Rockville, VA, USA
N868CA
Canadair CL-600-2B19
About 3 hours before takeoff, the dispatcher approved the flight release, which contained SIGMET Whiskey 8 for occasional severe turbulence from 14,000 feet to FL 280, and then went off duty. The turbulence box overlaid the departure airport and planned en route climb to altitude; however, the top of descent (TOD) and destination airport were clear of the turbulence. When the pilot printed the flight release, SIGMET Whiskey 8, had been replaced with SIGMET Whiskey 9. The turbulence box had moved east of the departure airport, and the TOD and destination airport remained clear of the turbulence box. The flight release also contained a single pilot report of severe turbulence from a Boeing 737 at FL 240, within the defined area of turbulence. Prior to departure, but after the flight release was signed by the pilot, the flight release was updated again, this time with SIGMET Whiskey 10. The turbulence box moved further east to cover the TOD and destination airport. Nearing his destination, the pilot was descended into the turbulence box defined by both SIGMET Whiskey 9 and Whiskey 10. These turbulences boxes ranged from Ottawa, Canada, to Florida, to Cleveland, Ohio. The pilot had turned on the seat belt sign, asked the flight attendant to be seated, and had already made an announcement for the passengers to remain seated as they were within 30 minutes of the destination airport. While descending through 17,800 feet, the flight encountered severe turbulence. The airplane was not equipped with ACARS. Flight crews were required to monitor dispatch frequency for updates, and encouraged to get weather updates en route. Weather updates were accomplished by direct radio contact between the dispatcher and pilots, or by the pilots accessing FAA facilities while en route. Although the operator had about 100 flights operating in the turbulence box, none were cancelled due to forecast turbulence, or reported to have encountered severe turbulence.
HISTORY OF FLIGHT On November 17, 2002, about 1800 eastern standard time, a Bombardier CL-600-2B19 (CRJ-2), N868CA, operated by Comair as Delta Connection flight 5109 (Comair 109), encountered severe turbulence while in a descent near Rockville, Virginia. There were no injuries to the 2 certificated pilots, 1 flight attendant, or 48 passengers. Night instrument meteorological conditions prevailed for the flight that departed from The William B. Hartsfield, Atlanta International Airport (ATL), Atlanta, Georgia. The flight was destined for Ronald Reagan, Washington National Airport (DCA), Washington, DC. An instrument flight rules (IFR) flight plan had been filed for the scheduled, domestic, air carrier flight that was conducted under 14 CFR Part 121. Prior to departure, the captain received and signed his flight release. The text above the space for the captain's signature stated: "I HAVE REVIEWED THE DISPATCH RELEASE FOR THIS FLIGHT AND BASED ON THE INFORMATION FURNISHED BY AN AUTHORIZED AIRCRAFT DISPATCHER I BELIEVE THAT THE FLIGHT MAY BE MADE WITH SAFETY - 121.663 -" Contained in the flight release were AIRMETS, a SIGMET for severe turbulence, and a pilot report of severe turbulence, all near or covering portions of the planned flight. SIGMET Whiskey 9 called for occasional severe turbulence between 13,000 feet and FL 280 (28,000 feet) due to wind shear associated with jet stream and middle/upper trough. The conditions were forecast to continue beyond 1820. The passengers were boarded, and the airplane was out of the gate at 1620. The flight departed at 1702. The en route phase of the flight was conducted at FL 290 in visual meteorological conditions. The cabin was prepared for arrival into Washington National Airport, and the seat belt sign had been illuminated. The flight attendant was advised to take her seat and remain seated. The air/ground communications tape between airplanes operating on the frequencies, was reviewed. In addition, a partial transcript of pertinent air/ground communications between airplanes operating on the same frequency, and the controllers with Washington Air Traffic Control Center (ZDC) was prepared. At 1748:21, Comair 109 reported that they were descending from FL 290 to FL 250. At 1748:38, USA1404 reported that they were experiencing light chop at FL 280. At 1748:42, while Comair was on the frequency, the controller told the USAir flight to expect continuous light and occasional moderate turbulence down to 12,000 feet. He also told the flight that