JPATS Weather - NETC

JPATS AVIATION WEATHER BOOKLET
ash cloud. Expect minor eye irritation if odors become noticeable (i.e., eyes watering). Remove
contact lenses if this occurs. Consider using oxygen when odors or eye irritation occurs.
If volcanic activity is reported, the planned flight should remain at least 20 NM from the area
and, if possible, stay on the upwind side of the volcano even when flying outside of the 20 NM
limitation. Volcanic ash clouds may extend downwind for several hundred miles and thousands
of feet in altitude. Volcanic ash can cause rapid erosion and damage to the internal components
of engines with loss of thrust within 50 seconds.
Since airborne radar cannot detect volcanic ash clouds, weather forecasts are occasionally wrong,
and ash clouds may be hidden by other clouds, inadvertent flight through an ash cloud may
occur. It may be difficult to determine if you are in an ash cloud when flying through other
clouds or at night. The following conditions may indicate you have inadvertently flown into an
ash cloud:
1. 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.
2. An acrid odor similar to electrical smoke may be present.
3. A rise in oil temperature could indicate dust-plugged oil cooler(s).
4. Torching (flames) from the engine tailpipe(s) may occur.
5. Volcanic ash/dust may be blown into the cockpit through the aircraft air conditioning
system.
6. Windshields become pitted so severely that they are translucent. In addition, the abrasive
cloud particles will sandblast the aircraft’s leading edges.
7. At night, St. Elmo’s fire and static discharges around the windshield are often visible. A
bright orange glow in engine inlets frequently occurs.
8. At night, or in dark clouds, landing lights cast dark distinct shadows in ash clouds (unlike
the fuzzy, indistinct shadows that are cast against moisture clouds).
9. 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 degree turn
immediately and leave the area. Consider also 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.
Version 3.2/Dec 08 4-25