Tag Archives: do-178b

AFuzion’s Aviation Development Certification Checklists Surpass 10,000 Users

15 Mar

AFuzion, the world’s premier aviation development and certification services company, announced their DO-178C and DO-254 Template and  Checklist Users now surpass 10,000 engineers worldwide.

With the 10th EVTOL aircraft developer procuring AFuzion’s DO-178C/DO-254 (Software/Hardware) avionics certification checklists, AFuzion’s templates and checklists are now in use by more engineers worldwide than all other competitors, combined.  AFuzion’s DO-178C Planning Templates/Checklists and DO-254 Planning Templates/Checklists were developed all-new in 2015 and continually improved since then by usage on civil, military, UAV, and EVTOL projects. In 2019, NASA’s new manned spacecraft project utilized four AFuzion engineers fulltime to deploy AFuzion’s processes within NASA/Suppliers and now five fulltime AFuzion engineers are onsite supporting further development for NASA’s manned spaceflight.

AFuzion aviation clients in the following countries have all deployed AFuzion’s DO-178C Processes/Checklists and/or DO-254 Processes/Checklists:

  • Australia
  • Austria
  • China
  • Denmark
  • Germany
  • Israel
  • Italy
  • Korea
  • Japan
  • New Zealand
  • Norway
  • UK
  • Slovenia
  • Spain
  • Turkey

For samples of the AFuzion DO-178C & DO-254 Templates and Checklists purchased by these clients, click here:

In addition to AFuzion’s aviation processes, clients in the above countries procured onsite and remote consulting and training by AFuzion: over 80 companies in just the past twelve months. Additionally, 9,000 engineers were trained by AFuzion’s expert team of senior Trainers in just the past 12 months:  5X more than all competitors’ trainers combined.

Says AFuzion’s Chris Jackson, Co-founder and Chief Counsel, “AFuzion’s success is clearly attributable to two things: integrity and originality. Our competitors are reselling our founder’s old templates and checklists from two decades ago:  imagine buying a used toothbrush 20 years old versus an all-new electric toothbrush for the same price.  It’s that simple: AFuzion’s D0-178 and D0-254 Templates and Checklists are the only ones all-new and also proven by over 10,000 engineers’ usage in 15+ countries. We also invest more each year into updating these new DO178 and DO254 templates and checklists than all our competitors combined. it’s an expensive and time-consuming process to keep these updated  – our competitors with their tiny, less-skilled staff simply cannot keep up. Personally, I can’t imagine buying a 20-year toothbrush and apparently the market agrees: 10,000 engineers can’t be wrong.”

For a DO-178 or DO-254 checklist free sample, simply select one from the following page and send your request to AFuzion: the difference will be readily apparent:  click here.

Santa, All We Want For New Year 2019 is … Seven More Avionics Engineers!

4 Jan

OK, time for honesty:  did everyone get what they wanted from Santa Claus ten days ago?!?   Yes, Santa was good for everyone here at AFuzion Inc. with our record-breaking year doubling last year’s $ results.  But one thing (actually seven things) were missing from under the Tree … yes, Engineers.

You see, we’ve been steadily increasing staff here the past five years to keep up with our growing business in 25 countries.  At our December planning meeting, we actually wrote a letter to Santa asking him ” Santa, please bring us 9 more engineers. To start work Jan 7, 2019.”  Really.  Now folks, all of us either have children, know children, or are still children.  My kids even say I’m just a big child during the holidays.  We BELIEVE in Santa Claus. (Santa, are you listening?)  When we were kids, we usually got some of what we wanted.  But this year, Santa only brought us two engineers.  2.  T-W-O.    Santa, can you spell “N I N E”?  As in “9”.  We asked for 9.  We got 2.

