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= 2014 September 05 Flight 4538 =

Summary
On September 5th 2014 an ExpressJet Airlines Embraer EMB-145LR while flying on a routine instrument flight flew through a large thunderstorm and encountered severe turbulence. The flight crew briefly lost control of the aircraft. Shortly after the aircraft returned to its designated flight path and continued to its destination where it landed safely with no injuries to the crew, passengers or damage to the aircraft.

Details
At 21:59 coordinated universal time the aircraft began maneuvering at the Grand Rapids Airport (KGRR) in preparation for departure. A local thunderstorm was present at the airport, in result of which the aircraft stayed on the ground for some time. While on the ground the pilots viewed weather applications on their phones to find the most suitable route to Newark Liberty International Airport (KEWR).

At 22:45 the aircraft departed it's airport of origin and flew in visual meteorological conditions parallel to a line of thunderstorms. Initial flight level that the airplane climbed to was flight level 330, where it remained for 1 minute, after which it climbed up to flight level 370. Light turbulence began during the climb.

Shortly after reaching flight level 370, the aircraft began to experience increasing turbulence. The crew was communicating with the Toronto Area Control Center (ACC) and received clearance to deviate from the planned flight route in order to avoid adverse weather conditions. The crew also established contact with the company dispatch to avoid the weather system. after 6 minutes the dispatcher advised the crew to proceed directly to Chris Hadfield Airport (CYZR) and then Erie International Tom Ridge Field Airport, subsequently the crew followed the advice.

At 23:14, after turning south, following the dispatcher's advice, the aircraft began experiencing even stronger turbulence. The aircraft began slowly climbing and accelerating.

For the next three minutes the aircraft experienced worsening turbulence, crew lost control of the airplane. During this time the aircraft firstly gained 600 feet, then lost 4,000 feet, descending to flight level 336, accelerated to over 0.80 Mach. The airplane constantly experienced varying pitch angles, angles of attack and back angles. The angle of attack fluctuated rapidly within the range of -11.9° to 3.8°. Peak vertical acceleration was recorded withing the range of 0.15g to 2.07g. During the period of loss of control the aircraft had sustained an average turn rate of 200° per minute, this changed the magnetic heading of the aircraft from 180° to 240°, at one point a peak descent rate of 9,300 feet per minute was recorded. During the encounter with severe turbulence at one point the aircraft also experienced severe icing, which triggered the ice-detection system. The anti-ice systems were auto-commanded ON for the wing, stabilizer, and engine surfaces.

At 23:17, at flight level 336 the aircraft's descent was arrested, after which the ice-detection indications stopped and the aircraft began climbing once again.

The aircraft did not encounter any more severe turbulence and safely continued to it's destination airport. After reporting the event to the operator, a severe turbulence inspection was performed on the aircraft and the flight data recorder was downloaded. No damage or discrepancies were noted. The aircraft was released back to service.

Crew
For most of the flight, the captain was the pilot flying. At the time he had about 10,000 flight hours, 7,000 of which were in type and 5,000 as pilot-in-command. He had been employed by the operator for 10 years.

The first officer had roughly 3,400 hours, 2,200 of which were in type. He had been employed by the operator for three years.

Weather phenomena thunderstorm, and its affects on the flight
The aircraft encountered meteorological phenomena called thunderstorm. Thunderstorm is described as a rain shower, with lightning and a acoustic effect called thunder. Thunderstorms are a result from rapid upward movement of warm, moist air. Thunderstorms are also associated with cumulonimbus clouds and icing conditions, especially in high altitudes. Thunderstorms also cause severe turbulence for aircraft flying inside them, because of the unstable meteorological conditions. Flight N16954, was instructed by ATC dispatcher to avoid flying through the thunderstorm and just to cross it near Sarnia. At 23:16, the ice-detection system indicated the presence of ice. The aircraft encountered severe icing conditions. Also while in thunderstorm according to a official report by transportation safety board of Canada, vertical acceleration peeked at 0.20 g and 1.7 g while disengaging the autopilot.

METAR information of the flight
METAR KGRR 052213Z 26014KT 3SM TSRA FEW016 BKN041CB OVC085 22/22 A2994

TSRA shows shower thunderstorm in the area, while the crew decides to commence the flight by checking the meteorological data provided by weather information on their mobile phones, making decision with ATC unit to change the planed flight path to circumvent adverse weather

METAR CYZR 052300Z AUTO 04012G20KT 9SM TS BKN031 BKN037 21/19 A2986

Normal thunderstorm clouds are present in the area the pilots decide to fly through thunderstorm

METAR CYZR 052314Z AUTO 02014G25KT 3SM +TSRARA BR FEW014 BKN033 OVC041

+TSRARA from this shows heavy thunderstorm with rain in the area of the flight experienced turbulence, indicating the conditions were present in the area.

Precipitation and ground radar information of the area
Radar information provided by United states meteorological authorities shows increased high precipitation near Sarnia and a front of moving rain clouds in the path of the flight

Using the charts provided the following information about the meteorological conditions during the flight can be interpreted. The weather radar observations clearly show a big formation of clouds stretching across the Ontario area and forming a wall that obscures the aircraft's planned flight plan. By using the skew-t chart and plotting a parcel temperature line on it we can clearly see that the atmosphere during that day was quite unstable which can result in formation of cumulus clouds and even thunderstorms. Formation of new cumulus clouds often results in strong turbulence forming, which might be a possible explanation for the incident.

The official report published by Transportation safety agency of Canada includes the meteorological charts on Ontario area which show a low pressure area and a cyclone in the area. Cold air front is parallel to the flight path of the flight 4538. Cyclone is a huge air mass that moves anti-clockwise in the circle around low pressure area.

Safety action taken by the operator
Express Jet airlines, took additional precautions due to the event and changed their operational procedures, according to the findings of Transport safety board of Canada


 * The operator has improved the dispatcher use of flight-following software; additional focus has been placed on using the lightning-strike functionality of the weather portion of the software.
 * Through the company safety management system, the operator has identified areas for improvement; all involved personnel received focused calibration training in various areas, such as pilot-in-command and dispatcher joint responsibility, with specific emphasis on issuing information necessary for the safety of the flight and radar interpretation of pilots.
 * The operator has developed a training module for all flight crew members that promotes weather radar utilization techniques both to identify developing storm activity and to avoid severe weather. This training is a proactive step to reinforce previously taught concepts and was integrated in company flight crew training program.