B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 180
Situational Awareness; Confusion; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft; Human Factors
At the gate; I adjusted the trim setting for a flaps one takeoff. It was a normal taxi to the runway. As FO; I was the Pilot Flying. As we climbed through 400 feet AGL; I noticed the trim switch on my control wheel was not operating. I called for Heading Select as per the departure procedure and at 1000 feet AGL called for 'Set Speed' and 'Climb Thrust'. (Still no trim response from my control wheel trim switch.) As we climbed out the 'speed trim' seemed to be picking up the slack and providing adequate trimming. As I called for flaps up I expected the speed trim to stop operating and again tried to trim through use of the control wheel trim switch; still nothing. I asked the Captain to try trimming forward on his trim switch. His was also inoperative. I requested VNAV at 3000 feet AGL. As power and speed was increased there became a pronounced nose high flight control pressure. The trim wheel continued to intermittently rotate. My thought was that the 'Speed Trim' was still somehow still active and was interfering with normal trimming. I waited to see if speed trim would catch up. It did not and excessive forward control wheel pressure continued to be required to maintain 250 knots in the climb. We were then cleared to 13;000 feet. We leveled off and began to troubleshoot the problem. I asked the Captain to take the controls while I re-adjusted my seat for better leverage on the control wheel. At that point the Captain and I agreed that he would fly the aircraft and I began working the check list; radios; and we would return to the departure airport. Although we still had reasonable control over the aircraft; I explained the problem to Approach Control and that we would need to return to the airport. I requested a straight in ILS Approach with vectors since the weather at the departure airport reported at 10 miles and 1000 feet and slight right cross-winds. I selected the ILS Approach to the departure airport as listed in the approach section of the FMS. The Captain was busy flying (without autopilot due to the trim issue) as I was setting up the radios; minimums; requesting landing information; talking to Flight Attendants and making the PA announcement that we would be returning to the departure airport; while still trying to do that 'Pilot Monitoring' thing. I thought I was still in the 'Green'. Apparently; I wasn't.I began putting inputs into the landing data request for returning to the 'DEPARTURE' airport. I had learned from the recent recurrent training to make sure I selected 'Non-Normals' on the Landing Conditions page. I selected the checklist for 'Inoperative Trim'. The notes called for a 15 degree flaps landing. So far; so good. I then sent the information. When the numbers came back; they were not even close to what the FMS had projected for flaps 15 landing speeds. The Captain questioned the data and we both assumed I had selected the original destination airport instead of the departure airport or for some reason we had excessive routing in the FMS. I then double checked the data and it indeed had returned the landing data for our departure airport to which we were landing. Time was now becoming compressed and we were being vectored to intercept the final approach course. The Captain elected to use the FMS generated speeds for landing which were much higher than the [calculated] landing data. We had plenty of runway. We landed uneventfully; underweight and without the requirement for brake cooling.We were in the 'Green' and back at the gate. But; I was still puzzled by the discrepancy of the FMS and [calculated] landing data.In hindsight; and through more discussions; the 'Clue Bird' landed. I had assumed that by selecting Non-Normals and then the checklist for 'inoperative trim' then requesting the data; [calculated data] would automatically recognize that I was requesting data for a 15 degree flap landing as per the Conditions Checklist. IT DOES NOT. If I had taken more time to look at thereturned data; I may have noticed that it probably returned landing speeds for a flaps 30; as that is always the default flap setting for landing data. I was apparently in the 'Yellow' due to time compression and did not realize it. Normally; I always check the flap setting request. But in this case; as a return to the departure airport; I was much more concerned with making sure the departure airport had been selected/loaded and that the FMS and [calculated data] had matched and reflected that request. The airport was correct; but I simply overlooked what I assumed was information for a flaps 15 landing speeds.
[Report narrative contained no additional information.]
B737 flight crew reported returning to departure airport after noting loss of stabilizer trim during initial climb. Workload and confusion led to procedural errors during the checklist phase.