Narrative:

Aircraft was exposed to moderate wind driven rain from the left rear with +3 degrees C while on the ground for about 1 hour. When aircraft was leveled off at FL350, elevator froze and would not move. Flew aircraft with primary and alternate trim. Descended to warmer air and elevator thawed out. Normal control was regained and landed without further problems. Callback conversation with reporter revealed the following information: the captain said that he was able to control the aircraft through use of the trim, but he also knew that as he descended he would find warmer air that would melt the ice. He said that he knew that the problem was caused by icing because the flight crew was unable to move the control column at all, whereas the flight crew can overpwr a jammed or frayed control cable or a malfunctioning autoplt. The reporter said that the flight characteristics of the DC9-30 are such that even if the elevator did not thaw until on the approach he could have still successfully flown the aircraft to that point. He does not think that the DC9-10 or the MD80 series could do this however. We discussed the mgmt of the anti-ice system on all of these aircraft. He said that he was unfamiliar with the practice of selecting tail anti-ice first on the MD80 system. He is conducting his own investigation into anti-ice practices at several airlines and he will submit the findings to his chief pilot.

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Original NASA ASRS Text

Title: AN ACR DC9-30 FLC HAD ICE FORM ON THE CTL SYS FOR THE ELEVATOR AND THEY HAD TO CTL THE ACFT PITCH BY USE OF THE PITCH TRIM SYS.

Narrative: ACFT WAS EXPOSED TO MODERATE WIND DRIVEN RAIN FROM THE L REAR WITH +3 DEGS C WHILE ON THE GND FOR ABOUT 1 HR. WHEN ACFT WAS LEVELED OFF AT FL350, ELEVATOR FROZE AND WOULD NOT MOVE. FLEW ACFT WITH PRIMARY AND ALTERNATE TRIM. DSNDED TO WARMER AIR AND ELEVATOR THAWED OUT. NORMAL CTL WAS REGAINED AND LANDED WITHOUT FURTHER PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT SAID THAT HE WAS ABLE TO CTL THE ACFT THROUGH USE OF THE TRIM, BUT HE ALSO KNEW THAT AS HE DSNDED HE WOULD FIND WARMER AIR THAT WOULD MELT THE ICE. HE SAID THAT HE KNEW THAT THE PROB WAS CAUSED BY ICING BECAUSE THE FLC WAS UNABLE TO MOVE THE CTL COLUMN AT ALL, WHEREAS THE FLC CAN OVERPWR A JAMMED OR FRAYED CTL CABLE OR A MALFUNCTIONING AUTOPLT. THE RPTR SAID THAT THE FLT CHARACTERISTICS OF THE DC9-30 ARE SUCH THAT EVEN IF THE ELEVATOR DID NOT THAW UNTIL ON THE APCH HE COULD HAVE STILL SUCCESSFULLY FLOWN THE ACFT TO THAT POINT. HE DOES NOT THINK THAT THE DC9-10 OR THE MD80 SERIES COULD DO THIS HOWEVER. WE DISCUSSED THE MGMT OF THE ANTI-ICE SYS ON ALL OF THESE ACFT. HE SAID THAT HE WAS UNFAMILIAR WITH THE PRACTICE OF SELECTING TAIL ANTI-ICE FIRST ON THE MD80 SYS. HE IS CONDUCTING HIS OWN INVESTIGATION INTO ANTI-ICE PRACTICES AT SEVERAL AIRLINES AND HE WILL SUBMIT THE FINDINGS TO HIS CHIEF PLT.

Data retrieved from NASA's ASRS site as of July 2007 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.