A320 experienced airframe vibrations; which increased in intensity above 250K.

Attributes
ACN	749289
Time
Date	200708
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 29000
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 240 flight time total : 13000 flight time type : 2500
ASRS Report	749289
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 250 flight time total : 13000 flight time type : 3800
ASRS Report	749288
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Experienced moderate airframe vibration during climb. Began troubleshooting per the aircraft vibration reporting form. Vibration continued into the cruise phase. Determined that the vibration intensity varied with airspeed and was minimized by flying at 250 KIAS. Contacted maintenance via comrdo and advised. Informed ARTCC that we would be flying at 250 KIAS for the duration of the flight due to the vibration. After handing us off to ZZZ ARTCC; ZZZ advised us that he knew that we were not declaring an emergency; but that he was going to declare one for us. Flight continued to destination normally and a normal landing was made. Callback conversation with reporter revealed the following information: the reporter stated that the vibration was strictly airspeed related; and vibrations were minimized by maintaining 250K or less. The flight crew maneuvered the aircraft to verify controllability; and after consultation with maintenance; decision was made to continue to destination airport. An emergency was not declared by the flight crew; ATC declared an emergency to transit restricted airspace. Apparently; airframe vibrations occur frequently in this fleet; and forms are available in the cockpit for documenting and describing these occurrences.

Original NASA ASRS Text

Title: A320 EXPERIENCED AIRFRAME VIBRATIONS; WHICH INCREASED IN INTENSITY ABOVE 250K.

Narrative: EXPERIENCED MODERATE AIRFRAME VIBRATION DURING CLB. BEGAN TROUBLESHOOTING PER THE ACFT VIBRATION RPTING FORM. VIBRATION CONTINUED INTO THE CRUISE PHASE. DETERMINED THAT THE VIBRATION INTENSITY VARIED WITH AIRSPD AND WAS MINIMIZED BY FLYING AT 250 KIAS. CONTACTED MAINT VIA COMRDO AND ADVISED. INFORMED ARTCC THAT WE WOULD BE FLYING AT 250 KIAS FOR THE DURATION OF THE FLT DUE TO THE VIBRATION. AFTER HANDING US OFF TO ZZZ ARTCC; ZZZ ADVISED US THAT HE KNEW THAT WE WERE NOT DECLARING AN EMER; BUT THAT HE WAS GOING TO DECLARE ONE FOR US. FLT CONTINUED TO DEST NORMALLY AND A NORMAL LNDG WAS MADE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT THE VIBRATION WAS STRICTLY AIRSPEED RELATED; AND VIBRATIONS WERE MINIMIZED BY MAINTAINING 250K OR LESS. THE FLT CREW MANEUVERED THE ACFT TO VERIFY CONTROLLABILITY; AND AFTER CONSULTATION WITH MAINT; DECISION WAS MADE TO CONTINUE TO DEST ARPT. AN EMER WAS NOT DECLARED BY THE FLT CREW; ATC DECLARED AN EMER TO TRANSIT RESTRICTED AIRSPACE. APPARENTLY; AIRFRAME VIBRATIONS OCCUR FREQUENTLY IN THIS FLEET; AND FORMS ARE AVAILABLE IN THE COCKPIT FOR DOCUMENTING AND DESCRIBING THESE OCCURRENCES.

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.