Flybe E195 at Exeter on Feb 28th 2019, rejected takeoff due to haze on board as result of maintenannce prompts evacuation
Last Update: September 17, 2020 / 13:26:11 GMT/Zulu time
The airline confirmed the aircraft was evacuated after haze developed in the cabin.
On Sep 17th 2020 the AAIB released their final bulletin concluding the probable causes of the accident were:
A lack of maintenance planning, training and control of resources led to an undesirable situation where a maintenance task was allocated to an engineer who was neither qualified nor competent to complete the task. A key step in the engine drying procedure was only described as ‘recommended’ and the engineer did not complete all the elements of the task. This resulted in residual cleaning solution remaining within the ECS system, causing smoke and fumes within the cabin and cockpit and leading to an emergency evacuation. The engine drying procedure has since been amended to require this step to be carried out.
Due to the order in which the emergency evacuation vital actions were performed, the flaps had insufficient time to travel to the selected position. This resulted in an increased drop to the ground for passengers evacuating via the overwing exits, with many reluctant to jump or slide off the wing. Additionally, despite the presence of a marked exit route on the wing with a non-slip surface, many passengers who exited via the overwing exits were uncertain where to go once out of the aircraft. Both of these factors increased the time taken for emergency evacuation to be completed.
The AAIB summarized the sequence of events:
Following completion of passenger boarding, the aircraft pushed back and taxied before being cleared to enter Runway 26, back-track and line up for takeoff. It was daylight, the visibility was in excess of 10 km and the wind was from 210° at 5 kt.
The APU was shut down as the aircraft entered the runway and the air conditioning packs remained on with air supplied from the engines. A few seconds later, while back-tracking, both pilots became aware of fumes in the flight deck with a different odour, which the co‑pilot described as being like paint or white spirit. The wind was behind the aircraft at this point, so they initially thought the fumes were due to exhaust gas ingestion. Upon lining up at the runway threshold the flight crew had a brief discussion about whether the fumes were decreasing and decided that they were.
Upon receiving takeoff clearance, the co-pilot advanced the thrust levers to 40% while holding the aircraft on the brakes and checked the engine indications, which were all normal. He then slowly advanced the thrust levers towards the takeoff setting, while still holding the aircraft on the brakes. As the engines reached approximately 55% power, he saw something out of the corner of his eye which he believed to have been a puff of smoke coming from an air conditioning vent. He immediately stated that he was not happy with the situation and retarded the thrust levers to idle. By then the smell of fumes had grown worse and smoke was visibly entering the flight deck.
The commander set the park brake and asked the co-pilot to turn the engine bleeds and air conditioning packs to off and the flight deck windows were opened to ventilate the flight deck. There were no EICAS messages or warnings.
The commander established contact with the senior cabin crew member (SCCM), who had simultaneously been trying to contact the flight deck. The SCCM reported that there was smoke and fumes in the cabin, but that the cabin crew could not identify the source.
The commander decided to evacuate the aircraft. The co-pilot immediately selected flap 5, notified ATC of the intention to evacuate and requested assistance. Both pilots then carried out the Emergency Evacuation ‘vital actions’. After the commander had given the order to evacuate over the passenger address system, the flight crew followed the EMERGENCY EVACUATION checklist on the back of the QRH.
The Airport Rescue Fire Fighting Services (ARFFS) arrived at the aircraft and were briefed on the nature of the emergency by the co-pilot through the flightdeck window. The ARFFS then assisted passengers on the ground as they exited the aircraft.
In their abstract the AAIB annotated:
Following an assessment of the situation, the commander initiated an emergency evacuation. During the evacuation, passengers who evacuated via the overwing exits reported being unsure of how to get down from the wing to the ground and several re-entered the cabin and exited via one of the escape slides.
The smoke and fumes were subsequently attributed to an incorrectly performed engine compressor wash procedure, which was carried out by maintenance personnel the night before the occurrence flight.
