Narrative:

On takeoff from fai aircraft was difficult to rotate due to stiff and ineffective elevator. During climb out elevator control still minimal. Declared emergency and continued to anc due to visibility in fai (1000 ft RVR, -45 degrees C). During climb, cruise and descent elevator not fully effective. At landing in anc it took several hard pumps with yoke to flare and land aircraft. Another flight in MD80 out of fai-anc experienced the same problem the day before. Cold temperatures seem to have been a factor. Callback conversation with reporter revealed the following information: the captain called back with the following explanation of the elevator control system. The control column moves the elevator control tabs which aerodynamically move the elevators. 2 separate elevators on the horizontal stabilizer are positioned aerodynamically by the tabs. An independent cable system on each control column operates a single control tab on each elevator. A torque tube connects the control columns. As each elevator moves, an additional tab geared to elevator movement moves to assist the control tab. On the MD80 each elevator has an anti-float tab outboard of the geared tab. The anti-float tab is geared to horizontal stabilizer movement and improves longitudinal trim in high nose up trim conditions. (That is with an aircraft with a forward center of gravity.) this is called a free floating gear tab. Each tab remains faired with its elevator until the stabilizer reaches approximately 10 degrees aircraft nose up trim position. Between 10 and 12 degrees of stabilizer trim, stabilizer linkage drives the anti-float tabs from their faired position to 25 degrees trailing edge down. This helps prevent elevator down float that would decrease pitch control. This downward pitch control is needed for any stall recovery maneuvers. The pitch control, via the stabilizer linkage, is driven by the elevator augmentation actuators. The elevator augmenter provides an aircraft nose-down command during extreme stall conditions. It activates when the elevator control tabs extend approximately 10 degrees trailing edge up. Hydraulic pressure drives the elevator trailing edges down, causing the aircraft to pitch down. The 2 actuators, one for each elevator, are powered by the left hydraulic system with a back up accumulator. The reporter believes that the pressure relief valve failed, from age, corrosion or whatever, allowing hydraulic pressure to flow to the back side of the actuator, thereby keeping the elevators at a nose down position during the takeoff roll. The actuator would normally allow the elevators to assume a 'neutral-faired' position near to 115 KTS. The flight data recorder indicated that the elevator did not 'level' until 155 KTS, well past the aircraft's rotation speed. Data research from the company indicated that there were the same indications exhibited on 5 other MD80S in the company's fleet. The company maintenance changed the pressure relief valve. A meeting was held from the associated government agencies, the company and the union safety department. Further research is ongoing with expected alerts to other users. The reporter stated that the deicing procedure that was carried out that morning in seattle was not a factor.

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Original NASA ASRS Text

Title: AN MD80 FLYING FAIRBANKS TO ANCHORAGE EXPERIENCES ELEVATOR CTL PROBS, DECLARES AN EMER AND LANDS SAFELY AT ANCHORAGE.

