EMB145 crew had violent aircraft shaking and pitch oscillations. The control yoke was operated in a ...

Attributes
ACN	594603
Time
Date	200309
Day	Tue
Place
Locale Reference	atc facility : zny.artcc
State Reference	NY
Environment
Flight Conditions	IMC
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	EMB ERJ 135 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	594603
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overrode automation other
Consequence	other other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Pitch oscillations when we reached cruise altitude. We encountered light occasional chop. Autoplt was flying when all of a sudden the aircraft started to shake violently. The nose of the aircraft felt like it was bouncing up and down without any roll movement and the control column was now moving back and forth in a very violent but distinctive cyclic pattern. At this point, I realized it was not turbulence and disconnected the autoplt and it immediately stopped. At this time we were still at cruise and in solid IMC when the captain suggested we turn the autoplt back on and try it out. Since I was flying, I told him that I would like to hand fly and not try the autoplt. He insisted that he had heard of a previous such incident and we were supposed to try it out. I informed him not while I was flying in IMC. Once we descended below 10000 ft, and we were between layers and had intermittent ground contact, the captain told me that he would like to try re-engaging the autoplt again. I told him once more not while I was flying and I was uncomfortable doing that at that point. Once in phl, called maintenance operational controller and crew MEL'ed the autoplt.

Original NASA ASRS Text

Title: EMB145 CREW HAD VIOLENT ACFT SHAKING AND PITCH OSCILLATIONS. THE CTL YOKE WAS OPERATED IN A VIOLENT BUT DISTINCTIVE CYCLIC PATTERN. DISCONNECTING THE AUTOPLT STOPPED THE SHAKING.

Narrative: PITCH OSCILLATIONS WHEN WE REACHED CRUISE ALT. WE ENCOUNTERED LIGHT OCCASIONAL CHOP. AUTOPLT WAS FLYING WHEN ALL OF A SUDDEN THE ACFT STARTED TO SHAKE VIOLENTLY. THE NOSE OF THE ACFT FELT LIKE IT WAS BOUNCING UP AND DOWN WITHOUT ANY ROLL MOVEMENT AND THE CTL COLUMN WAS NOW MOVING BACK AND FORTH IN A VERY VIOLENT BUT DISTINCTIVE CYCLIC PATTERN. AT THIS POINT, I REALIZED IT WAS NOT TURB AND DISCONNECTED THE AUTOPLT AND IT IMMEDIATELY STOPPED. AT THIS TIME WE WERE STILL AT CRUISE AND IN SOLID IMC WHEN THE CAPT SUGGESTED WE TURN THE AUTOPLT BACK ON AND TRY IT OUT. SINCE I WAS FLYING, I TOLD HIM THAT I WOULD LIKE TO HAND FLY AND NOT TRY THE AUTOPLT. HE INSISTED THAT HE HAD HEARD OF A PREVIOUS SUCH INCIDENT AND WE WERE SUPPOSED TO TRY IT OUT. I INFORMED HIM NOT WHILE I WAS FLYING IN IMC. ONCE WE DSNDED BELOW 10000 FT, AND WE WERE BTWN LAYERS AND HAD INTERMITTENT GND CONTACT, THE CAPT TOLD ME THAT HE WOULD LIKE TO TRY RE-ENGAGING THE AUTOPLT AGAIN. I TOLD HIM ONCE MORE NOT WHILE I WAS FLYING AND I WAS UNCOMFORTABLE DOING THAT AT THAT POINT. ONCE IN PHL, CALLED MAINT OPERATIONAL CTLR AND CREW MEL'ED THE AUTOPLT.

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.

EMB145 crew had violent aircraft shaking and pitch oscillations. The control yoke was operated in a violent but distinctive cyclic pattern. Disconnecting the autoplt stopped the shaking.