Once airborne you are only required to calculate and verify that you can stop within 100% of the available runway, the other figures quoted are for dispatching purposes. The NTSB proposes the FAA require a 15% margin be added to that in-flight requirement going forward. At SWA that has since been adopted. The onboard computer that night showed 560 feet stopping margin based on FAIR braking, and 30 feet margin based on POOR. The number included credit for thrust reverse as per Boeing data on the NG series of 737 aircraft. Braking action and tailwind proved worse than expected and when combined with lack of thrust reverse application in the initial landing rollout made the calculations invalid and led to the overrun.
Last edited by canyonblue737; 7th Oct 2007 at 04:41.