B737-700 flight crew at FL390 encounters severe up and down drafts while deviating around thundersto...

Attributes
ACN	739331
Time
Date	200705
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl bound lower : 37000 msl bound upper : 39000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 261 flight time type : 261
ASRS Report	739331
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather other anomaly other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : declared emergency flight crew : regained aircraft control
Supplementary
Problem Areas	Flight Crew Human Performance Weather
Primary Problem	Weather

Narrative:

While in clouds and navigating around a thunderstorm; with the aid of the WX radar and staying outside the green area; we experienced a large increase in mach number; from 0.76 to 0.82 in a matter of seconds. I pulled the power back and watched the winds on the mfd. At the same time; the vertical speed increased from zero to about 3000 FPM climb. I pushed forward on the yoke to maintain altitude. Abruptly; the airspeed decreased to 0.72 mach and the stick shaker actuated. I increased power and maintained forward pressure on the yoke. The aircraft started descending but was still below an airspeed where I was able to apply back pressure to maintain altitude and not stall the aircraft. The captain requested FL370 so we could continue a descent and regain a safe airspeed. ARTCC asked if we were declaring an emergency and we replied 'yes.' by this time we were in VMC and ARTCC called out traffic at 12 O'clock going right to left. We acknowledged seeing it and leveled the aircraft at FL370 at a safe airspace. All this happened within a very short time span of about 10 seconds. Navigation farther away from thunderstorms by a minimum of 5 NM.

Original NASA ASRS Text

Title: B737-700 FLT CREW AT FL390 ENCOUNTERS SEVERE UP AND DOWN DRAFTS WHILE DEVIATING AROUND THUNDERSTORMS; AND DESCENDS TO FL370 WITH STICK SHAKER ACTIVATED.

Narrative: WHILE IN CLOUDS AND NAVING AROUND A TSTM; WITH THE AID OF THE WX RADAR AND STAYING OUTSIDE THE GREEN AREA; WE EXPERIENCED A LARGE INCREASE IN MACH NUMBER; FROM 0.76 TO 0.82 IN A MATTER OF SECONDS. I PULLED THE PWR BACK AND WATCHED THE WINDS ON THE MFD. AT THE SAME TIME; THE VERT SPD INCREASED FROM ZERO TO ABOUT 3000 FPM CLB. I PUSHED FORWARD ON THE YOKE TO MAINTAIN ALT. ABRUPTLY; THE AIRSPD DECREASED TO 0.72 MACH AND THE STICK SHAKER ACTUATED. I INCREASED PWR AND MAINTAINED FORWARD PRESSURE ON THE YOKE. THE ACFT STARTED DSNDING BUT WAS STILL BELOW AN AIRSPD WHERE I WAS ABLE TO APPLY BACK PRESSURE TO MAINTAIN ALT AND NOT STALL THE ACFT. THE CAPT REQUESTED FL370 SO WE COULD CONTINUE A DSCNT AND REGAIN A SAFE AIRSPD. ARTCC ASKED IF WE WERE DECLARING AN EMER AND WE REPLIED 'YES.' BY THIS TIME WE WERE IN VMC AND ARTCC CALLED OUT TFC AT 12 O'CLOCK GOING R TO L. WE ACKNOWLEDGED SEEING IT AND LEVELED THE ACFT AT FL370 AT A SAFE AIRSPACE. ALL THIS HAPPENED WITHIN A VERY SHORT TIME SPAN OF ABOUT 10 SECONDS. NAV FARTHER AWAY FROM TSTMS BY A MINIMUM OF 5 NM.

Data retrieved from NASA's ASRS site as of January 2009 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.

B737-700 flight crew at FL390 encounters severe up and down drafts while deviating around thunderstorms; and descends to FL370 with stick shaker activated.