An embraer 145 on descent from FL200 to 11000 ft experienced a light but constant tail plane vibrati...

Attributes
ACN	426665
Time
Date	199901
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : phl
State Reference	PA
Altitude	msl bound lower : 11000 msl bound upper : 20000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Embraer Undifferentiated or Other Model
Navigation In Use	Other
Flight Phase	descent other
Route In Use	enroute airway : zny
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial
Experience	flight time last 90 days : 240 flight time total : 2800 flight time type : 900
ASRS Report	426665
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

Aircraft xyz, embraer regional jet. Descent from FL200 to 11000 ft at 315 KTS. Constant tailplane vibration. The vibrations would 'surge' from strong vibration to weak. Vibrations could be aggravated by pulling back on yoke and releasing back pressure (my concern -- metal fatigue over time). Callback conversation with reporter revealed the following information: the reporter stated the aircraft is an embraer 145 and has a light airframe harmonic wave vibration felt in the fuselage structure. The reporter said the vibration is never felt in the yoke but pulling back on the control column and releasing back pressure will increase the amplitude or intensity from light to moderate. The reporter stated the latest theory of the cause is the outer elevator horns and vortex generators were added to the lower surface of the horns as a test on one airplane but appears not to have helped. The reporter said the vibration is not present with the autoplt engaged. The reporter stated it is speed related and occurs around 270 KIAS. The reporter says the manufacturer installed sensors in the tail and the aircraft was test flown to duplicate the vibration but no results were published.

Original NASA ASRS Text

Title: AN EMBRAER 145 ON DSCNT FROM FL200 TO 11000 FT EXPERIENCED A LIGHT BUT CONSTANT TAIL PLANE VIBRATION FELT IN THE FUSELAGE STRUCTURE BUT NOT IN THE YOKE.

Narrative: ACFT XYZ, EMBRAER REGIONAL JET. DSCNT FROM FL200 TO 11000 FT AT 315 KTS. CONSTANT TAILPLANE VIBRATION. THE VIBRATIONS WOULD 'SURGE' FROM STRONG VIBRATION TO WEAK. VIBRATIONS COULD BE AGGRAVATED BY PULLING BACK ON YOKE AND RELEASING BACK PRESSURE (MY CONCERN -- METAL FATIGUE OVER TIME). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT IS AN EMBRAER 145 AND HAS A LIGHT AIRFRAME HARMONIC WAVE VIBRATION FELT IN THE FUSELAGE STRUCTURE. THE RPTR SAID THE VIBRATION IS NEVER FELT IN THE YOKE BUT PULLING BACK ON THE CTL COLUMN AND RELEASING BACK PRESSURE WILL INCREASE THE AMPLITUDE OR INTENSITY FROM LIGHT TO MODERATE. THE RPTR STATED THE LATEST THEORY OF THE CAUSE IS THE OUTER ELEVATOR HORNS AND VORTEX GENERATORS WERE ADDED TO THE LOWER SURFACE OF THE HORNS AS A TEST ON ONE AIRPLANE BUT APPEARS NOT TO HAVE HELPED. THE RPTR SAID THE VIBRATION IS NOT PRESENT WITH THE AUTOPLT ENGAGED. THE RPTR STATED IT IS SPD RELATED AND OCCURS AROUND 270 KIAS. THE RPTR SAYS THE MANUFACTURER INSTALLED SENSORS IN THE TAIL AND THE ACFT WAS TEST FLOWN TO DUPLICATE THE VIBRATION BUT NO RESULTS WERE PUBLISHED.

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.

An embraer 145 on descent from FL200 to 11000 ft experienced a light but constant tail plane vibration felt in the fuselage structure but not in the yoke.