Narrative:

In the middle of the afternoon, we were making a flaps 1 degree bleeds-off takeoff from a runway 34R in slc, temperature 32 degrees C, a few clouds at 10000 ft, winds 320 degrees at 7 KTS (not steady) as reported by the tower. Stabilizer trim was set at 4.9 as directed by the final weight and balance paperwork for a full passenger load. I was the captain and PF. Flying the heads-up guidance system, I heard the cockpit automatic 'voice' and the first officer called out 'V1' and noted the speed index in the heads-up guidance system passing V1 and approaching vr (2 KTS difference), whereupon I began a normal rotation. I expected the yoke to be slightly heavy due to the weight and flap confign, and was surprised when the resistance was a little lighter than anticipated and the rotation rate seemed more like a normal flaps 5 degree takeoff. As the aircraft became airborne, we heard and felt a 'thump.' immediately checking the gauges, we confirmed normal power, climb, and acceleration and continued monitoring the system as we decided to clean up and continue the departure for the time being to get to a safe altitude. Shortly thereafter, we received a call from the cabin crew asking about the 'thump' that they, too, had noticed. We confirmed the 'thump' and assured them that the aircraft was performing normally at this time and we would get back to them and the passenger when we had more information as we proceeded to search for the cause. As we continued our assessment, we concluded that the most plausible cause was a tail strike during takeoff. With all system performing normally, I xferred control of the aircraft to the first officer while I performed checklist procedures and appropriate coordination with assisting agencies. I then declared a 'precautionary' with ZLC and began preparations to return to slc for landing since the checklist directed us to not pressurize the aircraft due to possible structural damage. I elected not to return for immediate landing in an overweight landing condition, but to burn down fuel to get us below maximum landing weight so as not to compound any possible structural problems. We coordinated a holding area with ZLC, xferred aircraft control back to myself, burned down the necessary fuel, and accomplished a ctlability check in the landing confign prior to approach and landing, which were uneventful. After runway turnoff, maintenance met us on the taxiway for a quick inspection prior to approving taxi to the gate, gave us a 'thumbs up' and we taxied to parking. We requested a load audit which showed discrepancies in 3 of the 4 bins, resulting in an aft center of gravity movement from our programmed 25.5% mac to 27% mac, and a corresponding stabilizer trim of 4.7. The tailskid assembly shoe was worn down about 1 inch, and the crushable portion was just barely into the red stripe -- no damage beyond that was found and the aircraft was returned to service that evening after the tailskid assembly was replaced, having performed its exact prescribed function. The first officer stated that he had observed a hesitation in the acceleration between V1 and vr -- slight but noticeable. The ATIS was 40 mins old (possible temperature increase), the wind may have shifted slightly or been calm at that instant, and the weight and balance was definitely off (a third weight and balance report was found the next day that had all the correct data on it but had never been forwarded to us, even by ACARS). A line check airman was consulted and reported that he had seen numerous instances where the hgs had prematurely triggered the cockpit 'V1' callout by a few KTS. The fdr was analyzed and it confirmed the hesitation in the acceleration rate right around the V1 spot followed by a slightly early rotation and slightly higher than normal rotation rate. The weight was off the main gear when the tail strike occurred. Coupled with the slightly further aft center of gravity, the above findings together were enough to just place the aircraft into the tail strike envelope, minor as the occurrence was. However, it is doubtful that any one of the parameters listed would have caused the event to happen as it did, even the misloading of the aircraft in this case. Bottom line to me is that little things can add up when you arenear the edge in any situation, due diligence is mandatory at all times, with extra intensity necessary when non everyday procedures are called for, not necessarily just when we are performing checklist functions in an emergency or other non normal situation.

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Original NASA ASRS Text

Title: B737-800 CAPT AGGRESSIVELY ROTATED DURING TKOF CAUSING A TAIL STRIKE HEARD BY PAX AND CABIN ATTENDANTS, RESULTING IN A RETURN LAND AFTER FUEL BURN DOWN TO MEET ACFT LEGAL LNDG WT.

