2010-03 · NASA ASRS report 881137
MD11 flight crew experiences stick shaker shortly after takeoff while in a turn with moderate turbulence. Wings are leveled and airspeed increased. A second incidence of stick shaker is encountered at FL340 6.5 hours into the flight. A normal landing at destination ensues.
The preflight and taxi out were normal. The weather was 050/18 gust 31; 10 miles visibility and light rain. The OPS gave up Flex 43 and flaps 18 for the departure. We discussed the wind on the taxi out and we decided that with the lower flap setting; prevailing wind speed and direction down the runway; we'd stay with Flex thrust for takeoff. The departure roll and rotation were normal as was the initial climb out for a 620;000 pound takeoff with the exception of the continuous moderate turbulence on climb out. The departure clearance from ATC was [to] turn right to 155 degrees and climb to 5;000. As we were cleaning up at 1000 feet AGL we were given a further turn to 220 and climb to 16;000. As we were in the turn and being affected by the turbulence; we had a momentary activation of the stick shaker. At this weight and in the turn there is was no visible room between the PLI (Pitch Limit Indicator) and the FD. We were clean and I rolled the wings level and leveled the climb. We left the climb power and the airspeed climbed to 320 knots. Our clean wing climb out speed was 286 knots. As we rolled wings level on the 220 heading we started to climb again. Six and a half hours into the flight we experience moderate turbulence at FL340 and momentarily got the stick shaker again. The QRH charts for AOA; fuels burns; and INIT page 2 weight inputs were all re-verified. The Captain spoke with Dispatch; for approximately 10 minutes. The captain briefed him on both issues and determined that for our weight and altitude the PLI seems a little low but not out of the normal range. The PLI was sitting at 5 degrees and our pitch was 3 degrees ANU (aircraft nose up). We were at 470;000 pounds; .81 Mach; and FL340. CG (Center of Gravity) was 29.0 with a stab trim of 1.6; indicating 283 knots. We also encountered moderate turbulence on descent and landing which were both uneventful.
I became concerned that the PLI was excessively low for our weight and configuration; so we got out the QRH and checked the tables for airspeed; pitch; N1 settings to see if we had a bigger issue. We also checked our fuel burn to see if maybe we were loaded heavier than planed. We found all to be correct according to the charts and flight plan. I then check the INT page 2 to re-verify the weights were put in correctly and they were. I then called Dispatch and talked to him for about 10 minutes. I filled him in on both issues and we went over all possible scenarios; and determined that for our weight and altitude the PLI seems a little low; but not out of normal range.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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