Tail configurations
By:Nandita Balaji, Yatin Bawa, Nagaraj Thota, Bhavya
Bhardwaj
The empennage is a
structure at the rear of an aircraft consisting of the horizontal stabilizer,
the elevators, the vertical stabilizer, and the rudder. This is the part of the
aircraft that provides stability during flight.
An aircraft empennage can
be differentiated on the basis of the fin and the tailplane configurations.
Types of tails:
1.) T-Tail
It is a type of an
empennage configuration in which the fin is mounted by tailplane at top. It
looks like letter T, due to which the name is kept so. About 25% of the
aircrafts prefer this type of configuration.
Design
In commercial aircraft,
the tail is often seen in with their engines in the rear body instead of the
wings. However, models like BAe-146 break this rule, which is the same applying
in the T-tail freighters like C-17 Globemaster III or the IL-76 which all have
the wings with engines in the top of the fuselage
The design helps to keep
the horizontal stabilizer up in “clean air,” away from turbulent air created by
the wing and engine nacelles.
Advantages
- Allows
the horizontal tail surfaces to remain clear of the exhaust air flow from
the engines.
- A T-Tailed aircraft recovers from a spin
easier than aircraft with other types of tail configuration, as the
elevator is located above the rudder, thus creating no dead air zone above
the elevator where the rudder would be ineffective in spin conditions and
also keel effect plays an important role in this type of configuration.
Disadvantages
- As
the elevator is placed high they are more difficult to reach during
maintenance.
- Risk
of more pitching up.
Some aircrafts with
T-tails
BAC One Eleven, BAE-146, Boeing 717, Boeing 727, Douglas DC-9, ATR-42, Britten Norman Trislander, DHC-7, F-101 Voodoo, C-141 Starlifter, C-5 Galaxy, C-17 Globemaster III, Boeing
Sikorsky RAH-66 Comanche
In
T-tail configuration, The Boeing 727 is the only major trijet to have this
configuration also, The Britten Norman Trislander is the only aircraft of this
type to have three propellers; the tail one is in the top of the vertical
stabilizer.
2. V
Tail:
Unlike the conventional tail, a V tail
has only one stabilizer which is slanted in a v shape and the control surfaces
attached to it act both as a rudder and as an elevator and they are called as
ruddervators. This type of empennage configuration is generally found in
ultralight aero planes, UAVs, drones and fuselage mounted aero planes.
Advantages
It is generally used because there is
one less control surface which decreases the overall weight and structural
load, i.e. better
strength to weight ratio Also because of less components
theoretically they have lesser interference drag compared to most empennages.
They usually have less joints, less stress concentrations and their Reynolds
numbers are usually better.
Disadvantages
There is an interaction between the pitch and yaw functions
of the tail for both stability and control because of which airplanes with this
configuration require longer fuselages to prevent yawning. All this makes its
design very complex and difficult to build. It is rarely seen in aerobatic
models because of its yaw to roll coupling (dihedral effect). Also, since the control
surfaces are slanted, they are less effective when compared to conventional
tails as the force generated is divided into components thereby decreasing its
magnitude whereas in the conventional tail the force does not decrease.
The
most popular V-tailed aircraft that has been mass-produced is the Beechcraft
Bonanza Model 35, often known as the V-tail Bonanza or simply V-Tail.
3. Conventional
Tail:
The conventional tail
design is the most common design found in aircrafts, i.e., nearly 70%
of the airplanes have
conventional tail. It has one vertical stabilizer
placed at tapered tail section and one horizontal stabilizer dived into two
parts, one on each side of the vertical stabilizer.
Advantages
The conventional
tail is easiest to design, manufacture and can be modified easily in the
development phase of the aircraft. The horizontal stabilizers position can be
adjusted up to some extent. This design is for simple plane designs and is very
popular. This design provides more stability in turbulent conditions.
Disadvantages
But there are many
planes in which this design is ineffective due to the engine position, weight
of the aircraft and also produces more drag than intended. Hence in such
aircrafts T – tail or V- tail designs are preferred.