he thought it was clear of any severe turbulence and had not heard of anything about severe turbulence lately. At 1750:39, Comair 109 was instructed to descend and maintain FL 220. At 1755:07, Comair 109 reported moderate turbulence. At 1755:22, Comair 109 was instructed to descend to FL 190, and the pilots were advised they were going to be in "chop" down through 12,000 feet. After acknowledging the information, Comair 109 was instructed to change frequencies to another sector. At 1758:02, Comair 109 reported they were in moderate turbulence. At 1758:26, Comair 109 was instructed to descend to 10,000 feet. At 1759:53, Comair 109 reported an encounter with severe turbulence at 17,000 feet while on descent. The controller replied that this was the first severe turbulence report he had received in the last 40 minutes. Comair added that they encountered severe turbulence at 18,000 feet in the descent. When queried about a minute later about that altitude range for the severe turbulence, the pilots of Comair 109 reported that they were still in steady moderate turbulence while descending through 15,500 feet, and the severe turbulence was between 20,000 feet and 18,000 feet. The flight continued to Washington National Airport, landed at 1817, and arrived at the gate at 1825. The flight was met by emergency personnel. Several passengers were taken to area hospitals for observations; however, no injuries were reported. According to the captain's written statement: "...Before the encounter, only light with occasional moderate turbulence was experienced. The seatbelt sign was ON...[the first officer] had also warned the flight attendant to remain seated for her safety due to the turbulence." "During the descent into DCA, at approximately flight level 190, in IMC conditions; we encountered extreme turbulence. The aircraft was at 280 knots, with Continuous Ignition ON, all anti-ice systems ON, and autopilot ON in turbulence mode." "The aircraft encountered a positive gravitational acceleration followed by a negative and then a stronger positive gravitational acceleration. The extreme turbulence caused the autopilot to disengage, yaw damper to disengage, and the stall warning system to activate. I took manual control of the aircraft, returning it to a normal attitude and performance envelope. The encounter lasted approximately 5-7 seconds. The aircraft was undamaged and the flight continued safely to DCA." According to the flight attendant's written statement: "We were about 15 minutes out of DCA when we had some moderate turbulence. The...[captain] made a PA to tell us. Called and asked if everyone was ok. A few seconds later we had extremely severe turbulence that lasted 8 to 10 seconds. Rocking back and forth, up and down and dropping. I saw passengers hit their heads on the overhead bins and I had one passenger tossed out of his seat onto the floor....I yelled back "stay calm, stay on the floor, passengers around, hold him down." At that time there was no way I could get up or on the PA, I was being tossed around also side to side, I couldn't raise my arms from holding on. When I felt it was safe for him to move, I told him to hurry and get back into his seat. I then called the...[captain] and told him I had one passenger tossed out of his seat and landed on the floor. I asked him to have medical personnel to meet us in DCA. The aisles were full of things tossed around (purses, magazines, pillows, etc.)...." When interviewed, both pilots reported that their flight bags were emptied and the contents tossed about the cockpit. The captain further reported that he did not remember hearing other flights or the controller report any severe turbulence. He also reported that he was aware of the severe turbulence on the flight release and said that it covered the entire eastern seaboard. He said the dispatcher went over the weather with him, but did not mention any reports of severe turbulence. The first officer further reported that he was not aware that the flight release contained a severe turbulence forecast. After arrival in DCA, the airplane was given a visual inspection and released for a maintenance ferry flight to the Greater Cincinnati/Northern Kentucky International Airport (CVG), Covington, Kentucky. The incident occurred during the hours of darkness, in instrument meteorological conditions (IMC), at 37 degrees, 43.5 minutes north latitude, and 77 degrees, 42.9 minutes west longitude, while the airplane was descending through 17,800 feet. PERSONNEL INFORMATION