Date: 201310
Local time of day: 1801-2400
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Light: Night
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch; Taxi
ATC / advisory: Tower ZZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Human factors: Troubleshooting; Distraction; Confusion
Second reporter function: First Officer; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance; Ground Event / Encounter Ground Strike - Aircraft
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: There was a 1;500 LB increase when the final weights came in. The First Officer entered the revised takeoff gross weight (TOGW) and requested a revised takeoff performance message in ACARS. When the message came the airspeeds were significantly lower than the planned takeoff performance speeds. We were number one for takeoff. I told the crew; 'We need to discuss this;' [so] I stopped the aircraft short of the hold line to prevent blocking the runway and set the brakes. The First Officer and Relief Pilot reviewed the takeoff performance message. They both concurred that the numbers looked accurate. I did not look at the message until later. After a discussion of several minutes we accepted the airspeed changes and took the runway. The First Officer made the takeoff. He intentionally delayed rotation a few knots after 'rotate.' The rotation rate was normal; 2 1/2 degrees per second. I was looking at the engine instruments at the time of rotation and did not see the attitude indication on the EADI; but it felt normal and looked normal in my periphery vision out the windshield; not excessively nose high. I noticed a very subtle sensation at liftoff; but not the expected thump or bump. It felt as if the wheels hit a small puddle of water. It was so subtle I would not have mentioned it if the flight attendants had not called a few minutes later to report a scrapping sound on takeoff. We did not get a TAIL SKID EICAS message or any other abnormal messages or physical indications. Acceleration was normal; as was the climb rate.When we got above sterile cockpit level we sent a maintenance message saying we had a possible tail skid strike; based on what the Flight Attendant had told us. Then we reviewed the takeoff performance messages; both the planned message and the final. I noticed a difference of nearly 100;000 LBS in the assumed TOGW between the two. The First Officer had entered 286.5 as the TOGW when he should have entered 386.5.We then checked the QRH for tail strike procedures. The QRH directed that in case of a tail strike we should not pressurize. It made no mention of whether an EICAS message needed to be displayed to trigger the checklist. That prompted me to place a SATCOM call to Dispatch asking for a patch to Maintenance to get their input on whether we should depressurize and divert or continue. Duty Manager also got in on the discussion. The cabin pressure was holding steady and there were no unusual trim indications or vibrations. Maintenance; Duty Manager and I all agreed that the best course of action was to continue with the planned flight. A few minutes later Duty Manager sent an ACARS saying that he had consulted with the Training Center fleet specialists. They said that absent an EICAS; a pressurization problem or any other abnormal indication; QRH compliance is not required; and they concurred with the decision to continue.After block-in at our destination; a Mechanic came up and briefed us on the skid condition; including showing us a photograph. He said the scrape was minor and well within the normal wear limits of the skid. It needed only re-painting. There was no damage to other parts of the aircraft. He said he would follow-up with more inspection but he knew we wanted to know what had happened and thus came up to give us his initial assessment.In summary; the First Officer entered a wrong number. It was a simple mistake but it was the digit on the far left and that was the big one. That action produced an ACARS message that the three of us instantly recognized as odd. The flying First Officer then asked the non-flying Relief Pilot to double check the message. The Relief Pilot looked at the numbers and said they were OK. They both erred. My error was not keeping those brakes set until all doubt was removed. I was the last safety net. The responsibility is mine.A mitigating factor is the performance computer's takeoff performance logic. We have become accustomed to seeing speed bugconfigurations that we have never experienced in the past and I think that was a factor that lured us into the trap. But let it not be interpreted that I make this as an excuse. In summary I think we handled the threat well. We recognized the red flag; we verbalized; coordinated and asked for back-up support from each other. Error repair was our failure.


Second narrative: I was the Pilot Flying. Normal preflight and cockpit set-up was accomplished. ACARS numbers for Runway 09L showed an assumed weight of 384.2. After pushback; final weights printed showing a ZFW increase of 1;511 LBS. After entering the final ZFW in the FMC; the new gross weight showed 386.5. I then requested new performance numbers for Runway 09L due to the increase. We started the engines and began to taxi to 09L.After receiving the new performance numbers; I called out the new V-speeds based on the revised data. It seemed odd to me that the new numbers were lower than the original numbers. The Captain stated 'We need to discuss this' and stopped the aircraft. We were number 1 for takeoff. I looked over the data several times then handed the data to the Relief Pilot. He reviewed the data and agreed that it seemed correct. We then reviewed it together and concluded that the numbers seemed correct. We were then given instructions to line up and wait on 09L. All checklists were accomplished.With takeoff clearance; we started our takeoff roll. The Captain called V1 then rotate. A slow smooth rotation of 1-1.5 degrees per second was made. I called positive rate gear up and a normal climb out was performed. Aircraft performance seemed normal and the remainder of the takeoff profile was accomplished. We completed the after Takeoff Checklist.Upon further review of the performance numbers while airborne; it was discovered that the revised takeoff data was incorrect. When I entered the final gross weight in ACARS; I inadvertently pressed the '2' digit instead of the '3'. What I entered was 286.5. It should have been 386.5. The only reason I can think that this happened was that my finger slid from the 3 digit to the 2 digit then released leaving the 2 digit in the column. Unfortunately; this went unnoticed during our questioning of the revised performance numbers. The result was a minor tail scrape due to early rotation based on inaccurate takeoff data.


Synopsis: A B767 First Officer entered an ACARS revised takeoff weight one hundred thousand pounds too light; so after takeoff the aft flight attendants reported a tail strike. The flight continued to the filed destination where a minor tail strike with no damage was discovered.