Safety Recommendation A-00-090

At the October 3, 2003, meeting, the FAA stated that it believed the already-required public address (PA) and interphone systems on transport-category aircraft provide the same level of performance as the recommended system. In this letter, the Safety Board will review the data, previously supplied to the FAA, that has supported safety recommendations issued by the Safety Board to the FAA over the past 30 years to require evacuation alarms. The Board continues to investigate accidents and incidents in which the PA and interphone systems did not work at critical periods in an evacuation and in which an evacuation alarm was needed.

On June 27, 2000, the Safety Board released a safety study titled Emergency Evacuation of Commercial Airplanes, SS-00-01, which contained Safety Recommendation A-00-90. In this safety study, the Board investigated 46 evacuations that had occurred between September 1997 and June 1999 involving 2,651 passengers from 18 different aircraft types. Detailed investigations were conducted for 24 of these evacuations. In 2 of these 24 cases, the PA systems had been rendered inoperable by the crash forces, and, in a third case, an electrical failure prevented its use.

In two other cases in which the PA system had been used to initiate the evacuation, not all flight attendants heard the announcement.

The PA system is used to make announcements to the passengers, while the interphone system is used for communication among the crew in different parts of the airplane. The FAA believes that the PA and interphone systems together satisfy the need for an evacuation alarm. However, in the evacuation study, the interphone systems also failed to operate in the three cases in which the PA systems were not functional. If an evacuation alarm system with an independent power system, as recommended, had been available, the need to evacuate would have been known to all parts of the aircraft.

In another case in the study, following the October 24, 1998, collision of an ATR-42 with a ground power unit in San Juan, Puerto Rico, the flight attendant attempted to use the interphone to inform the flight crew of a fire outside the airplane 11 seconds after the collision. The flight attendant call chimes were audible in the cockpit for 14 seconds. During this time, the flight crew used the PA system to command passengers to remain seated. The flight attendant decided to initiate an evacuation after failing to contact the flight crew. Eight seconds later, the flight crew became aware of the fire outside the airplane.

There would have been no delay in notification of the flight crew if an evacuation alarm had been issued. The significant amount of data collected during the evacuation study indicating that the PA and interphone have not been adequate substitutes for an evacuation alarm led the Safety Board to issue Safety Recommendation A-00-90.

After the data collection phase of the evacuation study, the Safety Board investigated two additional incidents/accidents in which the PA and interphone systems did not obviate the need for an evacuation alarm. On March 15, 2000, a flight attendant on a Boeing 737 in Tampa, Florida, witnessed an engine fire and called the cockpit via the crew interphone, but she received no answer. Thirteen people evacuated while the engines were running. On March 5, 2000, a Southwest Airlines Boeing 737 overran the runway in Burbank, California. After the airplane stopped, the flight crew mistakenly gave commands regarding evacuation to the air traffic control tower instead of the cabin.

Further, the flight crew was unaware that, based on conditions in the cabin, an evacuation had already started. Had evacuation alarms been in place for the Tampa and Burbank incidents, no communication problems would likely have occurred.

Safety Recommendation A-98-22, stated below, on this same subject, was issued as a result of the Safety Board's investigation of the July 16, 1996, uncontained engine failure of Delta Airlines flight 1288, a McDonnell-Douglas MD-88, while on its takeoff roll from Pensacola Regional Airport, Florida.

A-98-22

Require that all newly manufactured passenger-carrying airplanes operated under 14 Code of Federal Regulations Part 121 be equipped with independently powered evacuation alarm systems operable from each crewmember station, and establish procedures and provide training to flight and cabin crews regarding the use of such systems.

Immediately following the engine failure, the circumstances in the aft cabin were markedly different than those in the forward cabin. The aft flight attendants were presented with structural damage, serious injuries, and an engine fire, any one of which was sufficient to initiate an evacuation pursuant to Delta's policy and procedures. The cockpit crew and forward flight attendant were unaware of these circumstances and, based on the absence of any indications of fire, the captain determined that an evacuation was not warranted.

Unaware that passengers were evacuating, the captain did not shut down the engines until the first officer, after walking through the cabin to assess the situation, alerted him to do so.

In this accident, the interphone system was inoperative at the critical moment when decisions were being made by both the aft flight attendants and by the captain. Neither of their decisions, nor the information on which they were based, could be immediately communicated to crewmembers at the opposite end of the airplane. By the time emergency electrical power was restored to the interphone and the first officer again attempted to contact the aft flight attendants, the flight attendants were no longer in a position to, and would not have been expected to, respond to calls over the interphone because they were carrying out the evacuation and attending to injured passengers.

