DCA99MA007

The first officer of AirTran Airways flight 890, which preceded AirTran flight 867 in the accident airplane, identified and reported a leak from the right engine of the Boeing 737-200 during a postflight inspection at William B. Hartsfield Atlanta International Airport (ATL), Georgia. AirTran mechanics at ATL identified the source of the leak as a chafed hydraulic pressure line to the right thrust reverser. They found the part in the illustrated parts catalog (IPC), which was not designed as a troubleshooting document and does not contain sufficient detail for such use. One of the mechanics telephoned an AirTran maintenance controller in Orlando, Florida, for further instructions. The mechanics who initially identified the source of the leak had little experience working on the Boeing 737 because they had worked for ValuJet Airlines, which flew DC-9s only, until ValuJet and AirTran merged in September 1997. On the basis of the information provided by the mechanic, and without questioning his description of the line or verifying the part number that he had provided against the IPC or some other appropriate maintenance document, the maintenance controller instructed the mechanic to cap the leaking line and deactivate the right thrust reverser in accordance with AirTran's Minimum Equipment List procedures. However, instead of capping the hydraulic pressure line, the mechanics capped the right engine hydraulic pump case drain return line. The mechanics performed a leak check by starting the auxiliary power unit and turning on the electric hydraulic pumps to pressurize the airplane's hydraulic systems; no leaks were detected. Although the mechanics were not required by company procedures to test their repair by running the engines, this test would have alerted the mechanics that they had incorrectly capped the hydraulic pump case drain line, which would have overpressurized the hydraulic pump and caused the hydraulic pump case seal to rupture. However, because the mechanics did not perform this test, the overpressure and rupture occurred during the airplane's climb out, allowing depletion of system A hydraulic fluid. Depletion of system A hydraulic fluid activated the hydraulic low-pressure lights in the cockpit, which alerted the flight crew that the airplane had a hydraulic problem. The crew notified air traffic control that the airplane would be returning to ATL and subsequently declared an emergency. The flight crew's initial approach to the airport was high and fast because of the workload associated with performing AirTran's procedures for the loss of hydraulic system A and the limited amount of time available to perform the procedures. Nevertheless, the crew was able to configure and stabilize the airplane for landing. However, depletion of system A hydraulic fluid disabled the nosewheel steering, inboard flight spoilers, ground spoilers, and left and right inboard brakes. The flight crew was able to land the airplane using the left thrust reverser (the right thrust reverser was fully functional but intentionally deactivated by the mechanics), outboard brakes (powered by hydraulic system B), and rudder. The flight crew used the left thrust reverser and rudder in an attempt to control the direction of the airplane down the runway, but use of the rudder pedals in this manner had depleted the system A accumulator pressure, which would have allowed three emergency brake applications. The use of the right outboard brake without the right inboard brake at a higher-than-normal speed (Vref for 15-degree flaps is faster than Vref for normal landing flaps) and with heavy gross weight (the airplane had consumed only 4,650 pounds of the 28,500 pounds of fuel on board at takeoff) used up the remaining friction material on the right outboard brake, causing it to fail. (The left outboard brake was still functional at this point.) The lack of brake friction material on the right outboard brake caused one of the right outboard brake pistons to overtravel and unport its o-ring, allowing system B hydraulic fluid to leak out; as a result, the left outboard brake also failed. Loss of the left and right inboard and outboard brakes, loss of nosewheel steering, and use of asymmetric thrust reverse caused the flight crew to lose control of the airplane, which departed the left side of the runway and came to rest in a ditch.

History of flight

On November 1, 1998, about 1734:48 eastern standard time (all times in this brief are eastern standard time based on a 24-hour clock), AirTran Airways flight 867, a Boeing 737-223, Irish registration EI-CJW, crashed after departing the side of runway 9L at William B. Hartsfield International Airport (ATL), Atlanta, Georgia, during an emergency landing. Of the 2 flight crewmembers, 3 flight attendants, and 100 passengers on board, 2 passengers received serious injuries, and 14 passengers received minor injuries. The airplane was substantially damaged. Flight 867 was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from ATL to Dallas?Ft. Worth International Airport, Texas.

Flight 867 was the airplane's second flight of the day. AirTran flight 890, from William P. Hobby Airport, Houston, Texas, to ATL, arrived at 1320. At the conclusion of flight 890, the first officer of that flight performed a postflight check of the airplane and discovered a fluid leak coming from the number two (right) engine. Two AirTran mechanics (referred to in this brief as the first and second mechanics), who were working the first shift of the day, reported in postaccident interviews that they opened the engine cowling and found a chafed hydraulic line with a "misting" or "spray" of hydraulic fluid leaking from the line. They inspected the hydraulic pump and associated areas and did not find any other leaks.

