REX SF34 at Sydney on Dec 4th 2014, retracted gear above maximum retraction speed

Last Update: June 7, 2016 / 14:02:26 GMT/Zulu time

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Incident Facts

Date of incident
Dec 4, 2014

Classification
Report

Airline
REX Regional Express

Flight number
ZL-473

Departure
Sydney, Australia

Destination
Narrandera, Australia

Aircraft Registration
VH-ZRJ

Aircraft Type
SAAB 340

ICAO Type Designator
SF34

A REX Regional Express Saab 340B, registration VH-ZRJ performing flight ZL-473 from Sydney,NS to Narrandera,NS (Australia), was climbing out of Sydney's runway 34L with the captain (ATPL, 12,810 hours total, 4,900 hours on type) being pilot flying and the first officer (ATPL, 8,300 hours total, 4,800 hours on type) being pilot monitoring. Significant weather was around the aerodrome, the crew discussed the possible impact of that weather on their departure route. Shortly after becoming airborne there were the calls "positive rate", "gear up". The captain, anticipating the first officer would now operate the gear lever, focussed on the weather on the left side where the aircraft was bound to turn to. The first officer however did not recall hearing the "gear up", the gear remained extended. The first officer also concentrated on the weather, activated the yaw damper and retracted the flaps, on initialing the left turn at 600 feet AGL the autopilot was engaged and the aircraft increased speed to 182 KIAS. The first officer established radio contact with departure control, both crew continued to monitor the weather to the west of Sydney. Both crew recognized the climb performance was less than anticipated but were unable to determine the reason. Climbing through 3800 feet MSL the captain called for the climb checklist, the first item required to check the status of the gear, the captain automatically called "up" then corrected "not up". The first officer instinctively selected the gear lever up only then realising that the aircraft was at 182 KIAS, 32 knots above the maximum gear retraction speed of 150 KIAS. The gear retracted without problems. The remainder of the flight was uneventful, the aircraft landed safely at destination.

Australia's TSB released their final report concluding the causes of the incident were:

Contributing factors

- During the take-off sequence both crew were focused on the departure procedures and local weather that, combined with the effects of fatigue on the first officer, likely led to the landing gear not being retracted.

- The first officer’s ability to assess their own level of fatigue was impeded by a lack of training and objective tools to do so, resulting in a decision to operate the flight instead of calling in fatigued.

- During the climb, the crew likely expected that the landing gear was retracted, reducing the likelihood that they would detect the indicators that it was still extended.

- When the crew identified that the landing gear was still extended, the first officer instinctively retracted the gear before identifying that the aircraft was above the maximum landing gear retraction speed.

Other factors that increase risk

- Although compliant with applicable regulations, the Rex rostering processes did not wholly account for the unforeseen extension of the first officer’s previous duty period or the effects on performance of conducting a check flight, both of which impacted the adequacy of the first officer’s sleep opportunity on the evening before the occurrence.

- The only checklist item to confirm that the gear was up was carried out when the aircraft’s airspeed was above the maximum landing gear retraction speed, increasing the risk that crew would retract the landing gear before slowing the aircraft.

The ATSB analysed:

Acute sleep disruptions are reductions in the quality or quantity of sleep that have occurred within the previous 3 days (Transportation Safety Board of Canada 2014). Losing as little as 2 hours of sleep will result in acute sleep loss, which will induce fatigue and degrade subsequent performance and alertness (Dinges and others 1996).

Other research has indicated that less than 6 hours sleep in the previous 24 hours can increase risk. Thomas and Ferguson (2010) examined the effects of different amounts of sleep on the performance of Australian airline flight crews. Crew error rates was higher during flights when the crew included a captain with less than 6 hours sleep or an FO with less than 5 hours sleep in the previous 24 hours.

The FO reported obtaining a total of between 4 and 6 hours sleep in the 48 hours prior to the occurrence. Accordingly, it is reasonable to conclude that the FO was experiencing a level of acute fatigue known to have at least a moderate effect on performance.

The types of errors made by the crew, including an error of omission that was not detected, are consistent with the effects of fatigue. However, as discussed in the following sections, there were other factors that could lead to the development and non-detection of such errors. While it is difficult to conclude that fatigue alone led to the FO’s errors on this occasion, it was considered contributory to the occurrence.

The ATSB analysed the first officer was based in Melbourne and had a low rate of rotations out of Sydney, hence needed to apply a high level of attention to the departure procedures. The first officer unintentionally missed the gear retraction and also did not make the "selected" call. The ATSB wrote:

When considering how the call ‘positive rate, gear up’ was not perceived, or how the action was not otherwise recalled, the following are relevant:

- Skill-based errors can occur when a pilot is undertaking highly-learned, well-developed behaviours that are essentially sub-conscious (Harris 2011). Retracting the landing gear was a frequent action for crew and therefore conducted automatically, with little conscious oversight.

- Omitting a step in a task is one of the most common types of human error. A step is more likely to be omitted if the instructions are given verbally (Reason 2007). Raising the gear was triggered by a standard verbal cue (that is, ‘positive rate, gear up’), and not retracting it could be considered an error of omission. The risk of making errors of omission can increase when experiencing fatigue.

- Reliance on predictable cues may make items more vulnerable to being forgotten when the cues are not available, or not perceived (Nowinski et al 2003). The verbal cue to raise the gear was not heard by the FO.

The crew did not detect the landing gear was still down although the call "Gear, selected" was missing, the gear lights still indicated green, the bleed value push button still illuminated and degraded climb performance. The ATSB wrote: "The crew likely expected that the landing gear was retracted, reducing the chance that they would detect that it remained extended. This is due to human attention being guided by two factors: expectancy (an individual will look where they expect to find information) and relevance (an individual will look to information relevant to their important tasks and goals)."

After the crew recognized the landing gear was still down, the first officer instinctively reached out to select the gear up. "The FO usually referenced the aircraft’s airspeed before any configuration changes, but in this case, the FO’s action was in response to the surprise of discovering that the gear was still extended."

With respect to detecting fatigue the ATSB analysed:

The FO felt that being tired was not a sign of fatigue, nor recognised that obtaining between 4 and 8 hours of sleep over the previous two nights was an indication of a significantly increased risk of experiencing fatigue that would likely impair performance.

When comparing the operator’s syllabus and available training material to the recommended industry approach, it was identified that the initial human factors/non technical training course included a discussion of factors that contribute to fatigue and some of the consequences. One topic in the syllabus was ‘identifying the signs of fatigue and how to counter its effects’, but this did not appear to be included in the presentation material for the course.

Overall, at the time of the occurrence the content of the provided fatigue training was limited to a general overview of fatigue, sleep and fatigue countermeasures which may not provide crew with an adequate opportunity to develop the skills or utilise tools that could best help them identify signs of fatigue in themselves or others. Noting that Rex was not required to comply with the new fatigue rules on training at the time of the occurrence, it could be expected that, as they work towards implementing those requirements by May 2017, the training content will be revised.