AVIATION MAINTENANCE: STANDARD OPERATING PROCEDURES AND THE IMPORTANCE OF FOLLOWING THESE PROCEDURES.
Background
Embedded as a customer within an overseas-based aviation contractor working on an aircraft avionics upgrade project, I observed and experienced multiple safety incidents related to standard operating procedures. Documented below are two examples which highlight the importance of following procedures, describe the consequences of not following procedures, and demonstrate poor communication within an aviation organisation. Arguably, these examples demonstrate defences preventing potential accidents.
INCIDENT 1: CAPTAIN YOUR TEST FLIGHT IS DELAYED.
During the flight testing program the aircraft was configured for a particular serial and dispatched by the contractor in preparation for flight. As a part of this standard procedure/process the contractor maintenance team was to brief the aircrew on the serviceability state of the aircraft (during the pre-flight brief). The brief included the following:
• Project installations which had occurred since previous flight,
• Maintenance and repair carried out on the aircraft since last flight,
• Long term acceptable defects to be carried on the flight,
• General servicing and replenishment information,
• And any other relevant information pertaining to maintenance on the aircraft.
On this occasion the brief was completed and it was announced that the aircraft was serviceable for flight. When aircrew pre-flight was complete the contractor produced its maintenance release form fully signed, the aircraft maintenance log book was signed and the aircraft was released for flight.
As the aircrew were strapping into their seat and the aircraft ladder was about to be lifted the contractor’s quality assurance lead wandered into my office and handed me some paperwork. The paperwork indicated that during the evening the nightshift maintenance team had carried out rectification on a long-term defect on the autopilot system. Further inspection of the paperwork suggested that after a re-wire of a connector in the autopilot system, no functional and independent functional had been carried out. These are standard maintenance procedures. The contractor who briefed the aircrew on maintenance made no reference to this autopilot work and in fact had no idea the work had been carried out over night by the other shift.
After a quick exchange of words with the contractor I immediately went out to the aircraft to explain to the captain that his flight was going to be delayed, and that he needed to sign the aircraft back to maintenance so the contractor could carry out the functionals prior to the aircraft flying. Of note, in 25 years of working in aviation maintenance it was the first time I had to prevent an aircraft from flying.
Potential Safety Implications
The safety implications of this maintenance error have the potential to be catastrophic. An example would be an incorrectly wired autopilot system has the potential to place the aircraft in an incorrect sense (attitude). A functional and independent function confirms the autopilot system operates in the correct sense.
Incident Cause
• Lack of adherence to standard operating procedures.
• Poor communication between the two functional elements in the contractor’s maintenance team.
Human Factors Lessons
It could be argued system defences captured this error prior to the aircraft taxiing but in reality it was a matter of timing which allowed this error to be picked up. Equally it could be argued if there was a problem on engaging the autopilot the pilot's skills, expertise and SOP's would mitigate the likelihood of an accident. However, if this maintenance error remained latent and lined up with other active and latent errors, and defences were breached, then a major accident could occur (Accident Causation Model).
Two important lessons can be derived from this incident:
• Standard operating procedures are an important element in a safety management system. Procedures are put in place to reduce error and mitigate consequences of error so they should be followed, and this ethos should be followed in all levels of the organisation.
• Communication is an important aspect of a safety management system. It allows information flow from top/down and bottom/up. The positive aspects of good communication contribute to safety and efficiency. In this case good communication between the maintenance shifts would have highlighted the functionals were not carried out and the customer would have been fully informed that the work had been completed.
INCIDENT 2: SAFETY LOCKING DEVICES AND PROCEDURES.
During standard post-flight maintenance on the aircraft described in incident one, the contractor’s maintenance staff were required to follow the customer’s standard operating/maintenance procedures, and these were laid out in the form of work cards.
On this aircraft there are two hydraulically activated large doors on the underside of the aircraft. To make these doors safe there is a safety pin (locking device) which is inserted at all times on the ground which prevents the inadvertent or accidental actuation of the doors with the aircraft hydraulic systems powered on the ground.
In short on two occasions this procedure was not followed correctly and the safety pin was inserted incorrectly, and on both these occasions the error was made by the same tradesman. On both occasions the error was noticed by customer representatives and brought to the attention of the contractor’s line management. Of note, no ground safety incidents were raised for these errors because an easily accessible, non-punitive and anonymous safety reporting system was not in place, and if there was it was not communicated well.
In the weeks following this incident another procedural issue occurred with contractor’s staff which involved the application of external power to the aircraft without using standard operating procedures. On this occasion, one of the aircraft hydraulic systems was left on when power was applied and there were people standing in area where the doors close. If this error had occurred with an incorrectly inserted safety pin and incorrectly positioned door switch (a part of external power on check), an accident would have been inevitable. This tradesman’s failure to follow procedures was investigated as a result of this incident and she was given remedial training.
Potential Safety Implications
The safety implications of this error have the potential to be fatal. In short, if a person was caught in these doors as they were being closed they would be literally cut in half.
Incident Cause
• Lack of adherence to standard operating procedures.
• Poor or lack of thorough training for the contractor maintenance team on aircraft type.
• The competence of the tradesman could be questioned.
• After discussing the incident with the tradesman he was hesitant about notifying his management of uncertainty or lack of confidence in carrying out the task correctly.
• Poor design on the aging aircraft which could allow the pin to be fitted incorrectly.
Human Factors Lessons
This incident highlights latent errors documented in the Accident Causation Model. Important lessons can be derived from this incident:
• Standard operating procedures need to be trained, followed and their use embedded in the organisations safety culture.
• Training to generate expertise is an important aspect to be managed in a safety management system.
• Building a safety culture with open communication is important in aviation organisations. A ‘rule with an iron fist’ type attitude has no place in aviation at all organisational levels. This would help to mitigate tradesman having fears of ‘putting their hand up’ when they are uncertain, uncomfortable or feel safety and efficiency is being compromised.
• The value in having an easily accessible, non-punitive and anonymous safety reporting system has a necessary place in aviation organisations to allow collection of data on near-misses, incidents and accidents. This will provide data for reducing error and mitigating error consequences.
• Redesign of the safety pin (locking mechanism) is a valid option.