To specifically identify the leaking line, the mechanics reported that they operated the right thrust reverser on the ground without running the engine. (This test was specified in the Boeing 737 Maintenance Manual.) The mechanics stated that they followed the leaking line to the hydraulic pump and found that the leak was from a pressure line that appeared to go to the thrust reverser. This line did not have an identification number, so the mechanics referred to the illustrated parts catalog (IPC) to identify the line by its part number. The first mechanic reported that a replacement line was not available, but caps of the proper size were available for repairing the line.

About 1415, the first mechanic telephoned an AirTran maintenance controller at Orlando International Airport (MCO), Florida, to report that the hydraulic leak was on the pressure line going to the number 2 (right) thrust reverser at the service panel where the thrust reverser cable goes over the thrust reverser pressure line. The first mechanic also told the maintenance controller the part number for the line that needed to be replaced. In a postaccident interview, the maintenance controller stated that he did not reference the IPC during the telephone call because he thought he was familiar with the location of the leak based on the mechanic's description of the problem.

The maintenance controller stated that he discussed the leaking hydraulic line with the AirTran manager of maintenance at MCO, who agreed with the controller that the line could be repaired rather than replaced if parts were available. The maintenance controller then instructed the mechanic to cap the line and deactivate the associated thrust reverser according to AirTran's Minimum Equipment List (MEL) procedures. (The MEL procedures allowed one thrust reverser to be inoperative provided it was deactivated and secured closed and a placard was placed in the cockpit indicating that the thrust reverser was inoperative.) Further, the maintenance controller told the mechanic that the damage to the hydraulic line would be further assessed at the airplane's next scheduled maintenance visit. According to the flight discrepancy sheet issued by maintenance control, the right engine thrust reverser hydraulic leak was to be repaired on or before November 4, 1998.

After capping the hydraulic pressure line, the first-shift mechanics performed a leak check by starting the auxiliary power unit and turning on the electric hydraulic pumps to pressurize the airplane's hydraulic systems. No leaks were reported. The mechanics did not start the right engine as part of the leak check, but they were not required by AirTran procedures to do so.

Two additional AirTran mechanics (referred to in this brief as the third and fourth mechanics), who were working the second shift of the day, were also involved in the repair operation. The third mechanic arrived early for his shift and assisted the first mechanic in deactivating the thrust reverser because the first mechanic had not previously performed this task on a 737. About 1530, the mechanics told the maintenance controller that they had deactivated the thrust reverser.

At the end of their shift, the first and second mechanics briefed the third and fourth mechanics on the status of the repair operation and told them the work that remained to complete the repair. The second-shift mechanics accomplished the remaining tasks, serviced the hydraulic fluid level, and performed the daily walkaround check (a brief visual check of specific areas of the airplane to detect any obvious discrepancies.) About 1600, the third mechanic signed off on the repair and indicated that the airplane was ready for flight.

Cockpit voice recorder (CVR) information indicated that, about 1710, flight 867 departed ATL. The captain was the flying pilot, and the first officer was the nonflying pilot. About 1719:57, the captain stated, "hydraulic pumps are [unintelligible word], I hope that's in error." About 3 seconds later, the first officer indicated, "I hope that's an error, too." Flight data recorder (FDR) data showed that the airplane was at an altitude of approximately 18,000 feet about this time. About 1721:50 and 1721:55, the captain stated, "well, there goes the A system" and "looks like we're gonna be going back to Atlanta." About 1722:34, the first officer notified air traffic control that the airplane needed to return to ATL. The controller asked whether there were any problems, and the first officer responded, about 1722:54, "…not at this time. we're having erroneous hydraulic system indication…we'll…keep you advised."

About 1723:56, the flight crew initiated AirTran's non-normal procedures for the loss of system A hydraulic pressure when the first officer stated, "system A flight control switches [unintelligible word] goes standby rudder?" and the captain replied, "you go ahead and do those." (AirTran's Aircraft Operations Manual, volume 1, indicates that the first action for the loss of system A hydraulic pressure is to select the standby rudder.) About 1724:35, the captain instructed the first officer to tell the air traffic controller that they would need a "long straight in" for landing. The first officer then informed the controller, who offered the flight crew the use of runway 9L or 9R; the flight crew chose runway 9L because it was longer. (Runway 9L is 11,889 feet long and 150 feet wide.) About 1726:54, the first officer stated, "…all right ground spoilers inboard spoilers nosewheel [steering] inoperative, thrust reversers are standby pressure, inboard brakes accumulator only…." About 1728:12, the first officer notified the air traffic controller that the field was in sight and that the airplane would be able to clear the runway but a tug would be needed for towing afterward.

About 1728:29, the first officer called for the approach briefing. The flight crew was also responsible for accomplishing the other tasks on AirTran's checklist for the loss of hydraulic system A. These tasks included setting the approach airspeed for a flaps 15 landing (the CVR indicated that the captain was planning an approach airspeed of 155 knots), extending the leading edge flaps and slats with the use of the standby hydraulic system, and extending the trailing edge flaps electrically. Further, the flight crew had to extend the landing gear manually and plan the landing witho