On June 2, 1983, Air Canada Flight 797, a McDonnell-Douglas DC-9-32 (S/N 47196) of Canadian Registry (C-FTLU), was on a regularly scheduled international flight from Dallas, Texas to Montréal, Quebec, Canada with an en route stop at Toronto, Ontario, Canada. The flight left Dallas at 1725 EDT.

Due to smoke from an uncontrollable fire in the lavatory, located aft of the passenger seating area, the aircraft made an emergency landing at 1920, at the Greater Cincinnati International Airport (now identified as Cincinnati/Northern Kentucky International Airport, CVG). Twenty-three of the 41 passengers were unable to exit the aircraft and succumbed to smoke and toxic gases prior to and/or after the flash fire that occurred 60 to 90 seconds after the emergency exit doors were opened.

History of Flight 797

Cockpit, First Indications

The NTSB reviewed six possible sources of the fire: incendiary or explosive device; deliberate ignition; burning cigarette; the toilet flush motor; the flush motor electrical harness; or arcing of the generator feeder cables. While extensive analysis was conducted, the origin of the fire was not conclusively identified.

A fire in the area of the flush motor was shown to have the capability to cause the flush motor circuit breakers to trip. The three-phase motor uses 115 Volt alternating current at 400 Hertz. The wiring to the motor is protected by three five-ampere phase-A, phase-B, and phase-C circuit breakers in the flight deck. Immediately prior to the circuit breakers tripping the Cockpit Voice Recorder (CVR) captured three instances of a sound similar to electrical arcing. The CVR wiring is near the generator feeder bundles, and voltage excursions can electromagnetically excite the cockpit area microphone. This excitation can be recorded by the CVR, but will not be audible to the pilots. This phenomenon is similar to listening to a transistor radio during a lightning storm. As lightning occurs near the receiver, the signal is disrupted and a short moment of static is heard. Following the circuit breaker trips, the pilot attempted to reset each one, but was unsuccessful. Nine minutes later, another unsuccessful attempt to reset the circuit breakers was made.

Cabin, First Indications

About the same time that the circuit breakers were reset for the second time, a passenger seated in the last row asked one of the flight attendants (FA, number 3, FA3) to identify a strange odor. The flight attendant, equipped with a portable CO₂ fire extinguisher, looked inside the aft lavatory and saw light grey smoke filling the lavatory. No flames were seen. The door was closed, and the flight attendant informed the next senior flight attendant (FA2), who in turn informed the flight attendant in charge (FAIC). FA2 went forward to inform the captain and then assisted FA3 in moving the passengers forward. In the meantime, the FAIC, equipped with the fire extinguisher, went to assess the situation in the lavatory. The FAIC opened the lavatory door and observed thick curls of black smoke emanating from the seams of the lavatory walls, at the top of the wash basin, behind the vanity, and at the ceiling. The FAIC sprayed CO₂ at the walls, seams, and the door of the trash bin. The trash chute and receptacle area for trash was equipped with a heat activated automatic Halon 1301 fire extinguisher. The NTSB concluded that the trash chute was not a factor or contributor to the fire.

Delayed Decision to Divert to Nearest Airport                                     

 At 1902:40 the flight attendant (FA2) informed the captain of the fire in the aft lavatory and that the FAIC had gone to "put it out." This flight attendant had not seen the condition of the lavatory, and was therefore unable to inform the captain where the fire was located inside the lavatory. The first officer went aft to investigate but did not take his smoke goggles with him. A flight attendant requested approval to move passengers forward after the first officer left the flight deck. The FAIC informed the first officer that CO₂ had been discharged, and that he believed it was not a trash chute fire.

At 1904:07 the first officer returned to the cockpit to retrieve goggles, as smoke had engulfed the last three rows of the aircraft. He told the captain that he couldn't go back, as the smoke was too heavy. He further stated that while it didn't have to be accomplished immediately, he recommended that they begin a descent and emergency landing. Immediately following, the FAIC entered the flight deck and informed the crew that the passengers had been moved forward and "...you don't have to worry, I think it's gonna be easing up." The first officer agreed that the smoke was starting to clear.

