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.

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Original NASA ASRS Text

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

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.

Data retrieved from NASA's ASRS site as of July 2013 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.