originally posted by jetblues
This all leads me to my next question then - what helps the most on an RTO - brakes (auto/manual), speedbrakes or thrust reversers ?
That very much depends on the aircraft and the conditions.
TRs will be far more effective, proportionally, on a wet runway, and brakes less effective, due to loss of braking mu.
Aircraft with energy limited brakes, or torque limited brakes, may find brake contribution to the RTO greater at lighter weights, as brake fade may affect braking at heavier weights.
Effectiveness of spoilers depends obviously on number of panels.
Fo a given aircraft you can gauge the relative effectiveness of each system to the RTO by looking at the penalties for various failures in the flight manual, for landing distances. While not the complete story, that will give you a rough guide to the relative effectiveness of these devices.