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Flight Operations Briefing Notes

Operating Environment Volcanic Ash Awareness

Flight Operations Briefing Notes Operating Environment Volcanic Ash Awareness


Flying through an ash cloud should be avoided by all means due to the extreme hazard for the aircraft. Experience has shown that damage can occur to aircraft surfaces, windshields and powerplants. Aircraftventilation, hydraulic, electronic and air data systems, can also be contaminated. Partial or total engine power loss events caused by volcanic ash ingestion, while not frequent, are major safety concerns. Simultaneous power loss in all engines has occurred, where the crew succeeded in restarting the engines, after application of operational procedures. As weather radar is not effective in detectingvolcanic ash clouds, crews must be informed by other means of the potential or effective presence of ash clouds on air routes. The aim of this Flight Operational Briefing Note is to provide information about volcanic ash effects on aircraft, and operational guidelines, in order to help preventing a volcanic ash cloud encounter.


Background Information

II.1 Statistical Data
The Pacific regionrepresents one of the biggest concentration of volcanoes in the world, with over 100 active volcanoes (See Figure 1). Active volcanoes are capable of sending volcanic ash up to altitudes greater than FL300 after explosive eruptions. Encounters affecting aircraft performance have occurred 2 400 NM from the ash source and up to 72 hours after an eruption.

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Flight OperationsBriefing Notes

Operating Environment Volcanic Ash Awareness

Figure 1 Active volcanoes in Pacific area Over 80 aircraft have reported to have flown into volcanic ash cloud between 1980 and 2000, with consequences ranging from increased wear of engines to simultaneous power loss in all engines. Alert messages (volcanic ash SIGMET) are issued by a Meteorological Watch Office (MWO) for its area ofresponsibility. Nine Volcanic Ash Advisory Centers (VAAC) have been designated by international organizations to provide an expert advice to MWO regarding the location and expected movement of volcanic ash clouds (see Figure 2).

(Credit: Alaska Aviation Weather Unit )

Figure 2 Volcanic Ash Advisory Centers area of responsibility

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Flight Operations Briefing Notes

OperatingEnvironment Volcanic Ash Awareness

II.2 Volcanic Ash Effects on Aircraft Components Abrasion
Volcanic ash are highly abrasive particles that may damage aircraft components, particularly forward facing surface of external parts and engine components. They are made of sharp rock fragments that will easily erode plastic, metal and even glass pieces. In service events show that aircraft maysuffer from extensive damage after volcanic ash encounter. In some cases, all the following parts were removed and replaced, after they were sand blasted: • • • • • • Windshields Forward cabin windows Navigation and landing lights cover Wing, stabilizer and fin leading edges Engine nose cowls and thrust reversers All pitot and static probes.

Engine Performance Deterioration
Ingestion of volcanicash by engines may cause serious deterioration of engine performance due to erosion of moving parts and/or partial or complete blocking of fuel nozzles. Volcanic ash contains particles, whose melting point is below engine internal temperature. In-flight, these particles will immediately melt if they go through an engine. Going through the turbine, the melted materials are rapidly cooled down, stickon the turbine vanes, and disturb the flow of high-pressure combustion gases. This disorder of the flow may stall the engine, in worst cases.

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Flight Operations Briefing Notes

Operating Environment Volcanic Ash Awareness

Abrasive particles can erode compressor blades edges, reducing compressor performance

Glass particles will melt in the combustion chamber, if high...
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