B727-200 aileron controls lock up after flying through heavy turbulence during descent for landing. Flight crew declared an emergency and after a hard landing, the ailerons were free.

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Attributes
ACN	507736
Time
Date	200104
Day	Thu
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : geg.airport
State Reference	WA
Altitude	msl single value : 24000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zse.artcc tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time total : 23500
ASRS Report	507736
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical inflight encounter : turbulence other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : aileron controls other flight crewa other flight crewb
Resolutory Action	aircraft : equipment problem dissipated flight crew : landed in emergency condition flight crew : overcame equipment problem flight crew : declared emergency
Consequence	other
Supplementary
Problem Areas	Weather Aircraft
Primary Problem	Aircraft

Narrative:

Shortly after starting descent from FL240, we encountered 2 sharp jolts of heavy chop. The second one had a loud bang with it inside the airplane. As we began to maneuver for landing, there was a racheting sound and the ailerons were not functioning. We declared an emergency and requested equipment and made a normal landing. The landing was firm because of a light tailwind and this apparently jarred whatever was binding the ailerons loose. Callback conversation with reporter revealed the following information: reporter stated that the aircraft aileron assembly was taken apart in an effort to find the problem, but none was found. He then test flew the aircraft and found that the aileron autoplt servo would sometimes not disengage when shutting off the autoplt. When this happened, the ailerons could only be moved a small amount, making banks very difficult. For this reason, he chose to land straight ahead with a tailwind instead of circle-to-land. However, the jar of the landing touchdown must have caused the electrical solenoid to be activated in the closed position and shut off the aileron servo.

Original NASA ASRS Text

Title: B727-200 AILERON CTLS LOCK UP AFTER FLYING THROUGH HVY TURB DURING DSCNT FOR LNDG. FLC DECLARED AN EMER AND AFTER A HARD LNDG, THE AILERONS WERE FREE.

Narrative: SHORTLY AFTER STARTING DSCNT FROM FL240, WE ENCOUNTERED 2 SHARP JOLTS OF HVY CHOP. THE SECOND ONE HAD A LOUD BANG WITH IT INSIDE THE AIRPLANE. AS WE BEGAN TO MANEUVER FOR LNDG, THERE WAS A RACHETING SOUND AND THE AILERONS WERE NOT FUNCTIONING. WE DECLARED AN EMER AND REQUESTED EQUIP AND MADE A NORMAL LNDG. THE LNDG WAS FIRM BECAUSE OF A LIGHT TAILWIND AND THIS APPARENTLY JARRED WHATEVER WAS BINDING THE AILERONS LOOSE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE ACFT AILERON ASSEMBLY WAS TAKEN APART IN AN EFFORT TO FIND THE PROB, BUT NONE WAS FOUND. HE THEN TEST FLEW THE ACFT AND FOUND THAT THE AILERON AUTOPLT SERVO WOULD SOMETIMES NOT DISENGAGE WHEN SHUTTING OFF THE AUTOPLT. WHEN THIS HAPPENED, THE AILERONS COULD ONLY BE MOVED A SMALL AMOUNT, MAKING BANKS VERY DIFFICULT. FOR THIS REASON, HE CHOSE TO LAND STRAIGHT AHEAD WITH A TAILWIND INSTEAD OF CIRCLE-TO-LAND. HOWEVER, THE JAR OF THE LNDG TOUCHDOWN MUST HAVE CAUSED THE ELECTRICAL SOLENOID TO BE ACTIVATED IN THE CLOSED POS AND SHUT OFF THE AILERON SERVO.

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.