Altdevs altitude excursions during cruise in proximity of thunderstorm activity.

Attributes
ACN	246569
Time
Date	199307
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : abq
State Reference	NM
Altitude	msl bound lower : 34100 msl bound upper : 35400
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab tower : edw
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 15000 flight time type : 2000
ASRS Report	246569
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 21651 flight time type : 1875
ASRS Report	246446
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

While cruising at FL350 with autoplt, automatic throttles, and altitude engaged, we experienced light turbulence while in solid cirrus clouds. We were deviating north of a thunderstorm when the 'autoplt limit' flag came into view. The aircraft accelerated from mach .84 to mach .86. We descended to 34100 ft followed by a pull up to 35400 ft. A pushover and second down cycle began. The autoplt was placed in control wheel steering and a pull-up was begun. During both pull-ups, mach or airspeed buffet was felt on the air frame. ZAB was advised and he stated he observed the deviation. The maximum altitude lost was 900 ft, gained 400 ft. It lasted 30-45 seconds or less. No more than light turbulence was encountered. Wind shifted 40 degrees and increased 50 KTS during excursion. Temperature change unknown. Suspect mountain wave action or possible wind shear.

Original NASA ASRS Text

Title: ALTDEVS ALT EXCURSIONS DURING CRUISE IN PROX OF TSTM ACTIVITY.

Narrative: WHILE CRUISING AT FL350 WITH AUTOPLT, AUTO THROTTLES, AND ALT ENGAGED, WE EXPERIENCED LIGHT TURB WHILE IN SOLID CIRRUS CLOUDS. WE WERE DEVIATING N OF A TSTM WHEN THE 'AUTOPLT LIMIT' FLAG CAME INTO VIEW. THE ACFT ACCELERATED FROM MACH .84 TO MACH .86. WE DSNDED TO 34100 FT FOLLOWED BY A PULL UP TO 35400 FT. A PUSHOVER AND SECOND DOWN CYCLE BEGAN. THE AUTOPLT WAS PLACED IN CTL WHEEL STEERING AND A PULL-UP WAS BEGUN. DURING BOTH PULL-UPS, MACH OR AIRSPD BUFFET WAS FELT ON THE AIR FRAME. ZAB WAS ADVISED AND HE STATED HE OBSERVED THE DEV. THE MAX ALT LOST WAS 900 FT, GAINED 400 FT. IT LASTED 30-45 SECONDS OR LESS. NO MORE THAN LIGHT TURB WAS ENCOUNTERED. WIND SHIFTED 40 DEGS AND INCREASED 50 KTS DURING EXCURSION. TEMP CHANGE UNKNOWN. SUSPECT MOUNTAIN WAVE ACTION OR POSSIBLE WIND SHEAR.

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.