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Updated: Feb 07, 2019 08:20 IST

The deaths of two Indian Air Force (IAF) test pilots in a Mirage 2000 crash at the Hindustan Aeronautics Ltd (HAL) airport in Bengaluru last week may have been caused in part by arrester barriers, critical airfield safety equipment, giving way, officials with first-hand information of the matter said on condition of anonymity.

The reason for the crash itself remain unknown — the black box of the fighter has been sent to France for analysis — but the death of the pilots could have been averted if the barriers, meant to stop the aircraft, had held, one of the officials added.

“Once the arresters gave way, there was little chance that the two had of bringing the aircraft to rest,” he said. The two pilots, Squadron Leader Samir Abrol and Squadron Leader Siddhartha Negi, died on the spot.

The arresters installed at HAL airport are expected to stop aircraft that weigh up to 30 tonnes travelling at speeds of up to 160-170 knots. The Mirage 2000 trainer weighs much less, 13-14 tonnes, and was travelling at a speed of less than 160 knots, the officials added.

Abrol and Negi were on an “acceptance sortie” of the Mirage 2000 trainer aircraft after it was overhauled by the Bengaluru-based, state-owned company. The sortie was taking place on the HAL runway in Yemalur in Bengaluru on February 1.

An HAL spokesperson declined comment. An Indian Air Force (IAF) spokesperson, too, declined comment because of the ongoing court of inquiry into the accident.

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The accident occurred a day after IAF chief Air Chief Marshal BS Dhanoa criticised HAL, and also pointed to the number of pilots who lost their lives testing the state-owned firm’s indigenously developed aircraft.

According to the officials, the number of times major snags have been detected by IAF at the time of delivery in an aircraft overhauled or manufactured by HAL is high. For instance, last June, an Su-30 was on an acceptance sortie (its 13th) when it crashed near Nashik. The pilot and the flight engineer ejected successfully. These sorties are done by IAF only after HAL has flown the aircraft a certain number of times and cleared them for acceptance.

In 2018-2019, the Russian designed Su-30Mki – the mainstay fighter of the IAF – manufactured by HAL required as many as six sorties as against the designated two sorties before they could be accepted. “The increased number of sorties is because snags were found,” a second senior government official said.

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Similarly, Mirage 2000 aircraft overhauled by HAL have, on average, required two sorties more than the mandatory number because of snags. And, Jaguars, the British made deep-strike bombers that are overhauled by HAL, have required, on average, three sorties more than the two sorties designated for acceptance. For the advanced light helicopters (ALH), flown by the Indian Army, Navy and Air Force, and also made by HAL, the numbers are equally bad.

“Every aircraft needs to go through a certain number of sorties testing various test points before it can be accepted by IAF for deployment. The fact that the more sorties are having to be flown to rectify the snags indicates either the process of testing is not being done properly by the manufacturer or the process lacks rigorousness at the HAL end,” said Air Marshal SBP Sinha (retd), who till recently was the Air Officer Commanding at the Central Air Command of IAF.

Arrester barriers are installed at the end of the runway to deal with exactly the kind of situation the overhauled Mirage 2000 trainer was facing. They are meant to stop an aircraft that has either aborted take-off or made an emergency landing from overshooting the runway with minimal damage to aircraft or injury to the crew.

In this case, the Mirage 2000 trainer came down seconds after take-off. The undercarriage of the aircraft was sheared off, most likely because of the impact. And the arrester barrier was the only way that the two test pilots could have brought the aircraft to a stop.

The black box of the fighter has been sent to France for a detailed analysis to assist the Court of Inquiry (CoI) that is investigating the crash. “Separately, inquiries are also being conducted on why the arrester barrier gave way,” said a senior HAL official who asked not to be named.