Flight crew of a DC10 lost control of aircraft for short time when flying into a mountain wave type turbulence. The aircraft descended 7000 ft before control was regained.

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Attributes
ACN	507767
Time
Date	200104
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : sny.vortac
State Reference	NE
Altitude	msl bound lower : 27000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Weather Elements	Turbulence
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdv.artcc tracon : p50.tracon
Operator	common carrier : air carrier
Make Model Name	DC-10 30F
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 10000 flight time type : 370
ASRS Report	507767
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 117 flight time total : 8500 flight time type : 1544
ASRS Report	507500
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter other other anomaly
Independent Detector	aircraft equipment other aircraft equipment : altimeter airspeed ind other flight crewa other flight crewb other other : 3
Resolutory Action	controller : issued new clearance flight crew : regained aircraft control
Consequence	Other
Supplementary
Problem Areas	Weather Environmental Factor Aircraft
Primary Problem	Weather

Narrative:

While in cruise flight, encountered mountain wave activity. Throttles closed to idle and aircraft experienced moderate vibration (not encountered by this pilot in his career). Crew is in agreement that autothrottles were somehow disengaged during this period aircraft slowed and crew pushed nose down to increase airspeed and get rid of unknown vibration. Received clearance to 12000 ft, descended to FL270, climbed back to FL310. Got aircraft back under control and had uneventful flight from that point forward. I think this was caused by strong up- and downdrafts compounded by crew's inadvertent disengagement of autothrottles. Additional factor: crew groggy/not totally alert at that time of night.

Original NASA ASRS Text

Title: FLC OF A DC10 LOST CTL OF ACFT FOR SHORT TIME WHEN FLYING INTO A MOUNTAIN WAVE TYPE TURB. THE ACFT DSNDED 7000 FT BEFORE CTL WAS REGAINED.

Narrative: WHILE IN CRUISE FLT, ENCOUNTERED MOUNTAIN WAVE ACTIVITY. THROTTLES CLOSED TO IDLE AND ACFT EXPERIENCED MODERATE VIBRATION (NOT ENCOUNTERED BY THIS PLT IN HIS CAREER). CREW IS IN AGREEMENT THAT AUTOTHROTTLES WERE SOMEHOW DISENGAGED DURING THIS PERIOD ACFT SLOWED AND CREW PUSHED NOSE DOWN TO INCREASE AIRSPD AND GET RID OF UNKNOWN VIBRATION. RECEIVED CLRNC TO 12000 FT, DSNDED TO FL270, CLBED BACK TO FL310. GOT ACFT BACK UNDER CTL AND HAD UNEVENTFUL FLT FROM THAT POINT FORWARD. I THINK THIS WAS CAUSED BY STRONG UP- AND DOWNDRAFTS COMPOUNDED BY CREW'S INADVERTENT DISENGAGEMENT OF AUTOTHROTTLES. ADDITIONAL FACTOR: CREW GROGGY/NOT TOTALLY ALERT AT THAT TIME OF NIGHT.

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.