Jazz DH8A at Sault Ste Marie on Feb 24th 2015, touched down short of runway

Last Update: March 9, 2017 / 15:44:29 GMT/Zulu time

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Incident Facts

Date of incident
Feb 24, 2015

Classification
Accident

Flight number
QK-7795

Aircraft Registration
C-GTAI

ICAO Type Designator
DH8A

A Jazz de Havilland Dash 8-100, registration C-GTAI performing flight QK-7795 from Toronto,ON to Sault Ste Marie,ON (Canada) with 15 passengers and 3 crew, landed on Sault Ste. Marie's runway 30 but touched down about 500 feet short of the runway threshold, contacted and destroyed an ODALS light before coming to a stop. There were no injuries.

NAV Canada reported the aircraft clipped the landing gear on the approach lights and came to a stop on runway 30.

The Canadian TSB reported on Mar 2nd 2015, that the damage of the aircraft is being assessed, the occurrence has been rated an accident.

On Mar 9th 2017 the Canadian TSB released their final report concluding the probable causes were:

Findings as to causes and contributing factors

- The company standard operating procedures require an approach speed of Vref + 5 knots; however, this is being interpreted by flight crews as a target to which they should decelerate, from 120 knots, once the aircraft is below 500 feet. As a result, the majority of examined approaches, including the occurrence approach, were unstable, due to this deceleration.

- Due to ambiguity in the guidance and uncertainty as to the required speeds during the approach, the crew did not recognize that the approach was unstable, and continued.

- On the approach, the pilot flying reduced power to idle to reduce the approach speed from 122 knots toward 101 knots at 200 feet above ground level. This steepened the aircraft’s vertical path.

- The rapidly decreasing visibility resulted in the airport environment and the precision approach path indicator lights becoming obscured; as a result, the steepened vertical profile went unnoticed and uncorrected.

- Although the loss of visual reference required a go-around, the crew continued the approach to land as a result of plan continuation bias.

- The terrain awareness and warning system did not alert the crew to the aircraft’s proximity to the ground once the aircraft was below 50 feet, possibly due to the rapid rate of closure. This lack of warning contributed to the crew not being aware of the aircraft’s height above ground.

- Due to the uncorrected steepened vertical profile, loss of visual reference, and lack of normal terrain warning, the aircraft contacted the surface approximately 450 feet prior to the runway threshold.

Findings as to risk

- If guidance provided to flight crews allows for large tolerance windows, and crews are not trained to recognize an unstable condition, then there is a continued risk that flights that are unstable will be continued to a landing.

- If approaches that require excessive deceleration below established stabilization heights are routinely flown, then there is a continued risk of an approach or landing accident.

- If crews do not report unstable approaches and operators do not conduct flight data monitoring but rely only on safety management system reports to determine the frequency of unstable approaches, there is a risk that these issues will persist and contribute to an accident.

The captain (more than 12,000 hours total, about 9,000 hours on type) was pilot flying, the first officer (about 6630 hours total, 1,300 hours on type) was pilot monitoring.

The captain briefed the approach into Sault Ste Marie considering marginal weather conditions which included the possibility of a go around and diversion. The crew computed their approach speed (Vref) at 96 knots and set their approach speed bugs at 101 knots (Vref + 5).

About 15nm from the aerodrome at 5000 feet the crew encountered ice crystals which reduced visibility and requested a VOR/DME approach to runway 30 instead of the planned visual approach and were cleared for the approach. While established on the VOR/DME approach descending through 3000 feet the aircraft broke out of cloud, the crew became visual with the runway but noticed that a snow shower was approaching the aerodrome from the west. The aircraft passed the final approach fix at 2840 feet AGL and 204 KIAS descending on a 3 degree glidepath maintained visually.

The crew subsequently reduced their speed to 181 KIAS while descending to 1500 feet AGL. 5nm before the runway threshold the crew received landing clearance, winds were reported by tower from 310 degrees magnetic at 22 knots gusting 29 knots, the weather was just about to reach the runway, the RVR had dropped to 1100 feet with runway lights at intensity 4, the runway lights were further turned up to intensity 5 subsequently.

Descending through 1000 feet AGL the flaps were extended to 15 degrees, the airspeed had reduced to 148 KIAS.

Descending through 500 feet AGL the airspeed was 122 KIAS (21 knots above target speed of 101 KIAS).

Descending through 200 feet AGL and 124 KIAS the captain reduced power to idle and the airspeed began to reduce rapidly. Although the pitch was gradually increased and the rate of descent was stable, the vertical profile steepened due to reducing airspeed and resulting reduction of ground speed and the aircraft went below the 3 degrees glidepath. The flight crew briefly lost visual contact with the runway and lights due to the incoming weather of blowing snow but continued the approach.

The Terrain Awareness and Warning System (TAWS) called 50 feet.

Descending through 20 feet AGL the power was increased to 30% torque, but 2 seconds later the aircraft impacted ground.

The TSB wrote:

At 1825:19, the aircraft contacted the ground approximately 450 feet prior to the runway threshold at an airspeed of 94 knots.

The ground preceding the runway was covered in approximately 8 to 12 inches of snow.

