USGS/Cascades Volcano Observatory, Vancouver, Washington
REPORT:
The 1991 Pinatubo Eruptions and Their Effects on Aircraft Operations
--
Thomas J. Casadevall, Perla J. Delos Reyes, and David J. Schneider, 1996,
The 1991 Pinatubo Eruptions and Their Effects on Aircraft Operations:
IN:
Christopher G. Newhall and
Raymundo S. Punongbayan (eds.), 1996,
Fire and Mud -
Eruptions and Lahars of Mount Pinatubo, Philippines:
Philippine Institute of Volcanology and Seismology and the University of
Washington Press, 1126p.
Abstract
The explosive eruptions of Mount Pinatubo in June 1991 injected enormous
clouds of volcanic ash and acid gases into the stratosphere to altitudes in
excess of 100,000 feet. The largest ash cloud, from the June 15 eruption,
was carried by upper level winds to the west and circled the globe in 22
days. The June 15 cloud spread laterally to cover a broad equatorial band
from about 10degreesS to 20degreesN latitude and contaminated
some of the world's
busiest air traffic corridors. Sixteen damaging encounters were reported
between jet aircraft and the drifting ash clouds from the June 12 and 15,
1991, eruptions. Three encounters occurred within 200 kilometers from the
volcano with ash clouds less than 3 hours old. Twelve encounters occurred
over Southeast Asia at distances of 720 to 1,740 kilometers west from the
volcano when the ash cloud was between 12 and 24 hours old. Encounters with
the Pinatubo ash cloud caused in-flight loss of power to one engine on each
of two different aircraft. A total of 10 engines were damaged and replaced,
including all four engines on a single jumbo jet. Following the 1991
eruptions, longer term damage to aircraft and engines related to
volcanogenic SO2 gas has been documented including crazing of acrylic
airplane windows, premature fading of polyurethane paint on jetliners, and
accumulation of sulfate deposits in engines.
Ash fall in the Philippines damaged aircraft on the ground and caused seven
airports to close. Restoration of airport operations presented unique
challenges, which were successfully met by officials at Manila
International Airport and at Cubi Point Naval Air Station, Subic Bay.
Lessons learned in these clean-up operations have broad applicability
worldwide.
Between April 12 and June 9, 1991, Philippine aviation authorities issued
at least eight aeronautical information notices about the preeruption
restless state of Mount Pinatubo. The large number of aircraft affected by
the Pinatubo ash clouds indicates that this information either did not
reach appropriate officials or that the pilots, air traffic controllers,
and flight dispatchers who received this information were not sufficiently
educated about the volcanic ash hazard to know what to do with the
information.
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05/03/00, Lyn Topinka