FAA Airline Transport Pilot (ATM)Meteorology and Weather ServicesMedium
A dispatcher receives a SIGMET advising of a volcanic ash cloud along the planned route at FL350. What is the recommended course of action for the flight?
- ADescend below the ash cloud and continue the flight at a lower altitude
- BReduce airspeed while transiting the ash to minimize engine damage
- CIncrease engine power to transit the ash cloud more quickly
- DReroute to avoid the ash cloud area completely
Show answer & explanationAnswer & explanation
Correct answer: D. Reroute to avoid the ash cloud area completely
There is no known safe concentration of volcanic ash for jet engine operation. FAA guidance and SIGMET procedures call for complete avoidance of known or forecast volcanic ash areas, as ash can cause engine flameout, abrasion damage, and loss of visibility through windscreens.
Why the other options are wrong
- A. Ash clouds can extend through a wide range of altitudes; descending does not guarantee avoidance.
- B. Reducing airspeed does not eliminate the engine damage risk from ash ingestion.
- C. Increasing power increases engine temperature, worsening ash ingestion damage.
Volcanic Ash SIGMET
A SIGMET issued for volcanic eruptions and ash clouds that pose severe hazards to aircraft, including engine damage and loss of visibility.
- No safe method exists to fly through ash — complete avoidance is required
- Ash can cause jet engine flameout and abrasion of windscreens/surfaces
- Volcanic ash SIGMETs remain in effect until updated or canceled by advisory centers
Memory trick: 'Ash Means Avoid' — there is no safe altitude through ash