At 1904:46 the first officer returned to the lavatory with smoke goggles and a smoke mask. A flight attendant informed the captain that the FAIC discharged CO₂ in the washroom, and the fire seemed to be subsiding. The FAIC stated that CO₂ was discharged inside the washroom, but the source of the fire could not be seen. The first officer, after donning smoke goggles, went aft to the lavatory a second time. He felt the lavatory door and, finding that it is hot, decided not to open it. He then returned to the flight deck.

At 1907:11 the first officer stated "...I think we better go down..." The captain agreed, and preparations for an emergency descent were made.

Cabin Safety

Flammability:  Under the basis of certification, the cabin interior materials were required to be flash- and flame-resistant, but did not provide compliance criteria. There were also no Advisory Circulars available to provide guidance. In June 1982, Air Canada had refurbished the passenger cabin. The right rear lavatory had been removed and replaced with a clothing storage area. Overhead luggage bins were installed, and the cabin walls and ceilings were replaced. The manufacturer of this new equipment had been required to demonstrate that the subject materials met the flammability standards of 14 CFR 25.853 (a)(b) as amended on May 1, 1972.

Cockpit Door:  Earlier in the flight, the louvered kick plate of the flight deck door came off. During the descent, the door was not closed, which allowed smoke to enter the flight deck.

Smoke Detectors:  Smoke detectors were not required in the passenger compartment or the lavatories.

Smoke in the Cabin:  It was estimated that the fire burned undetected for almost 15 minutes. An aluminum lavatory vent line was designed to remove lavatory air through a venturi, located forward of the lavatory in an access panel. A flex line for the waste tank flush and fill pipe was also located close to the inlet of the lavatory vent line. If this flex line melts the pipe will also become an overboard vent. Hot gases melted the aluminum vent tube and then impinged on the generator feeder cables. This high temperature resulted in faults on the left and right generators, and the protective circuits tripped them off line at just about the same time that the pilot declared an emergency at 1907.

During the descent and prior to landing the air conditioning and pressurizations packs were cycled on and off by the first officer in the belief that the airflow was feeding the fire. Although he did not know it, turning off the system accelerated the accumulation of smoke, heat and toxic gases in the cabin.

Almost all fires propagate upward and in the direction of surrounding airflow. The fire traveled behind the amenities section and the toilet shroud. As the fire consumed the lavatory structure, the smoke and burned and unburned gases moved up the lavatory frame channels and forward along the space between the airplane skin and ceiling panels. The smoke, fumes, and hot gases entered the cabin through the ceiling and sidewall panels, and began to collect in the upper portions of the cabin.

Passengers found relief from the smoke and fumes by breathing through wet napkins and towels passed out by the fight attendants, or by articles of clothing held over their nose and mouth. They all attempted to breathe in as shallow a manner as possible, as the smoke (which contained noxious by-products such as carbon monoxide, hydrogen chloride, hydrogen fluoride, hydrogen cyanide) hurt their noses, throats, chests, and caused their eyes to water.

Egress:  By the time the plane landed and was brought to a stop, the entire cabin, including the cockpit, had been engulfed with thick smoke. More than one or two feet above the cabin floor, visibility was non-existent. None of the passengers noticed if the emergency lights had been illuminated. The smoke was sufficiently thick that most of the passengers had to find the emergency exits by using seatbacks to feel their way along the aisle. Some passengers leaving through the over-wing doors found these exits because they had memorized the number of rows between their seats and the exits. Some passengers were able to breathe and see slightly better when on their hands and knees.

View the Air Canada DC-9 Flight Path Animation below:

Several factors limited the success of the evacuation of the passengers. The flight attendants at the forward doors were not able to make themselves heard inside the cabin. The location of the fatalities in the cabin tends to confirm that those who succumbed either made no attempt to move toward an exit or started too late and were overcome as they attempted to move toward an exit. Studies indicate that in the absence of commands, some passengers will remain seated and await orders, a phenomenon known as "behavioral inaction." It is also possible that some of the passengers were incapacitated because of exposure to toxic gases and smoke during the descent and landing.

A flash fire occurred within 60 to 90 seconds after the doors were opened and the cabin environment became non-survivable within 20 to 30 seconds after the flash fire began.

