Aircraft Hazard Research Articles

Microbursts: a hazard for aircraft

Microbursts are believed to have been responsible for several aircraft accidents in recent years. We report here laboratory experiments which show that when a descending column of dense fluid reaches the ground and begins to spread out horizontally, an intense vortex with a horizontal axis forms at the leading edge of the outflowing air. The intensity of this vortex results from the increase in vorticity due to the rapid stretching of the length of the leading edge. The properties of such a horizontal vortex with its associated updrafts and downdrafts are consistent with those found in microbursts which are a severe hazard to aircraft when taking-off or landing.

Ice detector evaluation for aircraft hazard warning and undercooled water content measurements

A Rosemount ice detector was installed on a Research Aviation Facility Queen Air for evaluation. It was used during a winter stratus cloud experiment at Muskegon, Mien. (1978) and during a cumulus cloud experiment (HIPLEX) in 1980 at Big Spring, Tex. Results indicate that the detector is an extremely sensitive instrument with a reasonable dynamic range. The instrument will provide a measure of icing severity and valid computed water content values only for conditions of small water content and/or low temperature. The dynamic range of this measurement technique for stratus cloud studies is probably adequate; its use at temperatures of -5 to -10 °C in cumulus clouds will provide only a relative measure of icing severity and large underestimates of the computed liquid water content.

Raptor and Vole Populations at an Airport

Changes in numbers among overwintering populations of 4 species of raptors were studied in relation to changes in abundance of meadow voles (Microtus pennsylvanicus) on Toronto International Airport from October to April of 1974-75 and 1975-76. Data from small-mammal trapping, analysis of raptor pellets, and direct observations of prey hunted and captured by the raptors indicated that meadow voles were the major prey of all 4 raptor species. Rough-legged hawks (Buteo lagopus) and short-eared owls (Asio flammeus) exhibited a greater numerical response to changes in vole abundance than did redtailed hawks (Buteojamaicensis). Changes in snowy owl (Nyctea scandiaca) numbers were opposite those of the other raptors. J. WILDL. MANAGE. 45(2):390-396 Birds may create a serious hazard for aircraft, and considerable effort has been expended on developing effective methods of reducing bird populations at airports (Blokpoel 1976). More basic information is required if accurate predictions of how bird populations respond to various control procedures are to be derived. On Toronto International Airport, 4 species of raptors (red-tailed hawk, rough-legged hawk, snowy owl, shorteared owl) are common winter residents. Frequently these raptors become abundant and create hazards for aircraft traffic. Previous control measures, including shooting and livetrapping, have had limited success in reducing raptor numbers on the airport. Our study was undertaken to develop a management program that would reduce the raptor population of the airport. The objectives were to determine the prey used by the 4 raptor species, the response of these raptors to changes in prey abundance, and other variables that may cause changes in raptor abundance. We thank R. W. Steele for use of his data; A. L. A. Middleton and D. E. Joyner for comments on the manuscript; W. King, S. Lane, and G. Nancekivell for technical assistance; and E. B. Hartwick for initial supervision of the project. Special thanks are expressed to U. Waterman, J. A. Mason, and airport personnel.

Study of the perforation of reinforced concrete slabs by rigid missiles —Experimental study, part III

The work described below is a contribution to the assessment of aircraft hazards for nuclear power plants. A series of tests was performed to outline the behaviour of reinforced concrete slabs impinged by rigid missiles. Prediction of results was tried by means of finite element computation with elastic-plastic constitutive law for the concrete. Although results are encouraging, no general correlation was carried out.

Technology forecasting: Aircraft hazard detection

This article describes the use of the scoring model technique to forecast aircraft hazard detection technology. The various factors relating to hazard detection were determined. These factors were combined into a single parameter which describes the relation of these factors to the technology being forecasted. The method of determining the value of each factor for the various detection systems utilized in the forecast are discussed. These include factors which were normalized, others which require judgemental evaluation, and one which was computed. The results of the forecast are presented, showing that the parameter derived adequately describes the hazard detection systems on which it was based.

Probabilistic assessment of aircraft hazard for nuclear power plants

As part of a general probabilistic safety analysis, the risk of structural damage to a nuclear power plant from aircraft crashes has been evaluated in a quantified manner. Frequency distributions of aircraft speed and weight and engine weight were constructed for small and large aircraft and for site locations adjacent to and remote from an airport. Based upon United States data an analysis of aircraft accidents is presented to establish the probability of an aircraft hitting a nuclear power plant. If an aircraft hits a building, either the whole building or just the local component may respond. It is shown that the response of the entire reactor building is negligible, and the damage to specific structural components is of concern. Components of a reactor building may experience structural damage in several modes as a result of an aircraft crash. It is essential that all modes of damage for any particular component are considered to establish the critical mode of damage. Further, depending upon various parameters involved, the critical mode of damage may vary for different components. For the specific case of an aircraft striking a reactor building, three modes of damage could be delineated. The aircraft engine might perforate the structural component. This type of damage is classified as perforation mode of damage. The second mode is classified as collapse mode of damage, where a local collapse of the structural system occurs. The third mode is classified as a cracking mode of damage, where the structural component ceases to function satisfactorily after the impact due to cracking. The 18-inch thick reinforced concrete sidewall of a typical boiling water reactor plant located at the top floor of the reactor building is used as an example. The probability of damage to this sidewall in the perforation and collapse modes is investigated. The results are compared to those obtained for the cracking mode of damage. Available empirical formulas for perforation of concrete are examined, and new formulas are proposed to cover the range of parameters encountered in aircraft engine impact. Uncertainties in formulation are discussed, and the probability of damage by this mode is determined using Monte-Carlo methods. The conditional probability of local collapse of the wall panel is evaluated by using probabilistic approaches and yield line theory. The striking location (and thus the critical yield pattern), moment, and rotational capacities are all treated as random variables. The probabilities of damage under the perforation and collapse modes are approximately of the same order of magnitude. Under the impact of an aircraft, the cracking mode of damage is estimated using elastic analyses. Solutions are obtained using a finite-element idealization and considering the maximum reactive force due to an aircraft strike as a static load. For the 18-inch wall under consideration, it is predicted that the cracking mode of damage occurs much earlier than the other two modes of damage. It is shown that the impact load level predicted for cracking mode of damage is very conservative. After a study of all modes of damage, it is concluded that the aircraft risk is usually acceptably low for the typical case studied here.