Mount St. Helens: An Historic Eruption into the National Airspace System
The eruption of Hawaii’s Kilauea in 2018 and the related temporary flight restrictions around the site served as a reminder of how volcanoes periodically disrupt aviation. But that volcanic activity on a relatively isolated Pacific island paled in comparison to the mother of all eruptions into the national airspace system.
Forty-two years ago today, Mount St. Helens exploded into geological and aviation history. The event began with a 5.1-magnitude earthquake, which in turn spawned the largest recorded debris avalanche in history, a sideways eruption that reached 19 miles away and 15 miles high, and volcanic mudflows that destroyed homes and bridges. A more traditional eruption burst straight into the sky about an hour later, followed by hot ash, pumice and gas flows for several hours. Fifty-seven people died.
From a terrestrial perspective, the eruptions changed the landscape. It knocked more than 1,300 feet off the top of Mount St. Helens, wiped out 230 square miles of forest, and lowered the channel depth and carrying capacity of two rivers. From an aerial perspective, the disaster awakened the aviation world to the risks that volcanoes pose to aircraft — and the FAA to the challenge of managing airspace around an explosive natural attraction.
‘It’s like a dogfight up there’
Although currently ranked No. 2 behind Kilauea among the most dangerous U.S. volcanoes, Mount St. Helens had been dormant for more than a century before it came to life in 1980. The first rumblings of trouble appeared March 16 in the form of small earthquakes, followed by a 4.2-magnitude temblor four days later. More than 10,000 quakes occurred through May 17.
Steam explosions poked a 250-foot hole in the mountaintop March 27, and the crater grew to 1,300 feet in diameter within days. Two cracks, one of them reported to the U.S. Geological Survey by aerial photographer Wildey (Bud) Kimball, ran the length of the summit. Next came a noticeable bulge, an indication of molten rock rising inside the mountain. It grew horizontally up to 6 1/2 feet per day.
As Mount St. Helens awoke from its slumber in this “classic pre-eruption pattern,” curious onlookers joined the geologists and journalists flocking to the area. Officials alarmed by the frenzy, which included sightseeing flyovers, warned people who didn’t need to be there to stay away. The government closed forest areas and roads as deterrence.
The U.S. Forest Service deployed pilots to circle the mountain in shifts in four twin-engine aircraft, according to a July 1980 story in Flying Magazine. To try to manage the surge in air traffic, they asked pilots to fly counterclockwise in 5- and 10-mile arcs under visual flight rules and monitored the vertical separation among the aircraft, keeping it at 500 feet.
At the request of the Forest Service, the FAA banned most flights near the mountain, but pilots routinely violated the ban. The agency tallied 109 breaches alone on April 3. A 1985 book about the disaster said some news outlets paid big money to pilots willing to flout the rules. Helicopters from two Seattle television stations reportedly landed on the summit.
On one Sunday, a forest official counted as many as 70 aircraft flying 500 feet apart in restricted airspace between 8,500 and 16,000 feet. “The frequencies were said to have sounded like Alvin and the Chipmunks,” the Mount St. Helens Institute recounted in an Instagram flashback. A pilot quoted in one news report said, “It’s like a dogfight up there.”
(Photo: Mount St. Helens Photos-Eight Mile High Group)
The FAA patrolled the restricted zone by air to identify unauthorized aircraft. Months after the eruption, United Press International reported that the agency suspended the licenses of 11 pilots, including one working for a Seattle TV station, for flying around the mountain while restrictions were in place. FAA inspectors investigated more than 50 alleged violations.
The FAA periodically adjusted the boundaries and altitudes of the temporary flight restrictions based on the changing circumstances and expert government advice. For instance, the radius of the restricted zone was initially 5 miles but was expanded to 10 miles. Seattle Center only allowed 10 aircraft at a time inside 10 miles when the restricted zone was 5 miles. The airspace outside the boundary remained congested, posing a challenge for air traffic controllers.
