What is wind shear and why is it dangerous?

7-1-25. PIREPs Relating to Volcanic Ash Activity
a. V olcanic eruptions which send ash into the upper atmosphere occur somewhere around the world several
times each year. Flying into a volcanic ash cloud can be extremely dangerous. At least two B747s have lost all
power in all four engines after such an encounter. Regardless of the type aircraft, some damage is almost certain
to ensue after an encounter with a volcanic ash cloud. Additionally, studies have shown that volcanic eruptions
are the only significant source of large quantities of sulphur dioxide (SO2) gas at jet-cruising altitudes. Therefore,
the detection and subsequent reporting of SO 2 is of significant importance. Although SO 2 is colorless, its
presence in the atmosphere should be suspected when a sulphur-like or rotten egg odor is present throughout the
cabin.
b. While some volcanoes in the U.S. are monitored, many in remote areas are not. These unmonitored
volcanoes may erupt without prior warning to the aviation community. A pilot observing a volcanic eruption who
has not had previous notification of it may be the only witness to the eruption. Pilots are strongly encouraged
to transmit a PIREP regarding volcanic eruptions and any observed volcanic ash clouds or detection of sulphur
dioxide (SO2) gas associated with volcanic activity.
Meteorology 7-1-61

AIM 2/20/25
c. Pilots should submit PIREPs regarding volcanic activity using the V olcanic Activity Reporting (V AR) form
as illustrated in Appendix 2. If a V AR form is not immediately available, relay enough information to identify
the position and type of volcanic activity.
d. Pilots should verbally transmit the data required in items 1 through 8 of the V AR as soon as possible. The
data required in items 9 through 16 of the V AR should be relayed after landing if possible.