Standard Operating Procedures

What is an SOP?

A Standard Operating Procedure (SOP) provides a flight crew with a step by step guide to effectively and safely carry out operations. A particular SOP must not only achieve the task at hand but also be understood by a crew of various backgrounds and experience within the organisation. SOP's can also be developed as time goes by to incorporate improvements based on experience, accidents, near misses or innovations from other manufacturers or operators to suit the needs of a particular organisation.
SOP's should not be designed too detailed and exhaustive that the pilot does not provide any form of cognition to the process and not be too relaxed where the crew have too options to decide between.
Of note, a Checklist is generally carried out as a part of an overall procedure; for example it would be a companies SOP to conduct the Landing checklist after the Landing gear is confirmed down and locked on finals during the approach.

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How are SOP's developed?

There is generally a framework which provides a logical structure to build an SOP, however to allow for flexible operations it can be a fluid arrangement. The four P's provides this framework from which management and operators can communicate the most effective manner in which to conduct operations.

The Four P's Model


There must be an overarching view from the companies management on how they want to operate. This philosophy will be influenced not only by the attitudes of the high level managers but the companies culture.
A philosophy may not necessarily be recorded in a document but it can be seen in the written policies and procedures and seen in the day to day practices of the organisation.


A policy is derived from philosophy focusing on a particular aspect of your operations, such as maintenance or ground handling. A single policy or a group of policies are then used to create procedures which allows for safe and efficient operations.


Procedures specify a set of sub tasks which need to be completed in any complex task or task where it is crucial that a particular aspect is completed or a switch is selected at a specific time.
A Procedure generally satifies the following requirements:

  • What is the task
  • When is the task to be conducted.
  • By whom is it to be conducted by.
  • How is the task completed.
  • The sequence for the task.
  • What form of feedback is required ( written, verbal, physical action).


The last 'P' is the actual practice or technique of the operator in response to a procedure. Because the framework can be quite rigid and the actual operating environment can cause the pilot or air traffic controller to deviate from procedure, this is important because when management are creating the philosophies, polices and procedures they need to keep in mind how the actual process will be used, misused or adjusted to suit particular operators. In the perfect world of course this would not happen, but in reality there is a lot of evidence to suggest that this is fact the case.
Humans by nature are innovative, so in any procedure they will use the technique which they believe best suits them and the situation. This is not necessarily a bad thing as long as the techniques are monitored and even incorporated if there is merit in their use.
The one method management have in determining 'practice' is standardisation of the procedures, this minimises confusion between operators because the training and feed back from it prevents different interpretations and deviations from SOP's.

Factors Affecting SOP Development

Although the four P’s model provides a frame work for SOP development, there are some other factors that need to be considered for the SOP's to work in the real world environment.

Organisational Factors:

1. Type of operation: If the carrier is mostly doing short haul routes with many legs per day, they may wish to minimise ground time. As such, at intermediate stops the pilots will stay in the cockpit and keep certain equipment powered on in order to achieve a faster turnaround time. The exact opposite maybe true for long haul operations where the pilot would perform a full shut down and leave the cockpit. Separate procedures and checklist will have to be produced to support to a specific type of operation. The reason for this being that any procedures or checklists produced without taking into account the differences will result in sub-optimal operation and a high rate of procedural deviation (Degani & Wiener, 1994, p. 21).

2. The influence of certain personalities within the company: A good example is a senior captain in Eastern Airlines insisted on using a QFE altimeter on approaches in addition to the standard QNH altimeter used by most airlines. And this became part of the Eastern Airlines procedure until an altitude related accident occurred prompting a change in this procedure (Degani & Wiener, 1994, p.21).

3. The organisational culture: It is known that in some airlines procedures are highly standardised and strict discipline and adherence is expected from the part of the pilots operating the aircraft. In these airlines it is there corporate philosophy, policy and culture that deviation from SOPs is considered grounds for action and control measures be taken to address these deviations even if it maybe a minor one that does not affect the safety and efficiency of the operation. For this reason the design of the SOPs in these airlines will have great detail and depth about every aspect of the operation. However it would be absolutely impossible and highly impractical to be able to design procedures for every little aspect of operations.

4. Economical factors: Some airlines may choose procedures that encourage operational efficiency. For example some airlines that do mostly short haul routes with fast turnaround times require pilots to avoid hard braking and fast turns in an attempt to get to the nearest high speed turnoff. On the other hand some airlines do not advise the pilots to use air brakes during descent in order to avoid the airframe vibrations and then the impending discomfort experienced by the passengers. Saving fuel costs is another economical factor that affects the design of procedures. According to Degani & Wiener (1994), “because the multipliers in airline operations over the fleets over time are so great, a procedural change yielding on any given leg, a seemingly small saving can result in a very considerable dollar saving annually”. Therefore aspects such as single engine taxiing, delayed engine starts and reduced use of APU all have very important procedural relevance.

