The emergency evacuation of Japan Airline flight 516 January, 2024 (https://www.bbc.com/news/world-asia-67865132) after it caught fire from a collision with another aircraft during landing is a representative example of an unplanned evacuation. They occur with little to no warning, provide no time for the cabin crew to prep the cabin, and disproportionally happen during take-off and landing. In a NTSB review of 46 emergency evacuations, 31 were unplanned. NTSB/SS-00/01 Emergency evacuation of commercial airplanes, 2000
Though details of the event will change with more investigation, preliminarily reports have said the initial fire was confined to one portion of the JAL aircraft for the first 90 seconds. All commercial airlines are required to be certified as able to evacuate all occupants in 90 seconds with 50% of the emergency exits blocked, the cabin darkened, and with debris on the aircraft floor.
Many recent actual emergency evacuations have taken longer than the 90-seconds required for certification. This has led some to critique the 90-second test as not representative of an actual event. The FAA acknowledges the test isn’t meant to duplicate a specific actual event, but strives to evacuate the aircraft before a fire has the chance to flash over the cabin. In the case of JAL flight 516, an Airbus A350-900 aircraft all 391 people on board we able to safely evacuate. Additionally, because of the fire, several of the emergency exits were not usable, lending further credibility to the FAA test.
Again, preliminary information is that none of the evacuating passengers on the JAL flight took their hand carry baggage with them; this certainly speeds up an evacuation. Although this is the correct answer, half of 419 passengers involved in actual prior emergency evacuations admitted they tried to retrieve their bags during their evacuation. NTSB/SS-00/01 Emergency evacuation of commercial airplanes.
Finally, many passengers on flight 516 said the cabin was dark and rapidly filled with smoke, further obscuring their ability to see during the evacuation. Since 1984 the FAA has required escape path lighting on commercial aircraft. This rule was implemented after several crashes / cabin fires occurred where the cabin visibility was completely “virtually nonexistent at heights higher than one foot above the cabin floor.” Aviation Safety Study SA9501
The presence of escape path lighting has been shown to increase the evacuation time of occupants by 20% in smoke filled cabins. RAeS, 2013