Ice AccretionAviation Meteorology — DGCA CPL practice questions
Question 1 of 23
Hoar frost occurs on airframe in clear air when the temperature of airframe is
All 23 questions — Ice Accretion
Aviation Meteorology · DGCA CPL. The correct option is marked on each.
Q1. 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
Why: Hoar frost forms by deposition only when the surface is below the frost point.
Q2. 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✓
Why: Below 0°C icing is typically mixed, intermediate between rime and glaze.
Q3. Opaque Rime ice is
- A.Light porous✓
- B.Solid
- C.Mixture of porous and solid
Why: Rime is white, opaque, light and porous due to trapped air.
Q4. Rime is formed by freezing of ……… supercooled water droplets on airframe when aircraft is flying through clouds
- A.Small✓
- B.Large
- C.Medium
Why: Small droplets freeze instantly on impact, trapping air to give rime.
Q5. Glazed ice is formed by freezing of ……… supercooled water droplets on airframe when aircraft is flying through clouds
- A.Small
- B.Large✓
- C.Medium
Why: Large droplets spread before freezing, producing clear glaze ice.
Q6. The ……… ice poses serious aviation hazard
- A.Rime
- B.Hoar Frost
- C.Glazed✓
Why: Glaze/clear ice is hard, heavy and adheres strongly, the greatest hazard.
Q7. 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
Why: Below −20°C droplets increasingly freeze to ice crystals, reducing supercooled water.
Q8. Ci, Cs and CC clouds consist mostly of ice crystals. Icing hazard is therefore
- A.Maximum
- B.Medium
- C.Negligible✓
Why: High ice clouds hold almost no supercooled water, so icing is negligible.
Q9. As, NS consist of supercooled water drops and ice crystals in varying proportion ……… icing is possible
- A.Maximum
- B.Light or moderate✓
- C.Negligible
Why: Mixed-phase middle clouds give light to moderate icing.
Q10. In AC clouds ……… icing is possible in mountainous areas
- A.Light
- B.Moderate
- C.Severe✓
Why: Orographic lift in mountains raises water content, giving severe icing in Ac.
Q11. 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✓
Why: Towering cumulus carry significant supercooled water to the −20°C level.
Q12. 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
Why: Below −20°C the cloud is largely glaciated, so severe icing is not significant.
Q13. 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
Why: Keyed teaching value for peak water concentration and ice formation is the −25°C level.
Q14. Carburetor icing occurs when air from intake passes through a ventury (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
Why: Venturi cooling and fuel vaporisation cause serious carb icing across roughly +30°C to −10°C.
Q15. ……… 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✓
Why: Deposition of vapour to feathery crystals in clear moist air is hoar frost.
Q16. ……… 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
Why: Small-droplet freezing at these colder temperatures gives rime.
Q17. 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 and clear ice
- C.Mixture of rime and clear ice✓
Why: A wide spectrum of drop sizes yields a mixture of rime and clear ice.
Q18. ……… occurs in AS, NS, AC and towering CU or CB between 0°C and −20°C, in warm front below 0°C, if the aircraft has rapidly descended from a colder region
- A.Glazed
- B.Rime
- C.Mixture of Rime and Clear ice✓
Why: Mixed drop sizes in these clouds/warm-front descent produce a mixture of rime and clear ice.
Q19. When fog freezes on parked aircraft it produces ………
- A.Hoar Frost
- B.Rime✓
- C.Clear ice
Why: Supercooled fog droplets freezing on a parked airframe deposit rime.
Q20. Icing ……… the stalling speed appreciably
- A.Decreases
- B.Increases✓
- C.Does not increase/decrease
Why: Ice disrupts airflow and adds weight, raising the stalling speed.
Q21. CI, CS and CC clouds consist mostly ice crystals. Icing hazard is therefore
- A.Maximum
- B.Medium
- C.Negligible✓
Why: Ice-crystal high clouds carry no supercooled water, so icing is negligible.
Q22. 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
Why: Serious carburettor icing occurs across roughly +30°C to −10°C.
Q23. ……… occurs in AS, NS, AC 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.Rime
- C.Mixture of Rime and Clear ice✓
Why: Fixed OCR: 'SC'→'AC', added minus in '−20°C', option 'Fume'→'Rime'; mixed ice is the keyed answer.