Volcanic Ash Advisory for 17 MAY 2010
ENGLISH PORTUGUÊS
On the flight to Sweden, in a moonless and cloudless sky at 0508 GMT on February 28, 2000, scientists onboard the DC-8 monitoring sensitive research instruments reported a sudden increase in measurements that indicated the presence of a volcanic ash cloud. The onboard sensor data is presented in figures below showing measurements of sulfur dioxide (SO2) concentration in parts per trillion by volume (pptv), and figure 7(b) showing aerosol data for the seven-minute encounter. This encounter was more than 200 mi north of the predicted maximum northerly extent of the plume and approximately 800 nmi from the volcano (fig. 6). The volcanic plume was about 35 hr old at this time.
No voo para Suécia, num céu sem Lua e sem nuvens às 05:08 GMT de 28 FEV 2000, cientistas a bordo da [aeronave] DC-8 monitorando instrumentos de pesquisa de sensibilidade relataram um súbito aumento nas medidas que indicavam a presença de uma nuvem de cinzas vulcânicas. Os dados do sensor a bordo apresentados nas imagens abaixo mostraram medições de concentração de DIÓXIDO DE ENXOFRE (SO2) em partes por trilhão por volume (pptv), e ainda os dados de aerossóis para SETE MINUTOS de encontro. Este encontro foi a mais de 200 milhas ao norte da prevista máxima extensão da contaminação e aproximadamente 800 milhas náuticas do vulcão. A plumagem vulcânica estava cerca de 35 horas envelhecida nesta hora [do encontro].
The flight crew noted no change in cockpit readings, no St. Elmo’s fire, no odor or smoke, and no change in engine instruments. They did notice that no stars were visible, but this is typical of flight through high cirrus clouds.
After seven minutes the crew noticed that the stars had reappeared, and at about this time the scientists reported that the research instrument readings had returned to normal. There was still no change in engine or airplane instrument readings. The DC-8 crew made an airborne encounter report to the appropriate oceanic control agency. This report is documented in VAAC #6 280751.
In this ash encounter, the crew verified that there was no change in engine instruments. As such, they did not reduce engine power nor attempt to exit the cloud. This was because of the complete lack of indication of a volcanic plume, other than the sensitive scientific instruments, and because the crew was not aware of the recommendation to reduce power to idle. In addition, over the polar ocean at night, using visual flight rules in a “Non-Radar Environment,” it was probably not prudent to reduce power and descend even if the crew had been aware of the recommended procedure.
A tripulação do voo não notou mudança nas leituras na cockpit, nenhum fogo-de-santelmo, nenhum cheiro ou fumaça, e nenhuma mudança nos instrumentos de motor. Eles notaram que nenhuma estrela estava visível, mas isto é típico de voo através de nuvens Cirrus altas.
Após SETE MINUTOS a tripulação notou que as estrelas tinham reaparecido, e a cerda desta hora os cientistas relataram que as leituras de instrumentos de pesquisa tinham retornado ao normal. Não houve ainda mudança nas leituras de instrumentos do avião ou de motor. A tripulação do DC-8 fez um relatório do encontro aéreo para a apropriada Agência de Controle Oceânico. Este relatório está documentado na VAAC #280751.
Neste encontro com cinza, a tripulação verificou que não houve mudança nos instrumentos de motor. De modo que, eles NÃO REDUZIRAM a potência de motor nem tentaram sair da nuvem. Isto foi por causa da completa falta de indicação de contaminação vulcânica, alternado com instrumentos científicos de sensíveis e porque a tripulação não estava ciente da recomendação para reduzir a potência para marcha-lenta. Em adição, à noite sobre o oceano polar, usando regras de voo visual [VFR] num "Ambiente Não-Radar", NÃO era provavelmente prudente reduzir a potência e descer mesmo se a tripulação tivesse estado ciente do procedimento recomendado.
Volcanic eruptions can eject huge quantities of solid and gaseous material into the atmosphere.
Large, solid material precipitates from the atmosphere near the volcano but small particles (< 15 microns) and gaseous material can be transported to high altitudes and distributed over large distances by atmospheric phenomena.
Volcanic ash particles in the 1–10 micron size range can be found more than 1000 mi from avolcano.
These ash particles typically have a melting point of approximately 1832 °F (1000 °C). Sulfur compounds and other aerosols can be found in ash clouds. At high altitudes, ice may form on ash particles, and electrostatic charges may also be present on ash particles.
Ash ingested by jet engines can lead to an immediate deterioration in engine performance and cause engine flameout. In the case of volcanic ash, the principal cause of engine flameout is the deposition of the ash in the hot sections of the engine. This buildup causes a very rapid increase in burner static pressure and in compressor discharge pressure, which at high altitude can lead to surge and flameout.
