Narrative:

Aircraft developed a significant vibration en route. It started with both control yokes shaking; most notable in the aileron movement; and less in the column itself. I observed the left aileron; outboard of the hinge attach point vibrating. As time went on; the vibration became worse; and the frequency increased. The 3 outboard static wicks were invisible; and the outboard portion of the aileron outside of the hinge point moved up and down and was 'a soft blur'. The O2 masks bounced off of the wall; the glareshield and floor...everything transmitted the vibration. The rudder pedals shook; enough to vibrate the loose portion of your pant legs with feet resting on the pedals. I asked the first officer to check his aileron; and he confirmed it was stable and not moving. We had a medium length final and configured early as we were unpressurized. When the prpm was brought full forward; there was little change; however as the aircraft did slow below about 150-140 KIAS; the vibration increased. Not in frequency; but in intensity. On an 8 mile final I observed the engine nacelle and the black portion of the inlet de-ice boot shaking as well. The spinner was not symmetrical in its rotation as well; observed by the shape of the spinner itself; not the yellow painted ice line. Needless to say the aforementioned was conveyed to maintenance upon landing. The explanation with the mechanic during the walk around; 'it is supposed to do that; there is no hinge out there'.... Later the accepting crew; (first officer) stated that the mechanic suggested that pilot write ups are because the pilot group is upset with management; and that write ups like these aren't helping the situation; and that we are going to lose saab 340 flying if we continued. Speaking frankly; I can't think of a faster way to lose a contract then to deliberately violate federal law; and do it with passengers. We need to be doing our job; cleaner and better then anyone else; and flying or being intimidated into flying broken or incorrect equipment will not advance this company or its standing with any current or future code share partners. Maintenance needs to approach the pilot group without the skepticism presented. It has; and will continue to; coerce some flight crews into operating defective equipment.

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Original NASA ASRS Text

Title: SF340 flight crew enroute experienced significant airframe vibration. Upon landing the encounter was conveyed to maintenance who dismissed the incident as another unwarranted gripe by flight crews.

Narrative: Aircraft developed a significant vibration en route. It started with both control yokes shaking; most notable in the aileron movement; and less in the column itself. I observed the left aileron; outboard of the hinge attach point vibrating. As time went on; the vibration became worse; and the frequency increased. The 3 outboard static wicks were invisible; and the outboard portion of the aileron outside of the hinge point moved up and down and was 'a soft blur'. The O2 masks bounced off of the wall; the glareshield and floor...everything transmitted the vibration. The rudder pedals shook; enough to vibrate the loose portion of your pant legs with feet resting on the pedals. I asked the First Officer to check his aileron; and he confirmed it was stable and not moving. We had a medium length final and configured early as we were unpressurized. When the PRPM was brought full forward; there was little change; however as the aircraft did slow below about 150-140 KIAS; the vibration increased. Not in frequency; but in intensity. On an 8 mile final I observed the engine nacelle and the black portion of the inlet de-ice boot shaking as well. The spinner was not symmetrical in its rotation as well; observed by the shape of the spinner itself; not the yellow painted ice line. Needless to say the aforementioned was conveyed to Maintenance upon landing. The explanation with the Mechanic during the walk around; 'it is supposed to do that; there is no hinge out there'.... Later the accepting crew; (First Officer) stated that the Mechanic suggested that pilot write ups are because the pilot group is upset with management; and that write ups like these aren't helping the situation; and that we are going to lose Saab 340 flying if we continued. Speaking frankly; I can't think of a faster way to lose a contract then to deliberately violate Federal law; and do it with passengers. We need to be doing our job; cleaner and better then anyone else; and flying or being intimidated into flying broken or incorrect equipment will not advance this company or its standing with any current or future code share partners. Maintenance needs to approach the pilot group without the skepticism presented. It has; and will continue to; coerce some flight crews into operating defective equipment.

Data retrieved from NASA's ASRS site as of April 2012 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.