Narrative:

Approximately 1:40 into a flight from chicago midway to oxnard, ca, at 45000 ft, the light transport I was flying encountered buffet and could not hold altitude. Leading to this event, we had blocked 430-450 and had been drifting up for 15-20 mins, maintaining 150-155 KTS IAS. At 44500 controller asked if we could accept 450. There was an air carrier large transport overtaking at 430. Weight was showing just under 14000 pounds, our maximum weight for 450. I told the controller 'yes', and we were cleared to maintain 450. Going up the last 500 ft our speed dropped to 140 KTS IAS. Level at 450 speed began to decay. At approximately 125-120 KTS IAS we encountered onset of buffet. I told the controller we had entered buffet and had to come down. He told me we couldn't come down because of traffic and that I should turn to the right 60 degrees until he could clear me down. We were encountering descending air. If we continued ahead I was sure we would stall or unport. Turning would take my away from the traffic but was not a safe maneuver. I told the controller I was turning and coming down and descended 1000 ft turning 60 degrees to the right. The airliner below and behind reported he had us visually and we were no problem. Subsequently, on being switched to denver, we learned there was mountain wave activity reported by airliners at 420. Cleared to 430 and stabilized at approximately 170 KTS IAS, we experienced up to 15 KT speed changes along with altitude changes as we encountered areas of ascending and descending air. Aside from the obvious (if we had known it was a trap we would not have entered it), I believe the action taken was the safest. I told the controller what I had to do. I believe he would have turned the large transport immediately if there was the slightest danger of a collision. 2 constructive suggestions: 1) a segment should be added to initial and recurrent training covering high altitude, thin air flying. This is at the edge of the envelope and there is nothing in the training syllabus covering it. 2) if there is not, there should be training for the controllers in aircraft problems at high altitude flight, i.e., a buffet is on the way to a stall or flame-out and any turns should be given to the aircraft which can safely make the turn, not the one in trouble.

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Original NASA ASRS Text

Title: GA LTT LOW SPD BUFFET AT FL450.

Narrative: APPROX 1:40 INTO A FLT FROM CHICAGO MIDWAY TO OXNARD, CA, AT 45000 FT, THE LTT I WAS FLYING ENCOUNTERED BUFFET AND COULD NOT HOLD ALT. LEADING TO THIS EVENT, WE HAD BLOCKED 430-450 AND HAD BEEN DRIFTING UP FOR 15-20 MINS, MAINTAINING 150-155 KTS IAS. AT 44500 CTLR ASKED IF WE COULD ACCEPT 450. THERE WAS AN ACR LGT OVERTAKING AT 430. WT WAS SHOWING JUST UNDER 14000 POUNDS, OUR MAX WT FOR 450. I TOLD THE CTLR 'YES', AND WE WERE CLRED TO MAINTAIN 450. GOING UP THE LAST 500 FT OUR SPD DROPPED TO 140 KTS IAS. LEVEL AT 450 SPD BEGAN TO DECAY. AT APPROX 125-120 KTS IAS WE ENCOUNTERED ONSET OF BUFFET. I TOLD THE CTLR WE HAD ENTERED BUFFET AND HAD TO COME DOWN. HE TOLD ME WE COULDN'T COME DOWN BECAUSE OF TFC AND THAT I SHOULD TURN TO THE R 60 DEGS UNTIL HE COULD CLR ME DOWN. WE WERE ENCOUNTERING DSNDING AIR. IF WE CONTINUED AHEAD I WAS SURE WE WOULD STALL OR UNPORT. TURNING WOULD TAKE MY AWAY FROM THE TFC BUT WAS NOT A SAFE MANEUVER. I TOLD THE CTLR I WAS TURNING AND COMING DOWN AND DSNDED 1000 FT TURNING 60 DEGS TO THE R. THE AIRLINER BELOW AND BEHIND RPTED HE HAD US VISUALLY AND WE WERE NO PROBLEM. SUBSEQUENTLY, ON BEING SWITCHED TO DENVER, WE LEARNED THERE WAS MOUNTAIN WAVE ACTIVITY RPTED BY AIRLINERS AT 420. CLRED TO 430 AND STABILIZED AT APPROX 170 KTS IAS, WE EXPERIENCED UP TO 15 KT SPD CHANGES ALONG WITH ALT CHANGES AS WE ENCOUNTERED AREAS OF ASCENDING AND DSNDING AIR. ASIDE FROM THE OBVIOUS (IF WE HAD KNOWN IT WAS A TRAP WE WOULD NOT HAVE ENTERED IT), I BELIEVE THE ACTION TAKEN WAS THE SAFEST. I TOLD THE CTLR WHAT I HAD TO DO. I BELIEVE HE WOULD HAVE TURNED THE LGT IMMEDIATELY IF THERE WAS THE SLIGHTEST DANGER OF A COLLISION. 2 CONSTRUCTIVE SUGGESTIONS: 1) A SEGMENT SHOULD BE ADDED TO INITIAL AND RECURRENT TRAINING COVERING HIGH ALT, THIN AIR FLYING. THIS IS AT THE EDGE OF THE ENVELOPE AND THERE IS NOTHING IN THE TRAINING SYLLABUS COVERING IT. 2) IF THERE IS NOT, THERE SHOULD BE TRAINING FOR THE CTLRS IN ACFT PROBLEMS AT HIGH ALT FLT, I.E., A BUFFET IS ON THE WAY TO A STALL OR FLAME-OUT AND ANY TURNS SHOULD BE GIVEN TO THE ACFT WHICH CAN SAFELY MAKE THE TURN, NOT THE ONE IN TROUBLE.

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.