B737-300 encounters severe clear air turbulence over ALS.

Attributes
ACN	455006
Time
Date	199911
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : als.vor
State Reference	CO
Altitude	msl bound lower : 30200 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : flight engineer pilot : multi engine pilot : instrument pilot : atp
Experience	flight time last 90 days : 200 flight time total : 11800 flight time type : 1100
ASRS Report	455006
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 4800 flight time type : 2400
ASRS Report	455120
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter : weather inflight encounter other other anomaly
Independent Detector	aircraft equipment : altitude alert aircraft equipment other aircraft equipment : altimeter other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Weather Environmental Factor
Primary Problem	Environmental Factor
Air Traffic Incident	other

Narrative:

While in clear air and smooth conditions we encountered severe instantaneous mountain wave turbulence. The autoplt was on and the aircraft climbed to FL313 in the space of about a second. The airspeed instantly climbed to the barber pole. The captain disconnected the autoplt and autothrottles and established and held a normal pitch attitude and cracked the throttles back. ARTCC was advised of our deviation and then in the space of about 3 seconds the aircraft dropped 800 ft to an altitude of FL305. Center was advised and a PIREP was given while the captain initiated a slight climb back to altitude. There were no other aircraft in the area to be in conflict with and the airplane was off from assigned altitude about 15-20 seconds even though the turbulence encountered last 45 seconds. No one was injured in the incident.

Original NASA ASRS Text

Title: B737-300 ENCOUNTERS SEVERE CLR AIR TURB OVER ALS.

Narrative: WHILE IN CLR AIR AND SMOOTH CONDITIONS WE ENCOUNTERED SEVERE INSTANTANEOUS MOUNTAIN WAVE TURB. THE AUTOPLT WAS ON AND THE ACFT CLBED TO FL313 IN THE SPACE OF ABOUT A SECOND. THE AIRSPD INSTANTLY CLBED TO THE BARBER POLE. THE CAPT DISCONNECTED THE AUTOPLT AND AUTOTHROTTLES AND ESTABLISHED AND HELD A NORMAL PITCH ATTITUDE AND CRACKED THE THROTTLES BACK. ARTCC WAS ADVISED OF OUR DEV AND THEN IN THE SPACE OF ABOUT 3 SECONDS THE ACFT DROPPED 800 FT TO AN ALT OF FL305. CTR WAS ADVISED AND A PIREP WAS GIVEN WHILE THE CAPT INITIATED A SLIGHT CLB BACK TO ALT. THERE WERE NO OTHER ACFT IN THE AREA TO BE IN CONFLICT WITH AND THE AIRPLANE WAS OFF FROM ASSIGNED ALT ABOUT 15-20 SECONDS EVEN THOUGH THE TURB ENCOUNTERED LAST 45 SECONDS. NO ONE WAS INJURED IN THE INCIDENT.

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.