Narrative: IN THE MIDDLE OF THE AFTERNOON, WE WERE MAKING A FLAPS 1 DEG BLEEDS-OFF TKOF FROM A RWY 34R IN SLC, TEMP 32 DEGS C, A FEW CLOUDS AT 10000 FT, WINDS 320 DEGS AT 7 KTS (NOT STEADY) AS RPTED BY THE TWR. STABILIZER TRIM WAS SET AT 4.9 AS DIRECTED BY THE FINAL WT AND BAL PAPERWORK FOR A FULL PAX LOAD. I WAS THE CAPT AND PF. FLYING THE HEADS-UP GUIDANCE SYS, I HEARD THE COCKPIT AUTOMATIC 'VOICE' AND THE FO CALLED OUT 'V1' AND NOTED THE SPD INDEX IN THE HEADS-UP GUIDANCE SYS PASSING V1 AND APCHING VR (2 KTS DIFFERENCE), WHEREUPON I BEGAN A NORMAL ROTATION. I EXPECTED THE YOKE TO BE SLIGHTLY HVY DUE TO THE WT AND FLAP CONFIGN, AND WAS SURPRISED WHEN THE RESISTANCE WAS A LITTLE LIGHTER THAN ANTICIPATED AND THE ROTATION RATE SEEMED MORE LIKE A NORMAL FLAPS 5 DEG TKOF. AS THE ACFT BECAME AIRBORNE, WE HEARD AND FELT A 'THUMP.' IMMEDIATELY CHKING THE GAUGES, WE CONFIRMED NORMAL PWR, CLB, AND ACCELERATION AND CONTINUED MONITORING THE SYS AS WE DECIDED TO CLEAN UP AND CONTINUE THE DEP FOR THE TIME BEING TO GET TO A SAFE ALT. SHORTLY THEREAFTER, WE RECEIVED A CALL FROM THE CABIN CREW ASKING ABOUT THE 'THUMP' THAT THEY, TOO, HAD NOTICED. WE CONFIRMED THE 'THUMP' AND ASSURED THEM THAT THE ACFT WAS PERFORMING NORMALLY AT THIS TIME AND WE WOULD GET BACK TO THEM AND THE PAX WHEN WE HAD MORE INFO AS WE PROCEEDED TO SEARCH FOR THE CAUSE. AS WE CONTINUED OUR ASSESSMENT, WE CONCLUDED THAT THE MOST PLAUSIBLE CAUSE WAS A TAIL STRIKE DURING TKOF. WITH ALL SYS PERFORMING NORMALLY, I XFERRED CTL OF THE ACFT TO THE FO WHILE I PERFORMED CHKLIST PROCS AND APPROPRIATE COORD WITH ASSISTING AGENCIES. I THEN DECLARED A 'PRECAUTIONARY' WITH ZLC AND BEGAN PREPARATIONS TO RETURN TO SLC FOR LNDG SINCE THE CHKLIST DIRECTED US TO NOT PRESSURIZE THE ACFT DUE TO POSSIBLE STRUCTURAL DAMAGE. I ELECTED NOT TO RETURN FOR IMMEDIATE LNDG IN AN OVERWT LNDG CONDITION, BUT TO BURN DOWN FUEL TO GET US BELOW MAX LNDG WT SO AS NOT TO COMPOUND ANY POSSIBLE STRUCTURAL PROBS. WE COORDINATED A HOLDING AREA WITH ZLC, XFERRED ACFT CTL BACK TO MYSELF, BURNED DOWN THE NECESSARY FUEL, AND ACCOMPLISHED A CTLABILITY CHK IN THE LNDG CONFIGN PRIOR TO APCH AND LNDG, WHICH WERE UNEVENTFUL. AFTER RWY TURNOFF, MAINT MET US ON THE TXWY FOR A QUICK INSPECTION PRIOR TO APPROVING TAXI TO THE GATE, GAVE US A 'THUMBS UP' AND WE TAXIED TO PARKING. WE REQUESTED A LOAD AUDIT WHICH SHOWED DISCREPANCIES IN 3 OF THE 4 BINS, RESULTING IN AN AFT CTR OF GRAVITY MOVEMENT FROM OUR PROGRAMMED 25.5% MAC TO 27% MAC, AND A CORRESPONDING STABILIZER TRIM OF 4.7. THE TAILSKID ASSEMBLY SHOE WAS WORN DOWN ABOUT 1 INCH, AND THE CRUSHABLE PORTION WAS JUST BARELY INTO THE RED STRIPE -- NO DAMAGE BEYOND THAT WAS FOUND AND THE ACFT WAS RETURNED TO SVC THAT EVENING AFTER THE TAILSKID ASSEMBLY WAS REPLACED, HAVING PERFORMED ITS EXACT PRESCRIBED FUNCTION. THE FO STATED THAT HE HAD OBSERVED A HESITATION IN THE ACCELERATION BTWN V1 AND VR -- SLIGHT BUT NOTICEABLE. THE ATIS WAS 40 MINS OLD (POSSIBLE TEMP INCREASE), THE WIND MAY HAVE SHIFTED SLIGHTLY OR BEEN CALM AT THAT INSTANT, AND THE WT AND BAL WAS DEFINITELY OFF (A THIRD WT AND BAL RPT WAS FOUND THE NEXT DAY THAT HAD ALL THE CORRECT DATA ON IT BUT HAD NEVER BEEN FORWARDED TO US, EVEN BY ACARS). A LINE CHK AIRMAN WAS CONSULTED AND RPTED THAT HE HAD SEEN NUMEROUS INSTANCES WHERE THE HGS HAD PREMATURELY TRIGGERED THE COCKPIT 'V1' CALLOUT BY A FEW KTS. THE FDR WAS ANALYZED AND IT CONFIRMED THE HESITATION IN THE ACCELERATION RATE RIGHT AROUND THE V1 SPOT FOLLOWED BY A SLIGHTLY EARLY ROTATION AND SLIGHTLY HIGHER THAN NORMAL ROTATION RATE. THE WT WAS OFF THE MAIN GEAR WHEN THE TAIL STRIKE OCCURRED. COUPLED WITH THE SLIGHTLY FURTHER AFT CTR OF GRAVITY, THE ABOVE FINDINGS TOGETHER WERE ENOUGH TO JUST PLACE THE ACFT INTO THE TAIL STRIKE ENVELOPE, MINOR AS THE OCCURRENCE WAS. HOWEVER, IT IS DOUBTFUL THAT ANY ONE OF THE PARAMETERS LISTED WOULD HAVE CAUSED THE EVENT TO HAPPEN AS IT DID, EVEN THE MISLOADING OF THE ACFT IN THIS CASE. BOTTOM LINE TO ME IS THAT LITTLE THINGS CAN ADD UP WHEN YOU ARENEAR THE EDGE IN ANY SIT, DUE DILIGENCE IS MANDATORY AT ALL TIMES, WITH EXTRA INTENSITY NECESSARY WHEN NON EVERYDAY PROCS ARE CALLED FOR, NOT NECESSARILY JUST WHEN WE ARE PERFORMING CHKLIST FUNCTIONS IN AN EMER OR OTHER NON NORMAL SIT.

Data retrieved from NASA's ASRS site as of July 2007 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.