|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||atc facility : gup|
|Altitude||msl bound lower : 34500|
msl bound upper : 35000
|Controlling Facilities||artcc : zab|
|Operator||common carrier : air carrier|
|Make Model Name||Medium Large Transport, Low Wing, 2 Turbojet Eng|
|Navigation In Use||Other|
|Flight Phase||cruise other|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
pilot : commercial
|Anomaly||altitude deviation : excursion from assigned altitude|
inflight encounter : weather
non adherence : clearance
|Independent Detector||other flight crewa|
|Resolutory Action||controller : issued new clearance|
flight crew : regained aircraft control
|Air Traffic Incident||other|
In the vicinity of gallup north M, cruising at 35000, a/C weight 127000, we noticed a slow deterioration in airspeed. The autothrottles advanced the power to EPR limit, and the airspeed continued to decrease. At approximately 235 KIAS, we requested a lower altitude from center and were told to stand by. At approximately 225 KIAS, we began to experience intermittent cow speed buffet. At this point the captain disconnected the a/P and began a descent, while the first officer informed center that we had a speed problem and were leaving FL350. We received no response. Leaving approximately 34500' we repeated the message to center, at which time we were cleared to FL310. In the descent, the airspeed increased to and stabilized at a normal value. We can only speculate that we experienced some sort of mountain wave effect, since all other factors were normal.
Original NASA ASRS Text
Title: ACR MLG ENCOUTERED MOUNTAIN WAVE AND HAD TO REQUEST LOWER ALT TO MAINTAIN AIRSPEED.
Narrative: IN THE VICINITY OF GALLUP N M, CRUISING AT 35000, A/C WEIGHT 127000, WE NOTICED A SLOW DETERIORATION IN AIRSPEED. THE AUTOTHROTTLES ADVANCED THE POWER TO EPR LIMIT, AND THE AIRSPEED CONTINUED TO DECREASE. AT APPROX 235 KIAS, WE REQUESTED A LOWER ALT FROM CENTER AND WERE TOLD TO STAND BY. AT APPROX 225 KIAS, WE BEGAN TO EXPERIENCE INTERMITTENT COW SPEED BUFFET. AT THIS POINT THE CAPT DISCONNECTED THE A/P AND BEGAN A DESCENT, WHILE THE F/O INFORMED CENTER THAT WE HAD A SPEED PROBLEM AND WERE LEAVING FL350. WE RECEIVED NO RESPONSE. LEAVING APPROX 34500' WE REPEATED THE MESSAGE TO CENTER, AT WHICH TIME WE WERE CLRED TO FL310. IN THE DESCENT, THE AIRSPEED INCREASED TO AND STABILIZED AT A NORMAL VALUE. WE CAN ONLY SPECULATE THAT WE EXPERIENCED SOME SORT OF MOUNTAIN WAVE EFFECT, SINCE ALL OTHER FACTORS WERE NORMAL.
Data retrieved from NASA's ASRS site as of August 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.