Santa, do you not do math at the North Pole?  When Susie or Johnnie ask for a new bike, do you simply bring them one tire?  Yes, the two engineers you brought were great. Really.  Truly.  Top 10% of their field which is our minimum standard.  Thank you Santa.  But again we asked for Nine.  We got TWO …

Santa, if you are listening, we won’t tell anyone if you secretly make another trip to our chimney and bring us seven more engineers.  Yes, these are for the USA so must be USA citizens.  Yes, these are for the western USA so hopefully they want to live in Los Angeles, Phoenix, or Dallas.  Please Santa, if you can’t bring the engineers directly to us, please just send us their contact info or CV to our email at info@afuzion.com.  Otherwise Santa, we’re going to spread the word that you sleep in funny red pajamas and live off cookies, milk, and … reindeer meat.  Santa, really.  Lay off the reindeer – just send us great Engineers please. ASAP!!!

Yours truly,

All the Engineers (Elves) at AFuzion Inc.

AFuzion Launches New CAST-32A Multi-Core Processing Training

18 Nov

AFuzion’s new CAST-32A Multi-Core Processing for Avionics and Safety-Critical developers has launched with strong acclaim. The future of embedded processing is via multi-core processors as the need for added processing power has surpassed the ability of CPU’s to keep up. However, multi-core processors utilize shared cache, shared memory, and shared communications I/O. This sharing between the MCP cores produces potential interference which can violate the very “determinism” requisite for certifiable safety-critical systems. For example, avionics DO-178C and DO-254 require adherence to CAST-32A recently updated by the worldwide Certification Authorities Software Team (CAST).

CAST-32A is the worldwide (America, Europe, Asia) Certification Authorities Software Team (CAST) guidance for ensuring safe implementation of Multi-Core Processing (MCP) within avionics systems. Increasingly MCP’s are used in avionics and understanding what must be done to plan for, implement, and verify deterministic “safe” MCP development via CAST-32A is the focus of this AFuzion 2-day private training course. Attendees will understand how to utilize multiple-cores providing simultaneous operations using deterministically shared resources such as cache, memory, and communications and performing MCP CAST-32A Interference Analysis. Attendees will also learn how to work with RTOS vendors and RTOS’s themselves to comply with CAST-32A and develop safer avionics.  For a free technical whitepaper on CAST-32A, download here: Click Here for Free AFuzion Technical Whitepaper “Understanding CAST-32A


CAST-32A is increasingly relevant to avionics developers but users find it vague and challenging to understand. AFuzion’s 2-day CAST-32A Training teaches attendees how to properly understand, deploy, and verify MCP-based applications. AFuzion’s training was recently provided with our industry partner Lynx Software to 45 senior MCP developers in Huntsville Alabama and it was a resounding success; all the attendees stated it was highly worthwhile and crisply delivered to provide a true practical understanding of CAST-32A deployment for avionics via DO-178C and DO-254. AFuzion’s CAST32A training syllabus is summarized below, with full details at AFuzion’s website, https://afuzion.com/training/cast-32a-multi-core-processing-training/



  • CAST-32A Introduction
  • Summary of DO-178C, for Multi-Core usage
  • RTOS Introduction & Scheduling, Processes, Tasks, and Threads
  • MCP What & Why
  • DO-178C & MCP – Plans, Standards, Activities
  • CAST-32A MCP Robust Partitioning Principles
  • RTOS Specifics – Technical Info
  • DO-254 & MCP
  • MCP Cert, Deadlines, Benchmarks & Reports
  • Overview: IMA, ARP4754A, ARP4761 & MCP
  • IMA & CAST-32A Modules and Partitioning
  • DO-178C’s & MCP Requirements, Design & Verification –
  • MCP & CAST-32A Best Practices for Planning, Testing, & Certification
  • MCP & CAST-32A WCET Mistakes & Best Practices

New Free Tech Webinar Friday, June 8: “Safety, Security, Agile Development: Pick Any 3!”

