Can someone clearly explain the advantages and disadvantages of ruddervators? I cannot find the answer anywhere else.
More induced drag
A disadvantage (especially critical during landing) is that there is more induced drag to make certain movements. The image below helps to understand this:
To yaw, you have to use both ruddervators (contrary to just a single rudder movement for a normal tail). This is done in order to compensate the unwanted vertical component. This leads to increased induced drag, which is a big problem during take-off.
Less interference drag
The number of intersections goes down. In the case of a conventional tail you have three intersections (fuselage - left elevator, fuselage - rudder, fuselage - right elevator), whereas for a V-tail you only have two (fuselage - left ruddervator, fuselage - right ruddervator). This reduces the interference drag.
The main advantages of the ruddervators (or V-tails are)
- They are typically lighter and have less wetted surface area compared to the conventional tail configuration as it has one control surface less (though this reduction is not as simple as reducing one third). As a result the drag is reduced.
- They are used in some cases to increase stealth. The canted surfaces reflect the radar away from the source, aiding in stealth. They also allow the engine to be mounted above the fuselage (like Global Hawk), reducing the infrared signature from below.
- In Cirrus SJ50, the 'V' tail is used to allow engine placement above and outside the fuselage,which is claimed to improve safety and reduce cabin noise.
The main disadvantages are:
- They require a much more complex control system compared to the conventional aircrafts as both the surfaces have to be move together.
- They are required to be structurally more robust compared to the conventional system due to the increased load involved. This reduces the advantage gained by eliminating a control surface.
- The amount of control forces required for operating the ruddervators are higher compared to the conventional ones and in some cases, it may be more.