5. Possible mergers and takeovers: When one airline merges or takes over another airline, the airline that is being taken over often has different operating procedures. This requires a lot of time and effort by the airline that is taking over to once again standardise and implement its own sets of procedures. Furthermore if the airline that is being taken over has procedures that are far more superior to that of the airline that is doing the takeover, then a procedural revision may have to take place.

Operational Factors:

1. Extra cockpit activities: These are external factors such as air traffic control, dispatchers, maintenance, and cabin crew and gate agents. The procedures designed should be compatible with the structure of these external demands and the methods the cockpit crew uses to respond to these demands. For example, some airline SOPs state that the pilots are to check the maintenance status of the aircraft by inspection of the maintenance logbooks prior to using any controls or switches of the aircraft. The logic behind this procedure being, that it prevents the pilots from operating any component that maybe inoperable and further damaging the aircraft (Degani & Wiener, 1998, p.8).

2. Intra-cockpit activities: These are activities relevant to when inside the cockpit. One very important aspect is to take particular note of the flow of the procedures in relation to the layout of the cockpit instruments. And as we all know cockpit instruments are arranged in certain ‘geographical’ locations depending on the frequency of use, how critical the instrument is, and various other human factors considerations. “In designing efficient and error resistant procedures, the steps must follow some logical and efficient motor and eye movement along the cockpit panels” (Degani & Wiener, 1998, p. 9).

3. Aircraft systems design considerations: For example, in certain aircraft types the gear and flap levers are located on the co-pilots side. However when the captain is flying it is normal practice for the captain to select gear up on takeoff and retraction of flaps on the climb out. But because of the location of these system actuators, it is difficult for the captain to reach out for these controls. There are two ways to deal with a situation like this. One is to either change the hardware or the other way is to change the procedure. And as we all know changing hardware in most cases would not be a feasible option so procedural change will have to take place.

4. Paper work and procedures consideration: “Documents, Manual, checklists and many other paper forms are used in the cockpit. The compatibility between the procedures and their associated devices (manual, checklists, cards etc.) effect procedural execution” (Degani &Wiener, 1998, p. 11).

Why do Pilots deviate from procedures?

Why do well trained, motivated and professional operators deviate from an SOP?


Pilots and engineers are individuals at the end of the day and generally they want to impose some form of their own character on a procedure, this is in part what differentiates us from computers. Whether it be a different technique to break the boredom, or to apply some form of critical thinking to a procedure, generally these deviations do not adversely affect the outcome. Gone unchecked however, it can break down standardisation and bring confusion to a flight deck if a co-pilot does not understand the deviations in procedure of his Captain.


This is the dropping of your guard during a repetitive task or the introduction of humour by deliberately mispronouncing words in a critical standardised task. The backstop to this is reinforced in CRM, where a pilot can correct repeated non-standardised responses to a checklist, preventing a deterioration in responses.


Being forced to conform to a seemly ridiculous procedure can provide justification to alter or amend the practice of a procedure. There are several ways to approach this problem; either raise the issue with management and have the policy or procedure changed or have training provided to explain why a procedure is conducted in a particular way so it no longer seems ridiculous.


As we all know without procedures it would be difficult to maintain effective and safe operations of aircraft due to the complicated nature of the systems involved. The process of designing procedures from both an organisational as well an operational perspective is a long and tedious process. How effective these procedures are can only be determined by constantly monitering how much procedure deviation takes place once it is put into place. There will never be a perfectly designed set of SOPs due to the ever changing factors in the environment and thus changes in procedures.

  1. Green, R. G., Muir, H., James, M., Gradwell, D., & Green, R. L. (1996)Human Factors for Pilots (2nd ed). Ashgate Publishing Ltd (Hants, England), 1996.
  2. Degani, A. & Wiener, E.L. (1994). Aviation Psychology in Practice. Avebury Technical (Aldershot, England), 1994.
  3. Degani, A. & Wiener, E.L. (1994). On the Design of Flight-Deck Procedures. California, USA: NASA Ames Research Center
  4. Degani, A. & Wiener, E.L. (1998). Design and Operational Aspects of Flight-Deck Procedures. Montreal, Canada: Proceedings of the International Air Transport Association (IATA) Anual Meeting

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Mishma HameedMishma Hameed

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