4 Jun

The most frequent question we get at AFuzion the past year from dozens of clients  is “How do I merge Agile Development into my safety-critical development while ensuring my software meets Security standards???”    If you’re into aviation, automotive, or medical devices, this question has Pass/Fail consequences.  If you’re programming a cappuccino machine, it has consequences … (imagine some hacker changing my espresso machine settings remotely to provide less caffeine in my morning routine (and afternoon; and evening).  TRAGIC!!

So we’re doing something about this, to avert more serious tragedies and enable developers worldwide to better merge AGILE development into their safety and security software.  Really.  This free technical webinar is limited to the first 500 registrants – click here for more info or to register:Free Registration June 7 Tech Webinar “Safety, Security, and AGILE Development – Pick Any Three!”



7 x 7 x 7: 7 Avionics Development Tips from 7 AFuzion Developer’s 7 Months in Japan

5 Mar


Seven AFuzion avionics software engineers recently completed a 7-month assignment in Japan on the new Mitsubishi Regional Jet.  What are the top 7 avionics software DO-178C and DO-254 hardware tips they learned?

Says Mr. A. Morita (AFuzion’s Japanese Client) “We are very pleased to acknowledge the success of AFuzion’s expert engineers and DER’s.  Half the work needed to be done onsite in Japan and the AFuzion engineers were very hard working and productive. The other half could be done offsite by AFuzion in USA and it was good also. Our engineers traveled to California and worked in AFuzion’s Los Angeles offices; it was very nice and productive. The AFuzion avionics engineers gave us DO-178C training and also DO-178C and DO-254 best practices.  The AFuzion DO-178C gap analysis was good and helped us understand the gaps.  Our only wish is that we engaged AFuzion sooner as we could have save even more money and time.”


Mr. Jack Jones states “I managed the onsite AFuzion Japan engineers plus three of our DER’s and was there for the entire 7 month engagement.  It is really a pleasure working with the Japanese as they are hard-working and diligent.  The Japanese culture is well-suited to successful avionics because DO-178C and DO-254 require diligence, skill, and plenty of checklists; we used the new 2016 AFuzion DO-178C and DO-254 checklists and they’re really great – note the lessons below.  I think we’ll be seeing much of Japanese aviation and avionics engineers in the future – we’re quite impressed and as you know AFuzion engineers aren’t easily impressed.  At the successful conclusion, we were.”


Here are the top 7 avionics development tips from AFuzion’s seven developers in Japan for seven months:

#1).  Understand that aviation and avionics are not “all-new” developments, but that there is much legacy foundational work.  While DO-178C and DO-254 seem to “presume” all-new custom development, the truth is that most avionics projects are upgrades to existing legacy systems and a combination of previously developed hardware/software, and reverse-engineering applies.  Read CAST-18 about Reverse Engineering for avionics (request a copy at www.afuzion.com or download the Top DO-178C Mistakes whitepaper at http://afuzion.com/do-178c-best-practices-for-avionics-development/ which further explains).

#2)  Go back and focus on requirements.  For system requirements, be sure to apply ARP-4754A but understand ARP-4761.  Get ARP-4754A training or at least read up on it (for a free introduction, just download and read “Understanding ARP-4754 Introduction”: http://afuzion.com/arp-4754a-introduction-avionics-systems/ )   Be sure to address Safety requirements and prove your Systems engineers reviewed this and QA audited it (note:  this wasn’t done when AFuzion first showed up onsite so we quickly had to rectify that)  Go back and add more detailed DO-178C and DO-254 requirements.  Address derived requirements explicitly.  Use a detailed requirement review checklist (request a free copy from AFuzion if you don’t have one).

