B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Situational Awareness; Troubleshooting; Workload
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance; Inflight Event / Encounter Weather / Turbulence
Flight Crew Requested ATC Assistance / Clarification
Airport; Chart Or Publication; Weather; Procedure; Environment - Non Weather Related; Company Policy
Dispatch remarks field on SABRE flight plan for Flight DEN-ZZZ said; 'planned bleeds off takeoff at 37 degrees off longer runway for best ATOG (Allowable Takeoff Gross Weight)'. The Planned Weight/Maximum Allowable weights on the flight plan were 160446/166777 lbs. Release 2 was issued due to ZFW increase of 1800 pounds.  The takeoff data requested at the gate was for runway 34L; bleeds off; planned TOW 161;300 lbs. SABRE returned a flaps 1 setting with max EPR (Engine Pressure Ratio) V1; Vr and V2 of 145; 158; 163. We had a discussion about the fact that the takeoff data message showed a reduced EPR line as a legal option. We decided using reduced EPR with bleeds off seemed ill-advised. Had we used this option; our v-speeds would have been higher at 152; 162; 166.On taxi out; we requested final takeoff data for runway 34L TOW 161;000 lbs. Again SABRE sent us flaps 1 with a reduced EPR option. We elected to use max EPR with its enhanced performance and lower v-speeds. I mentioned to the FO that in the previous three weeks out of Denver; we had been unable to extract anything other than flaps 1 bleeds off on runway 34L. An error was all we got; bleeds off; if other flap settings were requested. I also mentioned that I thought we had been very close to exceeding tire speed each time.In line for takeoff; ATC reported windshear and shifting winds on our runway. An aircraft gave a PIREP after takeoff that tailwinds were 16 kts until liftoff; when then shifted to a four kt headwind. The windsock was initially hidden by an aircraft body; but as we approached the number two position in line for takeoff; we saw very clearly that the sock showed a variable tailwind of 5-15 kts. We called up data for 34L with winds at 160/10. SABRE offered us flaps 5 bleeds off; with 10 kt tailwind. V-speeds were 134; 152; 157. We reset takeoff data and re-ran the checklists. The company aircraft ahead of us refused takeoff until more favorable winds developed. Tower seemed miffed at their reluctance to go; saying; 'I said 25 kt GAIN on runway.' In fact; as we waited in line; ATC was consistently reporting 'wind shear alert; 25 kt gain on the runway.' Sometimes the verbiage was '...25 kt gain over the numbers' for the landing runway 35R. At any rate; the aircraft in front was eventually satisfied the winds were acceptable. Tower cleared them for takeoff; reporting 34L winds as 360/9. Interestingly; the windsock clearly showed a tailwind. We were cleared for takeoff; with winds reported at 070/4. The windsock showed a slight tailwind. I had asked the FO to note our ground speed on liftoff. I was watching them also. At the Vr call; groundspeed was 192. At liftoff; groundspeed was 209. Rotation rate was normal; and the pitch at takeoff was 4.8. We wrote a logbook entry for the tire over speed.Clearly; the allowable TOW on both the SABRE flight plan and takeoff data messages do not take tire speeds into account. Had we carried the max allowable weight of 166;777 lbs (per flight plan); or 167;900 per takeoff data message; our tire speeds would've exceeded tire speeds even more. We mitigated our v-speeds as best we could (most of the time; out of Denver; only flaps 1 will work; but today we got lucky; I guess). Also; had we use reduced EPR (an option given us; but not appropriate considering the windshear); our v-speeds would've been higher. I don't see how B737s can takeoff during summertime out of Denver (or any high altitude airport) at these 'allowable' weights without grossly exceeding tire speed. In fact; I am sure tire overspeeds are routine.
B737 Captain reported departing DEN Runway 34L during variable windshear conditions and recorded 192 kts at Vr; 209 kts at lift off with indicated airspeeds of 158 kts and 163 kts respectively. The maximum tire speed was exceeded.