McDonnell Douglas DC-9-32 accident at Dallas, Texas, 2 Jun 1983

Accident narrative

On June 2, 1983, Air Canada Flight 797, a McDonnell Douglas DC-9-32 registered C-FTLU, was a regularly scheduled international passenger flight from Dallas, Texas, to Montreal, Quebec, with an en route stop at Toronto, Ontario. While en route at 33,000 feet, the cabin crew discovered smoke in the aft lavatory. After the crew declared an emergency and initiated a descent, air traffic control vectored the airplane to the Greater Cincinnati International Airport in Covington, Kentucky. The airplane landed safely, and 18 passengers and 3 flight attendants evacuated through the forward doors and overwing exits. The captain and first officer escaped through their cockpit windows. About 60 to 90 seconds after the exits were opened, a flash fire engulfed the airplane interior. Twenty-three passengers were unable to evacuate and died in the fire. The airplane was destroyed.

### The Flight

Flight 797 departed Dallas at 1625 central daylight time with 41 passengers and 5 crewmembers on board. The flight climbed to its assigned en route altitude of flight level 330.

The captain had flown about 13,000 hours, including 4,939 hours in the DC-9. The first officer had flown about 5,650 hours, with 2,499 hours in the DC-9.

About 30 minutes after departure, a louvered panel at the bottom of the cockpit door was accidentally kicked from its mounts and fell to the floor. The panel was placed to one side, and the flight continued.

### The In-Flight Fire

At 1851:14 eastern daylight time, the three circuit breakers associated with the aft lavatory's flush motor tripped in rapid succession. The captain immediately made one attempt to reset them, but they would not reset. Assuming the flush motor had probably seized, he took no further action at the time. At 1859:58, the captain again tried unsuccessfully to reset the breakers, telling the first officer that the circuit breaker "pops as I push it."

About 1900, a passenger seated in the last row asked the No. 3 flight attendant to identify a strange odor. The flight attendant took a CO2 fire extinguisher, opened the aft lavatory door a few inches, and saw that light gray smoke had filled the lavatory from floor to ceiling, though she saw no flames. She closed the door and asked the No. 2 flight attendant to inform the flight attendant in charge.

The flight attendant in charge instructed the No. 2 flight attendant to inform the captain and to assist in moving passengers forward and opening the air vents to direct air to the rear. He then opened the lavatory door about three-quarters open. He saw no flames but observed thick curls of black smoke coming out of the seams of the lavatory walls behind the vanity and at the ceiling. He discharged the CO2 extinguisher into the lavatory, spraying the paneling and the trash bin door, and then closed the door.

At 1902:40, the No. 2 flight attendant reached the cockpit and told the captain, "Excuse me, there's a fire in the washroom in the back, they're just...went back to go to put it out." The captain ordered the first officer to inspect the lavatory and donned his oxygen mask. The first officer left the cockpit without smoke goggles or a portable oxygen bottle. He found that smoke had migrated over the last three to four rows of seats and was too thick for him to reach the lavatory. The flight attendant in charge briefed the first officer on the CO2 discharge and stated he did not believe the fire was in the trash bin.

At 1904:07, the first officer returned to the cockpit and told the captain that the smoke prevented him from entering the lavatory and that he thought "we'd better go down." Before the captain could respond, the flight attendant in charge came to the cockpit at 1904:16 and reported that the passengers had been moved forward and that the smoke was "easing up." The first officer looked back, stated "it's starting to clear now," and offered to go aft again. The captain gave the first officer his smoke goggles and directed him to go aft.

At 1905:35, the airplane experienced a series of electrical malfunctions. The master caution light illuminated, indicating the left a.c. and d.c. electrical systems had lost power.

At 1906:52, the flight attendant in charge again told the captain the smoke was clearing. The captain later testified that he believed the fire was in the trash bin and expected it to be put out, which is why he did not decide to descend at that time.

Meanwhile, the first officer reached the aft lavatory, found the door hot to the touch, and instructed the cabin crew to leave it closed. He returned to the cockpit, got into his seat, and at 1907:11 told the captain, "I don't like what's happening, I think we better go down, okay?" The captain testified that the first officer's voice inflection indicated the fire was out of control and that they had to descend immediately.

At 1907:41, the master warning light illuminated, indicating the emergency a.c. and d.c. electrical buses had lost power. The attitude directional indicators tumbled. The captain ordered the first officer to activate the emergency power switch, which erected the gyros, but the loss of a.c. power left the stabilizer trim inoperative for the rest of the flight.

### The Descent and Air Traffic Control

At 1908:12, Flight 797 called the Indianapolis Air Route Traffic Control Center and declared, "Mayday, Mayday, Mayday." At 1908:47, the flight reported it had a fire and was going down. The Louisville radar high sector controller advised the flight it was 25 nautical miles from Cincinnati. The flight requested clearance to Cincinnati and was cleared to descend to 5,000 feet. At 1909:05, Flight 797 reported leaving flight level 330. The flight changed its transponder to the emergency code 7700, but because the transponder was inoperative due to the power loss, the code was never portrayed on the radarscopes.

