Know anyone who is afraid to fly?  Millions of people around the world say so. Yet flying commercial aircraft is ten times safer than any other form of transportation.  The problem is that airplane crashes are front-page news whereas automobile crashes killing over one million humans annually are largely unnoticed.  However, new government regulations mandatory for all commercial aircraft go into effect in 2024; their names are “ARP4754B” and “ARP4761A” and many believe they would have eliminated a majority of plane crashes of the last decade.  But what are ARP4754B and ARP4761A really?

The Society of Automotive and Aerospace Engineers (SAE) publishes along with EUROCAE various safety standards called Aerospace Recommended Practices (ARP).  ARP4754B is the upgraded Aircraft/Systems guideline while ARP4761A is the upgraded Aviation Safety guideline.  Both have been in work for over five years and will start being applied in 2024. But what are they really?

Consider a commercial office building, without plans and processes for such a building, there is no way to assess, or claim, a building’s architecture and construction are safe.  Since developing aircraft and avionics systems is typically vastly more complex than constructing a building, it is clear that aviation/systems require high-level planning, processes, requirements, safe development, verification/validation, and evidentiary proof of compliance. This is the basis for ARP4754B, “Guidelines for Development of Civil Aircraft And Systems.”  

With revision “A”, e.g. ARP4754A, numerous key improvements were made as shown in the following figure titled “ARP4754A Key Attributes & Rationale”:

SAE ARP4761A is the corollary to ARP4754B and is much more than a detailed guideline for aircraft and systems safety.  ARP4761A (formally released two weeks ago) is officially titled “Guidelines and Methods 

The just-released ARP4754B has numerous key updates over yesterday’s ARP4754A including:

• Better alignment of ARP4754B to the forthcoming ARP4761A (itself an update over ARP4761)
• Changes to Development Assurance Level (DAL) assignment and moving that to ARP4761A (see below)
• Model-based systems engineering (“MBSE”)
• Applying ARP4754B’s greatly enhanced “Modifications and Reuse” for aircraft and avionics systems
• Better examples for applying ARP4754B to actual real-world aircraft and avionics systems

for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment”. In reality, ARP4761 is rather a detailed tutorial on aviation safety/processes and describes how to apply various theoretical analysis to apply then assess ongoing development activities toward aviation safety. Clearly, ARP4761A is tightly integrated with ARP4754B and provides a foundation for the most fundamental tenets of aircraft regulations.

The safety assessment should answer the following questions for the aircraft, and then each system, as depicted below:

A key is to remember that the safety assessment process begins with an overall Functional Hazard Assessment, followed by a Preliminary Assessment; both of these are top-down.  Then, during and after implementation, the final System Safety Assessment is performed inclusive of FMEA which is bottom-up. This process is depicted below (excerpted from AFuzion’s ARP4761 Training):

Functional Hazard Assessment (FHA) per ARP4761A

The functional hazard assessments (FHAs) are carried out at both the aircraft and system levels. The objective of the FHA is to identify failure conditions of aircraft and system functions (loss of function, malfunction, etc.), and their classification (catastrophic, hazardous, major, etc.) so that aircraft and system designs may be proposed and achieved which decrease the probability of the occurrence of the failure conditions to acceptably lesser levels. In avionics certifications, all parties recognize the importance of the FHA. The applicant is responsible for identifying each failure condition and choosing the methods for safety assessment.  The applicant should then obtain early concurrence from the cognizant certificating authority on the identification of failure conditions, their classifications, and the choice of an acceptable means of compliance. 

With ARP4754B and ARP4761A, aviation will most certainly be safer.  Zero crashes ever?  No … but many fewer.