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1) Hoar frost occurs on airframe in clear air when the temperature of airframe is
a) below the frost point
b) frost point
c) just above the frost point
Explanation: Hoar frost forms on the airframe when its temperature is below the frost point, causing water vapor to deposit directly as ice crystals.
2) In clouds at temperatures below 0° C an aircraft may encounter icing of the type
a) only Glazed
b) only Rime
c) intermediate between these two
Explanation: In clouds below 0°C, an aircraft may encounter mixed icing, with both rime and glazed types depending on droplet size and temperature.
3) Opaque Rime ice is
a) Light porous
b) Solid
c) Mixture of porous and solid
Explanation: Rime ice is typically opaque and light due to trapped air within the ice, forming a porous structure.
4) Rime is formed by freezing of ……… supercooled water droplets on airframe when aircraft is flying through clouds
a) Small
b) Large
c) Medium
Explanation: Rime ice forms from small supercooled water droplets that freeze quickly on contact, trapping air and creating an opaque appearance.
5) Glazed ice is formed by freezing of ……… supercooled water droplets on airframe when aircraft is flying through clouds
a) small
b) Large
c) medium
Explanation: Glazed ice forms from large supercooled water droplets, which freeze more slowly, allowing the ice to spread and form a clear, dense layer.
6) The ……. ice poses serious aviation hazard
a) Rime
b) Hoar Frost
c) Glazed
Explanation: Glazed ice is dense and clear, posing a serious hazard due to its weight and potential to disrupt airflow over the aircraft surface.
7) Airframe icing occurs below 0°C. Its probability of occurrence decreases progressively below ­20 °C, as at lower temperatures the proportion of super­cooled water drops in a cloud
a) Increases
b) Decreases
c) Does not change
Explanation: The likelihood of icing decreases below -20°C as supercooled water drops are less likely to exist at these lower temperatures.
8) CI, CS and CC clouds consist mostly ice crystals. Icing hazard is therefore
a) Maximum
b) Medium
c) Negligible
Explanation: CI, CS, and CC clouds are primarily composed of ice crystals, which pose negligible icing risk compared to supercooled liquid droplets.
9) AS, NS consist of supercooled water drops and ice crystals in varying proportion…….. icing is possible.
a) Maximum
b) Light or moderate
c) Negligible
Explanation: AS and NS clouds contain supercooled droplets and ice crystals, creating a light to moderate icing risk.
10) In AC clouds ………….. icing is likely in mountainous areas
a) Severe
b) Light to moderate
c) Negligible
Explanation: In AC clouds, Severe icing can occur in mountainous areas due to the presence of supercooled droplets.
11) In TCU icing may range from light to severe type at least up to ………. level.
a) 40 °C level
b) 30 °C level
c) -20 °C level
Explanation: In TCU clouds, icing can be severe at altitudes up to the -20°C level due to high liquid water content.
12) In CB icing may range from light to severe type up to -20°C level. Below this temperature severe icing is
a) not significant
b) significant
c) maximum
Explanation: Severe icing in CB clouds is not significant below -20°C, as supercooled droplets are less common at colder temperatures.
13) Liquid water content is an important factor in icing. As the maximum water concentration is around ……, maximum ice formation in clouds may also be expected around that level.
a) 25° C level
b) 20° C level
c) -15° C level
Explanation: Maximum liquid water concentration is around -15°C, which is where maximum icing in clouds may occur.
14) Carburetor icing occurs when air from intake passes through a venturi (choke) and causes expansional cooling and vaporization of fuel. Serious icing can occur at extreme temperatures
a) 13 °C
b) 30°C to -10°C
c) 20 °C
Explanation: Carburetor icing can be severe between 30°C and -10°C due to expansional cooling and fuel vaporization.
15) ………… occurs in a moist cloudless air on an aircraft surface having temp. below 0° C, due to sublimation of water vapour onto feathery ice crystals.
a) Rime
b) Glazed
c) Hoar Frost
Explanation: Hoar frost forms in cloudless, moist air on cold surfaces below 0°C through sublimation, creating feathery ice crystals.
16) ………….. occurs in St, Sc, Ac, Cu, Ns at temperature ­10 to ­40° C and in Cb at temperature ­20 to ­40°C
a) Rime
b) Glazed
c) Hoar Frost
Explanation: Rime ice forms in these cloud types at these specific temperature ranges when supercooled water droplets freeze instantly on impact.
17) In clouds … occurs when a wide range of water drop sizes are present at temperatures between 0°C and ­40°C
a) Rime
b) Glazed
c) Mixture of rime and clear ice
Explanation: A mixture of rime and clear ice can form in clouds with a wide range of drop sizes and at temperatures between 0°C and -40°C.
18) ……… occurs in AS, NS, SC and towering CU or CB between 0° C and ­20° C, in warm front below 0° C, especially if the aircraft has rapidly descended from a colder region
a) Glazed
b) Fume
c) Mixture of Rime and Clear ice
Explanation: mixed ice can occur in these cloud types and conditions due to the presence of supercooled large droplets that spread before freezing.
19) When fog freezes on parked aircraft it produces...
a) Hoar Frost
b) Rime
c) Clear ice
Explanation: Hoar frost forms when fog or moisture freezes on a cold surface, creating a feathery ice layer.
20) Icing ………. the stalling speed appreciably
a) Decreases
b) Increases
c) Does not increase/decrease
Explanation: Icing increases the stalling speed due to the added weight and aerodynamic disruption, making the aircraft stall at a higher speed.

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