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1. The airplane was registered, equipped, and maintained in accordance with Canadian regulations, and it was operated within the Unites States in accordance with applicable Federal Aviation Regulations.
2. The flight crew and the cabin crew were qualified and trained in accordance with Canadian regulations and Air Canada requirements. Each crewmember had received the off-duty times prescribed by Canadian regulations.
3. A fire propagated through the amenities section of-the aft lavatory and had burned undetected for almost 15 minutes before the smoke was first noticed.
4. The fire was not set deliberately nor was it the result of an explosive or incendiary device.
5. The NTSB could not identify the origin of the fire.
6. The first malfunction to evidence itself to the flight crew was the simultaneous tripping of the three flush motor circuit breakers, about 11 minutes before the smoke was discovered. The flight crew did not consider this to be a serious problem.
7. The smoke in the aft lavatory was discovered by a flight attendant. The smoke was reported to the captain as a fire.
8. The source of the smoke was never identified either by the flight attendants or the first officer. The captain was never told, nor did he inquire as to the precise location and extent of the "fire," which had been reported to him. Crewmember reports that the fire was abating misled the captain about the fire severity and he delayed his decision to declare an emergency and descend.
9. Because of the delayed decision to descend, the airplane lost the opportunity for landing at Louisville. Had the airplane been landed at Louisville, it could have been on the ground three to five minutes earlier than at the landing time in Cincinnati. The delayed decision to descend and land contributed to the severity of the accident.
10. A faulty ATC handoff did not delay significantly Flight 797's landing at Greater Cincinnati Airport.
11. The fire consumed the lavatory walls, propagated into the ceiling, and then began to move forward. Smoke, toxic fumes, and heated gases began to enter the cabin, spread forward, and collect along the ceiling of the cabin.
12. The flight attendants' passing out wet towels to the passengers and instructing them to breathe through the towels or through articles of clothing aided in the survival of some of the passengers.
13. The first officer turned off the air conditioning and pressurization packs in the belief that the airflow was feeding the fire. The resulting loss of circulation accelerated the accumulation of smoke, heat, and toxic gases in the cabin and likely decreased the time available for evacuation.
14. Three of the four over-wing exit windows were opened by designated passengers who had been selected and briefed to open them by the flight attendants.
15. When the airplane stopped, smoke had filled the cabin and visibility within the cabin was almost nonexistent two to three feet above the cabin floor.
16. A flash fire occurred in the cabin within 60 to 90 seconds after the doors and over-wing window exits were opened. Flames from this fire were not evident until after the survivors had left the airplane. Flames from the original fire never were evident within the airplane or to persons on the ground.
17. This was a survivable accident.

The complete text of the accident report can be viewed at the following link: (Accident Report)

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Prior Recommendations

The NTSB made record of seven previous recommendations that are related to this accident based on four previous fires aboard aircraft.

1. Varig Airlines Boeing 707 accident near Paris, France, July 11, 1973, fire in the aft lavatory.
2. Pan American World Airways Inc., Boeing 707 accident at Boston, Massachusetts, November 3, 1973, fire in cargo compartment.
3. Boeing 747 on July 17, 1974, fire in lavatory, fire contained, aircraft landed safely.
4. Boeing 727 on August 9, 1974, fire in lavatory, fire contained, aircraft landed safely.

The 1973 and 1974 recommendations included: installation of smoke detectors in the lavatories; full face masks for crewmembers and automatic fire extinguishers in the lavatory waste bins; require operators to establish procedures to remove smoke; require transport category aircraft (airlines) to comply with Part 25.1439 (protective breathing equipment, PBE); one-time inspection of smoke goggles to assure conformance to Part 25.1439.

The complete text of the NTSB Recommendation Summaries are available at the following link: 7 Prior NTSB Recommendation Summaries

New Recommendations

The NTSB issued 18 recommendations relative to this accident. They included:

• Periodic inspections of the lavatory flushing pump motor, timer, and wiring as well as removal of waste and fluids;
• Installation of smoke detectors in the lavatories. Automatic Halon, or latest technology fire extinguishers, in the trash bins, full face masks for crewmembers, passenger seats with fire-blocking material, and tactile and lit aisle/exit markers with associated passenger briefing cards;
• Evaluation of electrical circuit protection of the lavatory flushing pump motor system;
• Development of standards and procedures for providing passengers with breathing protection from toxic atmospheres;
• Requirement to review procedures for control and continuous removal of smoke; flight attendant briefings indicating aisle/exit markers; training programs to take immediate and aggressive action to determine the source and severity of any cabin fire and put the fire out, otherwise begin an emergency descent for landing or ditching the aircraft; revision of manuals to include discussion and illustrations of where the fire axe can be used to gain access to the source of fire or smoke; and markings on panels or sidewalls of lavatories and galleys to identify where a fire axe can be used.

