DURING A 0 DEG FLAP DEP WITH A HIGH ROTATION SPD FROM A HOT ARPT; A CESSNA JET DEVELOPED A VIBRATION IN THE NOSEWHEEL. IN THE DEST TERMINAL AREA; THE CREW DECLARED AN EMER AND DIVERTED TO AN ARPT WITH LONG RWYS. THE LNDG WAS UNEVENTFUL.

Narrative

WHILE DEPARTING WITH 2 PAX; WE EXPERIENCED AN EXTREME VIBRATION JUST AS THE NOSEWHEEL WAS LEAVING THE GND. DUE TO THE INCREASED TEMPS; WE DETERMINED PRIOR TO OUR TAXI THAT IT WOULD BE REQUIRED THAT WE HAVE 0 DEG FLAPS (FULLY RETRACTED) IN ORDER TO MAINTAIN SUFFICIENT 2ND SEGMENT CLB PERFORMANCE. THESE CALCULATED V1 AND VR SPDS WERE CONSIDERABLY HIGHER THAN OUR 15 DEG FLAPS SPDS. WHILE WE TAXIED OUT FOR DEP WE; AS A CREW; COMPLETED THE TAXI CHKLIST AND I BRIEFED THE DEP; MAKING SPECIAL NOTE OF THE 0 DEG FLAPS; HIGH TEMP AND THE EFFECT THAT IT WOULD HAVE ON OUR RWY REQUIRED AND CLB PERFORMANCE. ONCE GIVEN TKOF CLRNC; WE COMPLETED THE BEFORE TKOF CHKLIST. I ELECTED TO MAKE FULL USE OF THE RWY AND TO STABILIZE THE PWR AT THE CALCULATED SETTING PRIOR TO BRAKE RELEASE. AS WE BEGAN OUR TKOF ROLL; OUR PERFORMANCE APPEARED TO BE AS LETHARGIC AS WE HAD EXPECTED IN THE HEAT. AS V1 WAS ANNOUNCED I REMOVED MY HAND FROM THE THROTTLES; AND VR WAS THEN CALLED. JUST AS I APPLIED GENTLE BACKPRESSURE ON THE YOKE A VIBRATION BEGAN. I COULD NOT DETERMINE WHERE IT WAS COMING FROM. I FELT THAT WITH THE HEAT THE NOSE WAS SLOW TO RESPOND TO MY STEADY INCREASE OF BACKPRESSURE. I DID NOT FORCE THE ACFT INTO THE AIR AND BOTH THE NOSEWHEEL AND MAIN GEAR REMAINED ON THE RWY FOR A LONGER PERIOD OF TIME THAN THEY WOULD IN COOLER CONDITIONS. THE VIBRATION CONTINUED TO STRENGTHEN THROUGH THIS PERIOD; AND ONLY BEGAN TO WEAKEN AFTER ABOUT 5 SECONDS OF BEING AIRBORNE. AS THE GEAR WAS RAISED; WE COULD CLRLY HEAR THE VIBRATION 'SPINNING DOWN.' I HAVE TAKEN OFF IN THE PAST AND HEARD A NOSEWHEEL THAT IS SLIGHTLY OUT OF BAL AND HAD THE ASSOCIATED VIBRATION. THIS WAS SIMILAR BUT MUCH MORE EXTREME WITH A LOWER PITCH SOUND. AT ITS HEIGHT; IT SHOOK THE WHOLE ACFT AND WE WERE UNABLE TO DETERMINE WHERE IT MIGHT BE COMING FROM. ONCE CLR OF THE TFC PATTERN AND WHILE BEING VECTORED ON THE DEP WE COMPLETED THE AFTER TKOF CHKLIST. WE BEGAN TO DISCUSS WHAT THE VIBRATION MIGHT HAVE BEEN CAUSED BY AND WHETHER ANY IMMEDIATE ACTION WAS REQUIRED. WE BOTH FELT THAT IT WAS SUITABLE TO CONTINUE WHILE CONTINUING TO DISCUSS THE SIT. ONCE AT CRUISE ALT; WE EXPLAINED TO THE PAX THAT; ALTHOUGH WE WERE NOT OVERLY CONCERNED WITH THE TKOF VIBRATION; THAT WE FELT THAT IT PRUDENT TO CHOOSE ANOTHER DEST; OTHER THAN THEIR ORIGINAL DEST. WE EXPLAINED THAT THE ORIGINAL DEST HAD A MUCH SMALLER RWY THAN WE WOULD PREFER SHOULD THERE BE THE SLIM CHANCE THAT THERE IS A PROB WITH THE ACFT THAT WE ARE UNAWARE OF. AS A CREW; WE DETERMINED THAT ZZZ1 WAS MORE SUITABLE DUE TO ITS MULTIPLE RWYS; AND A LITTLE BIT CLOSER; ALLOWING US TO CONSERVE FUEL IN CASE WE HAD TO REMAIN ALOFT FOR LONGER. AT ABOUT 30 MINS FROM ORIGINAL DEST; WE INFORMED ATC OF OUR REQUEST OF CHANGE OF DEST AND WERE GIVEN CLRNC TO ZZZ1. ONCE ESTABLISHED IN A DSCNT WE DECLARED AN EMER AND EXPLAINED WHAT OUR SIT WAS. 'WE HAVE REQUESTED ZZZ1 FOR ITS LONGER RWYS DUE TO AN UNUSUAL VIBRATION AS WE DEPARTED.' I CONTINUED; 'WE FEEL THAT WE ARE NOT IN A SITUATION OF DISTRESS BUT WOULD LIKE FIRE AND RESCUE STANDING BY AT THE ARPT. AT THIS TIME WE ARE UNSURE WHAT MIGHT HAVE CAUSED THE VIBRATION.' WE WERE GIVEN A CLRNC TO A FIX ON THE ILS AND ONCE ESTABLISHED; WERE CLRED FOR THE ILS. AS I HAD BRIEFED THE SIC; I HELD THE ACFT OFF THE GND FOR AS LONG AS I FELT I SHOULD AND MAINTAINED BACKPRESSURE THROUGH THE LNDG ROLL FOR AS LONG AS POSSIBLE TO KEEP THE NOSEWHEEL UP AS LONG AS I COULD BEFORE ALLOWING IT TO SETTLE GENTLY TO THE RWY. THE LNDG WENT EXTREMELY SMOOTH AND THE PAX VOICED THEIR APPROVAL FROM THE CABIN AS THE FIRE AND RESCUE TRUCKS FOLLOWED US TO THE FBO. I THANKED THE FIRE AND RESCUE CREWS FOR THEIR ASSISTANCE. A THOROUGH POSTFLT INSPECTION BY THE CREW REVEALED NO ANOMALIES THAT MIGHT HAVE CAUSED THE VIBRATION. I FELT THAT WE MADE THE PROPER DECISION TO CONTINUE TO A LARGER ARPT FOR WE DID NOT KNOW ABOUT WHAT MIGHT BE WRONG WITH THE AIRPLANE.