Volcanic ash, when heated by the engine combustor section, becomes molten glass that can coat fuel nozzles, the combustor, and turbine. This reduces the efficiency of fuel mixing and restricts air from passing through the engine. This can ultimately cause loss of thrust, surging, and possible flameout. Ash can also seriously erode moving engine parts, including the compressor and turbine blades, reducing engine efficiency. Molten ash can solidify inside cooling passages, clogging the passages and reducing or eliminating cooling airflow, increasing blade and vane operating temperatures, and shortening engine life.
Erupções vulcânicas podem efetar enorme quantidades de material sólido e gasoso na atmosfera. Material sólido grande, precipita da atmosfera perto do vulcão, mas pequenas partículas (menro que 15 micrômetros) e material gasoso podem ser transportados para altas altitudes e distrubuídos sobre distâncias grandes por fenômenos atmosféricos.
Estas partículas de cinza tipicamente têm um ponto de fusão de aproximadamente 1832 ºF (1000 ºC).
Combinação de ENXÔFRE e outros aerossóis podem ser encontrados em nuvens de cinza, Em altas altitudes, gelo pode se formar numa particula de cinza e cargas eletróstáticas podem também estar presentes nas partículas de cinza.
Cinza ingerida por motores à jato pode conduzir a uma deterioração imediata na performance do motor e causar apagamento do motor. No caso de cinza vulcãnica, a principal causa do apagamento do motor é o depósito da cinza na seção quente no motor,
Esta formação causa um muito rápido aumento na PRESSÃO ESTÁTICA DO QUEIMADOR e na pressão de discarga do COMPRESSOR, o qual em ALTA ALTITUDE pode conduzir a uma depressão e apagamento.
Flight track and time line of the events for the ash encounter. The DC-8 deployment flight began on February 27, 2000, from Edwards, California, to Kiruna, Sweden for a SOLVE study of the Arctic ozone.
On February 26, 2000, at 1830 Greenwich Mean Time (GMT), the Mt. Hekla volcano in Iceland erupted, producing an ash and steam cloud to 45,000 ft and a lava flow.
Conditions noted were:
Altitude 37,000 ft
Mach 0.792
Total temperature –54 °F (– 48 °C)
True airspeed 438 knots
And engine readings:
N1 88– 88.5%
N2 90– 91%
EGT 1165–1200 °F (630– 649 °C)
Fuel flow 2950 lb/hr per engine
Estudo de Voo ao Encontro com Cinzas Vulcânicas
Aeronave: DC-8
Altitude: 37,000 ft
Speed: Mach 0.792
Total temperature: –54 °F (– 48 °C)
True airspeed: 438 knots
LEITURAS DE MOTOR
N1 88– 88.5%
N2 90– 91%
EGT 1165–1200 °F (630– 649 °C)
Fuel flow 2950 lb/hr per engine
Partida: 27 FEB 2000 from Edwards, California
Destino: Kiruna, Suécia
Estudo: Camada de Ozônio Ártico
Erupção do vulcão Monte Hekla na Islândia
Time: 18:30 GMT em 26 FEV 2000
Produziu: cinzas e nuvens até 45.000 pés de altitude e fluxo de lava.
MICROFOTOGRAFIAS DOS FILTROS DOS INTERCAMBIADORES DE CALOR
Engine Conditions at Ash Encounter
The engines were being operated in the “long range cruise” mode at the time of the encounter.
In the last figure below estimated temperatures through the engine. Thrust was about 4300 lb per engine, and HPC discharge air (used for HPT cooling) temperature was 779 °F (415 °C). The combustor exit and HPT inlet temperatures were estimated to be well above the 1832 °F (1000 °C) ash melting temperature. The ash would have been expected to melt and fuse to the HPT vanes and blades both outside and on the inner cooling passages. The second- and third-stage LPT temperatures were estimated to be below 900 °F (482 °C), and since those blades are uncooled, no damage would be expected.
Condições dos motores no Encontro com Cinza
Os motores estavam sendo operados no modo "cruzeiro de longo alcance" na hora do encontro.
Na imagem abaixo há os registros de temperaturas estimadas através do motor. A potência estava cerca de 4300 libras por motor e a temperatura do ar de descarga no Compressor de Pressão Alta - HPC (usado para resfriamento da Turbina de Pressão Alta - HPT) era de 779 ºF (415 ºC). A saída de queimador e temperaturas de entrada da Turbina de Pressão Alta foram estimadas estar bem acima dos 1832 ºF (1000 ºC) da temperatura de fusão de cinza.
A cinza teria sido experada derreter e fundir as aletas e lâminas guias da Turbina de Pressão Alta, ambas do lado externo e no interior das passagens de resfriamento. As temperaturas do segundo e terceiro estágios da Turbina de Pressão Alta foram estimadas estar abaixo de 900 ºF (482 ºC), e desde que essas lâminas não são resfriadas, nenhum dano seria esperado.
