Falcon 10/100
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 200; Flight Crew Total 12000; Flight Crew Type 500
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed As Precaution; General Declared Emergency
Aircraft
Routine; uneventful climb up to FL380 on way to FL400 in no turbulence when several waves of rather severe vibration occurred thought airframe. Not able to [isolate] source; but reduction of power and airspeed improved situation; yet phenomenon reoccurred. Requested an emergency descent to lower flight level; finding things 'smoothed out' at FL350. Cleared to FL300 where we reported critical situation had resolved and emergency did not currently exist; yet passengers understandably did not what to continue flight in that aircraft. So; we requested 'normal' handling for a landing at [a nearby airport]. Uneventful descent and landing there.
[Narrative 2 had no additional information]
FA10 flight crew climbing through FL380 reported severe airframe vibration of unknown origin; so they declared an emergency and diverted to a nearby airport.