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Somebody here will no doubt know the answer to this - @Genghis the Engineer or @joe-fbs perhaps?

Where on the EASA website can I find the design (not maintenance) requirements associated with ELA1 aircraft?

In particular, anything associated with concessions (if any) from CS23, especially associated with acceptability of qualitative versus quantitative evidence against software safety case submissions.
To the best of my knowledge, ELA1 went nowhere as that specific concept, but the work from it span towards LSA (which EASA then mucked up by simultaneously applying no rigour at-all to initial approval, then pretty much full Part M maintenance once in service), and the FAA led part 23 re-write.

CS.23 was re-issued recently as issue 5, and EASA made a complete hash of it. Basically they moved all of the prescriptive (not to mention safe and well understood) material into AMC, without providing any firm guidance about alternative means. So at the moment it's completely unusable, and anybody with any sense will simply use issue 4 for the foreseeable.

If an aeroplane is not a microlight and under 750kg / 45kCAS Vso, my advice would be to simply work right now with CS.VLA, which is extremely well understood, has plenty of interpretative material, and declared to ICAO. If you're then looking towards kit sales, pretty much anybody (including LAA and BMAA in the UK) will accept VLA, and for that matter FAA are happy with it too.

If it's bigger or faster than that, I'd use CS.23 issue 4.

Last edited by Genghis the Engineer on Sat Dec 30, 2017 7:33 pm, edited 1 time in total.
You could possibly elect to comply with the ASTM standards that the FAA have used as the AMC/GM for the revised FAR23. It's surprising that a EASA haven't gone down the same route as the attempt was to harmonise the new FAR/CS.
EASA clearly do accept ASTM as an acceptable standard at least for CS23 as that's what Garmin, Dynon etc have used to certify EFIS systems with software that doesn't meet DO178B.
Hello DaveW,

I only look at this section occasionally so only just seen this request.

Off the top of my head, the airworthiness codes don't use those ELA1 and 2 break points but having moved away from certifying a CS-23 aeroplane in October 2015 to my current job with a very different flying machine, I may be out of date.

Trying to address your specific question, I am interpreting "software safety case " as something to do with design assurance for software (or complex hardware). In that case, my boss and I find figure 2 of FAA AC 23.1309 very useful. it says for single reciprocating powered aeroplanes of less than 6000 lb, you should use:

for failures causing Catastrophic outcomes, 10E-6, Design Assurance Level C.
for failures causing Hazardous outcomes, 10E-5, Design Assurance Level C (D if a secondary system).
for failures causing Major outcomes, 10E-4, Design Assurance Level C (D if a secondary system).
for failures causing Minor outcomes, 10E-3, Design Assurance Level D, primary systems only.

Not sure whether that is what you are asking, I think not, but happy to take email or PM to discuss further.