1. Look at the picture and predict what kind of aircraft it is. Explain why you think so.

2. Translate the text in a written form.

Flying wing is the generic designation given for a fixed-wing aircraft configuration which is capable of stable, controllable flight without the aid of lifting surfaces other than the main wing itself, that is, without auxiliary surfaces such as "tails" and "canards".

In it strictest sense, the Flying Wing also lacks a fuselage, or has only a rudimentary fuselage 'pod' barely extending from the wing itself. In this layout, most of the payload is transported inside the main wing, the latter comprising most of its structural volume. A pure flying wing also lacks any vertical stabilizers, although some aircraft commonly known as 'flying wings' have a vertical tail fin, vertical tail surfaces or a set of vertical stabilizers on the back part of their wings to help their stability in turns.

The less restrictive designation of "tailless aircraft" includes the flying wing aircraft, but also all aircraft without stabilizers or canards, but with a full-length payload bearing fuselage, such as delta aircraft.

Historically, the flying wing has been defended by many as potentially the most efficient aircraft configuration from the point of view of aerodynamics and structural weight. Such a notion usually comes from the idea that the absence of any aircraft components other than the wing should naturally provide those benefits. On the other hand, the aircraft's wing should be able to provide flight stability and control "by itself", a requirement which in principle imposes additional constraints to the wing design problem. Therefore, the expected gains in weight and drag reduction may be partially or wholly negated due to design compromises needed to provide stability and control.

Speaking

1. Analyse conventional wing and flying wing. Compare them. Highlight their similarity and difference. Make a report to your group mates. The following expressions might be helpful:

• The object of this report is …

• First of all I would like to ….

• It should be stressed …

• In comparison with ….

• Summimg up, I would like to …

UNIT 8

Tail Group

1. Look at these pictures. These are the types of tail group. Try to predict what types of aircraft they belong to. Share your ideas with your partners.

2. Before you read the text answer the following questions:

1. What are the movable parts of the tail unit intended for?

2. Is there any difference between the tail groups of civil and military aircraft?

Reading

1. Read the text and match the English words with their Russian counterparts.

1. elevator a. руль направления

2. fin b. площадь компенсатора

3. rudder c. руль высоты

4. tail plane d. форкиль

5. attitude e. киль

6. dorsal fin f. пространственное положение

7. precaution g. стабилизатор

8. balance area h. предосторожность

The tail group

A. In order to provide the necessary stability airplanes are fit­ted with a tail unit (a tail group, empennage) which usually consists of the horisontal tail surfaces — stabiliser and elevators and the verti­cal surfaces — fin and rudder. The stabilizer and the fin are fix­ed portions, the elevator and the rudder are movable.

B. A movable control surface called an elevator is hinged to the rear of the tail plane. It is intended to control the altitude of the aircraft in flight. It can be deflected upwards or downwards. Moving up the elevator reduces its angle of attack and creates a down load on the tail which raises the nose of the aircraft.

C. In order to secure directional stability the fin is used which is the vertical fixed control surface at the rear of the fuselage. The action of the vertical surface is quite clear. Since it has a great lever arm from the airplane's centre of gravity the vertical surface is able to stabilize the directional motion of the plane. Directional control of the airplane is achieved by means of the rudder, which is a movable vertical surface hinged to the rear of the fin. It can be moved to right or left or retained in the neutral position in line with the fin.

D. When the pilot needs to change his flight direction towards the right (or starboard) he moves the rudder to the right. The reaction of the stream on the surface produces a couple about the centre of gravity and the nose of the aircraft is turned to star­board. If it is necessary for the pilot to control the altitude of the aircraft and cause the nose to rise or fall this is done by means of the elevator.

E. In addition to the principal control surfaces there are some auxiliary ones such as trimming tabs (trimmers) which represent small adjustable areas arranged near the trailing edges of the movable surfaces. They are used to produce constant control de­flections to hold the airplane in a certain attitude of flight. They are adjustable from the cockpit.

F. There is also a dorsal fin placed along the upper side of the aft portion of the fuselage body.

G. On large fast airplanes it is usually necessary to provide the movable surfaces with some area called balance area. It re­duces the hinge moment needed to deflect the surface. This is often required because the hinge moment increases with size and speed. This dynamic balancing is one of the precautions taken to avoid flutter, a violent vibration of a wing or control surface.

H. The structure of the tail plane as well as that of a wing consists of longitudinal and transverse structural elements called spars and ribs.

Comprehension Check