Because the transponder was inoperative, an automated handoff to the Cincinnati Terminal Radar Control (TRACON) was not possible. The Indianapolis Lexington low altitude controller initiated a manual handoff via landline. At 1909:25, he told the Cincinnati approach controller he had an emergency for Air Canada 797. The Cincinnati controller observed a westbound beacon target on his scope and replied with its code and altitude: "Zero six six two, thirty-five thousand." This target was actually Continental Flight 383. The Indianapolis controller replied, "Yeah, thirty-three right now, he's twenty-five southwest." The Cincinnati controller accepted the handoff, mistakenly tracking the Continental flight.

At 1910:25, Flight 797 contacted Cincinnati approach, declared an emergency, and reported descending. The controller asked the flight to turn to 090 degrees. Seeing no response from the target he was watching, he realized the error. At 1912:54, the controller identified Flight 797's primary target. Knowing the airplane was too high and fast to land on runway 36, he decided to use runway 27L and provided a "no gyro" radar approach, issuing turn instructions because the flight's heading instruments were inoperative.

The captain flew the emergency descent at 310 knots indicated airspeed with the speed brakes extended. The rate of descent exceeded 6,000 feet per minute.

After leveling off at 3,000 feet, the captain ordered the first officer to depressurize the airplane in preparation for landing. The first officer complied and also turned off the air conditioning and pressurization packs. He later testified that he did so because the smoke was getting bad and he thought the packs were feeding the fire.

### The Landing and Evacuation

The captain flew the final approach at 140 knots indicated airspeed, extending the landing gear and incrementally extending the flaps and slats. At 1920:09, Flight 797 landed on runway 27L. The captain made a maximum effort stop using extended spoilers and full brakes. Because the antiskid system was inoperative, all four main wheel tires blew out.

After stopping, the captain and first officer attempted to enter the cabin to assist with the evacuation but were driven back by smoke and heat. They exited through their respective cockpit sliding windows.

In the cabin, the left and right forward doors, the left forward overwing exit, and the right forward and aft overwing exits were opened. The slides at the forward doors were deployed. Eighteen passengers and the three flight attendants evacuated through these five exits.

About 60 to 90 seconds after the exits were opened, the cabin interior burst into flames. Neither the survivors nor witnesses outside saw flames inside the cabin before the survivors left the airplane. Twenty-three passengers died in the fire.

Airport crash-fire-rescue vehicles had been positioned along the runway and followed the airplane until it stopped. Firefighters saw heavy smoke rolling out of the exits and initiated an exterior attack, discharging foam onto the fuselage. Once passengers were off the left wing, firefighters attempted an interior attack through the left aft overwing exit but were driven back by intense smoke and heat. A subsequent attempt to enter through the jettisoned tailcone was also repelled by intense heat. The fire was extinguished 56 minutes after firefighting began.

### Survival Aspects

During the descent, the cabin filled with black, acrid smoke from the ceiling down to about knee level. The flight attendants moved all passengers forward of row 13, except for two passengers who refused to move from their seats next to the right forward overwing exit. The attendants distributed wet napkins and instructed passengers to breathe through them or their clothing. Passengers reported severe distress, with the smoke hurting their noses, throats, and chests. By the time the airplane landed, visibility was so poor that passengers could not see their hands in front of their faces.

The flight attendants designated passengers to open the overwing exits. Three of the four emergency overwing windows were successfully opened by passengers.

The flight attendant in charge did not use the megaphone stowed in the overhead rack to issue evacuation commands, later testifying that the smoke was advancing rapidly and he thought it unwise to waste time retrieving it. Because the first officer had instructed the flight attendants to sit down before landing, the No. 2 and No. 3 flight attendants were seated in the forward and mid-cabin areas and were unable to reach their designated supervisory positions at the overwing exits.

Most of the fatalities were found in the aisle or seated in rows 2 through 9, with two fatalities found in the aisle at rows 14 and 16.

### What the Investigation Found

#### The Wreckage The cabin area of the upper fuselage down to below the windows was heavily damaged by fire. The aft lavatory was damaged extensively, with most of its interior walls burned away. The amenities section of the vanity, which contained the oxygen mask compartment and dispensers for paper products, was almost completely disintegrated along the outboard corner. The trash chute and container were intact, and paper trash inside the container was scorched but not burned. The automatic Halon fire extinguisher had discharged into the trash chute.

#### Tests and Research The Federal Bureau of Investigation laboratory analyzed samples from the lavatory and found no flammable accelerants.

Electrical components were tested, and while the static inverter was found to have short-circuited transistors, the generator control panels functioned normally.

The Board conducted a flush motor seizure test, simulating a frozen drive shaft. The internal motor temperature reached 617°F, and the stator windings eventually opened, but the 5-ampere circuit breakers did not trip. The accident motor showed no evidence of internal melting or electrical arcing.

Fire and heat tests were conducted on a DC-9 lavatory mockup. An overheated flush motor reaching