The captain held an airline transport pilot certificate with a multi-engine land rating, and a type rating for the CL-65. He held a commercial pilot certificate for single engine land airplanes, and a flight instructor rating for single and multi-engine airplanes and instrument airplane. He was last issued a FAA first class airman medical certificate on October 22, 2002. His last proficiency flight check was conducted on July 9, 2002. The captain reported his total flight experience as 4,500 hours, with 3,000 hours in make and model, and 230 hours in the preceding 90 days. The first officer held a commercial pilot certificate with single and multi-engine land ratings, and an instrument airplane rating. He also held a flight instructor certificate with a single engine rating. He was last issued a FAA first class airman medical certificate on February 22, 2002. His last proficiency check was conducted on October 16, 2002. The first officer reported his total flight experience as 2,300 hours, with 650 hours in make and model, and 250 hours in the preceding 90 days. The dispatcher held a dispatcher certificate. He had received training and became an assistant dispatcher in January 2000. He was upgraded to dispatcher in June 2000. AIRCRAFT INFORMATION The airplane was originally certificated by the Government of Canada, and in the United Stated through a bi-lateral agreement. The maximum allowable gross weight of the airplane was 53,000 pounds. The maximum allowable g loads were + 2.5 g, and -1.0 g. According to the load manifest for the incident flight, the basic operating weight of the airplane was 31,123 pounds; the zero fuel weight was 40,623 pounds, and the takeoff gross weight was 49,073 pounds. The mean aerodynamic chord (MAC) was about 14 percent at takeoff, and 16 percent at the zero fuel weight. The flight release projected a fuel burn of 3,661 pounds for the trip, and an elapsed time of 1 hour 11 minutes. The actual time en route was 1 hours 15 minutes. METEOROLOGICAL INFORMATION The flight release was reviewed by the dispatcher at 1338, who placed it in a queue, awaiting the pilot's call up. The dispatcher went off duty at 1430. The dispatcher reported that when he approved the flight release, it contained SIGMENT Whiskey 8, which referenced an area of forecast severe turbulence, and he was aware of its contents. Once a flight release was placed in the queue, it was not available for print from 10 minutes before the hour, until 5 minutes after the hour. This allowed the flight release to be automatically updated with the latest available weather. When the pilot printed out the flight release, SIGMET Whiskey 8, had been replaced by SIGMET Whiskey 9, which referenced a different area of severe turbulence. A review of SIGMETS Whiskey 8, 9, and 10 revealed the following. SIGMET Whiskey 8 was issued at 1020 - The approximate geographic limits were from Tampa, Florida; Albany, Georgia; London, Kentucky; Cleveland, Ohio; Toronto, Canada; Ottawa, Canada; Plattsburgh, New York; Harrisburg, Pennsylvania; and Tampa, Florida. The SIGMET forecast occasional severe turbulence between 14,000 feet, and FL 280. This was the valid SIGMET when the flight release was approved by the dispatcher, but was not contained in the flight release signed by the pilot. The turbulence area overlaid Atlanta, and upon departure, the airplane would climb through the turbulence box. The eastern edge of the turbulence zone was west of the planned top of descent (TOD), destination airport, and the turbulence experienced by flight 109. This was also the SIGMET that was active when the flight release for the preceding flight flown by the same pilots, Comair 5102 was prepared. The turbulence box was clear of the departure airport, Allentown, Pennsylvania, but overlaid the destination airport, Atlanta SIGMET Whiskey 9 was issued at 1420 - The approximate geographic limits were Cape Coral, Florida; Tampa, Florida; Columbia, South Carolina; Cleveland, Ohio, Toronto, Canada; Ottawa, Canada; Plattsburgh, New York; Harrisburg, Pennsylvania; East of Wilmington, North Carolina; and Palm Beach, Florida. The SIGMET forecast occasional severe turbulence between 13,000 feet, and FL 280. This was the valid SIGMET when the pilot signed the flight release, but was not on the flight release approved by the dispatcher. The turbulence box had been shifted to the east. There was no turbulence overlay above Atlanta. The planned TOD and destination airport were east of the turbulence box. However, the area