Bengaluru: The naval variant of home-grown Light Combat Aircraft (NLCA) is at a striking distance from undertaking the much-awaited, maiden carrier landing and taking off on board INS Vikramaditya. The Indian Navy is currently studying all the data before giving the go-ahead to the team to undertake deck landing on the mighty aircraft carrier.

According to military sources who are part of this ‘extremely complex’ mission, the 'Test Pilots' who are part of NLCA’s campaign in Goa have made several approaches to INS Vikramaditya in the last one month. This was part of the team’s (ADA, HAL, NFTC & Indian Navy) campaign from the Shore-Based Test Facility (SBTF) in Goa.

(SBTF simulates an aircraft carrier with ski-jump and arrested recovery facilities. It’s a recreation of a ship on the shore. The SBTF in Goa replicates a static model of the Indigenous Aircraft Carrier (INS Vikrant) being built at the Cochin Shipyard in Kerala.)

“NLCA has done quite a few wave-offs at INS Vikramaditya near Karwar shore to assess the winds and deck effects for carrier landing. We are only waiting for the go-ahead from the Indian Navy that will enable the aircraft to land on the carrier. The 'Test Pilots' are confident now and they have done a marvellous job,” says an official.

Once NLCA lands and takes off from INS Vikramaditya, India will become the sixth nation after Russia, United States, France, United Kingdom and China to have mastered the art of an arrested landing and ski-jump take-off on the deck of a carrier.

(Arrested landing deploys a cable on the carrier before the aircraft is about to land. While landing, the aircraft will deploy an arrester hook, which in turn will get attached to the cable. This will arrest or bring the aircraft to a halt within the available short distance on the carrier (about 95 m). In ski-jump, the aircraft takes off using the assistance of a curved ramp sloped upward. Here the aircraft achieves the required upward lift despite short runway and gains speed in air.)

The Flight Test team includes Commodore J A Maolankar, Capt Shivnath Dahiya, Commodore J D Raturi and Cdr Ankur Jain. The pilots have completed close to 30 arrested landings and more than 50 ski-jumps at SBTF ahead of approaching the aircraft carrier.

The mighty aircraft carrier INS Vikramaditya. Credit: Basani Satheesh Kumar/DPR/MoD

Both prototypes NP-1 (trainer) and NP-2 (fighter) were part of the campaign in Goa. The NP-1 did its first arrested landing at SBTF on September 13, 2019.

Difficult Tasks

The arrested-landings at SBTF have not been undertaken only with straight-in approaches, but also under various loading conditions and with roll and yaw.

“In some cases the NLCA was intentionally banked up to 5 degrees before landing, which is very extreme. This bank angle was generated to simulate the roll of the carrier. In some ways arrested landings and ski jump takeoff on SBTF are much more difficult than on the actual carrier due to the lack of headwind, despite the ship motion being absent. The ship can generate a guaranteed headwind of 15 to 20 knots by its forward motion” says an official.

“Two pilots from the test team have flown close to 30-plus approaches to INS Vikramaditya during the recent campaign. The pilots flew very close over the ship deck. The approaches were to understand the characteristics and controllability of the aircraft,” the official said.

Bolter Trials

The SBTF has two arrester wires on its ‘deck’ while INS Vikramaditya has three. The pilot normally aims for the middle wire on the ship and if he misses all the three wires, then he has to do a bolter (or instantaneous takeoff from the deck) as per the SOP (standard operating procedure.)

NLCA during its campaign at SBTF, Goa. Credit: ADA/DRDO

For naval aviators, a bolter happens when an aircraft fails to catch the arrester cable on the ship deck. The pilot then is left with no option but to go on a full throttle, get airborne and position for another attempt to land.

“Any arrester landing on a ship deck is done with full throttle to enable a bolter to be possible if the need arises,” says the official, while explaining the nuances of deck operations.

The NLCA pilots have undertaken over 300 FCLPs (Field Carrier Landing Practices) at SBTF without the arresting hook being deployed. These missions were executed at different sink rates (slope at which an aircraft is being lined in for landing.)

Incidentally, in all the arrested landings (about 30) carried out at SBTF, not a single miss has happened. However, the bolter mode was tested and fine-tuned by landing without the arresting wire before commencing arrested landings.

