On a/c with an approved engine failure warning system, certification allows one second for the pilot to recognise the failure, and commence the RTO. On a/c that do not have a engine failure warning system, the allowance is 3 seconds. i.e. 727-100 / 707 etc. It must be stressed however, that this 1 (or 3 as the case might be) second allowance is not to allow the line pilot more time to assess the situation at V1. During certification, test pilots typically commence the abort 0.3-0.5 seconds after the failure. These are reaction times unlikely to be repeated in a line situation, so the times are built up in recognition of the fact that RTO's are a rare occurance, and line pilots not as spring loaded as the test pilot,
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