion.
- If a crew does not consider the consequences of multiple threats, there is a risk that pilots will continue a landing under conditions that are not favourable.
- If the aircraft is drifting near the ground and pilots place the aircraft in low-energy landing regime, there is an increased risk of runway excursion.
- If crews are not trained to retake the controls at very low altitudes or during the low-energy landing regime, there is a risk that, in the event of a problem, the pilot monitoring will not have time to identify the problem and take the appropriate measures.
- If TC does not take action to develop the clear standards on avoiding thunderstorms during approach and landing called for in Recommendation A07-01, approaches in the presence of convective weather will continue, exposing aircraft to the multiple, unpredictable hazards associated with thunderstorms.
- If occurrence sites are not preserved, there is a risk that evidence essential to identifying factors that contributed to an occurrence will be lost.
- If dispatch is not aware of an aircraft communications, addressing and reporting system transmission failure, there is an increased risk that critical flight information is not received by the crew.
- Although the wind information at Montréal/Pierre Elliott Trudeau International Airport was transmitted to the flight by air traffic control in a timely manner, the information provided did not enable the crew to be fully aware of the rapidly changing weather conditions in the area of the runway.
- The runway excursion was not the result of a premature crab angle reduction manoeuvre, which is often associated with landing incidents in crosswind conditions.
The TSB reported when the aircraft descended through 11,000 feet MSL ATIS information V was active advising of cumulonimbus cloud in the area, winds were from 200 degrees at 7 knots, no precipitation, VMC prevailed. When the aircraft descended through 5000 feet the crew noticed the area north of the runway became dark consistent with heavy precipitation that was also shown on the aircraft weather radar. In response to the development of the weather the crew decided to increase their approach speed and discussed they might encounter windshear and heavy precipitation, however did not discuss the possibility of a go around.
On final approach, descending through 1900 feet AGL 5.5nm before the runway threshold ATC advised winds had changed to 280 degrees at 13 knots gusting 18 knots. The preceding aircraft reported light windshear below 400 feet, tower reported winds were now from 300 degrees at 18 knots gusting 24 knots, the controller also confirmed the presence of windshear below 400 feet. The crew observed a rainshower approaching near mid runway. Descending through 130 feet AGL and 0.4nm before the runway threshold the aircraft entered rain, the pilot flying requested the windshield wipers to maximum speed. The aircraft experienced a number of rolling oscillations, crossed the runway threshold on the runway center line at 50 feet AGL, at 30 feet AGL the thrust levers were retarded, the aircraft banked left and drifted quickly towards the left edge of the runway.
The rain reached maximum intensity degrading visibility, the pilot flying initiated the flare and banked slighty right, the right main gear touched down 1332 feet past the runway threshold and 57 feet to the left of the runway center line, the left main gear tyres collided with a runway edge lights, the left outboard tyres touched down on grass while the left inboard main tyres remained on paved surface on touchdown 1538 feet past the runway threshold and 97 feet to the left of the runway centerline. The aircraft took out two more runway edge lights before returning to the runway centerline. The rollout was without further incident.
The TSB stated the outboard tyres of the left main gear bogie travelled over grass for 2.3 seconds and 507 feet.
The TSB analysed:
The crew was able to observe the changing weather conditions at CYUL; however the wind and wind shear information provided by ATC was not in real time. Although the wind information at CYUL was transmitted to the flight in a timely manner, the information provided did not enable the crew to be fully aware of the rapidly changing weather conditions in the area of the runway. As a result, it can be concluded that the crew did not have the information necessary to make an informed decision whether to continue the approach and landing.
Thunderstorms are the source of several hazardous phenomena and constitute a significant threat to aircraft flying in their vicinity. The heavy precipitations associated with the thunderstorm led to a downburst of wind that reached the ground, leading to violent gusts in the western sector. Since the thunderstorm passed immediately to the north of the runway on a trajectory more-or-less parallel to the runway, the strong and unstable wind shifted from the west to the north, resulting in lateral shear.
The digital flight data recorder (DFDR) data indicate that a sudden increase occurred in the aircraft’s drift approximately 2° to the left during the flare. This change in drift coincided with a significant increase in rain showers. On this basis, it can be concluded that the aircraft experienced the effect of a downburst associated with the rain generated by the thunderstorm. A lateral wind shear generated by a downburst to the north of the runway suddenly increased the aircraft’s drift to the left during the flare.
Because of the thunderstorm, the crew found themselves in fading light conditions during the approach and landing. Furthermore, due to the absence of runway lighting and visibility reduced by heavy rain, the grey surface of the runway presented little contrast with its surroundings and offered few visual cues. It can be concluded that the environmental context made it difficult for the PF to keep the aircraft on the runway centreline and to detect lateral movement of the aircraft above the runway. Given the absence of runway lighting in reduced visibility conditions, it was difficult for the PF to detect the lateral movement of the aircraft over the runway and therefore to prevent the runway excursion.
CYUL 071800Z 26003KT 250V320 15SM FEW030TCU FEW070 SCT240 15/11 A2987 RMK TCU1AC1CI1 SLP115 DENSITY ALT 200FT
CYUL 071734Z 25006KT 15SM FEW030TCU SCT045 SCT070 BKN240 14/11 A2988 RMK TCU1SC2AC1CI1 PRESFR SLP117
CYUL 071700Z 27007KT 10SM -SHRA FEW030CB BKN044 OVC070 13/11 A2989 RMK CB1SC6AC1 SLP122
CYUL 071653Z 28008KT 10SM -SHRA FEW025CB BKN045 OVC080 12/10 A2989 RMK CB1SC4AC3 SLP123
CYUL 071636Z 27018G27KT 200V280 3SM -TSRA FEW012 BKN025CB OVC048 14/10 A2989 RMK SF1CB4SC3 VIS S 15 PRESRR SLP122
CYUL 071630Z 24006KT 2SM -TSRA FEW010 BKN025CB OVC050 17/12 A2987 RMK SF1CB5SC2E-S 8 SLP114 DENSITY ALT 400FT
CYUL 071623Z 20009KT 10SM TS FEW030CB SCT050 BKN070 BKN120 18/12 A2988 RMK CB2SC1AC3AC1 SLP117 DENSITY ALT 400FT
CYUL 071600Z 18007KT 12SM FEW020 SCT045 BKN090 BKN150 18/14 A2987 RMK CU1SC2AC3AC1 CB EMBD SLP115 DENSITY ALT 400FT
CYUL 071500Z 18010KT 12SM -SHRA FEW045 SCT065 OVC090 15/13 A2987 RMK SC2SC2AC4 SLP115 DENSITY ALT 200FT
CYUL 071425Z 16013KT 10SM FEW040 SCT065 OVC090 15/13 A2986 RMK SC2SC2AC4 SLP110
Date of incident
Oct 7, 2014
ICAO Type Designator
Airport ICAO Code
This article is published under license from Avherald.com. © of text by Avherald.com.
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