Axisymmetric & Thrust Vectoring Nozzles

What is the difference between two dimensional and axisymmetric nozzles?



The vast majority of jet-powered aircraft haveused what are known as axisymmetric nozzles. These nozzles, like those illustrated below, direct thrust purely along the axis of the engine, hence the name axisymmetric.
Comparison of axisymmetric (top)
 and 2D (bottom) nozzles



Two-dimensional nozzles, on the other hand, are capable of not only directing the thrust along the axis of the engine, but can deflect to vector the thrust and produce a force that points the nose of the plane in a different direction. This type of nozzle is at the heart of what is known as thrust vectoring. 

The nozzles depicted above are capable of vectoring the thrust up or down to produce an up force or down force. Down force will force the aircraft nose to pitch upward while up force has the opposite effect. The two nozzles can also be deflected deferentially (one producing up force, the other down force) to provide roll control. 



I suppose a nozzle that deflected thrust left or right would also be considered a 2D nozzle, so long as it was not capable of deflecting up and down as well. However, I've never heard of any aircraft employing such a nozzle, which could be used to improve maneuverability in yaw. A nozzle capable of deflecting both up and down as well as right and left is a 3D nozzle. To date, only a handful of aircraft have made use of 2D or 3D thrust vectoring nozzles. Probably the most well known of these are the American F-22 Raptor and Russian Su-37, both employing 2D nozzles for improved maneuverability in pitch.


F-15 ACTIVE showing its 3D nozzles


Only research aircraft are known to have tested 3D nozzle technology so far, these including the X-31 and F-15 ACTIVE (Advanced Control Technology for Integrated Vehicle). It is likely that this technology will eventually make its way into a production fighter, at least if becomes simple enough for a standard pilot (who doesn't have the catlike reflexes of a test pilot) to control.

Comments

Post a Comment

Popular posts from this blog

EASA : Module17 Propeller Question - Answer

Image
EASA : Module17 Propeller Question - Answer On which type of turbo-propeller would you expect to find a parking brake a) compounded twin spool b) free turbine c) direct coupled twin spool Ans:b * Propeller blade angle a) increases from root to tip b) decreases from root to tip c) is constant along the blade length Ans:b * The purpose of the pitch change cams is to a) convert linear motion to rotary motion. b) convert rotary motion to linear motion. c) prevent windmilling Ans:a * What does the torque meter reading indicate in a gas turbine engine? a) Torque reaction at the reduction gear b)  Engine torque c) The ratio between engine thrust and engine torque Ans:a * The gear type pump in a C.S.U. or P.C.U a) lubricates the entire propeller system b)  boosts engine oil system pressure c) assist the governor valve to move Ans:b * The gear segments on the blade roots of a hydromatic propeller mesh with the a) stationary cam b)  torque tubes and eye b...
Read more

Adverse yaw!!! Roll causes Yaw and Yaw causes Roll...

Image
Do you know what adverse yaw is and how to solve it? To understand what adverse yaw is, we need to first explain the axes of motion for an  airplane. An aircraft in flight can rotate around three different axes, as illustrated below. Aircraft control surfaces However, the effect of one control surface is not always limited to just pitch, roll, or yaw  alone. When the deflection of one control surface affects more than one of these  orientations, we say that the orientations are coupled. The most important of these  coupled interactions is adverse yaw. To better understand the concept, let's study a  picture of what happens when the pilot deflects the ailerons to roll the aircraft. As you can see, the aircraft rolls because one aileron is deflected downward while the other is deflected upward. Lift increases on the wing with the downward-deflected aileron because the deflection effectively increases the camber of that portion of the wing. Conversely, lift decreas...
Read more

Aircraft Landing Gear

Image
Why do aircraft have only three landing gear? Why not four? Most aircraft today have three landing gear. Two main landing gear struts located near the middle of the aircraft usually support about 90% of the plane's weight while a smaller nose strut supports the rest. This layout is most often referred to as the "tricycle" landing gear arrangement. However, there are numerous other designs that have also been used over the years, and each has its own advantages and disadvantages. Let's take a closer look at the various undercarriage options available to engineers. Tail-wheel or Tail-dragger :  Gear Though the tricycle arrangement may be most popular today, that was not always the case. The tail-wheel undercarriage dominated aircraft design for the first four decades of flight and is still widely used on many small piston-engine planes. The tail-dragger arrangement consists of two main gear units located near the center of gravity (CG) that support the majority of the p...
Read more