Narrative:

While departing with 2 passenger from scottsdale, az (sdl) to santa monica, ca (smo), we experienced an extreme vibration just as the nosewheel was leaving the ground. Due to the increased temperatures at scottsdale, we determined prior to our taxi that it would be required that we have 0 degree flaps (fully retracted) in order to maintain sufficient 2ND segment climb performance. These calculated V1 and vr speeds were considerably higher than our 15 degree flaps speeds. While we taxied out for departure we, as a crew, completed the taxi checklist and I briefed the departure, making special note of the 0 degree flaps, high temperature and the effect that it would have on our runway required and climb performance. Once given takeoff clearance, we completed the before takeoff checklist. I elected to make full use of the runway and to stabilize the power at the calculated setting prior to brake release. As we began our takeoff 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 aircraft into the air and both the nosewheel and main gear remained on the runway 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 clearly hear the vibration 'spinning down.' I have taken off in the past and heard a nosewheel that is slightly out of balance and had the associated vibration. This was similar but much more extreme with a lower pitch sound. At its ht, it shook the whole aircraft and we were unable to determine where it might be coming from. Once clear of the traffic pattern and while being vectored on the departure we completed the after takeoff checklist. 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 situation. Once at cruise altitude, we explained to the passenger that, although we were not overly concerned with the takeoff vibration, that we felt that it prudent to choose another destination, other than their original destination of santa monica. We explained that santa monica had a much smaller runway than we would prefer should there be the slim chance that there is a problem with the aircraft that we are unaware of. As a crew, we determined that lax was more suitable due to its multiple runways, and a little bit closer, allowing us to conserve fuel in case we had to remain aloft for longer. At about 30 mins from santa monica, we informed ATC of our request of change of destination and were given clearance to lax. Once established in a descent we declared an emergency and explained what our situation was. 'We have requested lax for its longer runways due to an unusual vibration as we departed scottsdale, az.' I continued, 'we feel that we are not in a situation of distress but would like fire and rescue standing by at the airport. At this time we are unsure what might have caused the vibration.' we were given a clearance to a fix on the runway 25L ILS and once established, were cleared for the ILS. As I had briefed the sic, I held the aircraft off the ground for as long as I felt I should and maintained backpressure through the landing roll for as long as possible to keep the nosewheel up as long as I could before allowing it to settle gently to the runway. The landing went extremely smooth and the passenger 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 airport for we did not know about what might be wrong with the airplane.

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Original NASA ASRS Text

Title: 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 FROM SCOTTSDALE, AZ (SDL) TO SANTA MONICA, CA (SMO), WE EXPERIENCED AN EXTREME VIBRATION JUST AS THE NOSEWHEEL WAS LEAVING THE GND. DUE TO THE INCREASED TEMPS AT SCOTTSDALE, 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 HT, 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 OF SANTA MONICA. WE EXPLAINED THAT SANTA MONICA 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 LAX 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 SANTA MONICA, WE INFORMED ATC OF OUR REQUEST OF CHANGE OF DEST AND WERE GIVEN CLRNC TO LAX. ONCE ESTABLISHED IN A DSCNT WE DECLARED AN EMER AND EXPLAINED WHAT OUR SIT WAS. 'WE HAVE REQUESTED LAX FOR ITS LONGER RWYS DUE TO AN UNUSUAL VIBRATION AS WE DEPARTED SCOTTSDALE, AZ.' I CONTINUED, 'WE FEEL THAT WE ARE NOT IN A SIT 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 RWY 25L 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.

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.