Flying in Volcanic Fumes Brings Extra Safety Concerns

posted in: May 1993 | 0

The safety of helicopter operations in Hawai’i has come under increasing scrutiny recently, largely in the wake of two serious accidents. Last November, a helicopter carrying a Paramount Pictures film crew fell to the floor of Pu’u O’o vent. All aboard survived, but rescue efforts were difficult and dangerous. Then, in January; a tour helicopter dropped into the ocean off Kamoamoa, where lava flows into the sea. The pilot was rescued; four Taiwanese passengers drowned.

The causes of the accidents are under investigation. But possible contributing factors have been the subject of some speculation.

In the case of the Paramount Pictures crash, attention has focused on the corrosive effects of certain gases in the fumes emitted by the volcano. The same fumes may have contributed to the failure of the helicopter at Kamoamoa as well. In that case, the Federal Aviation Administration has already determined that the helicopter operator, Kainoa Aviation, was in violation of FAA rules. The operator had what is known as a Part 91 certificate, which restricts flights to within 25 miles of their point of origin. When the helicopter went down, it was more than 25 miles from Hilo Airport, where the flight originated. According to the FAA, it has issued an emergency six-month revocation of the license of the pilot, Robert Ervin. The Paramount pilot has been similarly disciplined.

Laze and Lemon juice

Flying in and around an active volcano does pose safety problems that helicopter operators elsewhere may not face. These were described to the FAA by Thomas L. Wright, then scientist in charge of the U.S. Geological Service’s Hawaiian Volcano Observatory.

In a letter dated January 2, 1991, Wright noted that “volcanic gases are continuously released from three sources at Kilauea” – all of them popular helicopter destinations: the summit caldera (Halema’uma’u), Pu’u O’o, and the Kupaianaha lava pond. The Kilauea fumes contain sulfuric acid at concentrations as high as 35 parts per million up to several hundred meters from the erupting vents, Wright said. For this reason, “Kilauea fume may be of concern to helicopter pilots who fly at or below 2,000 feet above ground level… Sulfuric acid droplets in the fume could potentially result in turbine wheel embrittlement, caused by frequent and prolonged exposure of metals and machine alloys to high levels of acidic gases. A turbine engine failure of a Hughes 500 helicopter… at the Kilauea Military Camp in 1983 may have been caused by such exposure to volcanic gases.”

Wright went on to describe “laze” – short for lava haze. Laze is the plume that results, he said, “when lava flows into the ocean and vaporizes seawater.” He continued:

“On some occasions, the laze particles in plume clouds generated by vaporizing seawater reach a large enough size to actually ‘rain’ from the cloud. Analyses of rain from such clouds show that the droplets are seawater brines concentrated by a factor of 2 to 2.5 times due to boiling….

“The striking feature of laze is its exceedingly acidic character, despite an overall composition relatively similar to that of seawater. Measurements of the pH of rain droplets and of condensate from the plume cloud in the vicinity of where lavas flow into the sea gives values in the range of 1.5 to 2.0. These pH values indicate that the acidity of laze is approximately three to four times that of concentrated lemon juice.”

Hazards on the Ground

Wright’s letter is surely one of the most comprehensive compilations to date of the dangers of flying in volcanic areas. He goes on to describe further hazards:

“Measurements of plume cloud gases in the same vicinity have identified hydrogen chloride gas at concentrations up to 10 parts per million. The permissible OSHA exposure limit for HCl is a ceiling of 5 parts per million parts of air…. Within a closed helicopter, there is likely to be little effect on passengers or pilot unless the pilot hovers for several minutes directly downwind of the plume. However, HCl is a highly reactive gas, and contact with most metals corrodes them severely and forms flammable hydrogen gas. …Therefore, as with the vent fume described earlier, there is a definite danger to the aircraft from repeated exposure to the acid plume.

“Tour helicopters commonly hover directly over the active lava field at altitudes that would present a hazard to pilot, passengers, and helicopter if the pilot should lose control of the aircraft due to engine failure or loss of anti-torque (tail-rotor) control, and was unable to maintain altitude.”

USGS staff are put at risk by low-flying helicopters, Wright noted. In an earlier memo, dated October 29, 1987, Wright pointed out that helicopters can drown out the noise of lava moving or rocks cracking – vital warning signs for geologists working on the ground. The helicopters can blow fumes toward the geologists, causing breathing difficulties and temporary blindness. They can make impossible for the geologists to converse or to hear diagnostic instruments. The geologists can themselves become attractions to helicopter pilots. The helicopters can cause glass fragments and fine strands of “Pele’s hair” to come loose and to lodge in the eyes of people on the ground, “resulting in temporary blindness.”

Volume 3, Number 11 May 1993

Leave a Reply

Your email address will not be published. Required fields are marked *