Corporate flight crew of Hawker 850 XP at FL360 experienced a TCAS RA requiring descent; reporter indicating updraft resulted in a climb to 36;250; which likely caused the TCAS event.
Synopsis
Corporate flight crew of Hawker 850 XP at FL360 experienced a TCAS RA requiring descent; reporter indicating updraft resulted in a climb to 36;250; which likely caused the TCAS event.
Narrative
Flying at FL350 toward Hoxie on a heading about 30 miles West of DKK on the north side of Lake Erie. We were still in the thin tops and saw one cell at our 10 o'clock and if we went on a heading of twenty right we would split two cells with one at two o'clock. Tops were shown our XM as about 26;000. Light occasionally moderate turbulence and no precipitation or any hail. We asked and were granted FL360 to try and get on top. We were level at FL360 for about a minute and still not quite on top. I was looking down doing paperwork when I heard the TCAS 'descend; descend' as I felt the aircraft experience an updraft. As I looked up flying pilot had reduced power and began a descent in compliance with the TCAS RA. I believe I saw a maximum altitude of 36;250. I announced to ATC that we were in a TCAS descent. Not sure if ATC got it as there was a lot of static on the frequency at that time. When we began our climb back to FL360 I believe we bottomed out at about 35;000. This was due in part to what I believe was the down draft which followed the updraft we had just experienced. After leveling back at FL360 I told ATC that we were back and level at FL360. Before we left the frequency I asked if he had gotten my TACS descent alert and he said yes he had.
Second reporter narrative
While flying at FL350 toward HOXIE on a heading about 30 miles west of DKK on the north side of Lake Erie. We were still in thin tops and saw one cell at our 10 o'clock and another at our 2 o'clock. We as a crew decided to take a heading of twenty right of course so as to split both cells. Our XM radar showed the tops of the highest cell in our area to be at about 26;000 feet. We had been experiencing light to occasional moderate turbulence with no hail or precipitation. We asked for and were granted FL 360 to try and get on top. We were level at FL360 for about a minute; but not on top. The TCAS alert went off with a descend. As flying pilot I commanded the aircraft to follow the TCAS RA by reducing power and descending. I believe I saw a maximum altitude of 36;250! The non flying pilot announced to ATC that we were complying with a TACS RA alert. I am not sure if the Controller got our transmission because there was a lot of static on the frequency. We began a climb back to FL 360 after we had stopped descending at FL350. I believe that what we had experienced was severe updrafts initially followed by severe down drafts at the end. After leveling at FL360; the non-flying pilot told ATC were were level again at our assigned altitude. Before we left the frequency the non-flying pilot confirmed with ATC that he did get our TCAS descent alert; and he said yes!
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.