The FAA’s Airway Facilities Division established a discrete air-to-ground communications channel atop Larch Mountain near Olympia, Wash., well outside any eruption area. Seattle Center started using it in early May. In conjunction with federal, state and local officials, the FAA developed guidance for potential air evacuations and for avoiding ash clouds.
Heroes and scofflaws in the skies
The eruptions at Mount St. Helens settled for several days in late April and early May, but it was a brief interlude before the volcanic storm to come. Eleven days of small eruptions set the stage for the series of big ones that began at 8:32 a.m. on May 18.
Husband-and-wife geologists Keith and Dorothy Stoffel were circling the mountain in a chartered plane when the disaster started. With the aircraft at 11,000 feet and over the western part of the crater, the pilot tipped the wing to give the Stoffels a better view of history unfolding. They snapped pictures of “this landslide of unbelievable proportions.”
The Stoffels were just east of the summit when the mountain exploded. “From our viewpoint, the initial cloud appeared to mushroom laterally to the north and plunge down,” Keith Stoffel wrote in a paper for the Washington Department of Natural Resources. “Within seconds, the cloud had mushroomed enough to obscure our view. At about this time, the realization of the enormous size of the eruption hit us, and we focused our attention on getting out of there.”
The pilot dove to gain airspeed, reaching about 230 miles per hour. “Ash fall from the mushroom-shaped clouds was heavy,” Stoffel said. “Lightning bolts shooting through the clouds were tens of thousands of feet high. Soon, the ash cloud extended to elevations in excess of 50,000 feet.” The pilot landed in Portland, Ore., rather than heading back to Yakima, Wash.
By 8:45 a.m., the FAA heard about the eruption via pilot reports. The agency notified the National Weather Service of smoke and lightning in the cirrus clouds above the volcano. The NWS warned surrounding communities about flash flooding, the primary concern immediately after the unexpected lateral blast.
search-and-rescue efforts. (Photo: USGS)
The FAA supported the ensuing search-and-rescue operations. The agency sent a mobile air traffic control tower nicknamed “Moby Dick” to Kelso, Wash. Although mudflows on the Toutle River slowed the tower’s arrival, it was in place by 11 p.m. and handled 230 search flights the next day. Concerned about the mudflows, officials relocated search operations and the tower to Toledo, Wash., on May 20.
The FAA still had to contend with scofflaws in the sky, too, including daredevil pilots and the risk-taking geologists and journalists who hired them. “At no point did I ever consider the possibility of a secondary explosion which, on the scale of the first event, could easy have swatted all of the airplanes from the sky,” recalled Mike Ward, a charter pilot who took off after the eruption. “Like I later told friends, I was too stupid to be scared.”
Seattle Post-Intelligencer photographer Greg Haller earned “Picture of the Millennium” honors from the Associated Press for an aerial photo of Mount St. Helens in its eruptive glory. But the FAA hit pilot Salty Roark, who turned off his aircraft’s responder to avoid detection, with a $10,000 fine. The agency also lodged a complaint with the paper over the subsequent story.
Ashes everywhere!
Mount St. Helens erupted on and off for nine hours, all the while spewing 520 million tons of ash into the atmosphere. The ash spread as far as the central United States within hours, to some northeastern cities within two days and around the world within two weeks, creating challenges for the FAA, airports, airlines and pilots.
Undetectable by radar, volcanic ash is corrosive and abrasive enough to destroy navigational aids and aircraft engines, windshields and other parts. After Mount St. Helens erupted, these realities prompted airport closures in several Washington locations — Dayton, Deer Park, Grant County, Pullman, Ritzville, Spokane, Waterville and Yakima — as well as in Missoula, Mont., and Coeur d’Alene and Moscow, Idaho. The FAA suspended the license of a pilot who landed in Yakima.
Ash from subsequent eruptions on May 25 and June 12 interrupted operations at Portland International Airport.
