Until recently, Safety Management was considered almost devolved from all but flight operations, with reliability only concerning itself with operational metrics like ‘Despatch Reliability’. Nowadays, the introduction of other reliability metrics that are designed to project wear-out or failure rates has begun to address the requirement for Reliability to demonstrate Maintenance programme effectiveness. The question is could this have merely been the starting point to an evolutionary step-change in safety management by introducing an unbreakable link between reliability and airworthiness.
Can reliability also prove the effectiveness of Safety policies & procedures as well as those of reliability?
If it can be argued that airworthiness is a direct and key contributor to aviation safety, then it stands to reason that reliability is more than proving the effectiveness of an approved maintenance programme, but also, the basis of engineering and maintenance safety in that an effective and reliable programme of aircraft maintenance leads to an aircraft that is technically safe to operate.
Linking Safety & Reliability through Risk
The fundamental definition of reliability, is:
Reliability (Aviation)
Reliability in aviation is a broad term and is an expression of dependability and the probability that an item—including an aircraft, engine, propeller, or component—will perform the required function under specified conditions without failure for a specified period of time.
The introduction of the concept of probability or likelihood to the reliability equation together with the concept of Root Causes and potential safety outcomes and events in the opinion of the author is almost identical to the basic tenets of Safety risk!
However, there are some exceptions. Where reliability is concerned, engineers and safety professionals are concerned with the likelihood of a failure event not occurring, which, is opposite to safety management where the focus on a safety event or failure is its’ likelihood that it will occur.
Herein lies a curious yet symbiotic relationship between Safety and reliability, could Safety risk management data borne out of reliability data be utilised to optimize and even off-set engineering and maintenance safety risk?
The potential symbiosis between Safety Risk and Reliability Data?
Not necessarily!!! If there is sufficient reliability data in a well-designed reliability system, that produces reliable data against which corrective actions can be reliably formulated and acted upon, then YES, reliability data could be utilised as a safety risk management off-set.
However, where the reliability system is poorly designed, or suffers from a general lack or absence of available data, it would not be in the interests of the operator or the maintainer to include this data, and rely upon any potential safety off-set that the data may suggest.
Either way, both safety and reliability engineers must be careful not to disguise the nature of engineering and maintenance safety risk, and lull themselves into a potentially dangerous and false sense of security. In this way it is perhaps better to separate the two metrics, and allow operations and engineering managers the opportunity of judging for themselves, rather than providing a single and unified view of Engineering and Maintenance safety risk.
Statistical Reliability Calculations have now found their way into safety.
Overall, a well-designed and executed reliability system becomes an intrinsic part of safety management. This particular point is well documented in ICAO Annex 19, which refers to statistical analysis techniques (currently utilised in reliability calculations) in terms of Population or Sample Mean, Variance and most importantly, Standard Deviation which is now incorporated as an intrinsic part of the SARP. The author sometimes wonders if ICAO Annex 19 should be just called ‘Safety’ or ‘Safety & Reliability’?
The jury might well be out on that one!!
Rustom D. Sutaria – Avia Intelligence, Dubai, 2016
Join Rus Sutaria in the Middle East where he will be speaking at great depth about Reliability between 23rd and 26th January 2017.
See details of the Training Session in Dubai, UAE
For details and enquires please email team@sassofia.com