The aircraft was in a level pitch attitude when it contacted the surface and touched down with a peak vertical acceleration of 2.32g.

Following touchdown, the nose landing gear assembly and wheel struck and damaged an approach light located 300 feet prior to the runway threshold. The flight crew heard a thump, but had not seen the light and were unsure what had caused the noise.

The aircraft came to a stop on the runway centreline, approximately 1500 feet past the threshold. The flight crew assessed the ground visibility as very poor, due to the blowing snow.

Unsure of the aircraft’s status, the flight crew informed the tower controller that the aircraft may have landed short of the runway and may have clipped the nosewheel. The crew asked the control tower to send a vehicle to their position to assess the situation, and requested that a bus be sent to move the passengers.

When the emergency vehicles arrived and assessed the condition of the aircraft, no significant damage was noticed. Upon receiving this information, the flight crew elected to taxi the aircraft to the gate.

The aircraft taxied to the gate without further incident, and the crew shut down the engines and deplaned the passengers.

The crew did not believe there was damage to the aircraft and, therefore, did not pull the circuit breaker to prevent the cockpit voice recorder data from being overwritten. As a result, relevant data that would have been captured on the 30-minute cockpit voice recorder was overwritten while the aircraft remained electrically powered at the gate.

After exiting the aircraft at the gate, the crew was notified of damage to an approach light and contacted maintenance to have the aircraft inspected.

The aircraft sustained substantial damage to the nose gear and nose gear doors as well the area around the nose landing gear. In addition it was determined both main gear struts had exceeded their load limit and were replaced, too.

The TSB analysed:

The weather system moved in from the west very quickly, and rapidly reduced runway visibility, beginning at the departure end of Runway 30. Air traffic control (ATC) informed the crew several times of the decreasing visibilities sensed by the transmissometer at the end of the runway.

The crew had no way to ascertain the speed at which the weather system was advancing across the runway and, because the runway was in sight when they approached the minimum descent altitude (MDA), they chose to continue the approach.

The crew followed what they understood to be the correct speeds for the approach.

Both crew members set the approach speed bugs at 101 knots prior to commencing the approach, as per the standard operating procedures (SOP). This speed was understood to be the speed to which the aircraft should reduce, from 120 knots, after descending through 500 feet. It was the pilot flying’s (PF) regular routine to achieve this deceleration with power reductions at 200 feet. However, on the occurrence approach, the PF reduced power to idle to reduce the approach speed from 122 knots toward 101 knots at 200 feet above ground level. This steepened the aircraft’s vertical path.

The angle of the aircraft’s established vertical path before the power reduction at 200 feet would have resulted in the aircraft arriving near the normal touchdown zone of the runway, albeit at an airspeed in excess of Vref.

When the power was reduced toward flight idle at 200 feet, the aircraft began to decelerate rapidly. The aircraft’s nose-up pitch was gradually increased and vertical speed was relatively stable; however, the vertical path steepened due to the decreasing airspeed and resultant ground speed reduction.

Below 200 feet, the pilots would normally have visual contact with the runway environment and associated runway approach lighting. With these visual cues available, the resulting steepening of the vertical profile would normally be detected and corrected by further increased nose-up pitch or increased power where necessary.

On the occurrence approach, visual contact with the runway was lost somewhere below 200 feet. With a runway visual range (RVR) visibility of 1200 feet, the PAPI lights—normally the best source of visual vertical path guidance—would not be visible until the aircraft was almost over the runway threshold.

The rapidly decreasing visibility resulted in the airport environment and the PAPI lights becoming obscured; as a result, the steepened vertical profile went unnoticed and uncorrected.

The TSB analysed the confirmation bias:

The crew had no cues to ascertain the vertical approach path after leaving 200 feet. Once visibility had deteriorated in the blowing snow, the crew perceived that the aircraft was very close to the ground and, therefore, very near to the runway. This perception is indicative of reduced situational awareness.

The crew were experiencing a higher workload at this moment because the approach speed was unstable, and power and pitch needed to be altered to achieve the planned speed reduction. Focus was being divided between looking outside at the weather and looking inside to monitor approach parameters.

The flight crew perceived the aircraft to be in a stable condition, and had never before needed to carry out a go-around due to weather once the aircraft was already below the MDA. The aforementioned confirmation bias likely led the crew to focus on these positive factors suggesting that the approach was safe while diverting their attention away from the factors that would suggest otherwise.

The TSB analysed that examination of about 500 flights showed most crews performed decelerating approaches slowing the aircraft below 500 feet AGL and wrote: "The company SOPs require an approach speed of Vref + 5 knots; however, this is being interpreted by flight crews as a target to which they should decelerate, from 120 knots, once the aircraft is below 500 feet. As a result, the majority of examined approaches, including the occurrence approach, were unstable, due to this deceleration."

The TSB analysed that the operator's safety department was unable to identify any unstable approaches below 500 feet from their safety management system database although the assessment of flight data recorders by the TSB showed that more than 84% of all flights became unstable below 500 feet.
Incident Facts

Date of incident
Feb 24, 2015

Classification
Accident

Flight number
QK-7795

Aircraft Registration
C-GTAI

ICAO Type Designator
DH8A

This article is published under license from Avherald.com. © of text by Avherald.com.
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