steven landry
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  • Perceptual grouping in air traffic control
  • Paired approaches
  • Procedure following

    Perceptual groupings in air traffic control

    Subjects performing visual target tracking tasks have been shown to utilize perceptual organization. This organization has been shown to have both Gestalt features and goal-oriented features. Previous studies have attempted to use memory recall techniques to examine potential cognitive groupings in air traffic control tasks, with negative results.

    Analysis of eye movements has shown similar patterns of organization to the underlying visual tasks. Experiments were performed to evaluate whether recall or eye-tracking techniques can be used to extract perceptual groupings. Subjects’ memory of scenario information is generally poor, except where significant manipulation of targets occurred. For this reason it is suggested that recall techniques may not produce accurate clustering information. Fixation data, however, produced clustering consistent with Gestalt factors. Goal-oriented factors did not seem to affect grouping.

    Paired approaches

    By decreasing the spacing required for aircraft flying instrument approaches to closely spaced parallel runways, some of the capacity lost at these airports under instrument conditions may be regained. One method to accomplish this is called “paired approaches”. The paired approach concept utilizes “safe zones”, which are relative positions in which the two aircraft paired on approach to the parallel runways cannot pose a near midair collision danger and in which the wake vortex from the leading aircraft will pass behind the trail aircraft.

    A previous analytical evaluation of the safe zone has determined that there are few significant physical constraints to implementing paired approach procedures. A number of issues remain with respect to human performance, however. In addition to normal instrument approach tasks, a paired approach procedure will likely involve a tracking task, as the pilot attempts to remain within the safe zone, and a monitoring task, which would involve monitoring the relevant flight deck display. The former task will depend upon such factors as the length of the safe zone, and the rate of change of the safe zone. The latter task will depend not only upon the types and number of symbology elements, but also upon whether the information provides sufficient cues for the pilot to make correct judgments and decisions, which will in turn affect action.

    One additional issue is the source of the information. Real-time information broadcast from the aircraft may be available, which would permit calculations of the safe zone based upon current aircraft and environmental states. However, there is also information available in the form of the restrictions required by the procedure. These restrictions indicate likely speeds (and perhaps positions) for the aircraft. This information can be used to provide predictive information about where the safe zone is likely to be in the future, or to provide “worst-case” safe zone calculations. The real-time information is instantaneously accurate, but relatively dynamic, and may not provide sufficient lead-time for pilots to react to changes in the safe zone due to speed reductions, missed approaches, etc. The procedural information, on the other hand, provides a prediction of the likely position of the safe zone, is less dynamic, but may not be accurate if the aircraft are not following procedural restrictions. These two sources should be combined to provide the best possible information for the flight crews.

    A recently completed experiment utilized a part-task simulator and line pilots executing instrument approaches to closely spaced parallel runways, including scenarios in which the lead aircraft blunders towards the trail aircraft, and in which missed approaches are accomplished. The results should help determine if pilots are able to understand the various situations that may occur during the approach, and whether this understanding will reinforce compliance to desired pilot behavior. Additionally, it will provide some information concerning the utility of the real-time and procedural information, and how to incorporate that information into a display.

    Procedure following

    In my dissertation research I investigate information displays to support operators when executing procedures in order to aid performance and increase situational awareness and safety. Although the experimental efforts are focused on aviation procedures, the results have implications for other safety critical socio-technical systems (such as healthcare, manufacturing, nuclear power, and spacecraft operations). The intent of such displays is to assist operators in not only following operational procedures, but also in comprehending the context of the procedures, enabling them to understand why, when, and how to deviate from the procedures if necessary.

    The importance of this problem is reflected in the observation that the control of most systems in safety critical environments is highly proceduralized. While the extent to which procedures impact the work domain has been recognized, there has been little human factors work on procedure design and utilization until recently. Operators are expected to follow procedure and are faulted if they deviate from procedures, without considering whether the underlying procedure contributed to the operator’s error, or even whether the procedure should have been followed at all.

    Procedures themselves are typically developed informally, pieced together from diverse requirements and constraints on the system. The result is that the design philosophy behind procedures is not only sometimes highly variable from instance to instance, but is also almost never presented to the operator. Operators are expected to ardently adhere to procedure and still be able to make intelligent decisions when procedures fail, but are given little support to accomplish that goal.

    Procedures are frequently under-defined and limited in scope. Operators must translate the requirements of the procedure into action and can encounter situations that were not considered by those designing the procedure. Information about the assumptions made when the procedure was designed is typically lacking – there is often no training on when procedures do not apply (and what to do in those situations), and almost no display support is provided to the operator for following or interpreting procedures.

    Even less training and display support is provided on how to operate once the procedure has failed. One example of this is the Three Mile Island nuclear facility incident in 1979. A President’s commission conclusion was that the accident was due to human error caused by deficiencies in training for operating the plant under accident conditions, confusing and misleading operating procedures, poor control room displays for operating the plant during emergency situations, and a lack of training on previous accidents .

    Pilots of Alaska Airlines Flight 261 were unaware that normal troubleshooting procedures for flight control malfunctions were inappropriate with stripped threads on a horizontal stabilizer jackscrew nut, which contributed to this fatal accident . The NTSB indicated that insufficient guidance concerning the recognition of when an approach was unstabilized and a lack of indication that part of the pre-landing procedure was not followed contributed to a fatal accident in Little Rock, AR . Numerous other examples exist in the NTSB database

    The research described in this document is intended to examine how such support in understanding and following procedure might be provided to an operator and in what ways the information can aid the operator.

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    Last updated: March 4, 2004

  • flight simulator