The complete text of the NTSB Recommendation Summaries are available at the following link: 18 NTSB Recommendation Summaries

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The DC-9-32 was originally certified in the mid-1960s under Civil Aviation Regulations (CAR) 4b with amendments 4b-1 thru 4b-16. These regulations directly preceded, and as stated in the airplanes Type Certificate Data Sheet (TCDS) are considered equivalent to, the Federal Aviation Regulations (FAR) Part 25 (new) which became effective February 1, 1965. The regulations are currently (2008) referred to as Title 14 of the Code of Federal Regulation (CFR) Part 25.

The McDonnell-Douglas DC-9-32 series was added to the FAA A6WE type certificate on March 1, 1967. Air Canada took delivery of Serial Number 47196 on April 7, 1968.

1965 Part 25 Certification Basis

14 CFR 25.811, "Emergency exit marking," - described the minimum requirements for emergency exit marking. The minimum requirement was for exit marking and lighting: a source of light, independent of the main lighting system, must be installed to illuminate each passenger emergency exit marking.

14 CFR 25.851, "Fire extinguishers," - described the minimum requirements for fire extinguishers in general: the types and quantities of each extinguishing agent used must be appropriate to the kinds of fires likely to occur where used.

14 CFR 25.853, "Compartment interiors," - described the minimum requirements for interior material resistance to fire and the number, but not capacity nor type, of hand-held fire extinguishers in the passenger cabin.

14 CFR 25.1439, " Protective breathing equipment," - described the minimum requirement for breathing apparatus including masks covering either mouth, nose, and eyes or masks covering nose and mouth plus accessory equipment to cover the eyes.

1968 Part 25 Relevant Regulation

Not part of the Certification Basis but relevant to this incident is a new regulation that was defined in 1967, 14 CFR 25.812, "Emergency lightning."

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Crew (or Cockpit) Resource Management (CRM) was first adopted in 1981 by United Airlines following a 1979 NASA workshop. One of the reasons for CRM is to improve and address group decision making, ineffective communication, inadequate leadership, and poor task or resource management. Although not identified by an acronym, a delayed decision to declare an emergency and descend could be attributed to ineffective CRM, as the captain was never told nor did he inquire as to the precise location and extent of the "fire," which had been reported to him. In addition, crewmember reports that the fire was abating misled the captain about the fire severity. CRM training has since become a regulatory requirement (for more information see Resulting Regulatory and/or Policy Changes from the Eastern L-1011 in Florida accident.)

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Cockpit Door

According to the captain, about 30 minutes after departure, a 30-inch-long by 9-inch-wide louvered panel at the bottom of the cockpit door was kicked accidentally from its mounts and fell to the floor. The panel was placed to one side and the flight continued.

Flight crew did not close the cockpit door, thereby allowing smoke to actively enter the flight deck.

Lack of Equipment

A portable oxygen mask, either full face or mask and goggle, was not available for the cabin crew. An oxygen outlet was located in the oxygen mask compartment of the lavatory.

Smoke alarms were not present in the unoccupied spaces, specifically in the lavatories.

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The flight crew would don oxygen masks/smoke goggles when confronted and investigating an in flight smoke/fire event.

Not being told otherwise, the captain believed the fire was in the lavatory trash bin and he expected it to be put out.

Cabin lighting and exit markings are adequate for use in an emergency.

