Aviation Hazard Research Articles

Tracking volcanic sulfur dioxide clouds for aviation hazard mitigation

Satellite measurements of volcanic sulfur dioxide (SO2) emissions can provide critical information for aviation hazard mitigation, particularly when ash detection techniques fail. Recent developments in space-based SO2 monitoring are discussed, focusing on daily, global ultraviolet (UV) measurements by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite. OMI’s high sensitivity to SO2 permits long-range tracking of volcanic clouds in the upper troposphere and lower stratosphere (UTLS) and accurate mapping of their perimeters to facilitate avoidance. Examples from 2006 to 2007 include eruptions of Soufriere Hills (Montserrat), Rabaul (Papua New Guinea), Nyamuragira (DR Congo), and Jebel at Tair (Yemen). A tendency for some volcanic clouds to occupy the jet stream suggests an increased threat to aircraft that exploit this phenomenon. Synergy between NASA A-Train sensors such as OMI and the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite can provide critical information on volcanic cloud altitude. OMI and AIRS SO2 data products are being produced in near real-time for distribution to Volcanic Ash Advisory Centers (VAACs) via a NOAA website. Operational issues arising from these improved SO2 measurements include the reliability of SO2 as proxy for co-erupted ash, the duration of VAAC advisories for long-lived volcanic clouds, and the potential effects of elevated concentrations of SO2 and sulfate aerosol in ash-poor clouds on aircraft and avionics (including cumulative effects after multiple inadvertent transits through dilute clouds). Further research is required in these areas. Aviation community assistance is sought through continued reporting of sulfurous odors or other indications of diffuse volcanic cloud encounters, in order to validate the satellite retrievals.

Monitoring the fall of large atmospheric ice conglomerations: a multianalytical approach to the study of the Mejorada del Campo megacryometeor

Certain local atmospheric anomalies, such as the formation of unusually large ice conglomerations (megacryometeors), have been proposed to be a potential natural hazard for people and aviation, as well as geoindicators for fingerprinting larger-scale atmospheric environmental changes. On March 13th 2007, at approximately 10:15 am, an ice chunk weighing about 10 kg fell from the clear-sky and crashed through the roof (around 15 m) of an industrial storage house in Mejorada del Campo, a town located 20 km east from Madrid. The megacryometeor monitoring follow-up and the original investigation presented here includes, for the first time, both logistic and scientific collaboration between the Laboratory of the Environment, Criminalistic Service (SECRIM, the Spanish "Guardia Civil") and academic and scientific institutions (universities and the Spanish National Research Council). We propose that the management procedure of the incident, along with the detailed scientific research and combination of analytical methodologies in different laboratories, can serve as a protocol model for other similar events.

Retrieval of large volcanic SO2 columns from the Aura Ozone Monitoring Instrument: Comparison and limitations

To improve global measurements of atmospheric sulfur dioxide (SO2), we have developed a new technique, called the linear fit (LF) algorithm, which uses the radiance measurements from the Ozone Monitoring Instrument (OMI) at a few discrete ultraviolet wavelengths to derive SO2, ozone, and effective reflectivity simultaneously. We have also developed a sliding median residual correction method for removing both the along‐ and cross‐track biases from the retrieval results. The achieved internal consistencies among the LF‐retrieved geophysical parameters clearly demonstrate the success of this technique. Comparison with the results from the Band Residual Difference technique has also illustrated the drastic improvements of this new technique at high SO2 loading conditions. We have constructed an error equation and derived the averaging kernel to characterize the LF retrieval and understand its limitations. Detailed error analysis has focused on the impacts of the SO2 column amounts and their vertical distributions on the retrieval results. The LF algorithm is robust and fast; therefore it is suitable for near real‐time application in aviation hazards and volcanic eruption warnings. Very large SO2 loadings (>100 DU) require an off‐line iterative solution of the LF equations to reduce the retrieval errors. Both the LF and sliding median techniques are very general so that they can be applied to measurements from other backscattered ultraviolet instruments, including the series of Total Ozone Mapping Spectrometer (TOMS) missions, thereby offering the capability to update the TOMS long‐term record to maintain consistency with its OMI extension.

