An air carrier B747-100 lost 400 ft in a mountain wave.

Attributes
ACN	354990
Time
Date	199612
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : als
State Reference	CO
Altitude	msl bound lower : 32600 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab
Operator	common carrier : air carrier
Make Model Name	B747-100
Operating Under FAR Part	Part 121
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 pilot : cfi pilot : flight engineer
Experience	flight time last 90 days : 50 flight time total : 9500 flight time type : 500
ASRS Report	354990
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 non adherence : far non adherence : clearance other anomaly
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	other

Narrative:

In the area of front range of the rockies, we encountered moderate turbulence and moderate to severe mountain wave. Airspeed rapidly decreasing. I applied maximum climb thrust. Captain requested lower altitude now and advised ATC of mountain wave. Unable to maintain airspeed. ATC advised unable due to traffic. We requested and received a turn away from the conflicting traffic. Due to loss of airspeed, we were unable to maintain FL330. Aircraft descended to FL326, at the same time we received clearance to lower altitude. There was no conflict with traffic that we know of since our airplane is not equipped with TCASII. ATC never said anything about whether there was any traffic conflict. ATC was prompt to start advising other aircraft of our unexpected mountain wave.

Original NASA ASRS Text

Title: AN ACR B747-100 LOST 400 FT IN A MOUNTAIN WAVE.

Narrative: IN THE AREA OF FRONT RANGE OF THE ROCKIES, WE ENCOUNTERED MODERATE TURB AND MODERATE TO SEVERE MOUNTAIN WAVE. AIRSPD RAPIDLY DECREASING. I APPLIED MAX CLB THRUST. CAPT REQUESTED LOWER ALT NOW AND ADVISED ATC OF MOUNTAIN WAVE. UNABLE TO MAINTAIN AIRSPD. ATC ADVISED UNABLE DUE TO TFC. WE REQUESTED AND RECEIVED A TURN AWAY FROM THE CONFLICTING TFC. DUE TO LOSS OF AIRSPD, WE WERE UNABLE TO MAINTAIN FL330. ACFT DSNDED TO FL326, AT THE SAME TIME WE RECEIVED CLRNC TO LOWER ALT. THERE WAS NO CONFLICT WITH TFC THAT WE KNOW OF SINCE OUR AIRPLANE IS NOT EQUIPPED WITH TCASII. ATC NEVER SAID ANYTHING ABOUT WHETHER THERE WAS ANY TFC CONFLICT. ATC WAS PROMPT TO START ADVISING OTHER ACFT OF OUR UNEXPECTED MOUNTAIN WAVE.

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.