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The NTSB identified four precursor fire incidents:

1. Varig Airlines Boeing 707 accident near Paris, France on July 11, 1973, fire in the aft lavatory resulted in 124 fatalities and total destruction of the aircraft after a successful emergency landing.
2. Pan American World Airways Inc., Boeing 707 accident at Boston, Massachusetts on November 3, 1973, fire in cargo compartment.
3. Boeing 747 on July 17, 1974, fire in lavatory, fire contained, aircraft landed safely.
4. Boeing 727 on August 9, 1974, fire in lavatory, fire contained, aircraft landed safely.

Other accidents that involved fire in the aft section of aircraft:

November 26, 1979

Pakistan International Airlines Boeing 707-340C, near 30,000 feet a flight attendant reported a fire near the aft cabin passenger door, no survivors.

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Various rules were developed or modified based on the accident. This section focuses mainly on the rules that affected part 25 (Airworthiness standards: Transport category airplanes) of Title 14 of the Code of Federal Regulations (CFR).

Pre-accident changes to the rules

The certification basis of Flight 797 relied on requirements for flame resistant material in passenger and crew compartments that were designed primarily to prevent serious fires from passenger carelessness, such as cigarette burns. In 1966 a Notice of Proposed Rule Making (NPRM) 66-26 was released for public comment. Some of the areas that would be affected were emergency exit marking, a new section for emergency lighting, and compartment interiors which introduced a few methods and requirements for flame testing of materials.

The final rule (FR) of September 15, 1967, allowed an 18-month delay in implementation. The rules can be found at the following links: FR Docket 7522 & FR Docket 7522 revised.

NPRM 83-14 Flammability Requirements For Seat Cushions

This amendment established new flammability requirements for seat cushions used in transport category aircraft certificated under Part 25 and Part 29. It required that the cushions in transport category airplanes type certificated after January 1, 1958, and operating under Part 121, comply with these new requirements after November 26, 1987. The new requirements were in addition to the present flammability requirements contained in the Federal Aviation Regulations and represented a significant advancement in aircraft fire safety.

Link to final rule FR Docket 23791, paper copy FR Docket 23791, section 25.853, section 29.853.

NPRM 83-15 Floor Proximity Emergency Escape Path Marking

This amendment established new performance standards for floor proximity emergency escape path marking to provide visual guidance for emergency cabin evacuation when all sources of cabin lighting more than four feet above the aisle floor are totally obscured by smoke. The amendment was applicable to future type certification of transport category airplanes and, after November 26, 1986, to airplanes type certificated after January 1, 1958, and operating under Part 121. The standards represented a significant improvement in aircraft cabin safety and were in addition to the emergency lighting standards currently in the regulations at that time.

Link to final rule FR Docket 23792, paper copy FR Docket 23792, section 25.812, Advisory Circular AC 121-24B

NPRM 84-05 Lavatory Smoke Detection, Automatic Lavatory Trash Fire Extinguishers and Halon Fire Extinguisher Requirements

This amendment established equipment requirements to improve cabin fire protection for passenger-carrying transport category airplanes operated under Part 121.

• The amendment required that each lavatory be equipped with a smoke detector system, which provides warning to the cockpit or to the passenger cabin crew.
• It required that each lavatory trash receptacle be equipped with a fire extinguisher which discharges automatically upon occurrence of a fire in the receptacle.
• It increased the number of hand-held fire extinguishers required to be installed in the passenger cabins of airplanes with passenger seating capacities greater than 60 and requires that at least two of the hand-held fire extinguishers installed in each airplane have Halon 1211, or equivalent, as the extinguishing agent.

The amendment was the result of investigations of in-flight fires and an inspection survey of the U.S. air carrier fleet which indicated the need for an increase in protection against in-flight fires.

Link to final rule paper copy FR Docket 24073

NPRM 89-1 Lavatory Smoke Detection, Automatic Lavatory Trash Fire Extinguishers and Halon Fire Extinguisher Requirements

This amendment provides improved cabin fire protection for transport category airplanes by requiring:

• Each lavatory in an airplane with a passenger seating capacity of 20 or more to be equipped with a smoke detector system that provides warning to the cockpit or to the passenger cabin crew.
• Each lavatory trash receptacle in an airplane with a seating capacity of 20 or more to be equipped with a fire extinguisher that discharges automatically upon the occurrence of a fire within the receptacle.
• The number of hand-held fire extinguishers in the cabins of airplanes with passenger seating capacities greater than 200 to be increased.
• A specified number of the hand-held fire extinguishers in the cabin to contain Halon 1211 or equivalent as the extinguishing agent.
• One hand-held fire extinguisher in each galley that is located above or below the passenger compartment. In addition, one hand-held fire extinguisher would be required for certain all-cargo airplanes.

