Volcanic ash hazards and avoidance
Volcanic ash is an in-flight hazard, not just a ground contaminant.
Damage:
- Aircraft surfaces and windshields.
- Contaminates heat and vent, hydraulic, and electronic systems.
- Powerplant failure is common. Turbine engines particularly susceptible. Simultaneous power loss in all engines has occurred.
- Piston aircraft less likely to lose power, but severe engine damage likely after encountering an ash cloud only a few hours old (FAA AWH 18.1.9).
- Ash normally very heavy: accumulation within wings and tail has adversely affected weight and balance.
Reach:
| Factor | Value |
|---|---|
| Height | Can rise above FL 600, drifts far downwind |
| Distance from source | Performance-affecting encounters at 2,400 NM |
| Time after eruption | Performance-affecting encounters up to 72 hours |
- "Old" ash still a considerable hazard.
- No reliable minimum acceptable concentration.
- ATS surveillance not effective in detecting ash.
Avoidance:
- Ash cloud visible: avoid entering.
- Worse in IMC or at night: no visual warning.
- Check PIREPs, SIGMETs, NOTAM, satellite imagery, ash cloud trajectory forecasts. Any indicating possible ash: avoid that airspace until confirmed safe.
Unexpected entry at night:
- St. Elmo's fire usually the telltale sign. Rapid onset of engine problems may come first instead.
- Exit cloud expeditiously.
- Follow engine handling instructions in the aircraft flight manual.
Trap: assuming ash will be seen coming: in IMC or at night no visual warning, ATS surveillance will not show it, first clue may be St. Elmo's fire or the engines.
References
- TC AIM AIR 2.6
- FAA AWH 18.1.9