Sukhoi Su-30 MKI - Purpose of Thrust Vectoring

Hub question: What is the purpose of Thrust Vectoring Nozzle in Sukhoi SU-30 MKI? I read this on some site and interested in more details.

Hi friend. This is a really nice question for me to answer. The answer was too difficult so it took me 3 days to research to come to the whole conclusion. There are various websites on the net which have information related to the same and below is my input after going through the information available. I also contacted various students who are studying aeronautical engineering and pursuing a career in the same and I gathered the details from them also. Below are some of the most common questions about thrust vectoring control system.

What is thrust vectoring?

Thurst vectoring is one of the best feature in Sukhoi SU-30 MKI. The nozzle works such that we can direct the engine thrust in a desired direction, which enhances the maneuverability, and it is this reason due to which Su-30 can perform cobra maneuvers and which is quite beneficial during dogfight. India is the second country after Russia to have an aircraft in service with such thrust vectoring capability.

USA has TVC in F-22 , X-31 , AV-8B Harrier II

UK has EF 2000

Germany has EF 2000

The maximum tilt angle for the SU-30 is 32 degrees in horizontal and 15 degrees in vertical. Even Eurofighter Typhoon does not have thrust vectoring. There are two types of thrust vectoring systems, 2D and 3D. Read below for more details on them.

What is 2D and 3D thrust vectoring and what is the difference between them?

2D means directing the thrust in horizontal and vertical whereas 3D means directing the thrust in vertical, horizontal, and angular. In 2D, nozzles can be deflected in only one direction (either both vertical or horizontal) and in 3D case their has been not any correct information because a few days back I read an article which stated that 3D can be deflected in different planes and yesterday I read another article and it stated that nozzle of 3D can be deflected in opposite direction. So their is quite confusion about the working of 3D nozzle.

The most important aspect related to any moving machine/vehicle/aeroplane, etc. is the propulsion power/the type of propulsion, etc.

Aspects related to propulsion, etc. could be best studied when they are related to an aeroplane, especially due to the fact that there is ideally zero friction between the aeroplane and air/unlike the case in cars/bikes/ships, etc.

The concept of three dimensional vectoring can also be applied to a propellor based aircraft. The principles and the benefits will be good if not dramatic when compared to the jet/rocket power, etc. The earlier types of jet technology were purely axisymmetric and the thrust was on the lines of the axis of the jet engine.

The 2-dimensional thrust vector allows the propulsion to be deflected in two directions, up and down, or sideways, left or right.

3 dimensional thrust vector allows the propulsion to be deflected in all 4 directions, i.e., up and down and left and right. It is even possible to add roll control using differential ideology. Basically the propulsion of one jet is directed upwards while the other is directed downwards.

The 3 dimensional thrust vectors allow you to carry all types of complex maneuvers. You can very well say 3 dimensional thrust add 4 more controls to the aircraft. In the absence of 3 dimensional thrust the pilot had to depend heavily on the basic controls such as rudder/elevator/flap/airelon, etc. It is quite possible that some complex maneuvers can be carried out without using the basic controls at all. The response time is improved a lot by using such multi dimensional thrusts.

Now learn how the thrust-vectoring nozzle is controlled?

Presumably, the nozzle sense is controlled by the avionics inside it, right? But it is the pilot who is given a direct feed on the nozzle angle? Because maneuvers like the Pugachev's Cobra supermaneuvers are too complex to fathom.

Pugachev's Cobra or dynamic braking is a maneuver in which within 3-4 seconds, the nose of the aircraft is pulled up to high angles of attack (80°-110°) and then returned to normal horizontal flight. This causes intensive loss of airspeed. You can execute this maneuver from level flight at various altitudes and at indicated airspeeds of 350-450 kilometers per hour.

In level flight at the appropriate entry speed of 350 to 450 km/h, disable the AOA limiter. Execute the cobra by pulling the stick fully aft. As the nose reaches the vertical (pointed straight up) allow the stick to go to neutral and let the nose fall back down to level flight. Smoothly increase thrust towards the end of the maneuver. The AOA limiter will automatically re-engage after executing the cobra.

Two facts, which make thrust vectoring difficult for other planes

1. The main difficulty is to design a nozzle bearing that can work smoothly at extremely high engine exhaust temperatures, basically a problem of finding the right material. The Russians are using some alloy for this and some advanced lubricant they invented.
2. The second is a problem of flight control. Thrust vectoring changes the complete control law for your aircraft. As a simple example, one of the very difficult fields in aerospace is tethered vehicle flight dynamics because it involves an asymmetric thrust vector. Thrust vectoring is having that vector in your control law. This is the reason that Americans are behind the Russians and they want to integrate the TV into the flight computer, so that the pilot can still fly with a single joystick; however, the Russians who are more practical and generally just want results, have a separate control for controlling TV of the nozzle, and the pilot uses his own feel of the aircraft to fly and use the thrust vectoring appropriately.

India has manufactured AL-31 engines with TV nozzles under license at the Nasik plant (Hindustan Aeronautics Limited).

Which other aircrafts are using this facility?

1. Harrier 1 and 2.

1. Yakovlev Yak-141 which is the first supersonic VTOL fighter (Vertical Take-Off and Landing).
2. JSF which is a naval version still has some problems with the vertical take-off and landing thing out there, so the US engineers had to call on the Russian engineers from Yakovlev to help them fix this problem.
3. V-22 Osprey with VTOL and STOL (short takeoff and landing).

If anyone thinks that helicopters are using thrust vectoring, then I am too sorry because they do not come under the category of fixed-wing aircraft, as they are rotary wing aircrafts. All VTOL fixed wing fighters though have TV, they are not using it to achieve higher maneuverability. They simply use to bypass the engine exhaust through another duct pointing downwards. The challenge there is to achieve stability because for thrust pointing directly downwards, there are a lot of stability issues which pop up, not to mention conditions when there is high wind or gusts in the atmosphere which is very common on a ship in the ocean, but the main challenge as I pointed earlier in fighters when they use TV for maneuverability is that then you have to move the nozzles itself and not just bypass the exhaust through a separate duct, so designing the bearing becomes a difficult issue.

I will come up with more advanced answers related to thrust vectoring nozzle and maneuvers which are possible by using this system in my upcoming hubs.

Take care. Happy flying...........

P.S.: As I promised, I have created a new hub which is the second part of this hub - Thrust vectoring Sukhoi Su-30 MKI Part II

In this new article, I have written on thrust vectoring success by American's on V-22 Osprey and compared it with Sukhoi MKi