Loose wing panel causes vibration.

Attributes
ACN	271848
Time
Date	199405
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ctw
State Reference	OH
Altitude	msl bound lower : 21000 msl bound upper : 21000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 260 flight time total : 7000 flight time type : 900
ASRS Report	271848
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other other : unspecified
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

After a normal takeoff and climb, we noticed as we leveled off in cruise, an abnormal vibration in the control yoke. The vibration seemed to get worse as airspeed was increased, we decided to cruise at slower than normal speed. We had no visual clues of any kind to what was causing the vibration. The vibration was not violent, just very constant -- more like a type of flutter. We asked our cabin attendant if she could see or feel anything unusual, to which she responded that everything looked and felt normal. After conferring with our maintenance control over the radio, we went on to our destination where they said they would have a mechanic waiting for us. (We were about halfway there when we noticed the vibration). As passenger was deplaned at our destination, a couple of passenger made us aware that they had seen a loose panel just in front of the left aileron. When maintenance arrived, they found the panel, just in front of the aileron to be missing several screws, the panel could actually be lifted up a little bit, enough for it to be caught in the airflow while in-flight. According to what the passenger that saw the panel in-flight said, he did not notice it until about halfway into the flight, which was about the same time that we in the cockpit started to feel the vibration. The airplane had been picked up at our maintenance hangar, just prior to our flight, it was thoroughly preflted, with special attention to panels that can be opened for maintenance functions, gear doors, etc. All the paperwork that goes in the maintenance can was properly enclosed and current. It had a fresh 50 hour/7 day maintenance preflight signed off! The required signature on the daily flight log had also been signed off, indicating the aircraft was released from maintenance for return to service. The panel in front of the aileron that was missing the screws, is located on top of the wing, and is impossible to inspect during a normal preflight!

Original NASA ASRS Text

Title: LOOSE WING PANEL CAUSES VIBRATION.

Narrative: AFTER A NORMAL TKOF AND CLB, WE NOTICED AS WE LEVELED OFF IN CRUISE, AN ABNORMAL VIBRATION IN THE CTL YOKE. THE VIBRATION SEEMED TO GET WORSE AS AIRSPD WAS INCREASED, WE DECIDED TO CRUISE AT SLOWER THAN NORMAL SPD. WE HAD NO VISUAL CLUES OF ANY KIND TO WHAT WAS CAUSING THE VIBRATION. THE VIBRATION WAS NOT VIOLENT, JUST VERY CONSTANT -- MORE LIKE A TYPE OF FLUTTER. WE ASKED OUR CABIN ATTENDANT IF SHE COULD SEE OR FEEL ANYTHING UNUSUAL, TO WHICH SHE RESPONDED THAT EVERYTHING LOOKED AND FELT NORMAL. AFTER CONFERRING WITH OUR MAINT CTL OVER THE RADIO, WE WENT ON TO OUR DEST WHERE THEY SAID THEY WOULD HAVE A MECHANIC WAITING FOR US. (WE WERE ABOUT HALFWAY THERE WHEN WE NOTICED THE VIBRATION). AS PAX WAS DEPLANED AT OUR DEST, A COUPLE OF PAX MADE US AWARE THAT THEY HAD SEEN A LOOSE PANEL JUST IN FRONT OF THE L AILERON. WHEN MAINT ARRIVED, THEY FOUND THE PANEL, JUST IN FRONT OF THE AILERON TO BE MISSING SEVERAL SCREWS, THE PANEL COULD ACTUALLY BE LIFTED UP A LITTLE BIT, ENOUGH FOR IT TO BE CAUGHT IN THE AIRFLOW WHILE INFLT. ACCORDING TO WHAT THE PAX THAT SAW THE PANEL INFLT SAID, HE DID NOT NOTICE IT UNTIL ABOUT HALFWAY INTO THE FLT, WHICH WAS ABOUT THE SAME TIME THAT WE IN THE COCKPIT STARTED TO FEEL THE VIBRATION. THE AIRPLANE HAD BEEN PICKED UP AT OUR MAINT HANGAR, JUST PRIOR TO OUR FLT, IT WAS THOROUGHLY PREFLTED, WITH SPECIAL ATTN TO PANELS THAT CAN BE OPENED FOR MAINT FUNCTIONS, GEAR DOORS, ETC. ALL THE PAPERWORK THAT GOES IN THE MAINT CAN WAS PROPERLY ENCLOSED AND CURRENT. IT HAD A FRESH 50 HR/7 DAY MAINT PREFLT SIGNED OFF! THE REQUIRED SIGNATURE ON THE DAILY FLT LOG HAD ALSO BEEN SIGNED OFF, INDICATING THE ACFT WAS RELEASED FROM MAINT FOR RETURN TO SVC. THE PANEL IN FRONT OF THE AILERON THAT WAS MISSING THE SCREWS, IS LOCATED ON TOP OF THE WING, AND IS IMPOSSIBLE TO INSPECT DURING A NORMAL PREFLT!

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.