Cranfield University in the United Kingdom, working in collaboration with Virgin Blue Airlines in Australia, applied to the Australian Transport Safety Bureau for an aviation safety research grant in 2004. The grant was awarded to support a two-phase research project into evacuation commands used by cabin crew in managing passengers during evacuations. The first phase was a best practice forum and survey, supported by members of the Asia Pacific Cabin Safety Working Group of the Australian Society of Air Safety Investigators, to establish the commands, policies and procedures currently in use among Australian and Asian operators. The results of this survey informed the development of the research aims for the second phase of the project.
The second phase involved both survey and experimental work, with members of the public participating as passengers. Four groups of up to 40 members of the public were recruited to take part in this phase of the research; all participants completed questionnaires asking for demographic information. In addition, participants were asked about the commands that they would expect to hear in a range of safety-related and emergency situations. The data from these questionnaires were used to explore passenger expectations and comprehension of emergency commands. The results indicated that participants generally had a low understanding of why they might be required to take certain actions in emergency situations. This suggested that it is important that operators take passenger expectations and comprehension into account when devising evacuation commands.
The same participants then took part in one of four sessions of four evacuation trials at Cranfield University in the United Kingdom. In each test session, two evacuations were from the Boeing 737 cabin simulator, and two from the Large Cabin Evacuation Simulator (LCES). The aim of the experimental tests was to investigate the effectiveness of selected cabin crew commands in managing passengers during evacuations. All trials were video-recorded in order that footage from the trials could be time-coded and analysed.
In the Boeing 737 simulator, the first aim was to investigate the use of active and passive safety briefings. Two groups of participants received an active safety briefing, in which the cabin crew generated a high level of interaction in briefing passengers on safety procedures. On the other two test days, participants received a passive safety briefing. Research in cognitive psychology had suggested that actively-briefed passengers would be better able to recall and act on that information if (or when) the need arose. The Boeing 737 evacuation trials were also used to investigate the extent to which having the cabin crew provide passengers with additional relevant instruction would enhance evacuations in poor visibility conditions. The results indicated that while the active safety briefing did not improve evacuation times, passengers rated this briefing as significantly more useful and helpful, and stated that the active safety briefing significantly improved their confidence in evacuating the cabin.
In the LCES, the first aim was to investigate the influence of crew commands during evacuations from a wide-bodied cabin simulator, given that the exits and slides on such aircraft types are typically rated for a dual-lane flow1 . Dual-lane flows significantly increase evacuation rates, and yet results from Phase I showed that many operators do not require their cabin crew to command passengers to move through exits two at a time.
The second aim of the LCES tests was to manipulate the extent to which participants could see the cabin crew during the early stages of an evacuation. These tests aimed to gauge the effectiveness of gestures, eye contact and other non-verbal communications used by the cabin crew in managing passengers.
The results showed that evacuations without dual-lane flow commands were faster, but more disorganised. With a larger passenger load, dual-lane flow commands could be useful for managing the evacuation in a more orderly and less congested fashion. Visibility had a pronounced effect. The half-height bulkheads meant that cabin crew gestures could actually be seen be passengers, who rated the crew's non-verbal communication as significantly more useful in the high-visibility evacuations. The high visibility also gave passengers something to aim for in the evacuations - they had sight of the exit. Hence, it was significantly easier for them to move out of their seats and along the aisles in the half-height bulkhead conditions.
The results of this research could provide useful input to cabin crew training (initial and recurrent), to the design of best practice evacuation procedures and commands, and also potentially to the design of bulkheads and cabin configurations. In addition, the results could assist in designing safety information which is more closely aligned with passenger expectations, and therefore more likely to be effective.
- The over-wing exits in a typical wide-bodied jet aircraft are full size doors, which allow for dual-lane flow, rather than the smaller push-out exits typical of narrow-bodied jet aircraft.