#3.  Get good DO-178C training, ARP-4754A training, or DO-254 training.  If you can afford outside trainers, just Google and find the best (that’s easy – AFuzion’s engineers did the world’s first 30 years ago and have trained over 12,000 worldwide; over 1500 in just the past year).  If you can’t afford outside training, read the books on DO-178C and DO-254 and download the recent whitepapers (most were all written by AFuzion but AFuzion’s old ones are available from Atego and HIghRely; best to get the new ones (all free from AFuzion) and compare with the old ones our engineers wrote 15 years ago which are nicely still provided by Atego and HighRely – you can see how much avionics has changed in those 15 years and how NOT to do things by reading the latest versions; only available from AFuzion).  Also for free: a one hour seminar on DO-178C Mistakes – watch here for free:  https://attendee.gotowebinar.com/register/7350945891265140228


#4.  Qualify your test tools.  When AFuzion’s team first arrived in Japan, the engineers there were working hard re-reviewing all the code and tests manually, repeatedly.  Everything was changing and the amount of time spent on re-reviews was enormous. We taught them how to instead perform DO-330 tool qualification to avoid re-reviewing all the code and tests repeatedly. This alone saved our client over $500,000 in those seven months and probably $2-3M over the future lifetime.  If you don’t know how to do DO-330 tool qual, just download a free Do-330 Tool Qualification paper here:  http://afuzion.com/do-330-introduction-tool-qualification/


#5.  One great reviewer is better than many good reviewers. When we arrived in Japan, the well-intentioned customer engineers had 5-10 reviewers at every peer review.  Massive overlap but also some gaps. Instead, use professional checklists (AFuzion has the world’s latest and most thorough DO-178C checklists and also DO-254 checklists; not just the old rehashed open-source checklists from Boeing’s D6 document which everyone else sells, but real all-new DO-178C and DO-254 checklists).  Train reviewers to do complete reviews; if you can, use Agile DO-178C methods and CMMI review methods.  Make sure you capture the transition criteria for reviews and that QA audits those review transition criteria.  And always use one great, responsible and accountable reviewer instead of numerous weak reviewers.


#6.  Do a DO-178C gap analysis and DO-254 gap analysis.  Leverage 60-70% of your existing work and artifacts and keep them!  No need to change. But understand the gaps and close them.  If you can afford it, engage a professional gap analysis like this one:  http://afuzion.com/gap-analysis/    If you can’t afford an outside gap analysis, get training and do your own.  At least understand common mistakes and avoid those.  For example, here’s a free paper on how to avoid common DO-254 mistakes:  http://afuzion.com/do-254-top-mistakes-2/    But remember to keep review records of your reviews (again our Japanese client had great reviews but simply didn’t have great records to prove that).


#7.  Reward productivity.  Some engineers are 500% more productive than others.  Because they’re smarter?  Probably not – our Japanese client engineers were all exceptionally smart.  But teach productivity and reward it.  Make competition fun.  We gave weekly “bonus recognition” awards of a trip for two to the local sushi house on Saturday – many pounds of tuna were indulged in engineers who increased their productivity. At the end, everyone was much smarter, more productive and really enjoying work; three of our engineers will remain through 2017 and likely beyond. (AFuzion’s Jack Jones will remain in Japan only half-time so soon able to write many more technical articles – thanks Jack for all your many successes in Japan!)

“How To Fail at Aviation Software Development” (Then Hopefully Succeed!)

1 Nov

Too often “How to” guides present lofty goals which seem desirable, but at the same time are seemingly unattainable. This paper is different. An unhealthy software development diet is just like a poor nutritional diet: seemingly good tastes can become bad habits and result in real harm to health. But what ingredients go into an unhealthy airborne software diet?  Understanding and addressing airborne software failures is the first step towards better avionics health.  Remember: with knowledge, training, discipline, and practice, software engineers – just like athletes – can become winners.  The following is an excerpt from a new paper just written by Vance Hilderman of AFuzion (with Joao Esteves of CRITICAL Software); to download the entire paper, just visit http://www.afuzion.com and request a free download.  Free Technical Whitepapers, including “How To Fail”



