Can the HAL Lca Tejas perform Pugachev's Cobra maneuver?

Question

Can any variant of the HAL Lca Tejas (either the naval variant, the mark 1, mark 2 or later) perform Pugachev's Cobra? If not, why?

Answer 1

No.

With that delta wing shape it will have pitch control problems at higher angles of attack. The Cobra maneuver requires a small pitch-down moment over the post-stall region up to 110° angle of attack. I very much doubt that this wing planform will have such pitch characteristics, and without thrust vector control a docile pitch behavior is a prerequisite for the Cobra maneuver.

In the development of the LCA a high lift coefficient without leading edge devices was the main goal of the wing design. It should be able to operate in the vicinity of flocks of birds - birdstrike is a real risk on many Indian Air Force bases. At the same time, the small aircraft should be able to fly supersonically, which lead to the double-delta wing as the best way to achieve both goals, and poor post-stall pitch response had to be accepted.

When HAL switched from MBB to Dassault for technical support, leading edge devices were added in order to fulfil the take-off and landing requirements. Post-stall flight was not seriously considered at any point in the development.

Answer 2

No known variant of the HAL Tejas can perform the Cobra Maneuver.

This is for the simple reason that the aircraft was not designed nor was it expected to perform such a maneuver.

In a Cobra, the plane suddenly raises the nose to the veritical position (or beyond, usually 90$^{\circ}$ to 120$^{\circ}$) before dropping it back to the normal flight, maintaining more or less the same altitude through the entire maneuver.

Source: www.saddahaq.com

The cobra maneuver is a dynamic maneuver to a high angle of attack, beyond any equilibrium or trim point. Pitching angular momentum carries the aircraft to a peak angle of attack.

According to Airplane Stability and Control,

The Cobra is started from unstalled flight with a rapid application of full nose-up control, which is held up to the maximum angle of attack point, about 90 degrees. Control is neutralized for the recovery, assuming that the airplane has a negative or nose-down pitching moment at that point.

As can be seen from above, the performance of this maneuver requires control (and a pitch down moment at high aoa) in the high angle of attack region, though it can be done with conventional controls.

The Tejas is not designed with such characteristics. The main thrust in designing of Tejas was to get a 4(+) generation aircraft with relaxed static stability. Tejas is basically a replacement for Mig-21 (a process which is not going very well), and as such the main design goals were to produce a small, supersonic aircraft to excel in interception/air superiority role.

Towards this, the compound delta wing was chosen because it was small and lightweight compared to other designs available. Though the wing has good high-alpha characteristics and aircraft has good maneuverability, post-stall maneuvering was never considered for this fighter. As such, no variant of Tejas has the capability to do post-stall maneuvering and there are no plans to include them in the future.