B737 flight crew experiences an updraft during level off at 9;000 FT causing an overshoot and TCAS RA with opposite direction traffic at 10;000 FT.
Synopsis
B737 flight crew experiences an updraft during level off at 9;000 FT causing an overshoot and TCAS RA with opposite direction traffic at 10;000 FT.
Narrative
I was pilot flying climbing out on radar vectors to climb and maintain 9;000 FT. Aircraft was IMC during parts of climbout and we broke out of IMC at 8;000 FT enroute to 9;000 FT. There were three large convective cells in front of us less than five miles in range. I asked the Captain to request left deviation from ATC to avoid cells. As I recall; the autopilot captured and maintained 9;000 FT. ATC approved the left deviation at which time I began turning the aircraft left. I noticed a sudden updraft as we topped one of the cells and started pushing forward on the yoke; but was not overriding the force of the updraft. I noticed a target on TCAS less than 1;000 FT above our altitude (approximately 800 FT or so) and simultaneously a 'Monitor Vertical Speed' alert. I elected to break right in the opposite direction to avoid the conflict while continuing to push forward on the yoke. Forward pressure on the yoke overrode the autopilot and it disconnected. The Captain advised me that we were climbing still and assisted me with forward yoke pressure. The climb stopped at about 9;500 FT and we began a steep descent to avoid a conflict. I descended back to 9;000 FT. Once clear of traffic; the Captain advised ATC that we had lost the 1;000 FT separation due to storm updraft and the Controller advised that he understood. The Captain called an ATC Supervisor upon landing and explained the event. Had I known immediately that there was traffic above us when we leveled off I may have recommended that we continue present course and penetrate the cells in front of us and accept the imminent turbulence. The resultant updraft; coupled with an approved turn toward the traffic target; caused the deviation from altitude and the 'Monitor Vertical Speed' warning. Perhaps if we continued straight ahead into the cell; the aircraft might have passed behind us. Also; had I disconnected the autopilot manually a couple of seconds prior perhaps I could have gotten the aircraft into a descent more quickly. I'm not sure because I was fighting an uncommanded climb. Without knowing then that the updraft would cause an uncommanded climb; I then became focused on trying to keep the Vertical Speed on the VSI out of the red area to avoid the conflict. Taken individually I think each event could have been handled satisfactorily without incident but; in this particular case; everything happened simultaneously and there was a tremendous amount of information to prioritize in an instant. In the future; I might elect to disconnect the autopilot pro actively and fly directly into the cell using manual control inputs.
Second reporter narrative
During the climbout; we were given a turn to heading 090 and climb and maintain 9;000 FT. At about 8;000 FT; we broke out of the weather while we were getting a TA on the TCAS identifying traffic heading for us at 10;000 FT. This was not unusual because we had a high climb rate but it was distracting none the less. Meanwhile; we noticed two large weather buildups right in front of us that looked to be building fairly quickly and with tops above 9;000 FT (probably around 11;000 FT). They did not show up on our radar and we did not see them until we broke out of the overcast at 8;000 FT. We quickly asked for a deviation left; but it was too late and we were going into the top of the left buildup. As we entered the top of the buildup; I could see that we had an excessive climb rate going through 9;000 FT. I told the pilot flying to watch the altitude and I could see him pushing forward on the yoke and the autopilot had kicked off. Since he saw us heading for the traffic at 10;000 FT; he turned right as we both pushed forward to stop the aircraft from climbing. We stopped the climb at 9;500 FT and came out of the other side of the buildup. ATC asked us to confirm that we were given a climb to 9;000 FT. I confirmed this and told them we were back at 9;000 FT. It was apparent that we had lost 1;000 FT separation with the aircraft at 10;000 FT so I explained to ATC that we experienced an updraft from the buildup and we momentarily were above 9;000 FT. He told me that he understood. I called the ATC Supervisor when we landed and explained the event.As the pilot not flying; I could have been more aggressive at helping the pilot flying get the aircraft back on altitude. This situation developed very quickly and insidiously. I will be more diligent at watching for buildups in the future.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.