Narrative:

I was a prospective lca (line check airman) in training in the right seat of aircraft X from ZZZ. Departing from gate. This was my fifth right seat leg in the lca training. My first leg out of ZZZ and on this identification. All preparations flows and checklists went well and the performance data was loaded for a reduced takeoff from xyr at [taxiway]. The final weight manifest showed:tog: 159234TOW chg: -615 ZFW: 130634 cg: 23.6 takeoff data message showed: 3KT headwind 8KT crosswind tocg/trim 23.6 reduced numbers were V1 147 vr 149 V2 153 on taxiout we were given taxi instructions for a xxl departure. Runway xxl via [taxi route]. [En route during taxi] I reported going heads down to load the new runway and get new performance numbers. Ground traffic was light with minimal delays and minor ATC distractions encountered except for slowing to wait for a maintenance truck to move off and clear to the right as we turned onto victor taxiway. The new runway was loaded; performance requested and loaded; checklists completed; lineup and wait and takeoff clearance given. Takeoff roll and call outs were normal. As I recall; after the rotate call; the rotation felt normal. With the wheels still on the runway; and as rotation continued I felt an abnormal thump. We became airborne; began to climb and raised the gear. Initially; the captain thought we must have blown a tire on the right side and reported that possibility to the tower. We noted that the gear came up normally and that all the gear lights were out (normal indications). Tower informed us they would inspect the runway and report the results through ATC.I thought initially that it might be due to dissipating wingtip vortices from a B777 that had landed recently on xyc [intersecting runway]. While waiting for a response from ATC the captain called the flight attendants and ask if they felt the same anomaly. They confirmed that they felt the thump. We both suspected that ATC would confirm a tire failure. Somewhere close to the top of climb (FL340) ATC passed the word that ZZZ had completed a runway sweep and that no tire debris was located. We began to troubleshoot other options. Bird strike and cargo shift were briefly discussed and dismissed. I briefly considered tail strike but since my tendency is to rotate between 2-2.5 degrees per second; and my departure pitch is normally between 5-5.9 degrees (I can never recall more than 6.3 degrees); I thought it unlikely. However; since we were still stymied by the lack of tire failure confirmation I checked the [flight data unit]. To my surprise departure pitch was 11.2 degrees. On a B737-800 tail strike can occur at 11 degrees. I reported the discovery to the captain and he immediately informed dispatch as I pulled out the QRH. The captain suggested a return to ZZZ (nearest suitable). Dispatch wanted a conference call with [maintenance control] and the [chief pilot]. Ultimately the decision was made to divert to ZZZ1 (nearest suitable after the conference call).the landing in ZZZ1 was uneventful and upon gate arrival maintenance confirmed a tail strike with the tail shoe scraped. Red and green lines remained visible on the cartridge. While airborne and after we determined that a tail strike was the suspected event I retrieved all of the departure paperwork and reviewed it for errors or anomalies. What I found was: takeoff data for runway xxl that was loaded and executed was: 8KT hw 3KT xw cg 23.6 flaps 5 bleeds on assumed weight 130.8ASSUMED temperature 65CREDUCED EPR 89.8v1 127 vr 133 V2 138I had loaded and requested ZFW as my tog wt. What's worse is that after executing those to speeds we received an ACARS msg that said: ************warning'************ requested takeoff data message assumed weight 130.8 less than final weight manifest tog 159.3 I recall getting that message about the time the maintenance truck was becoming an issue. Wheni returned to look at the message my eyes went straight to 130.8 and I failed to read the entire message. I confirmed 130.8 on the tow page and accepted and executed the speeds for takeoff.this was clearly a costly error on my part and I make no excuses for my lack of attention to detail in this matter. Lack of experience in the right seat and ACARS performance work is no excuse. I also should have shown the captain the message which would have slowed me down and; I am confident; would have prevented the tail strike.

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Original NASA ASRS Text

Title: B737 flight crew reported tailstrike after having loaded incorrect takeoff data that went undiscovered.