DO-178C describes the integral processes spanning the software development lifecycle. Up to 71 formal objectives are summarized which cover the full range of software engineering activities, beginning with planning and ending with certification.  While some of these objectives are self-evident (for example, ‘develop requirements before design’, ‘develop design before code’), others are more nuanced.  Returning to our metaphor, the parallels between software health and human health abound: everyone knows that reducing fat and sugar intake while engaging in modest exercise yields health benefits.  But how can you identify the most cost-effective and healthy foods? And, when it comes to exercise, what types and frequency provide the greatest return on time while minimizing the risk of injury? DO-178C says nothing about reducing schedule, cost, or risk yet these things are paramount to the success of any avionics project.  95 of the world’s 100 most successful avionics companies have hired the authors of this paper (CRITICAL Software and Afuzion) to prove or improve airborne software health. Drawing on this experience, this paper explores the ingredients that contribute to BAD avionics software health and how to avoid them, in order to better understand the healthy practices that lead to successful airborne software development.


BAD Software Health: The Best (or Worst) Ways to Fail …

DO-178C’s 71 objectives are interspersed across ten categories of avionics software engineering activities. Failures can literally occur within any of these objectives or activities. But which objectives are most frequently misunderstood and which activities yield the greatest risk of failure? This paper summarizes the best (or worst!) ways to fail within each of DO-178C’s ten process categories. That’s right! Each of DO-178C’s ten process categories can be associated with major failures.  The secret is knowing what the potential failures are so that you can formulate advanced strategies to avoid them while maximizing your chances of success.  And, of course, maximizing success means minimizing risk, cost, and schedule times while simultaneously maximizing quality.  You’ve no doubt heard of the saying:  “You can have it fast, or cheap, or with high quality … so pick one.”  However, successful avionics projects truly require all three:  cost-effective and fast development processes, with acceptably high standards of quality.  Here, avoiding the common mistakes within each of DO-178C’s ten software engineering activities is paramount to success.


DO-178C’s Ten Process Categories

So we know that DO-178C covers ten categories of software engineering activities.  These ten categories and the common mistakes associated with each are depicted below:

DO-178C’s Top Ten Failures vs Activities


  1. Planning to Fail

Aviation, like athletic training, is all about preparation and planning. Before an aircraft takes off, a flight plan is conceived of, detailed, and then filed.  Similarly, a competitive athlete makes a training plan and smart, successful athletes use nutritionists and trainers to help them.  Success requires planning, and no one intentionally plans to fail. However DO-178C requires an advance planning activity yielding five detailed plans plus three standards; the planning recipe requires sufficient detail on the required ingredients of “what”, “who”, and “when” without too much detail on “how”.  As mentioned, avionics software health resembles human health in many ways: many factors come together to contribute to the overall state of health and, for avionics, those factors must be summarized in the five plans and three standards.



Some athletes find that despite their seemingly well-prepared exercise plans, their improvement quickly fades along with their dreams of success: and that their exercise plan simply lacks the ability to strengthen muscles.  Why?  Typically, the answer is that they are missing crucial details about diet, intensity and the duration of exercise and, most importantly, how to measure success.  Aviation is the same. It is all too easy with DO-178C to draft high-level plans which do not sufficiently define the key detailed aspects of your avionics system necessary for successful certification. Common aspects missing from DO-178C planning documents include:


  • Use of previously developed software. If used, how will it be certified or brought up to compliance standards?
  • Use of configurable software, where users may “reconfigure” software after certification by modifying off-board configuration data. It is imperative to follow DO-178C’s explicit Parameter Data Item (PDI) criteria for such activities.


  • Application of DO-330 for Tool Qualification, and identifying the full suite of software engineering tools planned for use then defining where the outputs of each will be verified. If verification is insufficient, formal DO-330 Tool Qualification will likely be required.


  • Application of Model-Based Development as per DO-331 and, when used, a brief synopsis of applicable Specification Model standard versus Design Model standard (these cannot be the same standard: like high-level requirements and low-level requirements, the Specification Model and Design Model are distinctly different and require sequential verification, in that order).


