The danger of the F/O calling STOP before V1
During recent type rating training on a 737 with pilots inducted into an airline, the syllabus called for demonstration of an outboard tyre failure 20 knots below V1. The pre-flight briefing included the advice that it is normally safer to continue the take off, rather than risk a high speed abort with degraded braking.
Despite this, when the tyre failed with noticeable vibration, the first officer called "STOP" and the captain under training immediately rejected the take off.
Both pilots had come from an operator where a rejected take off could be initiated if either pilot called "STOP" -without giving the reason for the call.
I understand this policy is common SOP at many airlines - the theory being the PNF may spot a problem which, in his personal opinion, requires an abort and that the other pilot was not aware of.
The B737 FCTM puts a different light on the subject by saying "the PM should closely monitor essential instruments during the take of roll and immediately announce abnormalities such as ENGINE FIRE, ENGINE FAILURE, or any adverse condition significantly affecting the safety of flight. The decision to reject the take off is the responsibility of the captain and must be made before V1 speed. If the captain is the PM, he should initiate the RTO and announce the abnormality simultaneously".
The executive word "STOP" as used by some operators, carries with it an awesome responsibility. A company policy that requires the captain to initiate an abort purely on another crew member's personal opinion, is fraught with legal issues. Perhaps that is why Boeing - ever vigilant to the risks of litigation - have not recommended the PM call "STOP" to start the rejected take off chain of events - but instead recommend the PM announce the problem rather than have the authority to call "STOP" with the full expectation the captain will follow his (the PM's) command.
I wonder how many captains crewed with an inexperienced first officer (quite common nowadays from reading Pprune) have been stunned to hear an F/O call "STOP" for a perceived serious problem, and have retorted "You have to be kidding" -and kept on going.
There are risks in any take off and a personal opinion call of "STOP" must be one of them. Personally, this scribe prefers the Boeing advice..
Thoughtful discussion appreciated.