Lecture 15: Function Allocation

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Lecture 15 Function Allocation
Readings Ch.11 of Handbook of Human Factors and
Ergonomics. NB Students in MIE240 are not
expected to read this chapter, but they are
expected to read and understand the lecture
notes. http//olias.arc.nasa.gov/publications/de
gani/DOP/DOP.html
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Goals

• Overview of Function Allocation Process
• Review Fitts List
• Case study Crew Systems Management
• Policies, Procedures, and Techniques

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Human-Machine Interaction
Who is doing what, when, and how?
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Requirements of Function Allocation Methods

• Systematic
• Multidimensional
• Capable of handling large- and small-scale
  functions
• Iterative
• Linked to earlier and later design decisions
• Face valid in an organizational context
  
• Promote participation

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Strategies for Dividing up Responsibility

• Human is solely responsible
• Computer offers a set of decision alternatives to
  the human who may choose either to ignore them or
  to select one
• Computer offers a set of decision alternatives
  for human to choose and computer to execute.
• Computer suggests an alternative, human can
  accept or pick a different one

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Dividing up Responsibility (continued)

• Computer carries out its suggestion only if human
  approves
• Human has to intervene to stop computer
  executives its preferred option
• Computer informs human of what it did
• Computer informs human if asked
• Computer informs human after the fact if it
  thinks it should
• Computer completely ignores the human

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Allocation of Functions
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Fitts List I Human Strengths

• Ability to detect small amounts of visual or
  acoustic energy.
• Ability to perceive patterns of light or sound.
• Ability to improvise and use flexible procedures.
  
• Ability to store very large amounts of
  information for long periods and to recall
  relevant facts at the appropriate time.
• Ability to reason inductively.
• Ability to exercise judgment.

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Fitts List II Machine Strengths

• Ability to respond quickly to control signals,
  and to apply great force smoothly and precisely.
  
• Ability to perform repetitive, routine tasks.
• Ability to store information briefly and then to
  erase it completely.
• Ability to reason deductively, including
  computational ability.
• Ability to handle highly complex operations, i.e.
  to do many different things at once.

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Case Study Flight Deck Procedures

• backbone of cockpit operations.
• structure by which pilots operate aircraft and
  interact with other agents
• Procedures are important in maintaining flight
  safety
• during both normal and abnormal conditions.

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Procedures What and Why?

• 1. What the task is.
• 2. When the task is conducted (time and
  sequence).
• 3. By whom it is conducted.
• 4. How the task is done (actions).
• 5. What is the sequence of actions
• 6. What type of feedback is provided (callout,
  indicator)

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Procedures for Starting an Aircraft

• 1. Before start checklist
• 2. Engine start process and callouts
• 3. After engine start configuration flow
• 4. SOP tasks and callout for coordination with
  ground crew

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NASAs View of Policies and Procedures
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Explanation of NASA Diagram

• 1. Philosophy Automation is just another tool to
  help the pilot.
• 2. Policy Use or non-use of automatic features
  (within reason) is at discretion of the crew.
• 3. Procedure On a Category-I approach, flight
  crew first decide what level of automation to use
  (hand-fly with flight director autopilot and
  mode control panel coupled etc)
• 4. Sub-tasks (or actions) (e.g., set decision
  height, select autopilot mode, etc.)

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Aviation Example
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Compliance
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Crew Practices May Deviate from Procedures
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SOPs (Standard Operating Procedures are Important)

• I called for clearance to Saint Louis (STL) as
  follows clearance delivery, company
  identification, ATIS information, federal aid to
  Saint Louis.'
• Federal aid was meant to mean FAA clearance in a
  joking fashion. The controller misinterpreted
  this to mean that we were being hijacked and
  called the FBI and airport police....
• Minutes later police arrived at the aircraft.

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Noncompliance

• A takeoff was observed in which the captain was
  the pilot flying. The first officer was supposed
  to make standard airspeed calls of V-1, V-r, and
  V-2.
• Instead, he combined the first two into a
  non-standard call of "V-one-r", and at V-2
  called, "two of 'em."
• Apparently, the captain knew what was meant by
  these strange calls
• while one cannot say that this was a dangerous
  compromise with safety, it did represent a
  potentially serious departure from SOPs.

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Example Handling Altitude Change
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Sharing Information

• Ideally, all information is known to all crew
  members
• this is not always practical.
• Not all information can be shared via SOP
• the amount of information can be enormous.
• In defining the task and the procedure, the crew
  coordination attributes must also be defined.

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An Aircraft Accident

• On August 19, 1980, a Saudi Arabian Lockheed L-
  1011 was returning to Riyadh Airport (Saudi
  Arabia
• cockpit warnings indicated smoke in the aft
  cargo compartment.
• The crew was searching for the appropriate
  emergency procedure in their flight documentation.

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Problem with Presentation of Procedures

• Crew spent 3 mins looking for the aft cargo smoke
  warning procedure.
• Due to split of the Emergency and Abnormal
  procedures into Emergencies, Abnormal, and
  Additional sections.
• Crew believed procedure was in the Abnormal
  section
• actually in the Emergency section.

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Catastrophic Result

• This, and several other factors led to a horrific
  accident in which 287 passengers and 14 crew
  members died of fire and toxic smoke inhalation.

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Pre-Flight Checklist Version I
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Pre-Flight Checklist Version II
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Early use of Procedures -gt Better Performance
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Lessons

• Function Allocation is Based on Human and Machine
  Capability
• Function allocation follows an orderly process
• Function allocation leads to tasks
• Critical tasks should follow procedures
• Different Techniques can be used for a specific
  procedure.
• Have to differentiate between requirements and
  guidelines