Aviation Applications for Satellite-Based Observations of Cloud Properties, Convection Initiation, In-Flight Icing, Turbulence, and Volcanic Ash

Advanced Satellite Aviation Weather Products (ASAP) was jointly initiated by the NASA Applied Sciences Program and the NASA Aviation Safety and Security Program in 2002. The initiative provides a valuable bridge for transitioning new and existing satellite information and products into Federal Aviation Administration (FAA) Aviation Weather Research Program (AWRP) efforts to increase the safety and efficiency of project addresses hazards such as convective weather, turbulence (clear air and cloud induced), icing, and volcanic ash, and is particularly applicable in extending the monitoring of weather over data-sparse areas, such as the oceans and other observationally remote locations. ASAP research is conducted by scientists from NASA, the FAA AWRP's Product Development Teams (PDT), NOAA, and the academic research community. In this paper we provide a summary of activities since the inception of ASAP that emphasize the use of current-generation satellite technologies toward observing and mitigating specified aviation hazards. A brief overview of future ASAP goals is also provided in light of the next generation of satellite sensors (e.g., hyperspectral; high spatial resolution) to become operational in the 2007–18 time frame.

Simultaneous retrieval of volcanic ash and SO2 using MSG‐SEVIRI measurements

Volcanic ash and sulphur dioxide masses from the November 2005 eruption of Karthala volcano, Comoros Islands, are simultaneously retrieved using rapid‐scan, multispectral infrared measurements from the Spin Enhanced Visible and Infrared Imager on board the Meteosat Second Generation geosynchronous satellite. Retrievals are made every 15 min, which show that the ash and SO2 separate in the vertically sheared atmosphere producing a fast moving upper level (∼12 km) SO2 cloud, a slower moving middle level (∼8 km) ash cloud and a boundary layer (<3 km) SO2 plume. The total mass of fine ash is 0.1 ± 0.05 Tg (SiO2), the upper level SO2 mass is 0.19 ± 0.01 Tg (S) while the boundary layer SO2 mass is 0.009 ± 0.01 Tg (S). These are the first simultaneous satellite measurements of ash and SO2 from an erupting volcano and confirm previous ideas about vertical separation. We suggest care must be exercised when using SO2 as a tracer for volcanic ash in aviation hazard warning systems.

Resuspension of Relic Volcanic Ash and Dust from Katmai: Still an Aviation Hazard

Abstract Northwest winds were strong enough to continuously resuspend relic volcanic ash from the Katmai volcano cluster and the Valley of Ten Thousand Smokes on 20–21 September 2003. The ash cloud reached over 1600 m and extended over 230 km into the Gulf of Alaska. Several factors influenced the resuspension of the ash: 1) the atmosphere and land surface were very dry prior to the event, further enabling the resuspension and subsequent atmospheric transport of the relic volcanic ash; 2) the production of winds strong enough to entrain and lift the ash over 1600 m into the atmosphere; 3) the complex terrain with numerous mountains interspersed with valleys, channels, and gaps; 4) the superadiabatic lapse rate for the troposphere below 850 mb; and 5) the presence of a strong subsidence inversion around 1400–1600 m. The authors propose that the strong winds are due to accelerations in a superadiabatic atmosphere below 850 mb that is buoyant to both upward and downward perturbations resulting in a hydraulic...

Height Restrictions near Airports: Physical Takings, Regulatory Takings, or Police Power Exercises?

Abstract A case pending before the Nevada Supreme Court could be a seminal decision in the often-litigated arena of takings law. The case, County of Clark v. Tien Fu Hsu, Lisa Family Trust, involves the constitutionality of a height restriction imposed by Clark County. The restriction affects privately owned buildings and structures near McCarran Airport (the airport serving Las Vegas). The restriction was intended to prevent the creation of aviation hazards for airplanes that might need additional maneuvering room close to the runways of the airport.

The February 2001 Eruption of Mount Cleveland, Alaska: Case Study of an Aviation Hazard

Mount Cleveland, Alaska (528499N, 1698579W), located on Chuginadak Island, erupted on 19 February 2001. The atmosphere‐volcanic plume interactions that occurred as part of this event led to several serious encounters of commercial aircraft with the ash. A number of continental and oceanic air traffic control areas were affected. Here, a detailed case study of the eruption, subsequent movement of the airborne plume, and operational response is presented. The likelihood of such encounters in the future may be reduced as a result of lessons learned from this event. Some potential new assets for improving the detection of and response to the airborne volcanic ash hazard to aviation also are discussed.