where the airplane encountered turbulence was within the confines of the turbulence box. SIGMET Whiskey 10 was issued at 1520 - The approximate geographic limits were Cape Coral, Florida; Tampa; Florida; Columbia, South Carolina; Cleveland, Ohio; Toronto, Canada; Ottawa, Canada; Plattsburgh, New York; Cape May, New Jersey; East of Wilmington, North Carolina; and Palm Beach, Florida. The SIGMET forecast occasional severe turbulence between 10,000 feet, and FL 280. This was the valid SIGMET when the flight was en route to Washington, DC. It was released after the pilot received the flight release, and prior to the departure of flight 109. The turbulence box was east of Atlanta; however, it covered the eastern seaboard, to the shore line. This included the TOD, destination airport, the location where the turbulence occurred, and the area of the pilot report of severe turbulence occurred. A weather study was prepared by a Safety Board staff meteorologist. The study revealed that the turbulence occurred within an area of localized high vertical and horizontal wind shears, and high values of spectrum width, a measure of turbulence, from the Doppler weather radar. The following definitions of turbulence were contained in the Aeronautical Information Manual (AIM). Moderate Turbulence - "...changes in altitude an/or attitude occur, but the aircraft remains in positive control at all times...It causes rapid bumps or jolts...." Severe Turbulence - "...large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control...." Extreme Turbulence - "...the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage...." Air traffic controllers are required to make a one-time announcement when SIGMETS, which cover their area of responsibility are released. However, there is no requirement for repetitive announcements. En route weather advisories were available to the pilots of Comair 109,through their dispatch system, and various FAA facilities. Flight Release A further review of the flight release for Comair 109 revealed it was 22 pages long. Pages 1 through 3 1/3 contained the basic flight plan information and the fuel summary for the flight. Pages 3 1/3 through 5 contained the computerized flight plan. Pages 6 through 9 1/4 contained center weather advisories (CWAs). Several of the bulletins were duplicated. One bulletin was repeated 6 times. Pages 9 1/4 through 17 1/4 contained AIRMETS and SIGMETS. Many were duplicated. SIGMET Whiskey 9 was repeated 9 times. Many of the items were outdated. The Arrangement placed AIRMETS before SIGMETS. AIRMETS included Sierra, Tango, and Zulu. Sierra AIRMETS are for mountain obscuration and instrument meteorological conditions, and are not applicable to instrument flight. Pages 17 1/4 through 22 contained the departure, en route, destination, and alternate airport weather. Also included were NOTAMS. The NOTAMS that were listed under the destination airport included airports with runways as short as 2,500 feet, and no instrument approaches. The investigation revealed that the weather used by the dispatcher to approve the flight, may not match the weather the pilot received when he printed out the flight release. There was nothing available to the pilot to assist him in determining what weather had been added, changed, or deleted from the flight release between the time the dispatcher approved the flight, and the pilot received his flight release. The route in the computerized flight contained on the flight release, specified the latitude and longitude of specific points along the route of flight and the top of climb (TOC), and TOD. The TOD was located about 14 nm from the Richmond International Airport (RIC), Richmond Virginia, on a magnet bearing of 020 degrees. The location of the severe turbulence encountered by Comair 109 was about 37 nm distant on a magnetic bearing of 310 degrees from the TOD. The flight release also contained a pilot report of severe turbulence from a Boeing 737 at FL 240. The event occurred at 1430, and the airplane's location was 22 nm northwest of the turbulence experienced by Comair 109. In interviews, both pilots reported that the flight release contained a lot of weather information. Further it was necessary to review a lot of non-pertinent data to arrive at the pertinent data. FLIGHT RECORDERS The cockpit
The PIC's inadvertent encounter with turbulence while operating in an area of forecast occasional severe turbulence.
Source: NTSB Aviation Accident Database
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