These safety protections against possible in-flight fires are currently required for operation of airplanes used in air carrier or commercial service. The amendment adopted these requirements as design standards for transport category airplanes.

Link to final rule FR Docket 25774, paper copy FR Docket 25774, sections 25.851 and 25.854

NPRM 85-17 Personal Breathing Equipment (PBE)

This final rule amends the regulations applicable to protective breathing equipment (PBE) by:

• Incorporating the requirements of § 25.19 of the Federal Aviation Regulations into current § 121.337.
• Providing new standards for PBE for crewmembers who may be required to fight in-flight fires.
• Requiring the performance of an approved firefighting drill using PBE.
• Requiring that, when possible, additional PBE be located within three feet of each required hand-held fire extinguisher in passenger airplane compartments.
• Clarifying certain emergency drill requirements.

This action was prompted by several in-flight fires and, in part, by a report on PBE by
the NTSB.

Link to final rule paper copy FR Docket 24792

Advisory Circular AC 25-9 Smoke Detection, Penetration, and Evacuation Tests and Related Flight Manual Emergency Procedures

The NTSB recommended evaluation of the FAA-approved Airplane Flight Manuals (AFM) and changes as necessary to control and remove smoke. The requirements are specified in 14 CFR 25.831 (b), (c), (d), (f) and 25.857 (a), (b), (c), (d), (f). In addition to reviewing the airlines AFMs, the FAA issued AC 25-9 in July 1986. It provided guidance for the conduct of certification tests relating to smoke detection, penetration, and evacuation and to evaluate related AFM procedures.

Closely related and developed at the same time as the requirements for seat flammability, a rule was developed for materials in the areas of the aircraft classified as cargo. Although specific to cargo material, the flammability testing also affected the cabin interior.

NPRM 84-11 Fire Protection Requirements for Cargo or Baggage Compartments

This amendment upgraded the fire safety standards for cargo or baggage compartments in transport category airplanes by establishing new fire test criteria and by limiting the volume of Class D compartments. This amendment was the result of research and fire testing and is intended to increase airplane fire safety.

Link to final rule FR Docket 24185, paper copy FR Docket 24185, section 25.853

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Pre-Existing Airworthiness Directives

In 1973 a Varig Airlines Boeing 707 experienced a fire in the aft lavatory. The FAA issued an airworthiness directive (AD 74-08-09) applicable to all transport category airplanes. It required recurrent inspection of all lavatory paper and linen waste receptacle enclosure access doors and disposal doors for proper operation, fit, sealing, and latching for the containment of possible trash fires. Any defects found were to be corrected. The AD was in effect at the time of the accident. The AD was revised in 1995 and 1996.

General Notices

A General Notice (GENOT 8320.283) was issued on July 1, 1983. It requested that the principal inspectors ensure that assigned operators have adequate programs to inspect areas susceptible to the accumulation of waste material or the accumulation of fluids which can cause corrosion of wire harnesses and other electrical components. (More information: NTSB Recommendation A-83-047)

A General Notice (GENOT 8320.285) was issued on July 20, 1983. It amended the information of GENOT 8320.283 by adding a requirement to ensure the removal of waste from all areas of the lavatory with particular attention to the enclosed areas in and around waste receptacles. (More information: NTSB Recommendation A-83-048)

These two general notices were in conjunction with determination of the health of the flush pump motor system. A recommendation for development of a procedure that airline maintenance personnel could employ to verify the integrity of the flush pump motor, timer, wiring for corrosion, or other adverse conditions. Additionally, a review of the electrical circuit protection needed to be evaluated.

ADs Issued as a Result of this Accident

SB 24-76 first issued November 7, 1984, and revised August 16, 1985
AD 85-07-10 mandated compliance to the SB. Replacement of the lavatory pump required that the wires for the motor pump and timer be unclamped and separated from adjacent wire bundle. Failure to reclamp the wires could result in damage to the wires. This SB rerouted and clamped the wires between the lavatory pump and timer away from adjacent wire bundle. This modification allows replacement of the pump motor without disturbing the adjacent wire bundle and clamps.

