Narrative:

Aircraft autoplt moved trim to full nose down, trim locked in this position until autoplt and electric trim were disconnected and trim wheel was freed by heavy hand pressure. Went through assigned altitude by about 500 ft. Callback conversation with reporter revealed the following information: this reporter is a captain on a cessna citation ii that is used rather often. The captain said that the aircraft flies about 900 hours a yr versus a design that anticipated use of about 300 hours per yr. After the trim stuck in the full down position, a condition that the captain had not heard of prior to this, the captain used both hands to rotate the wheel nose up to 'break it loose.' the captain said that he was very determined and used a great amount of effort, but this time it worked. He had tried earlier, but with only his right hand and had been unsuccessful. After the wheel 'broke loose' he was able to use electric trim normally. During routine flts the captain said that it was not unusual for the trim to go to the full nose down position during a high speed descent. Later he learned from his maintenance department that they had had reports of the trim sticking. The maintenance personnel found that rain or repeated washings had removed most of the grease from the jack screw that the trim system operates in the vertical stabilizer area. After they applied a new coating of grease the horizontal stabilizer worked as designed. The maintenance department is considering an increased inspection program. Prior to this event the jack screw would be inspected and lubed every 1200 hours. They are thinking that 900 hours would be more in keeping with their heavier use. Another area of discussion was the location and size of the autoplt out-of-trim light. This is a small light on the lower section of the center aisle stand, a panel of switches and warning lights that runs from the lower instrument panel at a 45 degree angle toward the throttle quadrant. The captain thinks that this light should be brighter and placed in a more visible location.

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Original NASA ASRS Text

Title: CPR FLC HAS THE MAIN HORIZ TRIM JAM IN THE FULL NOSE DOWN POS. THE MAINT DEPT IS THINKING OF CHANGING THE SCHEDULE OF INSPECTION AND LUBRICATION FOR THE TRIM JACK SCREW. THE RPTR WOULD ALSO LIKE THE OUT-OF-TRIM ADVISORY LIGHT MOVED TO A MORE VISIBLE LOCATION AND MADE BRIGHTER.

Narrative: ACFT AUTOPLT MOVED TRIM TO FULL NOSE DOWN, TRIM LOCKED IN THIS POS UNTIL AUTOPLT AND ELECTRIC TRIM WERE DISCONNECTED AND TRIM WHEEL WAS FREED BY HVY HAND PRESSURE. WENT THROUGH ASSIGNED ALT BY ABOUT 500 FT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS RPTR IS A CAPT ON A CESSNA CITATION II THAT IS USED RATHER OFTEN. THE CAPT SAID THAT THE ACFT FLIES ABOUT 900 HRS A YR VERSUS A DESIGN THAT ANTICIPATED USE OF ABOUT 300 HRS PER YR. AFTER THE TRIM STUCK IN THE FULL DOWN POS, A CONDITION THAT THE CAPT HAD NOT HEARD OF PRIOR TO THIS, THE CAPT USED BOTH HANDS TO ROTATE THE WHEEL NOSE UP TO 'BREAK IT LOOSE.' THE CAPT SAID THAT HE WAS VERY DETERMINED AND USED A GREAT AMOUNT OF EFFORT, BUT THIS TIME IT WORKED. HE HAD TRIED EARLIER, BUT WITH ONLY HIS R HAND AND HAD BEEN UNSUCCESSFUL. AFTER THE WHEEL 'BROKE LOOSE' HE WAS ABLE TO USE ELECTRIC TRIM NORMALLY. DURING ROUTINE FLTS THE CAPT SAID THAT IT WAS NOT UNUSUAL FOR THE TRIM TO GO TO THE FULL NOSE DOWN POS DURING A HIGH SPD DSCNT. LATER HE LEARNED FROM HIS MAINT DEPT THAT THEY HAD HAD RPTS OF THE TRIM STICKING. THE MAINT PERSONNEL FOUND THAT RAIN OR REPEATED WASHINGS HAD REMOVED MOST OF THE GREASE FROM THE JACK SCREW THAT THE TRIM SYS OPERATES IN THE VERT STABILIZER AREA. AFTER THEY APPLIED A NEW COATING OF GREASE THE HORIZ STABILIZER WORKED AS DESIGNED. THE MAINT DEPT IS CONSIDERING AN INCREASED INSPECTION PROGRAM. PRIOR TO THIS EVENT THE JACK SCREW WOULD BE INSPECTED AND LUBED EVERY 1200 HRS. THEY ARE THINKING THAT 900 HRS WOULD BE MORE IN KEEPING WITH THEIR HEAVIER USE. ANOTHER AREA OF DISCUSSION WAS THE LOCATION AND SIZE OF THE AUTOPLT OUT-OF-TRIM LIGHT. THIS IS A SMALL LIGHT ON THE LOWER SECTION OF THE CTR AISLE STAND, A PANEL OF SWITCHES AND WARNING LIGHTS THAT RUNS FROM THE LOWER INST PANEL AT A 45 DEG ANGLE TOWARD THE THROTTLE QUADRANT. THE CAPT THINKS THAT THIS LIGHT SHOULD BE BRIGHTER AND PLACED IN A MORE VISIBLE LOCATION.

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.