Section G. Search Visibility

 
Introduction
 This section describes the various factors of search visibility.
 
G.1.  Maximum Detection Range
 Maximum detection range is the distance at which an object can be seen and recognized from the height above ground or water at which the aircraft is flying.  This is a critical factor in determining the characteristics of the search pattern as it limits the sweep width of the pattern.  The maximum detection range is always less than the meteorological visibility.  The sweep width (W) is usually selected to be considerably less than twice the search visibility in order to increase the probability of detecting the search target.  (see Figure 11-1)
 
Sweep Width
 
 
Figure 11-1 Sweep Width
 
G.2.  Altitude
 Depending on the search object, altitude should be appropriate to the mission. (see Table 11-1) There are always trade-offs between higher and lower altitudes in searches.  Higher altitudes provide a greater margin of safety and potentially greater detection distance, but they may compromise search effectiveness when attempting to locate smaller objects.  Smaller targets, such as persons in the water, will remain difficult to detect regardless of the altitude, although they may be easier to detect at lower altitudes.  Lower altitudes require the pilot to be trained and current in the low-level flight regimen.
 

 
Table 11-1 Recommended Visual Search Altitudes
 
Search Target
 Terrain
 Altitude AGL
 
Person, Cars, Light Aircraft Crashes
 Moderate
 500
 
Trucks, Large Aircraft
 Moderate
 500-1000
 
Person, 1 Person Rafts, Surfboards, Light Aircraft Crashes
 Water or Flat
 500
 
Small to Medium Sized Boats, Life Rafts, Trucks, Aircraft
 Water or Flat
 1000-3000
 
Distress Signals
 Night - all
 1500-2000
 

 
G.3.  Low Pass Verification
 The chance of detecting a person in the water by air search is quite low.  Obviously, a low pass for verification in the event a person or debris is sighted in the water might be in order.  However, it is more prudent to take a latitude/longitude position and report the position to surface vessels.  Risk-reward factors, generally speaking, are not favorable for small fixed-wing aircraft.  As Auxiliary aviators we do not want to jeopardize our crew or aircraft and become part of the problem, rather than assisting in the solving of a SAR case.
Keep in mind that low altitude flights increase the risk factor and may be in violation of FAA regulations.
　
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：AUXILIARY AVIATION TRAINING MANUAL(110)