Narrative:

We were cleared for takeoff on the cowby departure with the previous aircraft in sight. After we cleaned-up the aircraft; the captain selected the autopilot on; selected VNAV; and reset the altitude window from 7;000 ft to FL190. Separation from company flight appeared normal for las; about 2.5 to 3 NM. Approaching 7;000 ft both aircraft began to level. I mentioned that we might get some wake turbulence since we were both at the same altitude. We seemed to be closing on the other aircraft a bit but I expected our paths or altitudes would diverge soon; as usual. I heard ATC give the other aircraft a climb and maintain FL190 clearance. I thought that with both of us at 250 KTS (obviously that was a bad assumption as the other aircraft must have been going much slower than 250 KTS) and him climbing that separation wouldn't be a problem. About a minute later; we started to get some of his wake turbulence. I noticed that we were getting much closer to him and he wasn't climbing. I mentioned to the captain that we were getting closer. At this point; he disconnected the autopilot and turned slightly to the right to increase separation and get out of his wake. A moment later we got an RA to climb. The captain followed the RA and I informed ATC. ATC then told us to climb and maintain FL190 and turn direct cowby; approximately 70-degree left turn. The other aircraft was to our left. The captain didn't want to take a hard turn into him so he began his climb and started a slow turn to the left trying to keep the other aircraft in sight. Shortly thereafter; we got a second climb RA. The captain followed that RA also. ATC queried the other aircraft about what they were doing and they confirmed that they had also received multiple ras. When the RA was resolved; we continued on course to cowby and climbed to fl 190. The other aircraft must have turned the other direction at roppr because we didn't hear or see them again. That spacing and procedure normally works well at las. If ATC had let us know that our paths would diverge at roppr or that we had a large overtake on the other aircraft; we could have reacted differently. It's difficult to tell closure rate in this situation.

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Original NASA ASRS Text

Title: B737-700 First Officer reported receiving multiple RA's and wake vortex turbulence on departure from LAS.

Narrative: We were cleared for takeoff on the COWBY Departure with the previous aircraft in sight. After we cleaned-up the aircraft; the Captain selected the autopilot on; selected VNAV; and reset the altitude window from 7;000 FT to FL190. Separation from Company flight appeared normal for LAS; about 2.5 to 3 NM. Approaching 7;000 FT both aircraft began to level. I mentioned that we might get some wake turbulence since we were both at the same altitude. We seemed to be closing on the other aircraft a bit but I expected our paths or altitudes would diverge soon; as usual. I heard ATC give the other aircraft a climb and maintain FL190 clearance. I thought that with both of us at 250 KTS (obviously that was a bad assumption as the other aircraft must have been going much slower than 250 KTS) and him climbing that separation wouldn't be a problem. About a minute later; we started to get some of his wake turbulence. I noticed that we were getting much closer to him and he wasn't climbing. I mentioned to the Captain that we were getting closer. At this point; he disconnected the autopilot and turned slightly to the right to increase separation and get out of his wake. A moment later we got an RA to climb. The Captain followed the RA and I informed ATC. ATC then told us to climb and maintain FL190 and turn direct COWBY; approximately 70-degree left turn. The other aircraft was to our left. The Captain didn't want to take a hard turn into him so he began his climb and started a slow turn to the left trying to keep the other aircraft in sight. Shortly thereafter; we got a second climb RA. The Captain followed that RA also. ATC queried the other aircraft about what they were doing and they confirmed that they had also received multiple RAs. When the RA was resolved; we continued on course to COWBY and climbed to FL 190. The other aircraft must have turned the other direction at ROPPR because we didn't hear or see them again. That spacing and procedure normally works well at LAS. If ATC had let us know that our paths would diverge at ROPPR or that we had a large overtake on the other aircraft; we could have reacted differently. It's difficult to tell closure rate in this situation.

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.