Volcanic Ash Clouds -Cont.

AVIATION WEATHER

CHAPTER FIVE

Airspeed indications may fluctuate greatly or appear unusually high or low due to volcanic

dust blocking the pitot-static system. Establish the proper pitch and power settings required by

the Dash One or the NATOPS Flight Manual for flying with an unreliable airspeed indicator.

An acrid odor similar to electrical smoke may be present.

A rise in oil temperature could indicate dust-plugged oil cooler(s).

Torching (flames) from the engine tailpipe(s) may occur.

Volcanic ash/dust may be blown into the cockpit through the aircraft air conditioning

system.

Windshields become severely pitted that results in translucence. In addition, the abrasive

cloud particles will sandblast the aircraft's leading edges.

7. St. Elmo's fire and static discharges around the windshield are often visible at night. A

bright orange glow in engine inlets frequently occurs.

At night or in dark clouds, landing lights cast dark distinct shadows in ash clouds (unlike

the fuzzy, indistinct shadows cast against moisture clouds).

Multiple engine malfunctions such as power surges, loss of thrust, high EGT, or

compressor stalls. These result from ash buildup and blockage of the high-pressure turbine guide

vanes and high-pressure turbine cooling ports.

10. More than one or all engines may flameout, since all engines are exposed to the same ash

cloud.

If you encounter volcanic ash in flight, the best procedure is to perform a 180 turn immediately

and leave the area. Additionally, consider a reduction in altitude, as hot ash has most likely

ascended in convective currents before forming the cloud. Reduce thrust to the minimum

practical and monitor your engine instruments for indications of a possible flameout. If engines

flameout, continue attempting restart procedures, as exiting the ash cloud may improve the

probability of light off. Declare an in-flight emergency as soon as practicable, and land at the

nearest suitable airfield. Transmit PIREPs to military weather stations to report the location of

the volcanic ash cloud (to warn other aircrews). As soon as safely possible, record the altitude,

location, duration of exposure, and any related malfunctions observed, since special aircraft

cleanup procedures are required after flight through volcanic ash.

Weather Hazards of Turbulence, Icing, Ceilings, Visibility, and Ash Clouds

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