During a flight, a pilot experiences a sudden, significant increase in headwind, followed almost immediately by a sharp decrease in headwind and an unexpected downdraft. This sequence of events is most characteristic of encountering a:
- ACold front passage
- BMicroburst
- CTurbulence from mountain waves
- DTemperature inversion
Show answer & explanationAnswer & explanation
Correct answer: B. Microburst
A microburst is a localized column of sinking air (downdraft) within a thunderstorm or rain shower, which spreads out upon reaching the ground, creating strong divergent winds. A common sequence for an aircraft flying through a microburst is an initial strong headwind (as it encounters the outflow on the leading edge), followed by a sudden calm or tailwind (as it enters the core downdraft), and then often a strong tailwind and downdraft on the other side. This scenario perfectly describes the often-fatal 'performance-increasing, then performance-decreasing' wind shear associated with a microburst.
Why the other options are wrong
- A. A cold front passage would bring a sustained wind shift and temperature drop but not this specific, rapid sequence of headwind increase, then decrease, and downdraft in such a localized manner.
- C. Mountain wave turbulence can be severe, but typically doesn't involve this specific headwind/tailwind shift in such a localized, rapid sequence associated with a downdraft.
- D. A temperature inversion can cause stable air or wind shear, but not this specific, violent sequence of wind shifts and downdraft.
Microburst
A localized column of sinking air within a thunderstorm or rain shower that produces an outward burst of damaging winds on or very near the ground.
- Extremely dangerous due to severe, rapid wind shear and downdrafts.
- Can produce wind speed differentials of 100 knots or more.
- Often associated with virga, dust rings, or heavy rain shafts.
Memory trick: Microburst's a sudden dive, headwind then tail, hard to survive.