Mountain wave turbulence causes altitude deviation excursion from assigned.

Attributes
ACN	293890
Time
Date	199501
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : che
State Reference	CO
Altitude	msl bound lower : 18000 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv
Operator	common carrier : air carrier
Make Model Name	Beech 1900
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 28 flight time total : 1650 flight time type : 26
ASRS Report	293890
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	other

Narrative:

En route from denver to hayden, co, we encountered some mountain wave turbulence due to some very strong winds aloft (moderate to severe turbulence had been forecast for the denver area). The altitude deviation was noticed almost immediately by both myself and the captain. I brought the power back to well below cruise power settings, and pushed over as we approached 300 ft above our assigned altitude but was unable to prevent the aircraft from climbing through our 300 ft limit (the entire event, from first encountering the wave to breaking 300 plus ft above our assigned altitude took no longer than 6-10 seconds we estimated).

Original NASA ASRS Text

Title: MOUNTAIN WAVE TURB CAUSES ALTDEV EXCURSION FROM ASSIGNED.

Narrative: ENRTE FROM DENVER TO HAYDEN, CO, WE ENCOUNTERED SOME MOUNTAIN WAVE TURB DUE TO SOME VERY STRONG WINDS ALOFT (MODERATE TO SEVERE TURB HAD BEEN FORECAST FOR THE DENVER AREA). THE ALTDEV WAS NOTICED ALMOST IMMEDIATELY BY BOTH MYSELF AND THE CAPT. I BROUGHT THE PWR BACK TO WELL BELOW CRUISE PWR SETTINGS, AND PUSHED OVER AS WE APCHED 300 FT ABOVE OUR ASSIGNED ALT BUT WAS UNABLE TO PREVENT THE ACFT FROM CLBING THROUGH OUR 300 FT LIMIT (THE ENTIRE EVENT, FROM FIRST ENCOUNTERING THE WAVE TO BREAKING 300 PLUS FT ABOVE OUR ASSIGNED ALT TOOK NO LONGER THAN 6-10 SECONDS WE ESTIMATED).

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.