RESULTADOS DE INSPEÇÃO GERAL DO MOTOR
RECOMMENDED PROCEDURE IF VOLCANIC ASH IS ENCOUNTERED
What to do in an Emergency
Unfortunately, it is not always possible to avoid an ash cloud and if a plane does enter one there are very specific steps that the flight crew must take in order to increase the chance of making it out of the dangerous area safely, according to Campbell, 1994:
• Immediately reduce thrust to idle. This will lower EGT, which in turn will reduce buildup on the turbine blades and hot-section components. The volcanic dust can cause rapid erosion and damage to the internal components of the engines.
• Autothrottles off (if engaged). The autothrottles should be turned off to prevent the system from increasing thrust above idle. Due to the reduced surge margins, limit changes with slow and smooth thrust-lever movements.
• Exit volcanic cloud as quickly as possible. Volcanic ash may extend for several hundred miles.
The shortest distance/time out of the dust may require an immediate, descending 180-degree turn.
Setting climb thrust and attempting to climb above the volcanic cloud is not recommended due to accelerated engine damage/flameout at high thrust settings.
• Engine and wing anti-ice on. All air conditioning packs on.
• Start the auxiliary power unit (APU), if available. The APU can be used to power the electrical system in the event of a multiple-engine power loss.
• Oxygen mask on and 100%, if required.
• Ignition on. For systems with autostart, switch to “on” position.
• Monitor EGT. If necessary, shut down and then restart engines to keep from exceeding EGT limits.
• Close the outflow valves.
• Do not pull the fire switch.
• Leave fuel boost pump switches “on” and open cross-feed valves.
• Do not use fuel heat.
• Engine restart. If an engine fails to start, try again immediately. Successful engine restart may not be possible until airspeed and altitude are within the airstart envelope. After the engine starts, land at the nearest airport.
REFERENCES
1. Miller, T.P., and T.J. Casadevall, “Volcanic Ash Hazards to Aviation,” Encyclopedia of Volcanoes, page 915, 1999.
2. Schneider, David J., David J. Delene, William I. Rose, and Shiming Wen, “Remote Sensing of Volcanic Eruption Clouds Using AVHRR,” http://www.geo.mtu.edu/volcanoes/research/avhrr/, July 2002.
3. Swanson, Samuel E., and James E. Beget, “Melting Properties of Volcanic Ash,” Volcanic Ash and Aviation Safety: Proceedings of the First International Symposium on Volcanic Ash and Aviation Safety, U.S. Geological Survey Bulletin 2047, page 87, July 1991.
4. Grindle, Thomas J., and Frank W. Burcham, Jr., “Even Minor Volcanic Ash Encounters can Cause Major Damage to Aircraft,” ICAO Journal, Volume 57, Number 2, page 12, March 2002.
5. Pieri, David C., and Robert Oeding, “Preliminary Analyses of Volcanic Ash on an Aircraft Windscreen: the December 15, 1989 Redoubt Encounter,” Airborne Hazards from Volcanic Ash Colloquium, Seattle, Wash., Boeing Aircraft Company, July 7, 1991.
6. Krueger, A.J., L.S. Walter, P.K. Bhartia, C.C. Schnetzler, N.A. Krotkov, I. Sprod, and G.J.S. Bluth,
“Volcanic Sulfur Dioxide Measurements from the Total Ozone Mapping Spectrometer Instruments,” Journal of Geophysical Research, Volume 100, Number C7, July 1995.
7. Schneider, David J., William I. Rose, Larry R. Coke, and Gregg J.S. Bluth, “Early Evolution of a Stratospheric Volcanic Eruption Cloud as Observed with TOMS and AVHRR,” Journal of Geophysical Research, Volume 104, Number E2, page 4037, February 1999.
8. Prata, A.J., “Observations of Volcanic Ash Clouds in the 10–12 μm Window Using AVHRR/2 Data,” International Journal of Remote Sensing, Volume 10, Numbers 4 and 5, page 751, 1989.
9. Baer-Riedhart, Jenny, NASA DC-8 Airborne Laboratory, http://www.dfrc.nasa.gov/PAO/PAIS/HTML/FS-050-DFRC.html , April 2002 .
10. SAGE III Ozone Loss and Validation Experiment, http://cloud1.arc.nasa.gov/solve/index.html, June 2001.
11. Rose, William I., Gregg Bluth, C.M. Riley, Matt Watson, Tianxu Yu, and Gerald G. Ernst, “Potential Mitigation of Volcanic Cloud Hazards Using Satellite Data — a Case Study of the February 2000 Hekla Event and an Unexpected NASA DC8 Encounter,” American Geophysical Union, 2002 Fall Meeting, Eos Trans. AGU, 81 (48), Abst. V61B-09.
12. Pieri, D., C. Ma, J. Simpson, G. Hufford, T. Grindle, and C. Grove, “Analysis of In-Situ Airborne Volcanic Ash from the February 2000 Eruption of Hekla Volcano, Iceland,” Geophysical Research Letters, Volume 29, Number 16, 10.1029/2001GL013688, 2002.
