After reviewing this information, the pilots determined that they were legal and safe to land on Runway 19 based on the airplane's landing weight, the existing wind, the weather and the “good” braking action that was reported on the first two-thirds of the runway.
The pilots decided they would touch down within the first 1,000 ft. of the runway and then make efforts to slow the airplane using automatic wheel brakes and thrust reversers as promptly as possible to maximize braking effectiveness while on the “good” braking action portion of the runway. To this end, during their preparations for landing, the pilots armed the speed brakes for automatic deployment after touchdown and selected the automatic wheel brakes to MAX AUTO setting.
Investigators determined that the approach to the runway was normal and that the airplane's touchdown was “firm” and about 600 ft. beyond the approach threshold, after which the struts unloaded momentarily. The captain (PM) called “[speed brakes] deployed.” Seconds later he announced, “Two in reverse.” But the first officer responded, “No reverse.”
The first officer tried to deploy the thrust reversers promptly after touchdown, but they did not deploy. After he made several attempts to get the reversers out, the captain took over the thrust reverser controls and eventually succeeded in deploying them with about 2,100 ft. of runway remaining. The pilots worked in a coordinated fashion to stop the airplane and the CVR indicates that they had no idea what had gone wrong. The airplane continued off the departure end of the runway.
At 11:38:13.9 the first officer radioed “and American, ah, twenty two fifty three is gon' off the end of the runway.” The tower responded “American twenty two fifty three, Roger.” (Both pilots told investigators later that they were unaware until after the airplane came to a stop that the speed brakes, which they had armed for automatic deployment, had failed to deploy after touchdown.)
When the airplane was stopped in the snow, the captain told the flight attendants not to evacuate immediately. He determined that it was safer for the passengers to remain in the airplane until help arrived. In the meantime, the first officer advised the JAC tower and American Airlines operations personnel that they had run off the end of the runway and would need assistance. All occupants remained on board the airplane until JAC ground personnel reached the airplane to help the occupants exit the Boeing. There were no injuries and only minor damage to the aircraft.
Obviously, the crew expected two things to happen immediately after touchdown: the speed brakes to deploy automatically, and the reversers to deploy after being commanded to do so. However, the speed brakes never deployed automatically, although they could have been operated manually, and the reversers were extended late probably because of the rapidity with which the PF attempted to get the levers over the hump. So, the Safety Board took a close look at these systems and the flight crew interactions with them. The airplane's automatic speed-brake system consists of six panels on the upper surface of each wing that can be activated automatically or manually at touchdown to disrupt the airflow over the wings, maximizing the weight on the landing gear and increasing wheel brake effectiveness.
Although automatic speed brakes are not generally required for landings (because pilots can manually deploy them at any time), use of the automatic speed brakes can (or at least, should) ensure their prompt deployment after touchdown, thus optimizing the airplane's deceleration during the landing roll.
To deploy the speed brakes automatically, the pilots move the speedbrake lever to its “armed” detent before touchdown. By design, when the lever is so positioned, the actuator automatically drives it to its full aft position after touchdown (indicated by the air/ground sensing system signal's transition from “air” mode to “ground” mode). This normally results in the extension of the speed-brake panels to their fully deployed position.
However, if the air/ground sensing system reverts back to “air” mode after the automatic speed-brake actuator has begun to extend (during a bounce, for example), the actuator will retract automatically and retract the speed-brake lever. If the air/ground sensing system signal subsequently transitions back to “ground” mode, the speed-brake system is designed to again drive the speed-brake lever to extend the speed brakes.