AIM Text
- Volcanic 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 SO2 is of significant importance. Although SO2 is colorless, its presence in the atmosphere should be suspected when a sulphur-like or rotten egg odor is present throughout the cabin.
- 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.
- Pilots should submit PIREPs regarding volcanic activity using the Volcanic Activity Reporting (VAR) form as illustrated in Appendix 2. If a VAR form is not immediately available, relay enough information to identify the position and type of volcanic activity.
- Pilots should verbally transmit the data required in items 1 through 8 of the VAR as soon as possible. The data required in items 9 through 16 of the VAR should be relayed after landing if possible.
Source: FAA Aeronautical Information Manual · current edition · paragraph 7-1-25.
The short answer
This AIM section is FAA advisory guidance encouraging pilots to file PIREPs on volcanic ash activity. It explains the hazard—at least two B747s lost all four engines after ash encounters—notes that volcanic eruptions are the only significant source of sulphur dioxide (SO2) at jet-cruising altitudes, and directs pilots to use the Volcanic Activity Reporting (VAR) form in Appendix 2.
Research Notes
Common Questions
How dangerous is flying into a volcanic ash cloud?
How can I tell if sulphur dioxide is present in the cabin?
Per the AIM, although SO2 is colorless, its presence should be suspected when a sulphur-like or rotten egg odor is present throughout the cabin. Volcanic eruptions are the only significant source of large quantities of SO2 gas at jet-cruising altitudes.
How do I report a volcanic eruption I observe in flight?
The AIM directs pilots to submit a PIREP using the Volcanic Activity Reporting (VAR) form in Appendix 2. Verbally transmit items 1 through 8 as soon as possible; items 9 through 16 should be relayed after landing if possible. If no VAR form is available, relay enough to identify the position and type of activity.