Indian Air Force test flight triggers sonic boom in Bengaluru

A test flight of an Indian Air Force (IAF) fighter jet had triggered a sonic boom over the city on Wednesday aafternnon, sending its residents and officials into a tizzy, an official said.

"It was a routine IAF test flight involving a supersonic profile, which took off from Bengaluru airport and flew in the allotted airspace outside the city limits," said a defence official in a tweet much later.

The mysterious sonic boom at around 1. 30pm rattled the citizens as well as the authorities in this aerospace hub, sparking rumours of an earthquake, an explosion or a fighter jet cruising at top speed.

The fighter aircraft was of the IAF's Aircraft Systems and Testing Establishment (ASTE), which uses the defence airport of the state-run Hindustan Aeronautics Ltd (HAL) in the city's eastern suburb for test flights.

The ASTE's test pilots and flight test engineers test out all military aircraft. The sonic boom was heard while the aircraft was decelerating from super-sonic to sub-sonic speed between 36,000 and 40,000 feet altitude.

"The fighter was far away from the city limits when the event occurred. The sound of a sonic boom can be heard even when the aircraft is flying 65-80 km away," said the official in another tweet.

Ruling out an earthquake as the cause of the unusual sound, a Karnataka State Natural Disaster Management Committee official said seismo meters did not capture any ground vibration, which occurs during a mild tremor.

"The activity is a loud unknown noise," said the official in a brief press note.

An NDMA official, however, attributed it to the effect of a heavy vacuum caused by sudden entry of cyclonic wind between hot and cold air, as it happened a year ago.

"The explosive sound is not because of a quake in the city and no need to panic," asserted the official.

A city fire brigade official told IANS the massive sound could be due to mining blast of rocks in a quarry for construction.

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