The Indian Express (Delhi Edition)
WHAT ARE EVACUATION SLIDES IN AIRCRAFT, WHY ARE THEY NEEDED?
SOON AFTER a Varanasi-bound Indigo flight received a bomb threat at the Indira Gandhi International Airport in Delhi on Tuesday, the 176 passengers on board the flight were quickly evacuated with the help of evacuation slides. A search of the plane found the threat to be a hoax.
What are evacuation slides?
An evacuation slide is an inflatable slide that allows passengers to safely exit the aircraft during an emergency, when no ladders can be put.
Slides are generally packed and installed within a door or into an external fuselage compartment. A lever on the interior door connects the slide to the door. At the start of every flight, the lever is in the “armed” position, and if the door is opened, the slide will be deployed. Notably, the door cannot be opened mid-flight due to the difference in air pressure inside the cabin and outside in the atmosphere.
There are four types of evacuation slides: inflatable slide, inflatable slide/ raft, inflatable exit ramp, and inflatable exit ramp/ slide.
The inflatable slide helps passengers exit the aircraft to the ground. An inflatable slide/ raft does the same job, but it can also be used as a life raft, in case the aircraft has to land on water.
The inflatable exit ramp helps passengers descend from certain overwing exits on to the wing (in case the exit doors are unavailable) — not to the ground. The inflatable exit ramp/ slide is there to assist in descending from an overwing exit to the aeroplane wing and then to the ground. It is a combination ramp and wing-to-ground slide.
The evacuation slides are typically made from carbon fibre and a nylon material coated with urethane for fire resistance. Strong fibres are used to build these slides so they don’t get torn as passengers use them.
They are inflated with the help of high-pressure carbon dioxide or nitrogen gas containers and ambient air through suction machines.
What are the protocols for deploying the 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 within 6-10 seconds, depending on its location.
It should be properly deployable in all weather conditions — as cold as minus 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 rainfall of up to one inch an hour and winds up to the speed of 46 km/hr at 45 degree angles around the aircraft.