CHAPTER 2 THE ATMOSPHERE (ATPL OXFORD)

An aircraft's critical Mach number is; a. The speed of the airflow when the aircraft first becomes supersonic

b. The speed of the aircraft when the airflow somewhere reaches the speed of sound

c. The Indicated Airspeed when the aircraft first becomes supersonic

d. The aircraft's Mach number when airflow over it first reaches the local speed of sound

d. The aircraft's Mach number when airflow over it first reaches the local speed of sound

Mach number is:

a. The aircraft True Air Speed divided by the local speed of sound b. The speed of sound in the ambient conditions in which the aircraft is flying

c. The True Air Speed of the aircraft at which the relative airflow somewhere on the aircraft first reaches the local speed of sound

d. The Indicated Air Speed divided by the local speed of sound sea level

a. The aircraft True Air Speed divided by the local speed of sound

When considering the relationship between different types of air speed:

1 - Calibrated Air Speed is Indicated Air Speed corrected for position error

2 - Equivalent Air Speed is Indicated Air Speed corrected for position error and compressibility

3 - Position error, which causes false Indicated Air Speed readings, is due to variations in the pressures sensed at the pitot and static ports 4 - The Air Speed Indicator is calibrated to read True Air Speed when the ambient density is that of the ICAO International Standard Atmosphere at sea level

The combination of correct statements is:

a. Non of the statements are correct b. 1, 2 and 4

c. 2 and 3

d. 1, 2, 3 and 4

c. 2 and 3

When considering the relationship between different types of air speed:

1 - True Air Speed (TAS) is read directly from the Air Speed Indicator

2 - Equivalent Air Speed is Indicated Air Speed corrected for position error

3 - Indicated Air Speed is not a speed at all, i's a pressure

4 - True Air Speed is the speed of the aircraft through the air Which of the above statements are true:

a. 1 only

b. 2 and 3

c. 3 and 4

d. 1 and 4

c. 3 and 4

When considering air:

1 - Air has mass

2 - Air is not compressible

3 - Air is able to flow or change its shape when subject to even small pressures

4- The viscosity of air is very high

5 - Moving air has kinetic energy The correct combination of all true statements is:

a. 1, 2, 3 and 5

b. 2, 3 and 4

c. 1 and 4

d. 1, 3, and 5

d. 1, 3, and 5

Why do the lower layers contain the greater proportion of the whole mass of the atmosphere:

a. Because air is very viscous

b. Because air is compressible

c. Because of greater levels of humidity at low altitude

d. Because air has very little mass

b. Because air is compressible

With increasing altitude, up to about 40,000 ft, the characteristics of air change: 1 - Temperature decreases continuously with altitude 2 - Pressure falls steadily to an altitude of about 36,000 ft, where it then remains constant 3 - Density decreases steadily with increasing altitude 4 - Pressure falls steadily with increasing altitude The combination of true statements is:

a. 3 and 4

b. 1, 2 and

3 c. 2 and 4

d. 1 and 4

a. 3 and 4

When considering static pressure:

1 - In aviation, static pressure can be measured in hectopascal=s

2 - The SI units for static pressure is N/m2

3 - Static pressure is the product of the mass of air pressing down on the air beneath

4 - Referred to as static pressure because of the air's stationary or static presence

5 - The lower the altitude, the greater the static pressure

The correct statements are:

a. 2, 4 and 5

b. 1, 2, 3, 4 and 5

c. 1, 3 and 5

d. 1 and 5

b. 1, 2, 3, 4 and 5

When considering air density:

1 - Density is measured in millibar=s 2 - Density increases with increasing altitude

3 - If temperature increases the density will increase

4 - As altitude increases, density will decrease

5 - Temperature decreases with increasing altitude, this will cause air density to increase