Dual-Polarization Radar to Identify Drizzle, with Applications to Aircraft Icing Avoidance

Freezing drizzle has been identified as a primary aircraft in-flight icing hazard. New evidence shows that it can be a greater hazard than freezing rain, even though the latter can be significant. Freezing drizzle may form by droplet coalescence without an intermediate melting process, so that it also can be more difficult to detect than freezing rain. Theoretical calculations of microwave scattering and verification by the initial field studies presented here demonstrate that freezing drizzle should be detectable and distinguishable from other hydrometeor types in short-wavelength, dual-polarization radar measurements of elliptical and linear depolarization ratios. A practical procedure is suggested for identifying and monitoring this aviation hazard with the radar and concurrent atmospheric temperature measurements. The WSR-88D radar (NEXRAD) has the potential to add dual-linear polarization to operationally apply this method, within certain constraints

Ultrasonic detection of icing onset and accretion thickness on aircraft

A major environmental hazard in aviation is ice buildup on aircraft. The development of a detector for the onset of icing and for accretion thickness measurement using ultrasonic waves is described. The detection is based on reflectivity change at a metal–ice interface and based on echo-ranging techniques using pulses of longitudinal and shear waves. The detector is sensitive to the onset of icing; ice layers as thin as 0.002 in. can be detected and accurate thickness can be measured from 0.015 in. onward. By using the ratio of an interface echo and an echo from an internal reference reflector, the quantitative measurement results are immune to changes in transducer coupling conditions. Using a combination of longitudinal and shear waves, the detector can also differentiate between ice and water. Laboratory tests were made for anticipated complications, such as rough or tilted surface of ice buildup and accretion of glaze versus rime ice. [Work supported by an Army SBIR grant to J-Tec Associates, Inc.]

Electrophoretic identification of bird species involved in collisions with aircraft

1. 1. The utility of biochemical genetic methods of bird identification was investigated for some common species which create a hazard for commercial aviation in Ireland. 2. 2. Sixteen enzyme loci were assayed in eight species, using starch gel electrophoresis; three larids, three corvids and two columbids. 3. 3. Genera were distinguishable using all but two loci. 4. 4. Differences within genera were small, but all species except for the gulls Larus argentatus and L. marinus, could be identified using one or more loci. 5. 5. Arising from the success of the method using fresh specimens, a protocol for the electrophoretic identification of traumatized remains of strikes is suggested.

Aircraft Crash Management in Australia and New Zealand

In the history of aviation there has never been a period when so much effort has been demonstrated to improve the safety standards of international and national airports. This has come about through the knowledge that aircraft crashes in recent years at some airports have been mismanaged because of bad or non-existent planning for such a disaster, and by poor emergency medical response.We share today a faith in the safety of the aircraft. We share, too, the awareness that more people have survived aircraft crashes than have perished, and that if there are survivors on board, in most cases there will be more survivors than dead (1).The encouragement to improve airport safety and crash management has come largely from the International Civil Aviation Organization (ICAO); from the Club of Mainz Association, who in 1979 set up a consultant committee to investigate and improve international airports; from the Flight Safety Foundation and from the US Airline Pilots Association. All these organizations have rightly questioned the quality of existing emergency medical response to an aircraft crash, and have offered expert advice to improve disaster preparedness and management. This article will report our response to this challenge, particularly in New Zealand, but will also concern our neighboring continent of Australia.New Zealand, set in the Pacific Ocean with its two long islands, has international flight contacts through its three major airports with North America, South East Asia, Japan and the South West Pacific. It has its own national aviation hazards of mountain chains, difficult landing approaches from the sea, made more hazardous with strong winds which are a feature of our capital city airport. Despite this, the safety record of New Zealand airports is extremely high.

Satellite imagery in the prediction of aviation hazards

Satellite meteorological informations in recent years have proved to be a unique tool in aeronautical operations. Although about 12000 stations throughout the world are taking surface synoptic observations several times a day and about 1200 stations upper wind and radiosonde observations twice daily to provide meteorological informations for aeronautical operations, still there are vast data sparse regions over the globe such as big deserts, Inaccessible mountain ranges and oceanic areas. With the launch of first U.S. weather satellite TIROS-l in April 1960, it was possible for the first time to get up-to-date information over the entire globe through visible and infrared imagery. The better quality pictures from polar orbiting satellites received in both visible and infrared channels have been very helpful to an aviation forecaster In recent years over Indian sub-continent. In the present paper, various cloud characteristics associated with potentially hazardous weather phenomena for aviation such as tropical cyclones, jet-streams, squall lines, tornadoes, fogs etc have been discussed with the special emphasis on the safety of the aircraft.

Solitary waves as aviation hazard

Scientists at the Australian National University in Canberra have found that wind shear produced by solitary atmospheric waves is a potentially serious hazard to aircraft operating at low altitudes. In recent years a significant number of aircraft accidents have been attributed to a sudden, unexpected encounter with low‐level wind shear during the landing or takeoff stage. In many cases it has been possible to associate the hazardous shear with one of a variety of well known meteorological wind shear conditions including intense thunderstorm down drafts, down‐draft‐produced density currents, cold frontal systems, and sea breezes. These sources are easily recognized and are usually predictable in the airport environment. In some instances, however, the identity of the wind shear source has been uncertain. Studies of the properties of large amplitude solitary waves in the boundary layer have shown that they produce intense, transient, horizontal and vertical wind shears which are comparable with the well known types of shear. Solitary wave activity may therefore account for some hitherto unexplained aircraft accidents.