“The big problem with the ash in eastern and central Washington is how to get rid of it from airport runways,” Jack Wichels, chief of the Northwest Region’s Airway Facilities Division, wrote to FAA headquarters. “Thus far, efforts at sweeping or blowing or plowing the ash from runways seems merely to get the ash airborne, and it eventually settles back on the runway.”
Grant County International Airport, a former U.S. Air Force Base then used as a jet training facility, is 120 miles from Mount St. Helens, but it accumulated 3–4 inches of ash. Wichels said the runway for instrument-rated aircraft landings had 50,000 cubic yards of ash. “Tail sections of 747s sticking out [of the hangars] caused major cleanup problems, and spring winds exacerbated problems,” the USGS added in a historical report.
After the eruption, the FAA took steps to protect its equipment. The actions included locking out all easily accessible standby engine generators; turning off non-essential blowers, fans and air-conditioning systems that drew outside air; and cleaning air filters regularly. “It’s no more difficult out there than it is in the Southern or Central regions, where they have to worry about hurricanes and tornadoes,” Wichels said of his team’s situation.
the crater several days after the eruption. (Photo: U.S. Air Force)
The seriousness of the threat that volcanic ash poses to aircraft wasn’t widely appreciated before Mount St. Helens erupted, but it quickly became evident. An Air West DC-9 traveling from San Francisco to Calgary, Canada, that ended up in the ash at 31,000 feet suffered damage to the windshield, the leading edge of the wings, the engine oil and compressor, and the air filters.
“The significant damage to that flight was an important part of the data we had to pass on to airlines,” an FAA official told The Washington Post. “There are many channels of communications. We wanted to hit them all. We hit them all. Our concerns were that we capture every aircraft in the system interested in flying, in addition to pilots coming to flight services to get their normal briefings.”
On June 6, the agency issued an advisory circular with maintenance and inspection recommendations for aircraft that were exposed to volcanic ash. The Command Center, air traffic facilities and flight service stations also updated pilots about the ash cloud’s location. Seattle-area commercial traffic was rerouted 200 miles away from normal flight paths.
‘Government at its uncelebrated best’
In the decades since Mount St. Helens exploded, the FAA has worked with the Forest Service, USGS and international counterparts to enhance volcano disaster preparation. Two other noteworthy incidents in the 1980s reinforced the need for such planning.
In 1982, a British Airways flight headed from Malaysia to Australia lost all four of its engines due to ashes that had drifted from Mount Galunggung in Iceland. The plane descended from 37,000 feet to 12,000 feet before regaining power. Seven years later, KLM Royal Dutch Airlines lost all four engines in a similar situation triggered by ash from Mount Redoubt in Alaska. The crew was able to restart all four engines and land safely in Anchorage.
(Photos: U.S. Forest Service, University of Washington)
To help prevent such incidents, the USGS now has five observatories to monitor volcanic activity and issue alerts. These include the Cascade Volcano Observatory in the Northwest and the Hawaiian Volcano Observatory that is providing ongoing updates about Kilauea. The USGS also specifically simulates the likely path of Mount St. Helens ash clouds for any given day, and it established a permanent regional office at Vancouver, Wash., after Mount St. Helens erupted. The Forest Service developed a Mount St. Helens response plan that outlines the agency’s coordination with the FAA.
The 1989 Mount Redoubt incident, meanwhile, prompted the FAA and NOAA to start tracking volcanic ash clouds and warning pilots via notices to airmen. Their joint system uses data from four NOAA satellites and human reports from U.S. military bases, USGS research stations worldwide and the Smithsonian Institution’s worldwide Scientific Event Alert Network (now the Global Volcanism Network).
Planning like that no doubt contributed to Post writer Haynes Johnson’s analysis in 1980: “What we’ve seen this last week — or have failed to see — in the extraordinary aftermath of the natural disaster in the West, is an example of the government performing splendidly, quietly, competently and efficiently,” he wrote. “The way the Federal Aviation Administration handled the threat to aircraft provides a case study of government at its uncelebrated best.”
This story originally appeared on the FAA’s internal website on May 18, 2018. It has been reprinted with permission.