  • Description of the means to analyse data and control flow coupling. This coupling analysis is about more than checking a box during a code peer review – it requires proper consideration of software design and the interfacing modules/data. Recent third-party tool improvements will help with coupling analysis but your plans must summarize coupling analysis activities via verification engineers.


  • Regression analysis: all projects have changes and the means to verify those changes depend on regression analysis. The processes used by verification engineers for regression analysis and retesting must be sufficient for the plan reviewer to assess adequacy – experienced verification engineers know how to apply the tools and techniques to semi-automate this process to ensure it’s done right, first time.



By considering the above common mistakes within your “avionics exercise plan”, your project has a chance to win the gold medal at the first attempt.



  1. The Requirements of Failure


The world’s leading software experts agree: most software defects are due to defective requirements.  Yet DO-178C provides scant details for ensuring that you have great requirements.  Yes, you could hire or outsource your development to world-class avionics developers, but what can you learn from them about developing great avionics software requirements?  First, experts know that the successful longevity of DO-178 is due in no small part to its careful balancing of 71 deterministic objectives versus flexibility on how these 71 objectives are met.  Yes, DO-178C could include many more pages of suggestions on how to improve software requirements:  but they would be just that – subjective suggestions. Consider that avionics projects span a vast variety of domains, complexity, criticality, and size. No single “How to” guide would suffice.  Instead, DO-178C uses structural coverage analysis to assess requirements:  for Design Assurance Levels (DALs) where people could be seriously injured or worse (beginning with DAL C), software structural coverage is required.  Simply put, software structural coverage objectives exist for multiple purposes, including assessing the degree of software structural coverage obtained when performing requirements-based functional tests.


In Brooks’ 1975 book Mythical Man Month, it is revealed that a leading cause of software defects is “assumptions”, and that these assumptions are often the result of weak requirements.  The first version of DO-178 was developed soon thereafter, fully cognizant of Brooks’ writings.   When a software developer cannot explicitly understand a desired result (“software output”), that developer is likely to make implementation assumptions.  Of course, the developer should instead strive to achieve an improved requirement. Yet developers are much more likely to simply power on and do what they think best, not necessarily what is right.  How do good avionics managers avoid this?  They employ the following best practices:


  • Utilize detailed software requirements standards which are reviewed at SOI #1, and which include examples of good, and not so good, high-level requirements and low-level requirements.


  • Have software testers review the requirements BEFORE the developers see them. Those testers then try to write deterministic test cases from those requirements without making any assumptions; where that is not obviously clear, feedback their questions to the requirements development process to yield improved requirements.


  • Use software modelling where systems engineers and software engineers use a shared-modelling platform and formal language (SCADE, SysML, UML, etc.). This shared language minimizes the very assumptions endemic to weak requirements.



  1. V = R + T  + A


Yes, engineers love equations!  The above equation is clear, but why is the “A” so small?  Again, it’s about health. Specifically, healthy verification of software requirements.


But is avionics software health really as simple as following an equation?  Almost.  But the equation must be properly understood:


V = R  + T  + A


Verification  =  Reviews  +  Tests  +  A Very Small Analysis


That’s right, in DO-178C, verification is performed via a combination of reviews, tests, and analysis:


  • Reviews: virtually everything is reviewed.  Plans, standards, safety, requirements, design, code, tests.


  • Tests:  requirements and code are tested via ground-based executable tests of flight software.


  • Analysis: when the above combination of reviews and tests does not completely satisfy DO-178C’s verification objective, additional analysis must be performed.


The verification equation is best satisfied when the requirements are sufficiently detailed that two independent verifiers could achieve equivalent assessment results.  Remember:  verification does NOT directly improve software. The goal of verification is to assess the software, specifically if the objectives of the DO-178C compliant plans and standards were fulfilled.  Actual software improvement then comes via the feedback process which then feeds into improving the requirements, design, and software.


