Officials have finally said that a Sukhoi-30MKI jet flew across Bengaluru skies but have not concluded that it was the source of the loud ‘boom’ that was heard over the city on Wednesday afternoon. Residents from multiple areas of the city described a “thunderous” noise” and many felt tremors as well.
The Air Force-Training Command on Wednesday evening denied that its sortie was involved, but confirmed that the flight may have been flown by the Indian Air Force’s (IAF) testing wing, known as the Aircraft & Systems Testing Establishment (ASTE) or by Hindustan Aeronautics Limited (HAL).
"No aircraft of Training Command was flying in the area. However, ASTE and HAL could have been undertaking their routine test flying, which necessitates going supersonic at times. These are done well beyond the city limits in specified sectors,” according to the statement. “However, considering the atmospheric conditions and reduced noise levels in the city during these times, the aircraft sound may become clearly audible even if it happened way out from the city," according to the statement.
TNM asked three former Indian Air Force officers whether a 'sonic boom' by a fighter jet would be allowed to occur within a city's airspace. The officers all explained that though fighter jets are allowed to fly in Bengaluru's airspace, it is rare that residents would feel the impact of a sonic boom.
Former Air Chief Air Marshal S Krishnaswamy said, “There are certain altitudes of above 10 kilometres from the surface [of the ground] and there are certain corridors on which we can fly at supersonic speeds. These corridors are away from the cities.”
“However, it is possible that due to certain weather conditions and wind conditions that the altitude has to be lowered. But normally for testing purposes, they are very well planned," he added.
He further stated that there have been other occasions in the past when window panes have shattered due to jets flying overhead.
Similarly, former Vice Chief of Air Staff, Air Marshal PK Barbora said that it is rare for armed forces to fly at supersonic speeds close to cities like Bengaluru.
“There are restrictions, as long as I was in the service and it is probably still there. We cannot go over populated areas. The sound waves can actually crack buildings. Unless there is an occasion in which the government authorises a sonic run, like a fire power or Navy Day demonstration, we then do it at a height and distance from the public so that there is no impact on human beings or structure,” he told TNM.
He added, “We are only allowed to do it within our own areas where no other aircraft are flying and we will do it at a height, as per our mission directive for training. So around 20,000 feet, there will be only impact on the sound you might hear. What happens when you cross the speed of sound, pressure waves are formed and it hits your eardrums. It sounds like a boom. Now depending on how close you are, the pressure wave can cause damage to human beings as far as eardrums are concerned.”
Former Air Force spokesperson and an ex-Group Captain Tarun Kumar Singha said pilots generally avoid flying close to the ground or near populated areas, except during the Aero India event or other such air shows in Bengaluru, to ensure there are no obstacles while flying.
“Otherwise it is always done at high altitude, even for testing purposes, where the sound which you hear from the ground is weaker than the sound of lightning,” he said.
However, he said broken glass panes may not necessarily be due to the sonic boom.
The mysterious noise was heard in the city’s Whitefield division, and as far as Cooke Town, Vivek Nagar, Ramamurthy Nagar, Hosur Road, HAL, Old Madras Road, Ulsoor, Kundanahalli, Kammanahalli, CV Raman Nagar, and HSR Layout.