N948VV

HISTORY OF FLIGHT

On May 7, 1998, about 1920 eastern daylight time, a Douglas DC-9-32, N948VV, operated by AirTran Airlines, Inc., as flight 426, encountered turbulence and hail near Calhoun, Georgia, while climbing through 20,000 feet above mean sea level (msl). Of the 2 flight crewmembers, 3 flight attendants, and 82 passengers who were on board, 1 flight attendant and 1 passenger received serious injuries during the encounter, and the remaining occupants were uninjured. The airplane was substantially damaged by hail. The flight crew performed a successful emergency landing at the Chattanooga Metropolitan Airport (CHA) near Chattanooga, Tennessee. Flight 426 was being operated as a scheduled domestic passenger flight under the provisions of 14 Code of Federal Regulations (CFR) Part 121 and was destined for Chicago Midway Airport (MDW), Chicago, Illinois, from Atlanta Hartsfield International Airport (ATL), Atlanta, Georgia.

On the evening before the accident, the flight crew arrived at Dallas-Fort Worth International Airport (DFW), Texas, after flying the first day's schedule of a two-day trip. The overnight stay at DFW was a scheduled rest period of 14 hours, and both pilots stated that they were well rested the next day. On the following afternoon, the flight crewmembers arrived at the DFW airport about 1400 to begin their preparations for a flight to ATL. Following a routine flight preparation, including a check of the airplane's weather radar, they departed DFW about 1500. The flight crew stated that the flight to ATL was uneventful and that they did not see any adverse weather conditions to the north of ATL. They arrived at ATL about 1740 and were scheduled to be on the ground for one hour before the next flight.

At the gate in Atlanta, the flight crew was given departure papers for the flight to MDW. The departure papers contained a flight plan, a preliminary load manifest and a weather package. The captain stated that he looked at a weather display in the AirTran operations area and observed a "line of weather" along the Georgia and Tennessee borders. He stated that he was not sure if the weather depiction was from a satellite or radar, but the line was significant. He stated that the line had red radar displays in north Georgia and was more like a "blob" instead of single cell. The first officer stated that he observed a radar display in the AirTran operations area that depicted a line of weather with red, yellow, and green colored cells along the Georgia and Tennessee borders.

The captain stated that after returning to the airplane, he briefed a flight attendant, telling her that he did not notice any hazardous weather around ATL, that MDW weather was improving, and that there was some adverse weather en route to MDW.

After a brief ground delay, the flight departed from runway 26L at 1907 and was assigned a 350-degree heading and a clearance to climb to 14,000 feet. The captain stated that during climb, the weather radar was on and selected to the 80-mile range in the "normal" mode with the gain set to "auto." He stated that the weather radar was showing a solid line with dark returns in northwest Georgia. He also visually observed the line by looking out of the cockpit windows. The captain stated that he decided to delay the 10,000-foot departure announcement to the flight attendants because he believed that it would have prompted them to begin meal service and he wanted them to remain in their seats. The pilots stated that they heard the forward flight attendant get up from her seat, so they opened the cockpit door to tell her to sit down.

Between 10,000 and 12,000 feet, the flight was cleared to continue the climb to 23,000 feet. At that time, the crew asked for and received a 330-degree heading to remain clear of weather. The pilots stated that they were in visual meteorological conditions at this time and that their radar showed a light area of precipitation west of the line of weather. They stated that their radar also showed an approximately 10-mile gap between two storm cells in the line of weather and that, through this gap, they were able to see that no adverse weather conditions were on the other side.

The flight crewmembers reported that as they proceeded through the gap, they observed an egg-sized piece of hail hit the center windshield, causing its outer pane to shatter. At the same time, they began experiencing turbulence that lasted about 10 seconds. They stated that approximately 1 to 2 seconds after the encounter with the first piece of hail, the airplane encountered significant hail, which lasted about 3 to 5 seconds and shattered the outer panes of the captain's and first officer's windshields. Both pilots stated that the hail caused significant damage to the skin of the airplane but that no control problems were noted. They stated the nose radome cover was torn off and that the noise level in the cockpit was high. They also stated that the airspeed indication was zero and the altimeter indications were erratic.

