Author Topic: Effect of search window size on SAR call-around performance  (Read 3127 times)

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Offline SARgirl

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Effect of search window size on SAR call-around performance
« on: November 25, 2009, 12:52:11 »
I did do a search before posting; hoping this thread is on the correct board.

For those interested in FWSAR and/or learning more about FWSAR, this is an interesting read.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA478989&Location=U2&doc=GetTRDoc.pdf
December 2007

To save yourself from a lot of re-reading of the same information, scroll down to page 15 and read from there.

' Brief ' description of a call-around from page 15:
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The second task is the call-around. The call-around begins when the observer detects an object and then verbally provides course change instructions to the pilot that will result in the aircraft over-flying or approaching the target for further action.

Also from page 15:
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Understanding the relationship between window size and call-around performance is important to setting aircraft requirements because there is a trade-off between window size and other aspects of mission performance.

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Conducting the experiment entirely using live flying was considered impractical. The large number of trials required to collect the necessary data would not be affordable and would take too much time from SAR personnel. Consequently, a two-stage approach was adopted. First, data would be collected using a simulation of the call-around. A synthetic environment was constructed that included a simulated SAR aircraft and a world where call-arounds on a search object could be performed. The search window at the observer position in the simulated aircraft could be adjusted on a trial-by-trial basis. By conducting a large number of call-arounds in the synthetic environment, a relationship between observer field of view and call-around performance could be calculated. Then, a live flying trial was conducted to validate the results obtained from the synthetic environment.  Finally, the synthetic environment was used to consider how the location of the search window, fore or aft of the wing, would affect call-around performance.

From page 33:
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4.2 Recommendations

1. If a FWSAR aircraft with a search window providing less than 120° field of view is considered by the project, the project should anticipate call-around performance being unreliable.  Fields of view between 120° and 160° provide increasingly reliable call-around performance. The primary search window should provide the observer with at least 160° field of view to enable the observer to attain their peak level of call-around performance. With this field of view, one can expect a probability of a successful call-around of at least 0.90 for four of six observers.

2. The positioning of the primary search window relative to the aircraft wing should be guided by factors other than the effect of the wing’s position in the field of view during call-arounds. The fore/aft location of the window relative to the wing was not found to affect call-around performance. Other factors, such as habitability, workflow, and aircraft loading for example, should be the more important factors in deciding the positioning of the search window ahead of, or behind, the wing.

3. When a field of view requirement is specified for a new SAR aircraft, it is critically important that the field of view be provided within the context of an ergonomically sound work station. A work station with poor ergonomics can reduce the performance of the observer provided with a particular field of view and it can reduce the nominal field of view. For example, a window that prevents an observer wearing a flight helmet from positioning his/her head in the window, may force the observer to remain farther from the window than the design intended, thus effectively reducing the field of view. Also a work station design that requires the observer to adopt straining postures to obtain the design’s intended field of view will lead to excessive fatigue, injuries, or adopting less demanding postures that reduce the effective field of view. All of these will undermine performance.

Q: Currently, the field of view on the Hercs and Buffalo, which are kitted for SAR... do they have the recommended 120° and 160° field of view or no?  Just curious, as I don't recall the details. 


Slightly off topic:
Q: Does anyone remember when they removed the bar from in front of the 3 o'clock and 9 o'clock Herc windows?



« Last Edit: November 25, 2009, 12:58:51 by SARgirl »
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Offline Ditch

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Re: Effect of search window size on SAR call-around performance
« Reply #1 on: November 26, 2009, 18:56:17 »
Buffalo search windows provide for 180 degrees of viewing - the ST's can see all the way forward and back along the fuselage without any real obstruction.  This is not the case for the Herc - as the landing gear gets in the way and their window is not a bubble.  The Cormorant search windows are similar to the Buff - except that the windows themselves are smaller and less comfortable to sit in.
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Offline SARgirl

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Re: Effect of search window size on SAR call-around performance
« Reply #2 on: November 30, 2009, 15:54:39 »
Thank you for the reply, much appreciated.  :)

This is not the case for the Herc - as the landing gear gets in the way and their window is not a bubble.
Yes, this I recall first hand. 

...still wondering what the ° field of view is for the Herc?  ...will try to find out at next opportunity.
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