Text 2c. Accuracy

Read and translate the following extract and answer the question.

1.What are the reasons of vertical errors?

2. Define a) random drift;

b) apparent drift.

Accuracy of the vertical must be a consideration. Vertical gyros are needed because we want an accurate reference line in space — and that line must be along the vertical. Any difference between the line and the vertical might cause errors somewhere in the systems referenced to the gyroscope.

There are at least three effects causing vertical error, and the amount of error depends upon the kind of erection control and the erection rate. There are: drift, acceleration and aircraft turns.

Drift errors are both random and apparent. Remember, random drift occurs because the gyro is not a perfect instrument. Apparent drift occurs because a gyro is fixed in space — not fixed relative to the earth. Suppose we have a gyro with a random drift: of 30 deg/hr. That is 0.5 deg/min. Added to this is the apparent drift due to earth's rate: a maximum of 15 deg/hr or 1/4 deg/min. Finally, if the gyro is in an airplane, there is an additional apparent drift due to earth's profile. If the plane is travelling at 300 mi/hr, the apparent drift is about 4.3 deg/hr or 0.07 deg/min. Therefore, the maximum drift would be 0.5 deg/min plus 0.25 deg/min plus 0.07 deg/min or 0.82 deg/min.

Exercises

EX.1. Find in the texts English equivalents for the following words and groups of words.

Как вы помните, во-первых, теперь, теперь когда, итак, поэтому, с другой стороны, во-вторых, поскольку.

EX.2. Read these abbreviations and units.

Oz- sq-in/sec means ...

Oz-in-sec means...

Deg/min means …

Rad/sec means ...

Rev/min means ...

Oz-in means ...

Lb-ft means …

Gm-cm means …

EX.3.Finish the following sentences without looking in the texts:

1. Torque is a force…..

2. Vector represents a physical …..

3. The greater the angular momentum …..

4. Drift errors are both…..

EX. 4. Define the terms:

1. inertia

2. precession

3. moment arm

QUESTIONS AND PROBLEMS

1. What is the difference between a scalar and a vector?

2. What is the right hand screw rule?

3. A man pulls against a 2 ft crowbar with a 60 Ib force. How much torque does he exert?

4. What is the law of gyroscopic precession?

5. State the law of gyroscopics.

6. Just what is precession?

7. Draw a sketch showing a gyro with torques applied.

8. Show how the right hand can be used for finding precession.

Unit 3. Vertical Gyro Components

Essential vocabulary

Cartridge,n – патрон, катушка

Directional gyro,n – гироскоп направления

Figure of merit,n – показатель качества, добротности.

Pitch and roll,n – бортовая и килевая качка

Rim, n – обод

Accomplish, v – выполнять, завершать.

Employ, v – применять

Converge, v – сходиться в одной точке, сводить воедино

Curve, n – кривая (линия), изгиб;

v – изгибать,

Give rise to, v – давать начало, приводить к результатам, давать повод.

Trust, v – доверять

Blind, adj – слепой

Explosive, аdj – взрывчатый, взрывной