Data from the digital flight data recorder (DFDR) indicate that at 1916:05, about 3 minutes before the hail encounter, the airplane's pitch angle decreased from 4 degrees to -4 degrees while the airplane climbed from 15,000 to 16,000 feet. The airplane's airspeed increased from 305 knots to 350 knots, its pressure altitude decreased from 15,600 feet to 14,600 feet, its vertical acceleration increased to 1.5 g, its longitudinal acceleration decreased to 0 g, its roll changed from 0 degrees to -6 degrees, its control column pitch became erratic, and its engine pressure ratios (EPR) decreased from 1.8 to approximately 1.4. About 1 minute later, at 1917:05, the DFDR parameters stabilized.

At 1918:30, while climbing through 20,500 feet, many of the DFDR parameters became erratic again. Roll degrees reached an extreme of about -40 degrees, and continued to oscillate between 20 and -10 degrees. Pitch angle increased to about 10 degrees, then decreased to -6 degrees, and remained erratic throughout the incident. Vertical acceleration oscillated between 2.9 g and -.9 g. Longitudinal acceleration fluctuated between 0 g and .15 g. Control column pitch became erratic, though generally increased, to a maximum of approximately 12 degrees. Indicated airspeed became erratic but generally decreased from 350 knots to 280 knots. At 1919:30 the EPRs decreased from approximately 1.9 to 1.5. Pressure altitude increased during the incident from approximately 19,500 feet to approximately 23,000 feet.

The flight crewmembers stated that as they emerged from the weather encounter, they told ATC what had happened, requested vectors to fly direct to CHA, declared an emergency, and asked to have emergency equipment standing by when they landed. ATC assigned a vector to runway 20 at CHA and a lower altitude. They requested that the controller provide a ground controlled approach and verbal ground speed readouts every 10 seconds. The first officer performed the normal checklists for landing and tuned in the frequency for the runway 20 instrument landing system. The captain and first officer stated that, when they were about 10 to 12 miles from the airport, they began to see the runway through small, unshattered areas of the windshields. They reported that while on the approach, they compared their altimeter data with the altitude information that was verbally provided by ATC and that the altimeters appeared to be providing correct altitude readouts. The landing was successful.

After landing, the fire department performed a fire inspection of the airplane and the airplane was taxied to a gate. The crew requested medical assistance. Upon arrival at the gate, medical personnel came on board to attend to the injured.

DAMAGE TO AIRPLANE

The airplane's radome had separated and portions of it had been ingested into the right engine. All three outer panes of the cockpit front windshield were shattered. The wing leading edge devices, horizontal stabilizer leading edge, vertical stabilizer leading edge, and both left and right engine inlet cowls were dented and damaged. Both engines sustained foreign object damage.

PESONNEL INFORMATION

The Captain

The captain, age 57, was hired by Valujet Airlines on January 23, 1993, as a DC-9 captain. He remained with the airline after it was acquired by AirTran Airways. Before his employment with Valujet, the captain served 21 years as a pilot for Eastern Air Lines and 6 years as a pilot in the U.S. Air Force. At the time of the accident, the captain held an airline transport pilot (ATP) certificate with type ratings in the DC-9. He accumulated about 7,200 hours in the DC-9 and about 4,800 hours as a DC-9 pilot-in-command. The captain's most recent Federal Aviation Administration (FAA) first-class medical certificate was issued on February 25, 1998, with the limitation that he wear corrective lenses.

A review of FAA and National Transportation Safety Board records revealed that on August 15, 1990, the captain failed the oral portion of his DC-9 type rating examination. He was retested and subsequently passed. On September 15, 1990, the captain failed the entire flight test portion of his DC-9 type rating check ride. He was retested and subsequently passed. On January 28, 1994, the captain was involved in an air carrier incident in which he lost control of a DC-9 during a takeoff roll in adverse weather conditions. The takeoff was aborted and the airplane departed the runway onto a grassy area. On July 5, 1994, the captain was involved in an air carrier accident in which he was in command of a DC-9 that encountered moderate convective turbulence during climbout, causing a flight attendant to suffer multiple leg fractures.

After the May 7, 1998, accident, the captain was reassigned as a first officer.

The First Officer

The first officer, age 30, was hired by Valujet Airlines on August 21, 1995, as a DC-9 first officer. He remained with the airline aft...