B727 maintaining 4000 ft 210 KTS. Slowed to 170 KTS by controller. As aircraft slowed and flaps extended, aircraft began to shudder and buffet. Was within the speed restr for selected flaps. Lost 400 ft during the incident. Controller cleared flight to maintain 3000 ft. Aircraft under control and no further problems.

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Attributes
ACN	360146
Time
Date	199702
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mci
State Reference	MO
Altitude	msl bound lower : 3600 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mci
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	360146
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
ASRS Report	360145
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	controller : issued new clearance flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Level at 4000 ft, 210 KTS, approach control gave us airspeed of 170 KTS. Selected flaps 2 degrees at 205 KTS in a right turn, 15 degree bank -- all was normal. Then selected flaps 5 degrees at 185 KTS and airplane shuddered and buffeted a lot. Also, bank angle increased to at least 30 degrees. Autoplt was disconnected and airplane nose dropped. While trying to regain control and trying to figure out what was going on, we lost about 400 ft of altitude. Before we could tell mci approach about our altitude loss, she gave us 3000 ft. After restoring control and descending to 3000 ft, all indications were normal - - such as led green light flap position indicators and flight control acted normal. Logbook entry was made. We were well above minimum flap speeds and below maximum flap speeds. The buffet was a lot more than when the flaps are out at too high a speed. We have no idea what caused this.

Original NASA ASRS Text

Title: B727 MAINTAINING 4000 FT 210 KTS. SLOWED TO 170 KTS BY CTLR. AS ACFT SLOWED AND FLAPS EXTENDED, ACFT BEGAN TO SHUDDER AND BUFFET. WAS WITHIN THE SPD RESTR FOR SELECTED FLAPS. LOST 400 FT DURING THE INCIDENT. CTLR CLRED FLT TO MAINTAIN 3000 FT. ACFT UNDER CTL AND NO FURTHER PROBS.

Narrative: LEVEL AT 4000 FT, 210 KTS, APCH CTL GAVE US AIRSPD OF 170 KTS. SELECTED FLAPS 2 DEGS AT 205 KTS IN A R TURN, 15 DEG BANK -- ALL WAS NORMAL. THEN SELECTED FLAPS 5 DEGS AT 185 KTS AND AIRPLANE SHUDDERED AND BUFFETED A LOT. ALSO, BANK ANGLE INCREASED TO AT LEAST 30 DEGS. AUTOPLT WAS DISCONNECTED AND AIRPLANE NOSE DROPPED. WHILE TRYING TO REGAIN CTL AND TRYING TO FIGURE OUT WHAT WAS GOING ON, WE LOST ABOUT 400 FT OF ALT. BEFORE WE COULD TELL MCI APCH ABOUT OUR ALT LOSS, SHE GAVE US 3000 FT. AFTER RESTORING CTL AND DSNDING TO 3000 FT, ALL INDICATIONS WERE NORMAL - - SUCH AS LED GREEN LIGHT FLAP POS INDICATORS AND FLT CTL ACTED NORMAL. LOGBOOK ENTRY WAS MADE. WE WERE WELL ABOVE MINIMUM FLAP SPDS AND BELOW MAX FLAP SPDS. THE BUFFET WAS A LOT MORE THAN WHEN THE FLAPS ARE OUT AT TOO HIGH A SPD. WE HAVE NO IDEA WHAT CAUSED THIS.

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.