Express E145 near London on Sep 5th 2014, loss of control results in loss of 4000 feet of altitude

Last Update: July 6, 2016 / 19:46:15 GMT/Zulu time

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Incident Facts

Date of incident
Sep 5, 2014

Classification
Report

Airline
Expressjet

Flight number
EV-4538

Aircraft Registration
N16954

Aircraft Type
Embraer ERJ-145

ICAO Type Designator
E145

An Expressjet Embraer ERJ-145 on behalf of United, registration N16954 performing flight EV-4538/UA-4538 from Grand Rapids,MI to Newark,NJ (USA) with 26 passengers and 3 crew, had been delayed due to a ground stop at Grand Rapids as result of a weather front moving across the aerodrome. The aircraft had already started to taxi and was unable to move further. The crew used the time to monitor the weather development via their mobile phones and weather radar and agreed, that there were sufficient gaps between thunderstorms cells to permit deviations around weather. After departure the aircraft climbed to initially FL330, a minute later climbed further to FL370 while deviating to the north around weather. Dispatch recommended based on present weather displays the aircraft should deviate around weather tracking to Sarnia,ON (Canada) near London,ON (Canada) and further to Erie,PA (USA). The aircraft entered Canadian Airspace near Sarnia and was tracking east parallel to a line of thunderstorms. The crew turned the aircraft southbound and soon the aircraft flying on autopilot and autothrust entered instrument meteorological conditions, then turbulence began to intensify over the next minute. Still on autopilot the aircraft encountered increasing vertical accelerations ranging from +0.49G to +1.42G, the engine thrust was reduced initially then increased, the aircraft's speed increased to 0.79mach, the aircraft climbed without ATC clearance. About a minute after the onset of turbulence a peak acceleration a peak acceleration of +1.7G occurred resulting in the autopilot disconnecting, the roll attitude became unstable with bank angles from 45 degrees left to 14 degrees right. The flight crew attempted to reconnect the autopilot, the aircraft hit another peak acceleration ranging from +0.20G to +1.7G, the autopilot disconnected again at 1.7 degrees nose down (angle of attack ranging from 9.9 nose down to 3.8 degrees nose up), the speed decreased to 0.68 mach climbing through FL375. The aircraft reached FL376, it's highest altitude during the encounter, at 45 degrees right bank, vertical accelerations fluctuated between +0.44G and +1.6G. The aircraft pitched down to 11 degrees nose down, the crew increased thrust and provided right roll inputs which rolled the aircraft further to 63 degrees right bank, the pitch reached 13 degrees nose down, the aircraft descended at 3100 fpm, the crew provided left roll inputs reducing the bank angle to 33 degrees. The ice detection system triggered warning encountering severe icing, the aircraft's anti-ice systems were automatically activated. Descending through FL368 the rate of descent had increased to 4400 fpm, the aircraft had again reached 42 degrees of right bank, the crew again applied right roll commands increasing the bank angle to 77 degrees, the nose pitched further down reaching 17 degrees below the horizon, the aircraft accelerated through 0.76 mach, the severe turbulence persisted. Descending through FL355 the rate of descent had increased to 6900 fpm, the crew reduced thrust over the next 6 seconds, during those 6 seconds the turbulence decreased to moderate and the pitch reduced to 6 degrees nose down. Descending through FL338 the rate of descent decreased to 2700 fpm. 3:16 minutes after the onset of the turbulence encounter the descent was arrested at FL336 after losing about 4000 feet, the ice detection ceased and the aircraft began to climb again. With urgency in their voices the crew requested vectors out of the weather, Toronto ATC suggested tracking south, the aircraft turned south, soon left the weather system and continued to destination for a safe landing without further incident. There were no injuries on board and no damage to the aircraft.

On Jul 6th 2016 Canada's TSB released their final report concluding the probable causes of the serious incident were:

Findings as to causes and contributing factors

- The flight crew were aware of the weather conditions and departed, anticipating that they would be able to navigate through an extensive line of thunderstorms. However, as the flight progressed, the line of thunderstorms intensified and, as a result, the flight crew's intended route became obstructed.

- The flight crew operated the aircraft through a mature thunderstorm and, as a result, an aircraft upset and loss of control occurred.

- During the loss of control, the flight crew momentarily applied flight control inputs that exacerbated the roll attitude of the aircraft. As a result, altitude loss and recovery time were increased.

Findings as to risk

- If flight crews operate aircraft outside of manufacturer recommendations, the risk of encountering an adverse consequence is increased.

- If aircraft are operated outside of manufacturer limitations, there is a risk of compromising flight safety, resulting in injury to the occupants or damage to the aircraft.

- If cockpit voice recordings are not available to an investigation, the identification and communication of safety deficiencies to advance transportation safety may be precluded.

