Infinitive Past Form Past Participle II Present Participle I
| act | acted | acted | acting |
| retarding | |||
| rotating | |||
| flying | |||
| moving | |||
| extending | |||
| applying |
Reading
Text. AIRPLANE STABILITY. AXES OF ROTATION
It should be obvious that airplanes should display ter its equilibrium is disturbed, to develop positive stability, or iperhaps neutral stability, but body to its original position. In other words, a and/or idynamic. Static stabilitylmeans that iftthe
airplane's equilibrium is disturbed, forces will be activated which will initially tend to return the
planeiseasytofly;however, this does not airplane to its original position. However, these mean that a pilot can depend entirely on stabil- restoringforcesmaybesogreatthattheywill
itytoreturn the airplane to the original condi- force the airplane beyond the original position tion. Even in the most stable airplanes, there and continue in that direction.
are conditions that will require the use of air- On the other hand, dynamic stability is a prop-
plane controls to return the airplane to the de- ertywhichdamperstheoscillationssetupbyasired attitude. statically stable airplane, enabling the oscilla-Stability is classified into three types: (1) tionstobecomesmallerandsmallerinmagni-
Positive stabilitycanbeillustrated by a tude until the airplane eventually settles down to ballinsideofabowl.Iftheballisdisplaced Therefore an airplane should possess positive sta-the bowl, it will eventually return to its original bilitywhichisboth static and dynamic innature.axes
of rotation around which movement takes place. These are (1) lateral axis – an imaginary line from wingtip to wingtip, (2) longitudinal axis – an imagi-nary line from the nose to the tail, and (3) vertical axis – an imaginary line extending vertically through the intersection of the lateral and longitudinal axes.
canbeillustrated by a ball on the top of an The airplane can rotate around all three axes simul-inverted bowl. Even the slightest displacement taneously or it can rotate around just one axis. These
oftheballwillactivategreater forces which axes are imaginary axes around which the airplane will cause the ball to continue moving in the turns, much as a wheel would turn around axes posi-direction of the applied force. tioned in these same three planes.
© НИЛ НОТ НИО УВАУ ГА(и), 2009 г
Aviation English Fundamentals | 15
The three axes intersect at the center of gravi-ty and each one is perpendicular to the other two.
Rotation about the lateral axis is called pitch, and is controlled by the elevators. This rotation is referred to as longitudinal control or longitudinal stability.
Rotation about the longitudinal axis is called roll, and is controlled by the ailerons. This rotation is referred to as lateral control or lateral stability.
Rotation about the vertical axis is called yaw and is controlled by the rudder. This rotation is referred to as directional control or directional stability.
Stability of the airplane then, is the combina-tion of forces that act around these three axes to keep the pitch attitude of the airplane in a normal level flight attitude with respect to the horizon, the wings level, and the nose of the airplane direc-tionally straight along the desired path of flight.
Ex. 15. Comprehension check.
1. What is stability?
2. How is stability classified?
3. What does static stability mean?
4. Why should an airplane possess positive stability? 5. How many axes of rotation does an airplane have? 6. What is lateral control?
Vocabulary practice
Ex. 16. Six of these words can be used in combination with center of. Which ones are they?
Center of
gravity
attraction
pressure
motion
rotation air
thrust lift
Ex. 17*. Form nouns from the verbs.
To descend, to fly, to increase, to weigh, to move, to rotate, to lift, to set, to control, to decele-rate, to gain, to activate, to stabilize, to displace, to extend, to oscillate, to intersect, to originate, to act, to pass, to imagine, to apply.
Ex. 18*. Fill in the chart to find the other parts of speech. Use your dictionary where necessary. Check the pronunciation.
| NOUN | VERB | ADJECTIVE |
| 1. application | apply | applicable |
| 2. … | fly | … |
| 3. acceleration | … | … |
| 4. … | weigh | … |
| 5. … | … | stable |
| 6. … | rotate | … |
© НИЛ НОТ НИО УВАУ ГА(и), 2009 г
Aviation English Fundamentals | 16
| 7. … | … | extensive |
| 8. intersection | … | … |
| 9. … | … | imaginary |
| 10. origin | … | … |
| 11. … | … | oscillating |
| 12. … | move | … |
| 13. … | … | controllable |
Ex. 19. Scan Text «Airplane Stability» to find antonyms. Example: Calm air – turbulent air.
| 1. Vertical | - … | 5. At the bottom | - … |
| 2. … | - Negative | 6. Finally | - … |
| 3. Static | - … | 7. … | - Disturbed |
| 4. Instability | - … | 8. Calm air | - … |