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16 ENTRY Preflight, the deorbit prep timeline appeared to be non-hurried, but in practice, there was no spare time. Donning entry clothing takes longer than one might think. Also, being very methodical in the DPS transitions and setting the entry switch configuration takes longer than in one-g. The bottom line is that the timeline is just about right and should not be shortened. The deorbit burn was nominal except for an "L OMS QTY" message early in the burn. Postflight we discovered that it was caused by a transducer transient known only by the ground. During entry at about a drag of 11 fps, we noted a vibration in the airframe each time the yaw jets fired. The vibration was eventually masked at the higher dynamic pressures below Mach 5. This effect, presumably caused by yaw jet excitation of the vertical tail first bending moment, appears to be more pronounced in Discovery than in Columbia. All PTI's were accomplished and appeared to be about the same as seen in the SMS preflight. CSS was selected at Mach 0.9 and the Orbiter was manually flown throughout landing and rollout. The lateral "slap" was noted with rapid roll inputs. The Orbiter was allowed to drift slightly outside the HAC causing a slight low energy condition that was corrected by the 3,000-foot point. All was nominal from there to touchdown at 195 KEAS on the runway centerline at 2,510 feet from the threshold. The Orbiter exhibited more positive pitch control than the STA. The CDR felt very comfortable throughout the subsonic phase of manual control because of the STA training. The STA training was invaluable and contributed immeasurably to pilot confidence and the success of the landing. At 185 KEAS, derotation was initiated and a slight pitch oscillation of one cycle was sensed. This tendency had been seen on numerous occasions in the SMS, and it is felt that the FCS design for this phase needs reevaluation, as there is potential for a PIO during derotation. As the nosewheel touched the runway, the Orbiter veered sharply to the right and almost full left rudder was spiked to arrest the turning torque. Rudder control was smooth and gave the expected response. The Orbiter was rolled out on the right side of the runway from that point using rudder modulation until reaching 120 KEAS and then differential braking thereafter. The turning torque decreased with airspeed. Post-landing inspection revealed that the right MLG strut was almost flat (3 1/2 inches low), which accounted for the turning moment. Rolling deceleration was approximately 6 fps2. When braking pressure was increased, attempting to achieve the desired 8 fps2 for the braking DTO, longitudinal deceleration was sensed that felt like alternate braking and no braking or skidding. After several attempts to brake with the same result, only light braking was used until wheel stop. This lurching is as yet unexplained. All crewmembers accomplished fluid loading preentry and five of six used the g-suit. Ample time post-landing was taken by all to get their one-g legs back. It is recommended that this practice be continued.
