Fail 12 Second Vertical Test, Pass 60 Second Vertical

[SAITAETGrad]

Just experienced some interesting feedback from our flammability engineer.

A 12 second vertical test (FAR 25 Appendix F Part 1 (a)(1)(ii)) burned a couple inches and failed to self extinguish in 15 seconds and therefore failed the criteria.

Another sample was applied to the 60 second test (FAR 25 Appendix F Part 1 (a)(1)(i)) and burned a couple inches and a little bit but then self-extinguished all but immediately - pass!

This was at first counter-intuitive, but it would appear that the more intense 60s test released the energy near the flame front without expanding the burn length more than "a little bit". With the accessible fuel consumed, the flame went out. The 12s test simply had enough fuel available to sustain the wick.

What can we do with this data? Per FAA Policy Statement PS-ANM-25.853-01, 60s test results substantiate all cases of the lesser 12s test. But, knowing that in this case, this assumption doesn't strictly hold under test conditions, could you justify using the 60s result? How would you frame your argument relative to the real world post-crash fire case? What concerns with regards to confirmation bias would you have?

 

[CoffinsCorner]

I am no expert, but do you not normally test either 12 sec (for minor appliances) OR 60 sec (major appliances)?
And secondly; are you not supposed to test three samples? Maybe the result of the third test could clarify...

Fell free to enlighten me, if I am wrong...

 

[Sparweb]

If the sample is a composite of several layers, is there evidence of a specific part that contributed more to the persistent flame than another? IE, did only the covering continue to burn or was the substrate also consumed? Also conceivable than an adhesive contributed to the first flame, but charring spread between layers during the longer flame exposure, removing the fuel. Have you examined them personally yet?

I've never had to deal with ambivalent or contradictory burn test results, (I must be lucky) so I would just be guessing with the second part of your question. Have you checked that this isn't addressed by FAA advisory material?


STF