The combination of correct statements is:

a. 4 only

b. 4 and 5

c. 5 only

d. 2, 3 and 5

a. 4 only

Air density is:

a. Mass per unit volume

b. Proportional to temperature and inversely proportional to pressure

c. Independent of both temperature and pressure

d. Dependent only on decreasing pressure with increasing altitude

a. Mass per unit volume

When considering the ICAO International Standard Atmosphere and comparing it with the actual atmosphere, which of the following statements is correct:

1 - Temperature, pressure and density are constantly changing in any given layer of the actual atmosphere

2 - A requirement exists for a hypothetical 'standard' atmosphere

3 - The values given in the International Standard Atmosphere exist at a the same altitudes in the actual atmosphere

4 - The International Standard Atmosphere was designed for the calibration of pressure instruments and the comparison of aircraft performance calculations

a. 1, 2 and 3

b. 2, 3 and 4

c. 1, 2, 3 and 4

d. 1, 2 and 4

d. 1, 2 and 4

When considering the ICAO International Standard Atmosphere, which of the following statements is correct:

1 - The temperature lapse rate is assumed to be uniform at 2°C per 1,000 ft (1.98°C. up to a height of 11,000 ft

2 - Sea level temperature is assumed to be 15°C

3 - Sea level static pressure is assumed to be 1.225 kg/m3

4 - Sea level density is assumed to be 1013.25 hPa

a. 1, 2, 3 and 4

b. No statements are correct

c. 1, 3 and 4

d. 2 only

d. 2 only

A moving mass of air possesses kinetic energy. An object placed in the path of such a moving mass of air will be subject to which of the following:

a. Dynamic pressure

b. Static Pressure

c. Static pressure and dynamic pressure

d. Dynamic pressure minus static pressure

c .Static pressure and dynamic pressure

Dynamic pressure is:

a. The total pressure at a point where a moving airflow is brought completely to rest

b. The amount by which the pressure rises at a point where a moving airflow is brought completely to rest

c. The pressure due to the mass of air pressing down on the air beneath

d. The pressure change caused by heating when a moving airflow is brought completely to rest

b. The amount by which the pressure rises at a point where a moving airflow is brought completely to rest

Dynamic pressure is equal to:

a. Density times speed squared

b. Half the density times the indicated airspeed squared

c. Half the true airspeed times the density squared

d. Half the density times the true airspeed squared

d. Half the density times the true airspeed squared

A tube facing into an airflow will experience a pressure in the tube equal to:

a. Static pressure

b. Dynamic pressure

c. Static pressure plus dynamic pressure

d. The difference between total pressure and static pressure

c. Static pressure plus dynamic pressure

A static pressure vent must be positioned:

a. On a part of the aircraft structure where the airflow is undisturbed, in a surface at right angles to the airflow direction

b. On a part of the structure where the airflow is undisturbed, in a surface parallel to the airflow direction

c. At the stagnation point

d. At the point on the surface where the airflow reaches the highest speed

b. On a part of the structure where the airflow is undisturbed, in a surface parallel to the airflow direction

The inputs to an Air Speed Indicator are from:

a. A static source

b. Pitot pressure

c. A pitot and a static source

d. Pitot, static and density

c. A pitot and a static source

The deflection of the pointer of the Air Speed Indicator is proportional to:

a. Dynamic pressure

b. Static pressure

c. The difference between static and dynamic pressure

d. Static pressure plus dynamic pressure

a. Dynamic pressure

The speed of sound:

a. Is dependent upon the True Air Speed and the Mach number of the aircraft

b. Is inversely proportional to the absolute temperature

c. Is proportional to the square root of the absolute temperature of the air

d. Is directly proportional to the True Air Speed of the aircraft

c. Is proportional to the square root of the absolute temperature of the air

Calibration of the Air Speed Indicator is based upon the density: a. At the altitude at which the aircraft is flying

b. At sea level ICAO International Standard Atmosphere temperature c. At sea level

d. At sea level ICAO International Standard Atmosphere +15°C temperature

b. At sea level ICAO International Standard Atmosphere temperature