SB 25-259 first issued May 11, 1984, and revised May 29, 1987
AD 85-16-07 mandated compliance to the SB. Low-flight-hour aircraft were found to have defects that could affect the fire containment capability of the waste container. Defects included gaps around the cleanout door, difficulty in sealing the upper chute due to trash door interference and cracks in the top surface and door hinge areas. This SB incorporated a modification to improve the service life of the lavatory towel waste container and provide improved container sealing capability to enhance fire containment.

Relative Service Bulletins

SB 24-69 April 16, 1984
Overheating of the flush pump motor may occur when the motor is exposed to either single-phase power or power with a locked rotor for an extended period of time. The SB replaced the five-amp lavatory flush pump motor circuit breakers with one-amp circuit breakers on the ground service bus circuit panel. The modification installed a circuit breaker incorporating a unique current-time characteristic that was designed to provide the maximum overheat protection without causing circuit breaker trips.

SB 25-264 first issued January 7, 1986, and revised June 9, 1987
Modular lavatory designs provided an improvement in fire containment in the event of a trash bin or other fire. This SB provided for closure of holes in the lavatory amenities area in the aircraft not equipped with modular lavatories.

SB 25-268 first issued July 7, 1986
Instances were reported of return failures of the door hinge of lavatory waste chute and gaps that may exist between the bottom of the waste container and the cleanout door. This SB replaced the upper towel door and hinge assembly and reinforced the lower door area. Accomplishment of the SB improves service life of the lavatory towel waste container and provides improved container sealing capability to enhance fire containment.

SB 33-39 first issued November 6, 1968, with latest on revision March 9, 1987
This SB installed additional Emergency Lighting

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Airplane Life Cycle:

• Operational

Accident Threat Categories:

• Cabin Safety / Hazardous Cargo
• Crew Resource Management
• Uncontrolled Fire / Smoke

Groupings:

• N/A

Accident Common Themes:

• Organizational Lapses
• Human Error

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Organizational Lapses

At the time of this accident, there were no formal Crew Resource Management (CRM) programs or training. The command structure was based on a hierarchy top-down model. Pertinent information was being given to the pilot; however, the information was not complete in detail on the location of the actual fire or the observation of smoke and from where the smoke was emanating.

Human Error

The delayed decision to land resulted in the fire propagating for three to five minutes longer due to the location of the nearest airport. This delay added to the severity of the accident.

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June 25, 1983

A few weeks after this accident on June 25, 1983, a DC-9 operated by Eastern Airlines had a fire in the right aft lavatory. As the aircraft was taxing to the gate, after a normal flight, a flight attendant positioned at the rear of the aircraft noticed smoke coming from underneath the lavatory door. The flight attendant opened the door but, because of the amount of smoke coming out, she immediately closed it and notified the flight crew. The captain notified the tower and proceeded to the gate where the passengers deplaned, and the fire was extinguished by the airport fire department personnel.

The fire started in the lavatory waste receptacle located behind and under the sink basin. The fire had propagated from the upper area of the waste chute to behind the vanity and had spread to the lavatory aft wall. If it had not been extinguished by the firefighters, the fire would have continued to spread.

September 2, 1998

Following takeoff from New York's Kennedy Airport, and while passing through Canadian airspace, an in-flight fire ensued in the area above the cockpit ceiling which caused loss or malfunction of numerous airplane systems and instruments. As the fire progressed, electronic navigation equipment and communications radios stopped operating, leaving the pilots with no accurate means of establishing their geographic position, navigating to the airport, or communicating with air traffic control. The investigating authority presumed that the intensity of the fire left the crew incapacitated, and/or damaged the flight control system to the extent that control could not be maintained. The airplane crashed into the Atlantic Ocean near Peggy's Cove, Nova Scotia, approximately 1 hour and 13 minutes after its departure.

See accident module

September 17, 1999

A McDonnell Douglas MD-88 operated by Delta Air Lines experienced an in-flight fire and made an emergency landing at Cincinnati and Northern Kentucky International Airport, Covington, Kentucky. The airplane sustained minor damage. There were no injuries to the 2 flight crewmembers, 3 flight attendants, 3 off-duty flight attendants, and 113 passengers during the evacuation.