The Dulles Airport Pressure Jump Detector Array for Gust Front Detection

Wind shear has long been recognized as one of the major aviation hazards in the airport environment. A principal source of dangerous wind shear is the thunderstorm gust front, a cold air outflow from the thunderstorm downdraft. The gust front is particularly hazardous not only because of the large surface wind shears associated with it, but also because of its highly localized character. Often the downdraft or downburst region producing such fronts is of the order of a few kilometers or less in dimension. As a result, vertically profiling wind shear detection techniques such as the hybrid acoustic–microwave radar system described in the companion paper by Hardesty et al 1977 do not provide adequate total protection. In this paper we describe an array of pressure sensors installed at Dulles International Airport in Washington, D.C., to detect and monitor gust fronts that could endanger aircraft operations. The pressure sensors (designed to respond only to sudden pressure increase) are so inexpensive that they can be used in dense networks of large spatial extent to monitor in detail the gust front progress as it approaches the airport. Some 125 sensors have been installed at Dulles. Indeed, a major cost of the installation is the cost of the phone lines required to return the information to a central data-processing location. The system has been operating unattended for extended periods of time, registering the frontal passages that have also been detected by the acoustic–microwave radar system as they pass overhead. Results are presented showing the complementary nature of the two monitoring methods.

The Dulles Airport Acoustic-Microwave Radar Wind and Wind Shear Measuring System

Wind shear has been recognized as a major aviation hazard in the airport environment. A dual, acoustic Doppler–microwave Doppler radar system has been installed at Dulles International Airport near Washington, D.C., to measure the vertical profile of wind from the surface to 510 m in 30 m height increments. The acoustic system gathers data under clear-air conditions, and the microwave radar takes over automatically when precipitation is present. System performance is being assessed by comparing its output with National Weather Service radiosondes and with balloon-borne anemometers and by intercomparing the acoustic- and microwave-measured winds under light precipitation conditions. The dual-sensor system has been operating for several months, registering the passage of fronts, some with potentially hazardous wind shears.

Studies of Rolling-Element Lubrication and Fatigue Life in a Reduced Pressure Environment

Ozone mixing ratio distribution on isobaric surfaces, discussing commercial aviation hazards, correlation with absolute potential vorticity and sandwich stratosphere

Incidence of Low Clouds at Bombay airport (Santacruz) with reference to Jet landings with the help of the Instrument Landing System (ILS)

Santacruz airport constitutes a high traffic density area, with a- substantial number of jet aircraft movements. Aviation hazards at this airport get particularly accentuated during the monsoon season on account of the occurrence of very low clouds, strong gusty winds and poor visibility conditions in mist or haze, or showers. There are a- few important hill features a-round the airport, not far from the landing area.
 
 The airport is equipped with standard radio navigational aids, namely, very high frequency omnidirectional range (VOR), Instrument Landing System (ILS), the Aerodrome Surveillance Radar (ASR). A precision approach radar (PAR) will become operational at this airport shortly. On the ILS the glide path angle has recently been reduced from 4 degrees to 3.3 degrees above the horizon, necessitating the approach of the aircraft generally at a lower altitude, the altitude above the middle marker being of the order of 561 ft only. The distance of the middle marker from ARP is 2972 m (1.6 n.m.). Fig. 1 is the instrument approach chart for the Bombay airport.
 
 The aviation hazards that may be encountered by the jet aircraft especially in the monsoon season, on the phase of the final approach, have been discussed in this note with reference to climatological statistics and the synoptic climatology of this airport. It is hoped that the result arrived at will be of some practical value to pilots operating jet aircraft and to air traffic controllers.

DROWNINGS—AVIATION HAZARDS—SCUBA DIVING

DROWNINGS—AVIATION HAZARDS—SCUBA DIVING

Squalls at Begumpet

Begumpet (Lat. 17°27' N, Long. 78°28'E) is an important aerodrome in the aviation map of India. Main aviation hazards here during the pre-monsoon and monsoon periods include thunderstorm activity with associated surface squalls. A study of the features of the surface squalls during the year is made in this paper, with the aid of the anemo-grams and barograms of Begumpet. This study is made more or less on the lines of Ra,makrislman(1957).