Genghis, following on from
MFS; historically this appears to one of those areas - 'don't ask just meet the requirements', but there are few requirements, only advice, conditions, etc.
With increased engine and system reliability there is more interest in crew reaction, not necessarily time, but more in the understanding of a situation.
I recall a conversation about different failure conditions for large fan engines. Some situations the fan continues to rotate at high speed with few indications of failure, more so with fixed wing auto-rudder application; alternatively a catastrophic failure could beat the auto-rudder, requiring pilot compensation, which confusingly has to be reversed when the auto-rudder activates. Hence the issue is much wider that just the engine.
Another cautionary area - the words.
'Startle' appears more related to degraded cognition - a condition, involving a range of time span depending on the depth of impairment, individual susceptibility related to experience, training, or uniqueness of the event, and some recent studies suggest a longer term build up in an evolving situation without a major failure.
'Surprise' is often described as a mental reaction relating to a situation, with or without startle, etc, and might involve subconscious physical action.
Best avoid making words up - what is response lag …
Longtime away from regulations, but I too recall 1 sec reaction time followed by a further 1 - 3 seconds for action. e.g. autopilot deviation max rate was 4 sec in the cruise, but could be reduced to 2 sec during an approach, claiming that followup hands-on-the-stick quickened awareness.
Another example was the measured head-down to head-up transition to acquire sufficient awareness for manual landing was at least 4sec, similarly for head-down to head-up reversal, but not so for an auto-land decision - differing requirements for 'awareness' and type of decision.
Beware proposing new or novel approaches to reaction time; perhaps best enhance awareness of the failure with auto detection and alerting, guidance as to a suitable course of action, instrument displays.
RAE research was tied to particular operations - low visibility.
Other research is science based, often differing due to the subjective nature of behavioural assessment.
See
https://econtent.hogrefe.com/doi/pdf...?download=true
and other work from the authors.
https://www.researchgate.net/publica...on_Perspective
Also:
https://pure.tudelft.nl/portal/files...on_startle.pdf
https://www.ncbi.nlm.nih.gov/pmc/art...0817723428.pdf
https://pdfs.semanticscholar.org/61c...3eaefdf6a3.pdf
I am dubious of work by EASA, FAA, FSF, or those citing training solutions; much of this is highly subjective interpretation of previous research.