Air carrier mdt declared an emergency for airframe vibration after takeoff from mke.

Attributes
ACN	198560
Time
Date	199201
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mke
State Reference	WI
Altitude	msl bound lower : 1200 msl bound upper : 1200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : mke
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Flight Phase	climbout : initial climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 7050 flight time type : 40
ASRS Report	198560
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 55 flight time total : 4800 flight time type : 3
ASRS Report	198666
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : declared emergency other
Consequence	Other Other
Supplementary
Primary Problem	Aircraft

Narrative:

Taxi and takeoff were normal. All checklists completed professionally and legally. Shortly after gear retraction, aircraft began to shake and shudder violently. Initial reaction was that aircraft was entering a stalled condition. This was immediately ruled out due to the fact that we had positive aircraft control, albeit in a violent shaking/shuddering condition. As we had no idea why this was happening, or what was causing it to occur, we elected to return to milwaukee for immediate landing, as well as to declare an emergency and have equipment standing by. The violent motion of the aircraft subsided after 3-5 mins which was followed by an uneventful landing. Company maintenance personnel could find no problem with the aircraft, which was signed off as 'could not duplicate' and subsequently returned to revenue service. This was a most violent shuddering of still unknown causes and for the short period of time the aircraft was airborne, a great danger existed. There are no simulator drills for this type of emergency, nor are there any checklist procedures published (no exceedences, engine or airframe limitations appeared) for this situation. The only thing that saved the flight was the professionalism, coolness, and past training by all crew members aboard. I am extremely lucky to have been scheduled with the crew I was with. My hat is off to each and every one of them.

Original NASA ASRS Text

Title: ACR MDT DECLARED AN EMER FOR AIRFRAME VIBRATION AFTER TKOF FROM MKE.

Narrative: TAXI AND TKOF WERE NORMAL. ALL CHKLISTS COMPLETED PROFESSIONALLY AND LEGALLY. SHORTLY AFTER GEAR RETRACTION, ACFT BEGAN TO SHAKE AND SHUDDER VIOLENTLY. INITIAL REACTION WAS THAT ACFT WAS ENTERING A STALLED CONDITION. THIS WAS IMMEDIATELY RULED OUT DUE TO THE FACT THAT WE HAD POSITIVE ACFT CTL, ALBEIT IN A VIOLENT SHAKING/SHUDDERING CONDITION. AS WE HAD NO IDEA WHY THIS WAS HAPPENING, OR WHAT WAS CAUSING IT TO OCCUR, WE ELECTED TO RETURN TO MILWAUKEE FOR IMMEDIATE LNDG, AS WELL AS TO DECLARE AN EMER AND HAVE EQUIP STANDING BY. THE VIOLENT MOTION OF THE ACFT SUBSIDED AFTER 3-5 MINS WHICH WAS FOLLOWED BY AN UNEVENTFUL LNDG. COMPANY MAINT PERSONNEL COULD FIND NO PROBLEM WITH THE ACFT, WHICH WAS SIGNED OFF AS 'COULD NOT DUPLICATE' AND SUBSEQUENTLY RETURNED TO REVENUE SVC. THIS WAS A MOST VIOLENT SHUDDERING OF STILL UNKNOWN CAUSES AND FOR THE SHORT PERIOD OF TIME THE ACFT WAS AIRBORNE, A GREAT DANGER EXISTED. THERE ARE NO SIMULATOR DRILLS FOR THIS TYPE OF EMER, NOR ARE THERE ANY CHKLIST PROCS PUBLISHED (NO EXCEEDENCES, ENG OR AIRFRAME LIMITATIONS APPEARED) FOR THIS SITUATION. THE ONLY THING THAT SAVED THE FLT WAS THE PROFESSIONALISM, COOLNESS, AND PAST TRAINING BY ALL CREW MEMBERS ABOARD. I AM EXTREMELY LUCKY TO HAVE BEEN SCHEDULED WITH THE CREW I WAS WITH. MY HAT IS OFF TO EACH AND EVERY ONE OF THEM.

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.