Navy board

The Navy has constituted a high-level board to study the feasibility of NLCA landing on the deck of INS Vikramaditya.

“The Navy wants to ensure that the ship will be safe. The board is looking to the safety aspects from the ship’s point of view. Teams from HAL and ADA have visited INS Vikramaditya and studied all the support required on deck once the aircraft needs to land,” an official said.

“The board is thoroughly studying the data from various trials both at SBTF and while doing low approaches over INS Vikramaditya. In addition, a team from CELIMAC (Centre for Military Airworthiness and Certification) too is analysing the data before clearing the aircraft for deck landing,” says the official.

With the Indian Navy wanting a twin-engine platform for its deck-based operations the current single engine configuration will provide important inputs for design of the operational aircraft.

“Navy's requirement is NLCA Mk-2 which will be a twin engine aircraft. From 2016 till now we have looked at the twin-engine seriously for the AMCA (Advanced Medium Combat Aircraft). Navy is looking at MiG-29 K replacement by 2030-31 and the NLCA Mk-2 should be the answer. The first flight is expected by 2026,” says the official.

Interestingly, the ADA-HAL combine is currently readying NLCA NP-5, which they call it as the Mk-1 production variant. It is expected to fly by mid of 2020.

“We are happy that the Indian Navy has shown interest in NLCA. The confidence is high and we are ready to design and develop the required twin engine platform for Indian Navy,” says the official.

Carrier challenges

Naval experts and scientists say landing on carriers is an extremely complicated task. The landing runway on carriers is about 95 m long and is too short for the aircraft to stop on its own from the landing speeds of about 250 km per hour.

An arresting gear mechanism is provided on carriers with steel cables and an arresting hook is provided on the aircraft. On touch down the aircraft hook has to engage the cable, and then the arresting gear can stop the aircraft in about 95 m. Landing with aircraft hook ending up at a precise touchdown point while maintaining precise speed and heading is a fairly tough task.

On the SBTF, the landing and takeoff is made more difficult by the fact that the headwind (if any) is what is offered by nature. In many cases, there is a strong crosswind as well.

Opposed to this, on the carrier a guaranteed 15 to 20 knots headwind is available due to the motion of the carrier. On the carrier ship, there are added variables of ship due to its rolling, pitching, heaving due to sea waves, and wind disturbances (wake) right behind the ship due to its motion.

“These can cause variations in touch down point and larger landing forces on the aircraft. Pilot needs to be aware of these and make suitable adjustments to aircraft trajectory for a safe landing. On the SBTF, many arrested landings were done with the aircraft intentionally rolled and yawed before touchdown to simulate the effect of landing on ship which is expected to have some roll and yaw due to the sea state,” says the official.

Over 30 approaches were made to INS Vikramaditya by NLCA at varying speeds and winds (to characterize the behavior of the aircraft in the ship wake.)

The pilots are said to have experienced in excess of – 3G (minus) deceleration while attempting carrier landings. (Negative G force is experienced when you decelerate faster than the rate of natural freefall.)

Finally, Team NLCA says that the desi bird is ready for a date with the mighty carrier, to script another aviation history.

Unique Facts

 The flight control system software for NLCA single-seater and two-seater aircraft is a unified code unlike the Tejas, where the development of fighter and trainer software, are two parallel verticals.

 The ski-jump takeoff of NLCA at SBTF is completely autonomous. With a single press of a button commanding ski-take off, the flight control computer of the aircraft takes it off the ramp and hands over the control to the pilot after positioning the aircraft to a safe altitude and speed.

 The landing gear of the aircraft is indigenously designed and is quite bulkier as compared to its IAF counterpart mainly due to the high sink rate experienced while deck landing.

 There are additional control surfaces on NLCA wing front called the Leading Edge Vortex Controllers (LEVCON) that are driven by the rotary actuators enabling the aircraft short take off and landing.

 The arrestor hook system of NLCA is also an indigenous technological masterpiece. Developed for the first time in India, this system helps in arresting the aircraft while landing on the ship deck.

 The landing of the aircraft is mainly controlled by the throttle as against the conventional way of landing through pilot control stick.

(The writer is an independent aerospace and defence journalist, who blogs at Tarmak007 and tweets @writetake.)