CFC Meteorological Briefing & Interpretation 4 — Questions and Answers
Question 1: Which type of structural ice is considered most dangerous to aircraft because it forms a hard, clear coating that is difficult to detect?
- Clear (glaze) ice (Correct answer)
- Rime ice
- Mixed ice
- Frost
Correct answer: Clear (glaze) ice
Clear (glaze) ice forms from large supercooled water droplets that spread before freezing, creating a smooth, transparent, and aerodynamically disruptive layer.
Question 2: Low-level wind shear (LLWS) is most hazardous during which phase of flight?
- Takeoff and landing below 2,000 ft AGL (Correct answer)
- Cruise above FL180
- Descent from high altitude
- Ground roll only
Correct answer: Takeoff and landing below 2,000 ft AGL
LLWS poses the greatest risk during takeoff and landing when aircraft are at low altitude with limited energy to recover from sudden lift changes.
Question 3: Which atmospheric condition is most associated with moderate-to-severe clear air turbulence (CAT)?
- Strong jet stream with significant wind shear at flight level (Correct answer)
- Surface-based temperature inversion at night
- Widespread stratiform precipitation
- Low pressure system at sea level
Correct answer: Strong jet stream with significant wind shear at flight level
CAT occurs most frequently near jet streams where strong vertical wind shear exists at high altitudes.
Question 4: A flight communicator receives a PIREP indicating 'LLWS -10KT 200FT FINAL RWY 28L'. This means the aircraft experienced:
- A 10-knot airspeed loss due to wind shear at 200 ft on the final approach (Correct answer)
- 10-knot tailwind component gain at 200 ft AGL
- Windshear with 10-knot crosswind below 200 ft
- Loss of 10 knots groundspeed at the threshold
Correct answer: A 10-knot airspeed loss due to wind shear at 200 ft on the final approach
A negative LLWS value indicates an airspeed decrease (headwind loss or tailwind gain) — a critical hazard on final approach.
Question 5: Structural icing is most likely to occur at temperatures between:
- 0°C and -20°C (Correct answer)
- 0°C and +5°C
- -20°C and -40°C
- -40°C and -60°C
Correct answer: 0°C and -20°C
Supercooled liquid water droplets, needed for structural ice, exist most prevalently between 0°C and -20°C.
Question 6: Mountain wave turbulence is most severe:
- In the rotor zone below the wave crests downwind of the ridge (Correct answer)
- Directly above the mountain peak
- On the windward side of the mountain slope
- Above the tropopause downwind of the ridge
Correct answer: In the rotor zone below the wave crests downwind of the ridge
The rotor zone beneath mountain wave crests contains the most violent, unpredictable turbulence associated with mountain wave activity.
Question 7: A weather briefer issues a PIREP with 'IC INTMT SEV'. During a flight communicator relay, 'INTMT' means:
- Intermittent icing (Correct answer)
- International moderate icing
- Intensity moderate threshold
- Intensive icing measurement technique
Correct answer: Intermittent icing
INTMT is the PIREP abbreviation for intermittent — the severe icing occurs periodically rather than continuously.
CFC Meteorological Briefing & Interpretation 4
Which type of structural ice is considered most dangerous to aircraft because it forms a hard, clear coating that is difficult to detect?