Lightning struck the auxiliary power unit (APU) of a stationary IndiGo aircraft bound for Agartala, carrying 141 passengers, during a thunderstorm and rain on Friday morning, triggering a power failure and panic on board.
No passengers were injured. Two IndiGo ground handlers engaged in baggage loading and the driver of another airline’s pushback vehicle were taken to hospital. Airport officials said they were later discharged in stable condition.
Flight 6E6068, operating from Calcutta to Agartala, was parked at stand 56L and connected to an aerobridge when the lightning struck between 9.25am and 9.30am.
“The aircraft’s power went off after lightning struck the APU. Boarding had been completed,” said an airport official. As a precaution, passengers were deboarded and later transferred to another aircraft for departure from the city. The flight was originally scheduled to depart at 9.20am. The replacement aircraft took off at 12.50pm.
An airport official said he had never seen a stationary aircraft struck by lightning in over 30 years of service. “There are earthing systems at Calcutta airport designed to arrest lightning,” the official said.
The lightning did not directly strike the aircraft body but hit the APU — a small gas turbine engine located in the tail cone. The unit provides electrical power for lighting, air conditioning and cockpit avionics before engine start-up, and also helps initiate main engine ignition.
An IndiGo official said both the aircraft and its APU are designed to be lightning-resistant.
A senior pilot of an airline said aircraft are equipped with features to handle lightning strikes. “Static discharge probes are installed in the wings, tail and vertical fin. These safely dissipate electrical charge from the aircraft body,” he said. “There is usually no major damage, though parts can sometimes be affected. The nose of an aircraft is more vulnerable during flight,” he added.
Static discharge probes are needle-like devices that release accumulated electricity.
Lightning is an electrical discharge caused by an imbalance of charge between clouds and the ground or between clouds. It heats air to temperatures hotter than the surface of the sun, causing rapid expansion that produces thunder that follows lightning.
Streaks of lightning were reported across several districts of south Bengal on Friday morning, including North 24-Parganas, according to the Met office.
A Met official said cloud-to-ground strikes appear closer, as seen in Dum Dum, and are more dangerous as they are responsible for fatalities, unlike cloud-to-cloud lightning, which occurs at higher altitudes.
“Moisture within storm clouds increases electrical imbalance, with clouds becoming negatively charged and the ground positively charged. Nature seeks to neutralise this imbalance by passing current between the two,” the official explained.
Bengal is prone to lightning activity. According to the South Asia Lightning Report 2020, the state recorded the highest number of cloud-to-ground strikes per square kilometre in India. On May 7, 2021, lightning strikes led to 27 deaths across the state.