Bengaluru: A Light Combat Aircraft (LCA) Tejas from the roster of No 45 Squadron, Flying Daggers, had to cut short its routine sortie on Tuesday after losing one of its external drop tanks (that carries fuel) soon after taking off from Air Force Station Sulur, near Coimbatore in Tamil Nadu.
According to Indian Air Force (IAF) officials, the incident happened around 8.30 am. “The aircraft landed back safely after the incident. No damage was reported on ground,” they said.
Tejas has been maintaining an outstanding safety record since its maiden flight in Bengaluru on January 4, 2001. Barring tyre-bursts, software niggles and minor electrical supply issues, none of the platforms from the Tejas flight-line ever had any major concerns in the last 18 years.
“Soon after taking off, the aircraft was climbing up and the drop tank fell off into an open area. Not sure how this has panned. We are investigating the incident,” an official said.
It is confirmed that the 1200-litre drop tank fitted on the left side of the Tejas SP-4 fell off into an agriculture field in Irugur village, near Coimbatore.
Tejas can carry fuel on both wings (700 litres each), fuselage (850 litres) and in two drop tanks (1200 litres each).
Villagers shocked
“The villagers were shocked to see the drop tank banging on to their fields. The impact has caused minor fire. Owing to drip irrigation, the field was partially wet. We have recorded statements of few villagers as well,” an official said.
Tejas is equipped with a quadruplex digital fly-by-wire flight control system. Hence, issues of asymmetry don’t arise even if there is a loss of mass, be it in the form of drop tanks or weapons.
“External drop tanks assure long endurance and range to fighters and in case of emergency they can be always delinked or jettisoned. In this case, we have to find out what exactly has happened,” an official said.
“Jettisonable drop tanks also ensure the pilot a quick getaway from enemy territory, in addition to dealing with emergency situations,” he added.
From the photographs that were available from the incident site, the pylon itself seems to have sheared off, that might set off alarm bells during investigation.
IAF operates 14 Tejas fighters from AFS Sulur and two more are set to join the squadron soon from Hindustan Aeronautics Limited (HAL).
Interestingly, it was only last week that an IAF Jaguar fighter had to dump its fuel tanks and practice bombs following a bird hit at Air Force Station Ambala. The pilot landed back safely on managed to land the aircraft with one functional engine.
An HAL official told Onmanorma that there are many in-flight redundancy systems in place on board Tejas even if there are technical snags.
“Our teams have already got the initial assessment reports from AFS Sulur. Our technical team will now get on to the root cause to assess the reasons behind the incident. Drop tank jettisoning is part and parcel of fighter flying profiles,” the official said.
Tested tanks
It was in December 2010 that the PV3 platform from Tejas testline performed the first ever drop tank test at the Aeronautical Test Range in Challakere near Chitradurga in Karnataka.
Eight years later, in December 2018, a team from Advanced Seismic Testing and Research Laboratory, the Fatigue and Fracture Laboratory and the CSIR-Structural Engineering Research Centre had evaluated Tejas fuel tanks through a series of qualification tests.
During the tests, the drop tanks underwent 25 hours of sloshing and vibration so as to see of it could have a life in excess of 3,000 flying hours.
These tests were part of the Final Operational Clearance (FOC) mandate. Tejas was eventually granted FOC in February 2019, during Aero India.
As on July 1, this year all Tejas platforms from its test line with HAL and Aeronautical Development Agency have completed 4506 incident-free flights logging in 2896 hours.
For the record, Flying Daggers officially completed one year of moving to AFS Sulur on July 1.
