Soon after a Varanasi-bound Indigo flight received a bomb threat at the Indira Gandhi International Airport in Delhi on Tuesday (May 28), the 176 passengers onboard the flight were quickly evacuated with the help of ‘evacuation slides’. A search of the aeroplane found that the threat was a hoax. Here is a look at what evacuation slides are, and how they are deployed. What are ‘evacuation slides’? An evacuation slide is an inflatable slide which allows passengers to safely exit the flight during an emergency, especially when the flight door is high above the ground. There are four types of evacuation slides: inflatable slide, inflatable slide/raft, inflatable exit ramp, and inflatable exit ramp The inflatable slide helps passengers descend to the ground from an aircraft exit door. In case they cannot use the doors, they can try to reach either of the aircraft wings. From there, they can use the slide to reach the ground. As mentioned in a European Union Aviation Safety Agency (EUASA) report, inflated rafts or mats may be placed on the ground to protect the passengers. The inflatable slide/raft does the same job as the slide, but it can also be used as a life raft in case the aircraft has to land on water. The inflatable exit ramp is installed to help passengers move from certain overwing exits (or aircraft emergency exits) to the wings, if that path looks better for reaching the ground. The inflatable exit ramp/slide is there to assist in descending from an overwing exit or aeroplane wing to the ground. It is a combination ramp and wing-to-ground device. The evacuation slides are typically made from carbon fibres and a nylon material coated with urethane for fire resistance. Strong fibres are used to build these slides so that passengers are not able to tear them while descending. Slides are generally packed and installed within a cabin door or into an external fuselage compartment. “A lever on the interior door links the slide to a door.[When the flight begins to move] this lever is in the ‘armed’ mode, and if the door is opened, then the slide will deploy,” according to simpleflying.com. Notably, the door cannot be opened mid-flight due to the difference in air pressure inside the cabin and outside in the atmosphere. They are inflated with the help of high-pressure gas carbon dioxide or nitrogen gas containers and ambient air through suction machines. What are the protocols for deploying evacuation slides? An evacuation slide must be deployed when the distance between the ground and the flight exit door is six feet or more. The European Union Aviation Safety Agency’s guidelines say that a slide should be automatically deployed, once the door is opened. The slide must be inflated between six and 10 seconds, depending on its location. It should be properly deployable in all weather conditions — as cold as -40 degree Celsius and as hot as 71 degree Celsius, according to the US Federal Aviation Administration’s guidelines. The slide should be able to sustain a rainfall of up to one inch an hour and winds up to the speed of 46 km/hr which would be coming 45 degree angles around the aeroplane.