The AAIB further annotated with respect to the evacuation:
Passengers evacuating via the overwing exits reported that once out on the wing, there was confusion as to how they should get off the wing down to the ground. Passengers still in the cabin reported that this led to a bottle-neck forming around the overwing exits. Two passengers who evacuated via the left overwing exit were able to jump down from the wing and assist other passengers to the ground. Despite this, several passengers commented that it was a very long drop to the ground and some landed awkwardly, sustaining minor injuries. Many of the passengers who exited via the overwing exits commented that the wing surface was “very slippy” and one fell over resulting in a minor injury. The overriding comment from those who had exited via the overwing exits was that it was not obvious to them that they were meant to climb off the wing via the trailing edge and some re-entered the cabin to find an alternative exit route. A 61 cm-wide walkway was demarcated at the wing root in black paint, with arrows pointing towards the trailing edge (Figure 1). None of the passengers mentioned noticing this, but several did mention a lack of instructions, support or guidance once they were out on the wing.
Several passengers commented that they found the rear slides very steep and were surprised by the speed at which they slid down them. The slides at the rear do not round out at the bottom unlike the front slides, which means that individuals slid very fast onto the ground. This, and attempts by passengers to slow themselves on the slides, were the principal causes of the reported injuries. Two passengers assisted other passengers at the bottom of the rear slides. A number of passengers suffered minor cuts and grazes and one elderly passenger who had exited via D2R sustained a broken ankle. Two cabin crew members who exited via the rear slides, one carrying the megaphone and the other carrying the first aid kit, reported that this made it difficult to slow themselves down and one sustained an ankle injury.
Cabin crew noticed that some passengers hesitated when instructed to jump and slide. They therefore advised the passengers to sit and slide rather than jump and slide.
When the cabin crew believed that all passengers had left the aircraft, they checked the cabin and found several passengers stood on the wings unwilling to jump due to the height above the ground. These passengers were escorted back into the cabin and subsequently exited via the rear slides.
The AAIB reported with respect to the flaps setting: "A review of the DFDR data confirmed that the flap selector lever was moved from the takeoff flap setting (flap 1) to flap 5. Although the flaps started moving in response to this selection, the engine 1 and 2 selectors were set to the off position approximately 2 seconds later when the flight crew shutdown the engines. This removed electrical power to the flaps and prevented them from travelling to the selected position. In the flap 1 position the flap angle had been 6.9° ; the flaps reached 7.2° before stopping."
The AAIB analysed:
On the aircraft’s first flight of the day fumes became apparent in the cockpit during the latter stages of the taxi out and were subsequently accompanied by smoke as the thrust levers were advanced for takeoff. The takeoff was discontinued after which the intensity of the smoke and fumes increased. Following the flight crew’s assessment of the situation, and confirmation from the SCCM of fumes and smoke in the cabin, the commander made the decision to evacuate.
An engine compressor wash had been performed on the aircraft’s No 1 engine during overnight maintenance on the night before the accident. A high-power engine ground run was not performed following the compressor wash, resulting in residual cleaning solution remaining in the compressor bleed air ducts. This can lead to fumes or unusual odours entering the cockpit and cabin.
Source of the smoke and fumes
During the engine dry-out procedure following the compressor wash, the engines were run only at idle power. At idle power the engine power setting would have been insufficient for the engine bleed source to switch to the HPC fifth stage bleed. To dry out the fifth stage bleed ducts, the procedure recommended running the engine up to 65% N1. By not performing a high-power engine ground run, residual cleaning solution remained within the fifth stage bleed ducts.
As the thrust levers were advanced for takeoff the ECS bleed source would have switched to HPC fifth stage engine bleed, allowing smoke and fumes from the residual detergent to enter the cockpit and cabin.
Compressor wash and dry-out procedure
The ESM task for ‘Engine performance recovery’ is comprised of many subtasks covering several wash, rinse and drying scenarios. It contains multiple notes and cautions, not all of which stand out from the main text and some of which contain critical information. In particular, the information relating to the need to perform a high-power engine run during the dry-out procedure is included in a note rather than in a procedural step. The ESM indicated that this was a recommended rather than required action. The AAIB questioned the engine manufacturer’s rationale for this step being recommended rather than required.
They advised that for consistency with the other strong cautions throughout the ESM task, conducting a high-power engine run should be a required step following a compressor wash with detergent. In June 2020, it updated ESM subtask 72-00-00-410-004 task to reflect this.