The TSB reported that during the upset as result of the turbulence encounter the aircraft encountered vertical accelerations between +0.20G and +2.01G were encountered, the aircraft reached a turn rate of 200 degrees per minute (3.3 degrees per second) changing the aircraft heading from 180 to 240 degrees magnetic and a peak rate of descent of 9300 fpm occurred.

The captain (10,000 hours total, 7,000 hours on type) was pilot flying, the first officer (3,400 hours total, 2,200 hours on type) was pilot monitoring. The crew had received weather information from their dispatch within their preflight briefing. The TSB reported: "A complete weather assessment provided by Environment Canada after the occurrence indicated that the weather at the time of the occurrence was generally as forecasted."

The TSB analysed that the investigation did not find any evidence of a system malfunction or failure throughout the event.

The TSB analysed:

The National Oceanic and Atmospheric Administration (NOAA) radar weather depiction reviewed by the TSB indicated that, at the time of departure, there were gaps in the line of thunderstorms. However, the size and intensity of thunderstorms can change rapidly as they mature or dissipate.

After departure, the flight crew attempted to navigate through an extensive line of thunderstorms. However, as the flight progressed, the line of thunderstorms intensified and, as a result, the flight crew's intended route became obstructed.

As the aircraft continued eastward, the flight crew could not locate an opening that would enable them to continue flying toward their destination. The crew therefore requested assistance from a company dispatcher to help them find a route through the line of thunderstorms.

The dispatcher provided an opinion on which route to take, based on what he observed on his display and his assessment of the weather. According to his display (Figure 2), the route was feasible, given the aircraft position and the location of the adverse weather.

However, shortly after turning in the direction suggested by the dispatcher, the aircraft encountered severe turbulence and experienced a loss of control, suggesting that the thunderstorm was more severe at that location than had been indicated by the dispatcher's display.

After the occurrence, the dispatcher's display (Figure 2) was compared with the NOAA radar weather depiction. In the NOAA depiction (Figure 3), the thunderstorm was shown as larger and more contiguous than on the dispatcher's display. The difference in the 2 depictions was due in part to radar reflectivity types. The dispatcher's display is a base reflectivity product, which uses the lowest reflectivity angle, while the NOAA display shows a composite radar return, which uses the maximum reflectivity from all of the multiple elevation angles.

Therefore, the NOAA depiction that showed the weather as more intense was not representative of what the dispatcher was seeing at the time of the flight crew's request for assistance. The dispatcher made a decision based on the flight-following software, which is designed for proactive weather monitoring and flight following. When it is used proactively, a flight can be rerouted before encountering adverse weather, such as a line of thunderstorms. The entire storm area can be avoided by a wide margin.

In this occurrence, when the flight crew requested assistance from dispatch, the aircraft was already positioned in the line of thunderstorms, and the flight crew were navigating between individual storm cells. As a result, the flight-following software was not used as intended (i.e., as a proactive tool to avoid weather), but rather as a reactive response to a thunderstorm encounter. Had the flight crew requested dispatch assistance earlier, a suggestion to help them avoid the weather system completely may have been provided.

The TSB analysed: "During the initial stage of the loss of control, the aircraft exceeded the maximum operating altitude. During the rapid descent, the speed increased, and the maximum operating Mach number (MMO) was exceeded. Both exceedances were above the aircraft limitations. Although these limitations were exceeded unintentionally, if aircraft are operated outside of manufacturer limitations, there is a risk of compromising flight safety, resulting in injury to the occupants or damage to the aircraft."

The software being used by the operator permits real time weather monitoring and flight following allowing the aircraft operator to proactively avoid weather. The TSB wrote: "Through use of those functions, a line of thunderstorms, such as that facing this flight crew, can be avoided, and the aircraft can be rerouted before coming within proximity of the storm."

The aircraft was equipped with a Honeywell Primus 660 weather radar. The TSB wrote: "The weather radar has several features, such as range, tilt (manual control of the antenna angle), and gain (how much of the energy leaving the antenna is focused in a particular direction), which must be used correctly during operation. If these tools are improperly managed, weather targets can be missed or underestimated. As the FDR does not record parameters from the weather radar unit, it could not be determined with certainty which settings the flight crew were using on the on-board weather radar unit. It also could not be determined how the flight crew were using the weather radar. There were no data to suggest that the weather radar was faulty."

The TSB complained that although flight data and cockpit voice recorders were installed, they were not protected following the occurrence. The occurrence was reported to the TSB only 24 hours after the occurrence at which time the cockpit voice recorder had already been overwritten. The flight data recorder contained 26 hours of flight and the last 17 flights of the aircraft.
Incident Facts

Date of incident
Sep 5, 2014

Classification
Report

Airline
Expressjet

Flight number
EV-4538

Aircraft Registration
N16954

Aircraft Type
Embraer ERJ-145

ICAO Type Designator
E145

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