January 11, 2003

A Boeing 757-222 passenger jet was at a cruise altitude of 37,000 feet msl and approximately 95 nautical miles south of Salt Lake City (SLC), when a flight attendant called from the aft cabin and stated there was a fire in the left aft lavatory. The flight attendant also reported that another flight attendant was fighting the active flames with a Halon extinguisher. The captain declared an emergency, requested priority handling for landing at SLC, and made an uneventful landing.

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Technical Related Lessons:

Appropriate crew reaction to an emergency situation is dependent upon correct and concise intercrew communication. (Threat Category: Crew Resource Management)

• In this accident, the captain was receiving contradictory information from the first officer and cabin crew that may have delayed his decision to declare an emergency and prepare for an immediate descent and landing. As the fire progressed, multiple assessments by the first officer and members of the cabin crew may have confused the captain as to the severity of the fire, and whether or not it was abating. Within a few minutes, the consensus became that the fire was progressing, and that an emergency landing should be made. Had the earlier communications regarding the fire been more accurate, the decision to land may have been earlier, and the result may have been less severe.

Lavatory compartments require adequate smoke/fire detection. (Threat Category: Cabin Safety/Hazardous Cargo)

• At the time of this Air Canada DC-9 accident, there had been previous accidents involving onboard fires, including a fire on board a Boeing 707 operated by Varig Airlines in 1973. Following the Varig accident, recommendations were made that included both installation of smoke detectors in the lavatories, and automatic fire extinguishers in the lavatory waste bins. However, it was not until after the 1983 air Canada accident that these proposals were adopted. The 1984 regulatory changes prohibited smoking in the lavatories and further required provisions for self-contained receptacles capable of withstanding a trash fire. Some airplanes in the world fleet, including the Air Canada DC-9 in this accident, had been equipped with a Halon extinguishing system for the lavatory waste receptacles. At the time of installation of these systems (pre-1984), there was no requirement for such installations. However, as the origin of the Air Canada fire was determined not to be the trash receptacle, it was not until implementation of the smoke detector requirements that a lavatory fire originating outside the trash receptacle was detectable. 

Adequate cabin emergency lighting substantially enhances successful passenger egress in cases where visibility is limited by smoke. (Threat Category: Cabin Safety/Hazardous Cargo)

• It was determined after this accident that exit marking signs and illumination were not sufficient for a smoke-filled cabin. Some passengers stated that they were only able to escape by having memorized the number of rows between their seats and the exit and then counting the rows by feeling the seatbacks as they moved to the exit. 

Cabin materials should be flame resistant to a wide variety of fire threats in order to reduce the risk of uncontrolled cabin fires. (Threat Category: Cabin Safety/Hazardous Cargo)

• The certification basis of this aircraft required material to be "flame resistant", without providing any performance standard defining an adequate level of resistance. In 1982, the right aft lavatory was removed and replaced with a clothing storage area. Overhead luggage bins were installed, and the cabin walls and ceilings were replaced. The materials had to meet the flammability standards of 14 CFR 25.853 (a)(b) as amended on May 1, 1972. This regulation did not provide a standard as to how the material should be tested, leaving the flame resistance method up to the discretion of the manufacturer. Various methods were used at the time, ranging from a 90 degree burn test orientation, to other orientations. The definition of the test burner, flame temperature, and pass/fail criteria were also not specified. Although the DC-9 did include early flammability standards as part of its certification basis, the lessons from subsequent accidents, and improvements in technology related to cabin materials, have steadily improved cabin safety.

Common Theme Related Lesson:

When an in-flight fire is confirmed, planning for an emergency descent and landing should begin as soon as possible. (Common Theme: Human Error)

• A fire in the cabin may rapidly progress beyond containment. A flight crew has limited resources available to extinguish such a fire. A fire that initiates in an inaccessible compartment and does not extinguish may lead to cascading failures of aircraft systems. Investigators concluded that flight crew delay in initiating an emergency descent may have contributed to the severity of the fire, and the eventual catastrophic outcome. 

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