Degani & Wiener's Four P's
The four P's of cockpit operations is a model described by Degani and Wiener (1991). It represents the process required to develop strong standard operating procedures (SOP).
The four P's were developed on 1991 in response to a study carried out by Lautman and Gallimore (1988) which concluded that 33% of hull loss accidents between 1977 -1984 occurred because the crew deviated from basic operating procedures. As such, the question as to why this occurred was raised and it was hypothesised that rather than error existing at the user level, the infrastructure that developed these procedures was flawed. (i.e. the procedures may have been inadequate for the task, not consistent or logical or not trained correctly.)
Degani and Wiener hence concluded that the development of SOP required an analysis of philosophy, policy, procedures and practices.
This is the corner stone of any procedure. It is determined by airline management and is a conclusive statement on how business at the airline is conducted. Company culture will have an impact on such a philosophy. Like culture, flight operations philosophy may not be clearly stated but will be inferred from procedures, policies and practices (Degani & Wiener, 1991).
Subsequent to the development of a companies procedural philosophy, policies will be formulated. These are specifications in which management describe how certain operations are to be performed. Management will have policies that described training, maintenance, line operations and personal conduct etc. They are developed based on the company philosophy but further determined by commercial and operational factors.
Finally, procedures should be developed that are in line with company philosophy and policy. Degani and Wiener specify the six functions of procedures:
- What the task is
- When the task is conducted (time and sequence)
- By whom it is conducted
- How the task is done (actions)
- The sequence of actions
- What time of feedback is given (callouts and actions etc.)
Practices are the actual activities that occur on the flightdeck and crew are responsible for ensuring that the these are in line with standard operating procedures. However, deviations occur when these actions differ from company procedure. Deviations can be minor or major occurrences and in some cases can lead to an incident or accident. Several reasons for "deviant behavior" exist.
- Individualism - Occurs because pilots are individuals and may interpret or react differently to SOP.
- Complacency - Attention will not always be at its peak on the flight deck due to the long periods of boredom. Repetition can also lead to a feeling of invulnerability.
- Humor - Is related to the need for diversity in our everyday endeavors, and whilst it may break the day up. It should still be seen as a departure from standard producers and as such may have negative consequences.
- Frustration - The flight crew may feel compelled to deviate from procdures that are, in their opinion, not appropriate or ineffective. Because the ability to change these tasks is out of their control, frustration can occur.
The following is an example of how the four P's apply to an airline in relation to the way aircraft will be flown on an approach.
Philosophy = Airline X operate a safe, efficient fleet and our procedures are in line with best industry practice.
Policy = A stable approach gate will be applied to all operations and shall be enforced by the pilot in command.
Procedure = At 500 feet above the aerodrome level on approach, the aircraft shall:
- Be on the correct vertical and horizontal flightpath
- Be in the landing configuration
- The rate of descent shall not exceed 1000fpm down
- Be at the threshold landing speed (Vref) to Vref+20 knots.
Should the aircraft not be in this "stable" configuration, an immediate missed approach will be carried out.