Date: 201309
Local time of day: 0001-0600
Location: LAS.Airport, NV
Aircraft: B737-900
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Ground LAS; Tower LAS
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: During taxi out to the departure runway; Ground Control notified us of a new ATIS which included a tailwind for our takeoff (090/04). The First Officer then made a manual request for new takeoff performance data because of the tailwind component. As we approached the threshold; the Tower called us to line up and wait. We told him that we were waiting for new numbers; so he then told us to hold short. He said to notify him when we were ready; and that he showed winds were calm. I noticed at that time that he seemed somewhat upset that we were not ready.  As we waited for our numbers to upload into the FMC; the Tower cleared an MD-80 for takeoff from intersection B1; followed by a B757-300. We notified him that we were ready; and he cleared us to line up and wait. We went into position on the threshold; and just after the 757 took off (rotated); the Tower cleared us for takeoff. I asked the Tower Controller (before accepting the clearance and before starting our takeoff roll) if we had enough separation with the 757. My transmission was blocked during my first try; then I asked again to confirm. The Tower Controller stated; in a very stern and condescending tone; that we had 'twice the required separation' and that we were cleared for takeoff. I stated that I was just double checking; and then read back that we were cleared for takeoff. By that time; the 757 was far enough upwind that I felt safe enough to takeoff. I asked him initially because of my concern for our safety following a B757 so closely due to wake turbulence. I was not certain that our B737-900 could out climb the B757 that preceded us. Again; he initially cleared us for takeoff just after the 757 rotated. I don't recall in my professional career ever being cleared for takeoff so soon behind a heavy jet; so I did not feel comfortable with our situation.  At approximately 400 FT AGL; the Tower Controller then began to reprimand us for my question. He stated that he never remembers '[my company]' asking for a delay; and stated other things that I don't recall. This reprimand started at about the same time we had to start important cockpit procedures and tasks. It was very distracting; and in my opinion a safety risk. He spoke to us until we past 1;000 FT AGL. At 1;000 FT AGL; we had more cockpit procedures. The First Officer called for those; and I complied. I was not able to respond to anything the Tower had said until they were completed. I then responded; but unfortunately my oxygen mic mask switch was on by accident. He called us one more time and I answered him by only stating our call sign and also saying; 'Go ahead.' He sternly replied by only telling us to switch to Departure. I feel that the Tower Controller was upset with us as soon as we had to wait for our takeoff numbers. Then; when I questioned the lack of delay behind the B757; it made things worse. I was only trying to assure the safety of my aircraft; crew; and passengers. No more; no less. That is my job and chief concern as the Captain. I was not certain that our B737-900 could out climb the B757 that preceded us. I felt that his reprimand as we were climbing out was completely unprofessional; distracting; and an extreme risk to our safety. The situation could have been dealt with in a much more profession manner. He should have had more respect and concern for our situation and for my authority as Captain.


Second narrative: Per instructions; we contacted Ground Control at Spot 1. They issued clearance to taxi to 25R; and announced that the hourly update to the ATIS was out; and that the wind was now '090 at four knots'. This triggered the need to update our performance numbers; as we now were departing downwind. Approaching the end of 25R; as I was preparing to brief and scan for the new numbers (the Taxi and Takeoff Checklists were still 'to go'; though I had given the PA to the cabin); Tower cleared us to line up and wait; and expect an approximately one minute delay due to traffic on the crossing runway. I responded that that should work out since we were updating our numbers for the downwind departure. Tower responded by rescinding the clearance onto the runway 'If you don't have your numbers yet. The wind is calm.' The Captain acknowledged holding short of the runway; and I acknowledged to Tower. In point of fact; in spite of what Ground Control had said; the new ATIS stated the wind as 160 at 4; a direct crosswind - so technically; the update was unnecessary. BUT; we had already made the decision based on what Ground Control had said - PLUS the windsocks were all showing a trend toward an easterly breeze. After we advised Tower that we were ready; the Controller held us short while they departed several aircraft from intersection A2. The last of those was a 757. The 757 rolled a long way. It was barely airborne; if at all; when Tower cleared us for takeoff. The Captain asked me; 'Can we do that?' He queried the Tower to verify that a proper wake turbulence interval was provided. 'BLOCKED' was the next thing either of us heard. Tower then repeated our takeoff clearance. The Captain repeated his query. The response was; 'Calling McCarran Tower; say again?' The Captain repeated his query again. At this point; the Tower Controller's tone became overtly hostile. Paraphrasing: 'There's no wake turbulence! The distance between you and the departing traffic is...you have twice what you need! Cleared for takeoff!' The Captain acknowledged and we departed. When we were approximately 400 feet AGL (I know; because I was still waiting to make my 'verify LNAV' call); the Controller began a tirade (paraphrasing; again): -'In the future; if you want extra wake turbulence separation; you need to tell us that before you are in position on the runway!' {We appropriately didn't respond.} -{800 feet AGL} 'Callsign; Tower!' -the Captain tried to say 'Roger;' or 'Standby;' or something; but was experiencing difficulties transmitting. I was busy flying and making calls. REMEMBER - this is the SHEAD departure - one of the most complicated; threat-rich; brainpower-sucking departure procedures in our system! I kind of felt I had to keep the Captain focused on the procedure instead of the Tower - I called for the ATO checklist at least twice. -{Somewhere between 1;000 and 2;000 feet; prior TO the first turn on the SID; and before completion of the ATO checklist} 'Callsign; MCCARRAN TOWER; OVER!' -When the Captain had an appropriate break in his aviating and navigating duties; he answered. At that point; all the Tower said was 'CONTACT DEPARTURE!!' The primary cause of this event; and my primary reason for submitting this report; is the very significant safety hazard (severe distraction at an extremely critical phase of flight) created by a Tower Controller's angry response to the hassle we created for him in the course of properly performing our duties.


Synopsis: B737 flight crew reports a difference of opinions with a Tower Controller at LAS concerning wake turbulence separation.