Some aircraft manufacturers have published general guidance applicable to their fleets, and ALPA expects others to do so in the near future. This material is general and expands on that which ALPA has released earlier this week. These general guidelines, for both airborne and ground operations are shown below, and in all cases, flight crews should refer to their company’s operating manuals and follow published procedures. Remember, as Pilot In Command, you are the final authority as to the SAFE operation of your aircraft. Use all available information and exercise your judgment and authority.

1. Avoidance or immediate escape remains the safest course of action:

• Review all available information about volcanic events and known ash sightings that could affect a particular route. Update information during flight when possible.

• Remain upwind of volcanic ash and dust.

• Remember that airborne weather radar is ineffective in identifying ash.

• Identify alternate and/or escape routes to avoid/exit airspace containing volcanic ash. A 180-degree descending turn is recommended for inadvertent encounter. Climbing out of the ash could result in increased engine debris buildup leading to damage or flameout.

2. Be alert for signs of inadvertent ash-cloud penetration:

• A smoky or acrid odor like electrical smoke, burned dust, or sulfur. Ensure that any electrical smell is not due to actual electrical malfunctions.

• Haze or dust inside the cabin.

• Engine surging, torching from the tailpipe, or flameouts. Engine temperatures can change unexpectedly, and a white glow can appear at the engine inlets.

• If volcanic ash fouls the pitot tube, the indicated airspeed can decrease or fluctuate erratically.

• Cabin pressure changes, including loss of cabin pressurization.

• Static discharges, similar to St. Elmo’s fire, or glow outside of the windshield at wing leading edges or engine inlets.

3. If ash penetration or contamination is suspected:

• Refer to the Volcanic Ash non-normal guidance in the quick reference material.

• Consider use of flight-deck oxygen at the 100 percent setting and manual deployment of the passenger oxygen system.

• Disengage autothrottle(s).

• If conditions allow, reduce thrust to idle immediately. By reducing thrust, engines may suffer less buildup of molten debris on turbine blades and hot-section components. Idle thrust allows engines to continue producing electrical power, bleed air for pressurization, and hydraulic power for airplane control.

• Turn on continuous ignition, if available.

• If an engine flames out or stalls, attempt to restart. During restart, the engines may take longer than normal to reach idle thrust due to the combined effects of high altitude and volcanic ash ingestion. Flight crews should remember that the airplane may be out of the airstart envelope if the encounter occurs during cruise.

• Turn on engine and wing anti-ice devices, and all air conditioning packs. These actions improve the engine stall margin by increasing the flow of bleed air.

• Start the Auxiliary Power Unit (APU), if available. Flight crews should remember that multiple APU start attempts can shorten battery life.

• Monitor engine Exhaust Gas Temperature (EGT). Because of potential engine debris buildup, the EGT can climb excessively. The flight crew should prevent EGT exceedances. Shut down the engine and restart it if the EGT is approaching limits similar to a hung start.

• Monitor airspeed and pitch attitude. Watch for abnormal indications from pitot static system indicators. If necessary, follow the non-normal checklist for flight with unreliable airspeed.

4. Ground Operations:

• Ensure ash is removed prior to flight.

• Ensure any material installed to protect against ash is removed prior to flight.

• Use caution for ash-contaminated pavement during ground operations.

ALPA will continue to maintain close contact with manufacturers and regulators. Our members are encouraged to check the website frequently for any updates. We anticipate continued interest, by both legislators and scientists, in the study of volcanic ash, its effect on aircraft, and ways to predict airborne hazards. ALPA will remain engaged in these discussions with the goal of developing the most accurate information possible for flight crew use.

See previous updates: Volcanic Ash Update II, 4/21 | Volcanic Ash Update, 4/19

Air Line Pilots Association, Int’l
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