<< >> NASA ASRS Report 290333, November 1994

Reporter, first officer, alleges captain allowed flight in mach buffet for 5-7 seconds before slowing.

Attributes
ACN	290333
Time
Date	199411
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : boi
State Reference	ID
Altitude	msl bound lower : 27000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 2480 flight time type : 1000
ASRS Report	290333
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Aircraft was just under maximum landing weight at top of descent at 104500 pounds (maximum landing weight is 105000 pounds). Captain was flying and started descent from 29000 ft at 290 KTS/.76 mach. Aircraft entered into mach buffet at 27000 ft at .77 mach and stayed in mach buffet for 5-7 seconds before the captain pulled back and recovered into a normal descent. Flight attendants all went to the floor without injury and no passenger were standing during the mach buffet. Normal buffet speed for the B-737-200 is .79-.80 mach at higher altitudes than 29000 ft. Some B-737-200's have been known to buffet at slower and lower altitudes as this case illustrates. No injuries were observed by the flight attendants or flight crew members.

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Original NASA ASRS Text

Title: RPTR, FO, ALLEGES CAPT ALLOWED FLT IN MACH BUFFET FOR 5-7 SECONDS BEFORE SLOWING.

Narrative: ACFT WAS JUST UNDER MAX LNDG WT AT TOP OF DSCNT AT 104500 LBS (MAX LNDG WT IS 105000 LBS). CAPT WAS FLYING AND STARTED DSCNT FROM 29000 FT AT 290 KTS/.76 MACH. ACFT ENTERED INTO MACH BUFFET AT 27000 FT AT .77 MACH AND STAYED IN MACH BUFFET FOR 5-7 SECONDS BEFORE THE CAPT PULLED BACK AND RECOVERED INTO A NORMAL DSCNT. FLT ATTENDANTS ALL WENT TO THE FLOOR WITHOUT INJURY AND NO PAX WERE STANDING DURING THE MACH BUFFET. NORMAL BUFFET SPD FOR THE B-737-200 IS .79-.80 MACH AT HIGHER ALTS THAN 29000 FT. SOME B-737-200'S HAVE BEEN KNOWN TO BUFFET AT SLOWER AND LOWER ALTS AS THIS CASE ILLUSTRATES. NO INJURIES WERE OBSERVED BY THE FLT ATTENDANTS OR FLC MEMBERS.

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.