CASIE
DESERT SEARCHES: THE EFFECTIVENESS OF HELICOPTERS

INTRODUCTION

Arizona Revised Statute 11-441C states that the Sheriff of each of the 14 Arizona Counties shall conduct or coordinate search and rescue within their jurisdiction and assist the Sheriffs of other Arizona Counties upon request. The Pima County Sheriff's Department has assumed an active role in both search and rescue. Two Deputies assigned to the Sheriff's Search and Rescue (SAR) section are responsible for the investigation and management of SAR related incidents. This Department has managed 663 search and rescue missions during the period of 1975 through 1980. These missions occurred throughout the State of Arizona and in Mexico; 371 of these SAR missions began as searches for people lost or overdue from a wilderness outing.

Search and rescue in Pima County is a multiagency team effort involving the cooperation of numerous professional and volunteer agencies. A typical search may involve the response of volunteer members of the Search and Rescue Council Incorporated, trackers from the United States Border Patrol, search dogs from local law enforcement agencies, and various air support resources.

In the area of air support resources, the Pima County Sheriff's Department works extensively with the United States Air Force Aerospace Rescue and Recovery Service, the Arizona Department of Public Safety Air-Rescue, the United States Border Patrol, the United States Customs Service, and the United States Army National Guard, each of which has excellent air-search capabilities.

Upon examination of Pima County's historical SAR data involving the helicopter resource (for the period January 1978, through February 1981), it is noted that the median time spent on an air search was 4 hours. An extreme case involved 55 hours of unsuccessful air searching. In daytime mountain searches (elevation 4,000 to 10,000 feet) of all the victims found as a direct result of the SAR effort, 53% were found by the helicopter resource. In daytime desert searches (elevation 1,500 to 4,000 feet) of all the victims found as a direct result of the SAR effort , 78% were found by the helicopter resource. However, it should be noted that clue conscious ground search teams provided significant guidance to the air resources in many of these successful finds. Nevertheless, these data show that the helicopter air-search is a valuable search aid.

The search manager is responsible for attaining maximum levels of effectiveness and efficiency through proper direction of the available resources. The achievement of these goals requires an understanding of the effectiveness (or probability of detection, POD) of SAR resources, because an understanding of this resource effectiveness allows the search manager to forecast both the extent of multiple coverage and the search time required to reach an acceptable level of coverage. (For an explanation of the terminology, see the Appendix.)

Consequently, a knowledge of the PODs for each of the SAR resources would be valuable. Unfortunately almost no information is available on efforts to measure the PODs of SAR resources in the inland search for lost persons. The one exception is the notable contribution of Wartes [1] involving grid search teams in the dense Pacific Northwest forest.

This research is being conducted to establish a conservative measurement of the probability of detection, POD, of the United States Air Force helicopter rescue teams searching Sonoran desert terrain for lost persons. The experiments were designed to simulate average conditions encountered on the desert search. The results of this effort indicate significant differences in helicopter search effectiveness, which depend not only on the vegetation density and the victims' actions, but also, surprisingly, on the cloud coverage of the search area.

Finally, it should be added that the material contained within this study will be useful in applications other than searching for lost persons. Military, law enforcement and corrections agencies can utilize this management aid in air searches of desert terrain for military targets, wanted criminals and escaped prisoners, because these objectives may be in situations similar to those considered in this document.


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