Therefore, because of problems with a lack of communication among crewmembers in the front and back of the airplane, crewmembers in the cockpit were unaware that emergency conditions existed and an evacuation was ongoing in the rear of the airplane. Even if this information would not have affected the captain's determination not to evacuate the entire airplane, at the very least it likely would have prompted him to immediately shut down the engines to minimize the hazards to those passengers who were evacuating. The lack of communication resulting from use of the existing PA and interphone system would not have existed if an evacuation alarm had been used in this accident.

In response to this recommendation, the FAA stated it had concluded that sufficient rules already exist to address this safety concern, noting that under existing rules, the crew can be notified of an impending emergency using the crew interphone, and flight attendants can notify the passenger cabin using the PA system. The FAA further stated that the crew interphone and PA systems were redundant to an evacuation alarm.

The Safety Board replied that it believes that an evacuation alarm system with an independent power supply is the most effective means to provide necessary redundancy and to ensure that all crewmembers are notified of the need to evacuate and that accident and incident investigations continued to identify problems with use of the PA and interphone systems to provide communication in aircraft without alarm systems. On March 23, 2000, Safety Recommendation A-98-22 was classified "Closed--Unacceptable Action."

Two other accidents investigated by the Safety Board highlight problems with the PA and interphone systems in situations where an emergency evacuation may be started. During the investigation of the June 8, 1995, uncontained engine failure and resulting fire in Atlanta, Georgia, of Valujet flight 597, a Douglas DC-9-32, the Safety Board discovered problems that showed the need for a self-powered evacuation alarm system. In this accident, the pilot's first

On March 23, 2000, the Safety Board classified Safety Recommendation A-98-22 "Closed--Unacceptable Action." The FAA states that since its December 12, 1999, response to Safety Recommendation A-98-22, no new data have been presented to the FAA that would warrant a change in its position on mandating the installation of independently powered evacuation alarm systems.

In its recommendation letter for Safety Recommendation A-00-90, the Safety Board noted that it continues to investigate evacuation incidents that are hampered by inefficient methods of communication and cited a case in Tampa, Florida, in which the flight attendant witnessed an engine fire and called the cockpit via the interphone. After receiving no answer, an evacuation was initiated, and 13 passengers evacuated while the engines were running. The recommendation letter also cited an incident in which a 737 overran the runway in Burbank, California.

The flight crew attempted to issue instructions to the passengers to remain seated, but inadvertently issued these instructions over the aircraft radio, as opposed to the PA system; the crew never issued instructions to evacuate. Further, during an evacuation following an APU torching that was cited in the evacuation study, a flight attendant called the cockpit on the interphone, but no one answered. In another case cited in the evacuation study, the flight attendant called the cockpit following a ground collision of an ATR-42 that resulted in a fire. The flight crew, unaware of the fire, commanded passengers to remain seated and did not answer the flight attendant's interphone call.

The flight attendant started an evacuation. The cockpit crew did not become aware of the fire until 8 seconds after the evacuation began. In three other cases cited in the evacuation study, neither the PA nor interphone systems were functional. The Safety Board notes that these cases, which were cited in the evacuation study and in the recommendation letter and were available after December 12, 1999, show that an evacuation alarm system is needed and that the PA-interphone system are not an acceptable alternative for an evacuation alarm. Pending the FAA's taking the recommended actions, Safety Recommendation A-00-90 is classified "Open--Unacceptable Response."

Letter Mail Controlled 11/14/2000 4:39:44 PM MC# 2001688 On February 26, 1998, the Board issued Safety Recommendation A-98-22, which is identical to Safety Recommendation A-00-90. The FAA concluded in response to Safety Recommendation A-98-22 that sufficient rules already exist to address this safety concern. On December 12, 1999, the FAA told the Board that under the existing rules, the crew and other passenger cabins can be notified of an impending emergency. The flight attendants can notify the flightcrew using the crew interphone. The crew interphone system also has visual indication in the cockpit.

In addition, the flight attendants can notify the passenger cabin using the public address system. The crew interphone and the public address systems are redundant to an evacuation alarm, especially if used in accordance with approved training procedures. If training procedures are not followed, neither the public address system nor the evacuation alarm would be effective. Both the public address system and the interphone system are required by 14 CFR Part 121. The FAA further stated in response to Safety Recommendation A-98-22 that airplanes operating under 14 CFR Part 121 must comply with 14 CFR 121.318, Public Address System, and 14 CFR 121.319, Crewmember Interphone System.

14 CFR 121.318(d) requires that each floor-level passenger emergency exit, which has an adjacent flight attendant seat, have a microphone that is readily accessible to the seated flight attendant. 14 CFR 121.318(g)