Captain of a DC9-50 made a 30 degree bank turn at FL350 and experienced a brief aircraft buffet and was not sure if it was caused by insufficient airspeed or turbulence.

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Attributes
ACN	474002
Time
Date	200005
Day	Thu
Local Time Of Day	0601 To 1200
Place
State Reference	IN
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	DC-9 50
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	arrival star : n/s
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 100 flight time total : 12000 flight time type : 8000
ASRS Report	474002
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	inflight encounter other other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : acft controls other flight crewa
Resolutory Action	none taken : anomaly accepted none taken : insufficient time
Consequence	Other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

While inbound to mem on flight while level at FL350, I made the turn to join the STAR arrival as I passed over pocket city VOR. Cruise speed was about .760 or .770 mach. I had been experiencing intermittent light chop. To make the turn, I used the heading bug and autoplt, which resulted in a bank of about 30 degrees. When in the turn, I felt about 3-5 seconds of what I thought was more light turbulence. Just as the desired heading was achieved and the bank returned to zero, I realized that the 'light turbulence' I experienced seemed somehow different than the earlier turbulence. I think in retrospect that I experienced not 'light turbulence' during the turn but instead a buffet. Further, I think it may have been a high speed buffet, though I have never experienced a high speed buffet before and I am therefore not certain I know what one feels like. It felt like a slow speed buffet, but with a higher frequency to the buffeting. No action was taken on my part because of the short duration of the event. By the time I began to suspect that it was something other than light turbulence, it had ended.

Original NASA ASRS Text

Title: CAPT OF A DC9-50 MADE A 30 DEG BANK TURN AT FL350 AND EXPERIENCED A BRIEF ACFT BUFFET AND WAS NOT SURE IF IT WAS CAUSED BY INSUFFICIENT AIRSPD OR TURB.

Narrative: WHILE INBOUND TO MEM ON FLT WHILE LEVEL AT FL350, I MADE THE TURN TO JOIN THE STAR ARR AS I PASSED OVER POCKET CITY VOR. CRUISE SPD WAS ABOUT .760 OR .770 MACH. I HAD BEEN EXPERIENCING INTERMITTENT LIGHT CHOP. TO MAKE THE TURN, I USED THE HDG BUG AND AUTOPLT, WHICH RESULTED IN A BANK OF ABOUT 30 DEGS. WHEN IN THE TURN, I FELT ABOUT 3-5 SECONDS OF WHAT I THOUGHT WAS MORE LIGHT TURB. JUST AS THE DESIRED HDG WAS ACHIEVED AND THE BANK RETURNED TO ZERO, I REALIZED THAT THE 'LIGHT TURB' I EXPERIENCED SEEMED SOMEHOW DIFFERENT THAN THE EARLIER TURB. I THINK IN RETROSPECT THAT I EXPERIENCED NOT 'LIGHT TURB' DURING THE TURN BUT INSTEAD A BUFFET. FURTHER, I THINK IT MAY HAVE BEEN A HIGH SPD BUFFET, THOUGH I HAVE NEVER EXPERIENCED A HIGH SPD BUFFET BEFORE AND I AM THEREFORE NOT CERTAIN I KNOW WHAT ONE FEELS LIKE. IT FELT LIKE A SLOW SPD BUFFET, BUT WITH A HIGHER FREQ TO THE BUFFETING. NO ACTION WAS TAKEN ON MY PART BECAUSE OF THE SHORT DURATION OF THE EVENT. BY THE TIME I BEGAN TO SUSPECT THAT IT WAS SOMETHING OTHER THAN LIGHT TURB, IT HAD ENDED.

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.