B737-700
Flight Crew Last 90 Days 195; Flight Crew Type 7932
Distraction; Troubleshooting; Workload; Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Aircraft; Chart Or Publication; Procedure
The first indication of the problem occurred during climb out. The Captain was the pilot flying and noted that his elevator trim switch was intermittent. After our initial level off; the Captain engaged Autopilot A. Within a few minutes we noted the Stab Out of Trim light had illuminated; but extinguished within approximately 10 seconds as the autopilot began to trim the aircraft once again. A few minutes later the light illuminated again. We also noted a momentary Speed Trim Fail light. The Stab Out of Trim light illuminated and extinguished again several times.The Captain asked me to run the Stabilizer Out of Trim Checklist from the QRH. As I was running the checklist; the autopilot kicked off and the trim wheel had stopped moving. The Captain noted heavy down force pressure on the control column as he flew the aircraft by hand. He slowed the aircraft to around 270-280 KTS to lighten the control column pressure. I completed the Stabilizer Out of Trim Checklist and began the Stabilizer Trim Inoperative Checklist. ATC was step-climbing us behind another aircraft and the constant radio calls; climbs and level offs were very distracting. By the time we realized the extent of our malfunction; we were half way to our destination. We were only able to trim nose down; either manually with the trim wheel or with the electric trim switches. I discovered that I was able to move the trim wheel nose up; a little at a time; if I moved the trim wheel very slightly nose down first. But we moved it only enough to keep the aircraft controllable because it was binding. After completing the first portion of the Stabilizer Trim Inoperative Checklist; we traded off hand-flying the aircraft. We contacted Dispatch and determined it would be best to continue to our filed destination. We declared an emergency with Center; and once with Approach Control; requested vectors for a 10-mile straight-in to Runway XXL. The airport was landing another runway; but Runway XX gave us an additional 3;083 FT and worked with the winds. The Captain discussed the situation with the flight attendants after we had determined our course of action and had me convey to them that we anticipated a normal landing after we were fully configured and the aircraft was controllable. We determined to not notify the passengers. We completed all required items on the Stabilizer Trim Inoperative Checklist and landed without incident. Once cleared by the responding emergency vehicles; the Captain taxied the aircraft to the gate.
The First Officer's report is exactly how it happened. My only question is why is the stab clutch disconnect switch only mentioned in the jammed Flight Control Checklist for aileron; elevator and rudder. I guess Boeing figures the stabilizers to be a secondary flight control. It is never referred to in the Stab Trim Inoperative Checklist. Only on left side of QRH for jammed or restricted flight control for aileron; elevator or rudder. No mention for Stab Checklist.
A B737-700 stabilizer trim siezed during climb with Stab Out of Trim light and Speed Trim Fail lights illuminated but the crew could manually trim nose up after a slight nose down input. The QRH was completed and an emergency was declared for the landing.