Engineer 1 was more accustomed to working on another aircraft type. He had never performed a compressor wash on an E195 before, had limited experience in conducting engine runs on the E195 and was not qualified to conduct high-power engine runs. This, coupled with the fact that the procedure only recommended rather than required, a high‑power engine run, likely influenced his decision to proceed with and certify the task without alerting his supervisors of the need for a high-power ground run.
The operator’s internal investigation identified that complex maintenance tasks, such as that for a compressor wash would benefit from a company process sheet to supplement manufacturer’s procedures.
Organisational factors Maintenance planning, both at the operator and hangar level, did not adequately identify the resources required to undertake the compressor wash, nor attempt to match the requirements of the task to the capabilities of the oncoming hangar shifts. Systems in place did not assist maintenance planners and managers to easily establish the competence and approval status of individual engineers.
As a result, this maintenance task was allocated to a shift which did not have the correct competence and approvals to carry out and certify the task, or to release the aircraft to service. Had Engineer 2 fully understood the requirements of the task, the resources required to complete it and the approval status of the engineers on the night shift, it is likely that the task would have been rejected by the night shift instead of being allocated to Engineer 1. Similarly, had Engineer 4 understood these aspects, it is likely the task would have been deferred when it could not be completed by the day shift. The operator’s internal investigation found that willingness to get the job done, may have led to opportunities to stop the task being missed and existing policies may have placed too much reliance on individual engineers to identify tasks that could not be safely accomplished.
With regard to conducting engine ground runs, the operator’s internal investigation identified a lack of suitably trained engineers, trainers and training opportunities. It also identified a lack of specific training or assisting documentation for conducting engine compressor washes and using compressor wash rigs.
Many of the compressor wash rigs were found to be in poor condition. There were no records of when they were last replenished, the type or concentration of detergent used or on which aircraft they had been used. The lack of records meant that it was not possible to determine the concentration of cleaning solution that had been in the rig, prior to its replenishment by Engineer 3.
Although night shift engineers permanently worked nights, no fatigue risk assessment had been carried out to understand the potential impact on individual performance. Both Engineer 1 and 2 disclosed that they had been experiencing personal issues, which could have been affecting their mental state. Although aware, it was not determined whether their managers had taken any steps to determine whether they were capable of being on duty and certifying aircraft, and the operator’s internal investigation identified that only minimal training was available for supervisors and managers in this regard.
The operator had taken several safety actions to address these and other issues. However, it ceased operations before all intended safety actions could be fully implemented.
The commander’s decision to evacuate was based on his concern that there may have been a fire on the aircraft and was likely influenced by the increase in intensity of the fumes, the appearance of smoke in the cockpit and confirmation of smoke and fumes of unknown origin in the cabin.
The flight crew actioned the emergency evacuation vital actions (memory items) followed by the QRH EMERGENCY EVACUATION checklist. Both the memory actions and the QRH checklist require the flight crew to set the emergency/parking brake to on, select flap 5 and then move the thrust levers to idle. In this case, as the aircraft was stationary the thrust levers had already been retarded to flight idle and the parking brake set. The vital actions were therefore performed somewhat out of sequence and proceeded more rapidly than might be expected if an emergency evacuation followed a rejected takeoff or emergency landing scenario. Therefore, despite selection of flap 5, the flaps had insufficient time to travel to the selected position before the engines were shutdown. This resulted in an increased drop to the ground for passengers evacuating via the overwing exits, with many reluctant to jump or slide off the wing, leading to an increase in the time taken to complete the evacuation.
The emergency evacuation vital actions use the term ‘confirm flap 5,’ which suggests that this action requires the flight crew to confirm that the flaps have already travelled to flap 5. The commander commented that in training, an emergency evacuation is most often practiced following a rejected takeoff scenario and flap 5 is selected as soon as the decision to reject is made and before the aircraft has been brought to a stop. The flaps would therefore have travelled to the selected position by the time the emergency evacuation vital actions were actioned.
This article is published under license from Avherald.com. © of text by Avherald.com.
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