This came up during simulator training recently. On this particular B737 simulator a button on the instructor panel causes the leading edge devices to retract 20 knots below V1 causing a flap/LED disagreement light to come on as well as the take off configuration warning to sound. An obvious abort situation.
But occasionally the stunned mullet phenomenon occurs and while the crew mull over noises and lights and the can't believe whats happening look, the aircraft is rapidly accelerating towards VR. Now, regardless of the rights or wrongs let's say the decision is made to continue the take off with this unknown LED problem. Can anyone suggest what speed above VR would you accelerate to before venturing to rotate? For example there is 15 knots difference in VREF between landing a 737 Classic with all flaps up and landing with only trailing edge flaps up, suggesting this 15 knots is the key to a VR 15 knots in excess of the planned VR. I appreciate there should be no question the crew should abort but if for some reason they did not abort, then what would be a safe VR with LED retracted?