It is imperative that requirement granularity be sufficient to devise robustness tests based on those requirements. Robustness should answer the question “does the software behave consistently and deterministically under less benign conditions of error values, boundary values, performance testing, illegal state transitions, off-nominal timing values, etc.?  In other words, the “rainy day” scenarios.   After robustness testing, DAL C, B, and A verification includes “white-box” tests, where actual software attributes and structural coverage are assessed. One objective is to assess the absence of dead code (code which has no reason or requirement to be there and which could and should be removed) and the sufficiency of mechanisms to ensure non-execution of deactivated code.  Experienced systems engineers elicit detailed requirements and expert avionics testers are adept at devising test cases to assess software/requirements robustness and dead/deactivated code.


Voila:  V  =  R  +  T  +  A




  1. Designing Software Failure


Design is like that distant uncle you see only once a year at Christmas or Thanksgiving. If you span across the entire life cycle nothing is as forgotten as design is. People often fail at requirements but plenty has been written and debated in conferences and training sessions about the importance of them. The same is true for V&V and testing.  Code has always been the gravity center – more emotionally than in terms of its actual impact on quality output.    What is left over and abandoned then? Design!  Indeed, design is often treated as a distant uncle and not a very wealthy one. And to some degree, agile processes (which may be helpful when well applied) are kicking design even further from the road. That is why frameworks and standards like AUTOSAR exist. It is not necessarily just to enable modularity, integration and reusability, but also because most people are bad at design and do not realize just how bad they are. Therefore, DO-178C applied properly can provide a useful framework for acceptable design. In the past, V&V was the subject of software developers’ bigotry – a set of activities left to those that were not sufficiently skilled at programming and were therefore relegated to the back seats in IT’s second class – but for a few years now, even non-safety-critical industries, such as banking, have started to view V&V as very important, explicitly procuring such services.


Back to our metaphor. Winning athletes focus on optimizing their capacity for physical movement, knowing that they cannot fundamentally alter their body’s “design”.  In athletics, the design of the human body is the ultimate equalizer: most bodies have fundamentally similar “designs”. Not so in avionics:  each system has an implementation customized to its particular design. Avionics software developers thus depend upon a robust and flexible design to yield the necessary consistency and determinism while affording the possibility of future system evolution. So what are the causes of failure in the design of avionics systems?  Over the past 25 years, the engineers at CRITICAL Software and AFuzion have worked on 300+ avionics systems – here are the most common design techniques observed which can result in failure:


  • Reusing prior designs which are poorly understood or documented. If you are inheriting such a design, first document it, then analyse it to see if it is even worth modifying. Like modifying an old or decrepit building, it may be more cost effective to simply start over, the right way.


  • Failing to have, and verify conformance to, a software design standard that specifies:
    • Details for all external and internal interfaces, including full bit patterns, encoding rules, use of any variant records, and source and destination information for all data items (remember: include internal interfaces).
    • Rules for defensive design/coding
    • Health monitoring details
    • Task prioritization schemes
    • RTOS and BSP usage and limitations plus a reference to allowable API’s (those designated “DO-178C certifiable”).
    • Rules for controlling coupling, which provide sufficient details to perform subsequent coupling analysis.


  • Failing to encapsulate hardware dependencies to yield portability.  Remember, for successful avionics programs, the question is not “Will it ever be modified?” but rather “When will it be modified?”. Most successful avionics systems are eventually updated with newer hardware and increased functionality.  Only by pre-planning future portability can such future upgrades be accommodated.  Plan for common core functionality which should not be changed and partitioned away from hardware-specific functionality which is then encapsulated within its own modules. Minimize the scope of change so that the vast majority of software modules, objects/classes and design elements can remain unchanged and unscathed. 


Bad design is also the key source of V&V difficulties when it comes to incremental testing, data and control flow analysis, effective development of test stubs and many more issues. What is strange is that one will often see people pointing fingers at the requirements or V&V team without realizing that disastrous design is actually the fundamental cause.