Narrative: ON TKOF FROM FAI ACFT WAS DIFFICULT TO ROTATE DUE TO STIFF AND INEFFECTIVE ELEVATOR. DURING CLBOUT ELEVATOR CTL STILL MINIMAL. DECLARED EMER AND CONTINUED TO ANC DUE TO VISIBILITY IN FAI (1000 FT RVR, -45 DEGS C). DURING CLB, CRUISE AND DSCNT ELEVATOR NOT FULLY EFFECTIVE. AT LNDG IN ANC IT TOOK SEVERAL HARD PUMPS WITH YOKE TO FLARE AND LAND ACFT. ANOTHER FLT IN MD80 OUT OF FAI-ANC EXPERIENCED THE SAME PROB THE DAY BEFORE. COLD TEMPS SEEM TO HAVE BEEN A FACTOR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT CALLED BACK WITH THE FOLLOWING EXPLANATION OF THE ELEVATOR CTL SYS. THE CTL COLUMN MOVES THE ELEVATOR CTL TABS WHICH AERODYNAMICALLY MOVE THE ELEVATORS. 2 SEPARATE ELEVATORS ON THE HORIZ STABILIZER ARE POSITIONED AERODYNAMICALLY BY THE TABS. AN INDEPENDENT CABLE SYS ON EACH CTL COLUMN OPERATES A SINGLE CTL TAB ON EACH ELEVATOR. A TORQUE TUBE CONNECTS THE CTL COLUMNS. AS EACH ELEVATOR MOVES, AN ADDITIONAL TAB GEARED TO ELEVATOR MOVEMENT MOVES TO ASSIST THE CTL TAB. ON THE MD80 EACH ELEVATOR HAS AN ANTI-FLOAT TAB OUTBOARD OF THE GEARED TAB. THE ANTI-FLOAT TAB IS GEARED TO HORIZ STABILIZER MOVEMENT AND IMPROVES LONGITUDINAL TRIM IN HIGH NOSE UP TRIM CONDITIONS. (THAT IS WITH AN ACFT WITH A FORWARD CTR OF GRAVITY.) THIS IS CALLED A FREE FLOATING GEAR TAB. EACH TAB REMAINS FAIRED WITH ITS ELEVATOR UNTIL THE STABILIZER REACHES APPROX 10 DEGS ACFT NOSE UP TRIM POS. BTWN 10 AND 12 DEGS OF STABILIZER TRIM, STABILIZER LINKAGE DRIVES THE ANTI-FLOAT TABS FROM THEIR FAIRED POS TO 25 DEGS TRAILING EDGE DOWN. THIS HELPS PREVENT ELEVATOR DOWN FLOAT THAT WOULD DECREASE PITCH CTL. THIS DOWNWARD PITCH CTL IS NEEDED FOR ANY STALL RECOVERY MANEUVERS. THE PITCH CTL, VIA THE STABILIZER LINKAGE, IS DRIVEN BY THE ELEVATOR AUGMENTATION ACTUATORS. THE ELEVATOR AUGMENTER PROVIDES AN ACFT NOSE-DOWN COMMAND DURING EXTREME STALL CONDITIONS. IT ACTIVATES WHEN THE ELEVATOR CTL TABS EXTEND APPROX 10 DEGS TRAILING EDGE UP. HYD PRESSURE DRIVES THE ELEVATOR TRAILING EDGES DOWN, CAUSING THE ACFT TO PITCH DOWN. THE 2 ACTUATORS, ONE FOR EACH ELEVATOR, ARE POWERED BY THE L HYD SYS WITH A BACK UP ACCUMULATOR. THE RPTR BELIEVES THAT THE PRESSURE RELIEF VALVE FAILED, FROM AGE, CORROSION OR WHATEVER, ALLOWING HYD PRESSURE TO FLOW TO THE BACK SIDE OF THE ACTUATOR, THEREBY KEEPING THE ELEVATORS AT A NOSE DOWN POS DURING THE TKOF ROLL. THE ACTUATOR WOULD NORMALLY ALLOW THE ELEVATORS TO ASSUME A 'NEUTRAL-FAIRED' POS NEAR TO 115 KTS. THE FLT DATA RECORDER INDICATED THAT THE ELEVATOR DID NOT 'LEVEL' UNTIL 155 KTS, WELL PAST THE ACFT'S ROTATION SPD. DATA RESEARCH FROM THE COMPANY INDICATED THAT THERE WERE THE SAME INDICATIONS EXHIBITED ON 5 OTHER MD80S IN THE COMPANY'S FLEET. THE COMPANY MAINT CHANGED THE PRESSURE RELIEF VALVE. A MEETING WAS HELD FROM THE ASSOCIATED GOV AGENCIES, THE COMPANY AND THE UNION SAFETY DEPT. FURTHER RESEARCH IS ONGOING WITH EXPECTED ALERTS TO OTHER USERS. THE RPTR STATED THAT THE DEICING PROC THAT WAS CARRIED OUT THAT MORNING IN SEATTLE WAS NOT A FACTOR.

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.