Narrative:

As flight was climbing thru FL275 a sudden airframe vibration occurred. We advised ATC we would like FL280. At FL280, I reduced engine thrust and speed while trying to isolate the origin of the bad vibration. Changes in engine thrust and airspeed had no effect on the frequency or amplitude of the airframe vibration (the vibration was a low frequency medium amplitude). While reducing speed we checked all system and all system were normal, flight controls operated normally. The bad vibration lasted about 2 mins. After we contacted dispatch and maintenance, we diverted to ZZZ at 270 KTS (we deviated above 270 KTS at one time). We landed at ZZZ without incident. Callback conversation with reporter revealed the following information: the reporter stated the maintenance action taken to correct the airframe vibration is unknown as maintenance has released no information to the reporter. The reporter said this vibration was of a low frequency and high amplitude lasting 2 mins. The reporter stated the vibration was unlike the vibration associated with airworthiness directive 2002-08-20, which is a high frequency vibration. The reporter said changes in the airspeed and engine thrust had no effect on the vibration. The reporter stated on landing, a conference call was initiated with the carrier's system engineer, maintenance and a boeing engineer and the vibration was discussed. Callback conversation with reporter acn 552694 revealed the following information: the reporter stated the corrective action taken by maintenance is unknown. The reporter said in passing through the station recently the reporter discussed the airplane with a technician and was told some parts were replaced in the tail. The reporter stated the vibration was of a low frequency and much different from the high frequency related to the airworthiness directive.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-700 IN CLB AT FL275 DIVERTED DUE TO A LOW FREQ HIGH AMPLITUDE AIRFRAME VIBRATION LASTING 2 MINS. CHANGE IN ENG THRUST OR AIRSPD HAD NO EFFECT.

Narrative: AS FLT WAS CLBING THRU FL275 A SUDDEN AIRFRAME VIBRATION OCCURRED. WE ADVISED ATC WE WOULD LIKE FL280. AT FL280, I REDUCED ENG THRUST AND SPD WHILE TRYING TO ISOLATE THE ORIGIN OF THE BAD VIBRATION. CHANGES IN ENG THRUST AND AIRSPD HAD NO EFFECT ON THE FREQ OR AMPLITUDE OF THE AIRFRAME VIBRATION (THE VIBRATION WAS A LOW FREQ MEDIUM AMPLITUDE). WHILE REDUCING SPD WE CHKED ALL SYS AND ALL SYS WERE NORMAL, FLT CTLS OPERATED NORMALLY. THE BAD VIBRATION LASTED ABOUT 2 MINS. AFTER WE CONTACTED DISPATCH AND MAINT, WE DIVERTED TO ZZZ AT 270 KTS (WE DEVIATED ABOVE 270 KTS AT ONE TIME). WE LANDED AT ZZZ WITHOUT INCIDENT. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING INFO: THE RPTR STATED THE MAINT ACTION TAKEN TO CORRECT THE AIRFRAME VIBRATION IS UNKNOWN AS MAINT HAS RELEASED NO INFO TO THE RPTR. THE RPTR SAID THIS VIBRATION WAS OF A LOW FREQ AND HIGH AMPLITUDE LASTING 2 MINS. THE RPTR STATED THE VIBRATION WAS UNLIKE THE VIBRATION ASSOCIATED WITH AIRWORTHINESS DIRECTIVE 2002-08-20, WHICH IS A HIGH FREQ VIBRATION. THE RPTR SAID CHANGES IN THE AIRSPD AND ENG THRUST HAD NO EFFECT ON THE VIBRATION. THE RPTR STATED ON LNDG, A CONFERENCE CALL WAS INITIATED WITH THE CARRIER'S SYS ENGINEER, MAINT AND A BOEING ENGINEER AND THE VIBRATION WAS DISCUSSED. CALLBACK CONVERSATION WITH RPTR ACN 552694 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CORRECTIVE ACTION TAKEN BY MAINT IS UNKNOWN. THE RPTR SAID IN PASSING THROUGH THE STATION RECENTLY THE RPTR DISCUSSED THE AIRPLANE WITH A TECHNICIAN AND WAS TOLD SOME PARTS WERE REPLACED IN THE TAIL. THE RPTR STATED THE VIBRATION WAS OF A LOW FREQ AND MUCH DIFFERENT FROM THE HIGH FREQ RELATED TO THE AIRWORTHINESS DIRECTIVE.

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.