Narrative: I was a prospective LCA (Line Check Airman) in training in the right seat of Aircraft X from ZZZ. Departing from gate. This was my fifth right seat leg in the LCA training. My first leg out of ZZZ and on this ID. All preparations flows and checklists went well and the performance data was loaded for a reduced takeoff from XYR at [taxiway]. The final WT manifest showed:TOG: 159234TOW CHG: -615 ZFW: 130634 CG: 23.6 TAKEOFF DATA MSG SHOWED: 3KT HEADWIND 8KT CROSSWIND TOCG/TRIM 23.6 REDUCED NUMBERS WERE V1 147 VR 149 V2 153 On taxiout we were given taxi instructions for a XXL Departure. RWY XXL via [taxi route]. [En route during taxi] I reported going heads down to load the new runway and get new performance numbers. Ground traffic was light with minimal delays and minor ATC distractions encountered except for slowing to wait for a maintenance truck to move off and clear to the right as we turned onto Victor taxiway. The new runway was loaded; Performance requested and loaded; checklists completed; lineup and wait and takeoff clearance given. Takeoff roll and call outs were normal. As I recall; after the rotate call; the rotation felt normal. With the wheels still on the runway; and as rotation continued I felt an abnormal thump. We became airborne; began to climb and raised the gear. Initially; the Captain thought we must have blown a tire on the right side and reported that possibility to the tower. We noted that the gear came up normally and that all the gear lights were out (normal indications). Tower informed us they would inspect the runway and report the results through ATC.I thought initially that it might be due to dissipating wingtip vortices from a B777 that had landed recently on XYC [intersecting runway]. While waiting for a response from ATC the Captain called the flight attendants and ask if they felt the same anomaly. They confirmed that they felt the thump. We both suspected that ATC would confirm a tire failure. Somewhere close to the top of climb (FL340) ATC passed the word that ZZZ had completed a runway sweep and that no tire debris was located. We began to troubleshoot other options. Bird strike and cargo shift were briefly discussed and dismissed. I briefly considered tail strike but since my tendency is to rotate between 2-2.5 degrees per second; and my departure pitch is normally between 5-5.9 degrees (I can never recall more than 6.3 degrees); I thought it unlikely. However; since we were still stymied by the lack of tire failure confirmation I checked the [Flight Data Unit]. To my surprise Departure pitch was 11.2 degrees. On a B737-800 tail strike can occur at 11 degrees. I reported the discovery to the Captain and he immediately informed Dispatch as I pulled out the QRH. The Captain suggested a return to ZZZ (nearest suitable). Dispatch wanted a Conference Call with [Maintenance Control] and the [Chief Pilot]. Ultimately the decision was made to divert to ZZZ1 (nearest suitable after the conference call).The landing in ZZZ1 was uneventful and upon gate arrival maintenance confirmed a tail strike with the tail shoe scraped. Red and green lines remained visible on the cartridge. While airborne and after we determined that a tail strike was the suspected event I retrieved all of the departure paperwork and reviewed it for errors or anomalies. What I found was: TAKEOFF DATA FOR RWY XXL that was loaded AND EXECUTED was: 8KT HW 3KT XW CG 23.6 FLAPS 5 BLEEDS ON ASSUMED WT 130.8ASSUMED TEMP 65CREDUCED EPR 89.8V1 127 VR 133 V2 138I had loaded and requested ZFW as my TOG wt. What's worse is that after executing those TO speeds we received an ACARS msg that said: ************WARNING'************ REQUESTED TAKEOFF DATA MESSAGE ASSUMED WT 130.8 LESS THAN FINAL WEIGHT MANIFEST TOG 159.3 I recall getting that message about the time the maintenance truck was becoming an issue. WhenI returned to look at the message my eyes went straight to 130.8 and I failed to read the entire message. I confirmed 130.8 on the TOW page and accepted and executed the speeds for takeoff.This was clearly a costly error on my part and I make no excuses for my lack of attention to detail in this matter. Lack of experience in the right seat and ACARS performance work is no excuse. I also should have shown the Captain the message which would have slowed me down and; I am confident; would have prevented the tail strike.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.