An LJ45 captain reports elevator and control yoke anomalies on approach; with the yoke moving 1 to 2...

Narrative:

Configuring the aircraft for approach and land; flaps 40 degrees; gear down; 5 nu; level flight; N1 70%; autoplt on and off; speed decreasing from 160-140 KTS the yoke oscillates +/-1 inch without any aircraft pitch change; both autoplt on and autoplt off. Power through speed and lowered nose; normal flight resumed; further flight check confirmed event in approach and landing configuring; consultations with maintenance and manufacturer representatives; for troubleshooting. No EICAS or aircraft warnings observed; reconfigured the flaps 20 degrees; gear down; level flight N1 70; decreasing through 160 KTS aircraft yoke pumped back and forth; +/-2 inches; greater with decreasing airspeed; aircraft pitch did not change with yoke movement; power up and lowered nose aircraft recovered. Maintenance stated that the main elevator cable was off pulley and wrapped around elevator servo also over the servo cables and was 45 pounds less than normal cable tension. Operation check flight the following day failed. Callback conversation with reporter revealed the following information: reporter stated there is still some confusion in troubleshooting this incident; and maintenance is unsure if it is an autopilot or flight control issue.

Original NASA ASRS Text

Title: AN LJ45 CAPTAIN REPORTS ELEVATOR AND CONTROL YOKE ANOMALIES ON APPROACH; WITH THE YOKE MOVING 1 TO 2 INCHES FORE AND AFT WITH NO CORRESPONDING ELEVATOR MOVEMENT.

Narrative: CONFIGURING THE ACFT FOR APCH AND LAND; FLAPS 40 DEGS; GEAR DOWN; 5 NU; LEVEL FLT; N1 70%; AUTOPLT ON AND OFF; SPD DECREASING FROM 160-140 KTS THE YOKE OSCILLATES +/-1 INCH WITHOUT ANY ACFT PITCH CHANGE; BOTH AUTOPLT ON AND AUTOPLT OFF. PWR THROUGH SPD AND LOWERED NOSE; NORMAL FLT RESUMED; FURTHER FLT CHK CONFIRMED EVENT IN APCH AND LNDG CONFIGURING; CONSULTATIONS WITH MAINT AND MANUFACTURER REPRESENTATIVES; FOR TROUBLESHOOTING. NO EICAS OR ACFT WARNINGS OBSERVED; RECONFIGURED THE FLAPS 20 DEGS; GEAR DOWN; LEVEL FLT N1 70; DECREASING THROUGH 160 KTS ACFT YOKE PUMPED BACK AND FORTH; +/-2 INCHES; GREATER WITH DECREASING AIRSPD; ACFT PITCH DID NOT CHANGE WITH YOKE MOVEMENT; PWR UP AND LOWERED NOSE ACFT RECOVERED. MAINT STATED THAT THE MAIN ELEVATOR CABLE WAS OFF PULLEY AND WRAPPED AROUND ELEVATOR SERVO ALSO OVER THE SERVO CABLES AND WAS 45 LBS LESS THAN NORMAL CABLE TENSION. OP CHK FLT THE FOLLOWING DAY FAILED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THERE IS STILL SOME CONFUSION IN TROUBLESHOOTING THIS INCIDENT; AND MAINTENANCE IS UNSURE IF IT IS AN AUTOPILOT OR FLIGHT CONTROL ISSUE.

Data retrieved from NASA's ASRS site as of January 2009 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.

Attributes
ACN	767633
Time
Date	200712
Place
Locale Reference	airport : zzz.airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Operator	common carrier : air taxi
Make Model Name	Learjet 45
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	767633
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	none taken : unable
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

An LJ45 captain reports elevator and control yoke anomalies on approach; with the yoke moving 1 to 2 inches fore and aft with no corresponding elevator movement.