  1. Encoded Code


DO-178C requires that the “software language for humans to program avionics computers” is clearly understood by developers, reviewers, testers, and auditors. In other words, that it is absolutely NOT “encoded”.  The software languages used to program avionics computers must be common languages subject to defined compilation rules. Virtually any software language can be used (C, C++, Java, Assembly, Ada, Jovial, etc., none of which ever require compiler qualification or validation). However, for DAL A, B, and C there must be a defined coding standard. That coding standard must restrict unsafe constructs and operations while ensuring determinism, and the resulting source code must be verified against the designated and approved coding standard.  In avionics software development, the assumption is “guilty until proven innocent”.  So what are the best ways to fail at the level of code?


  • Failing to select a software language which has a coding standard that is accepted as safe by the aviation community. C, C++, and Ada are the most commonly used aviation software languages and all of them conform to safe coding standards.    


  • Failing to perform static code analysis prior to exiting the coding stage. While not required by DO-178C, static code analysis is performed via various commercial third-party tools. These tools can be formally qualified (see DO-330 Tool Qualification above), in which case the code peer review may not be required. However, even unqualified tools are usually better (and exceptionally faster) at finding hundreds of types of the most common software coding errors committed by humans.


  • Failing to define complexity metrics within the project’s required software coding standard and failing to enforce them. Complex code (measured via cyclometric complexity) is a harbinger of disaster. However defining in a way that is “too complex” is a subjective judgement and so such a definition is not provided within DO-178C. That does not mean that any project is free to have overly complex code. Quite the opposite:  complexity metrics must be defined and properly enforced.


  • Failing to realize that DO-178C’s coupling analysis is not solely performed by parsing or reviewing source code. Coupling analysis requires the consideration and analysis of software design and interfaces, not merely local source code reviews.


  • Failing to read between the lines of DO-178C to understand that there are six inputs required for software code reviews:
    1. Source code
    2. Source code checklist
    3. Software coding standard
    4. Software design
    5. Software requirements
    6. Trace matrix showing which software requirements are allocated to the source code under review


Each source code review must identify each of the above inputs, along with the artefact version identifier used for that review.

Hope you enjoyed the first half of this free technical whitepaper “How To Fail at Aviation Software Development (and How To Succeed!)”  To download the full paper, just visit AFuzion in the above referenced link and request a free download.

For information on public or private DO-178C training classes, visit AFuzion at: Public and Private DO-178C Training Classes:

For a fun 1-minute video “What is AFuzion” click here: What is AFuzion? Fun 1-Minute Video:


Fall 2016 Important Avionics Development Dates: Conferences, Webinars, & Training

23 Aug


Important Avionics Development Dates – Fall 2016

 Avionics Conferences, Webinars, & Training 


Sept 13-15, 2016:  FAA Bi-Annual Certification Conference, Dallas Texas USA.  (Limited to 350 Attendees)        Info & Register :  www.faa.gov

Sept 14-16, 2016: Software Safety for Airborne Systems Conference, Berlin Germany.                                      Info & Register: http://www.avionics-system-safety.com/

Sept 26-27, 2016: Public DO- 178C Training via SAE, Hartford CT USA:                                                               Info Request: vance.hilderman@afuzion.com

Sept 29, 2016: Free Technical Webinar 10 a.m. EST: “Managing Safety-Critical Requirements” – Jama Software & AFuzion. Register:  http://go.jamasoftware.com/developing-safety-critical-system-requirements-best-practices-registration.html?utm_source=afuzion

Oct 13, 2016: Free Technical Webinar 9 a.m. EST:  “How To Fail (and how NOT to Fail) at Airborne Software Development”   Register: https://attendee.gotowebinar.com/register/6879917310589589249

✔ Oct 25-26, 2016:   Electronic Valley Aviation & Avionics Development Conference, Ankara Turkey.              Info & Registration: http://www.ev-seminars.com/seminar2016

Nov 14-15, 2016: Public DO-178C Training via SAE: London UK.                                                                            Info & Registration: http://sae-europe.org/aerospace-training-week/