FAA Aircraft Dispatcher (ADX)MeteorologyHard
A dispatcher receives a report of a volcanic eruption producing an ash cloud that may affect a planned route. Which statement about the SIGMET issued for this hazard is correct?
- AIt is only advisory and does not require rerouting consideration
- BIt is valid for 2 hours, the same as a convective SIGMET
- CIt is treated identically to an AIRMET Sierra for IFR conditions
- DIt is valid for 6 hours, longer than a standard non-convective SIGMET
Show answer & explanationAnswer & explanation
Correct answer: D. It is valid for 6 hours, longer than a standard non-convective SIGMET
SIGMETs for volcanic ash (and hurricanes) are valid for up to 6 hours, longer than the standard 4-hour validity period for other non-convective SIGMETs and the 2-hour validity of Convective SIGMETs. Volcanic ash poses a serious hazard to jet engines and must be treated as a significant flight-planning consideration, not merely advisory information.
Why the other options are wrong
- A. Volcanic ash can severely damage jet engines and must be actively avoided, not treated as merely advisory.
- B. Convective SIGMETs are valid for 2 hours, but volcanic ash SIGMETs have a longer 6-hour validity.
- C. AIRMET Sierra addresses IFR/mountain obscuration conditions, an entirely different hazard category than volcanic ash.
Volcanic Ash SIGMET
A SIGMET issued for volcanic eruptions producing ash clouds hazardous to aircraft, valid for up to 6 hours.
- Valid for 6 hours (vs. 4 hours for standard non-convective SIGMETs)
- Volcanic ash can cause jet engine flameout and severe airframe/windscreen damage
- Issued regardless of location, since ash can spread far from the eruption site
Memory trick: 'Volcanoes and hurricanes get extra time'—6 hours, not 4.