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Flight crew of MD80 experience speed and altitude fluctuations during encounter with mountain wave over northern new mexico.
| Attributes | |
| ACN | 631494 |
| Time | |
| Date | 200409 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : cim.vortac |
| State Reference | NM |
| Altitude | msl single value : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Weather Elements | Turbulence |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zab.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | MD-82 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 10200 flight time type : 2000 |
| ASRS Report | 631494 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter other other anomaly |
| Independent Detector | other flight crewa other flight crewb |
| Resolutory Action | flight crew : exited adverse environment flight crew : regained aircraft control |
| Supplementary | |
| Problem Areas | Aircraft Environmental Factor |
| Primary Problem | Environmental Factor |
Narrative:
We encountered moderate to severe mountain wave. Winds aloft were out of the southwest around 80 KTS. Autothrottles were disengaged and aggressive action was taken to control airspeed and altitude. Approximately aircraft weight was 130000 pounds, below the maximum weight of 140000 pounds for the altitude (mach buffer). Airspeed excursions started from a steady .766 mach to .74 and then to .78 mach and then the next excursion went up to .80 mach (with throttles reduced) down to .71 mach (throttles maximum thrust). High speed mach buffet was felt, but never low speed buffet. Both the captain and I were ready to start an emergency descent but the airspeed was starting to increase once again and slowly stabilized. Altitude excursions were up to +/-150 ft over and below assigned altitude. No prior aircraft/ATC reports were given. We did report the encounter with ATC.
Original NASA ASRS Text
Title: FLT CREW OF MD80 EXPERIENCE SPD AND ALT FLUCTUATIONS DURING ENCOUNTER WITH MOUNTAIN WAVE OVER NORTHERN NEW MEXICO.
Narrative: WE ENCOUNTERED MODERATE TO SEVERE MOUNTAIN WAVE. WINDS ALOFT WERE OUT OF THE SW AROUND 80 KTS. AUTOTHROTTLES WERE DISENGAGED AND AGGRESSIVE ACTION WAS TAKEN TO CTL AIRSPD AND ALT. APPROX ACFT WT WAS 130000 LBS, BELOW THE MAX WT OF 140000 LBS FOR THE ALT (MACH BUFFER). AIRSPD EXCURSIONS STARTED FROM A STEADY .766 MACH TO .74 AND THEN TO .78 MACH AND THEN THE NEXT EXCURSION WENT UP TO .80 MACH (WITH THROTTLES REDUCED) DOWN TO .71 MACH (THROTTLES MAX THRUST). HIGH SPD MACH BUFFET WAS FELT, BUT NEVER LOW SPD BUFFET. BOTH THE CAPT AND I WERE READY TO START AN EMER DSCNT BUT THE AIRSPD WAS STARTING TO INCREASE ONCE AGAIN AND SLOWLY STABILIZED. ALT EXCURSIONS WERE UP TO +/-150 FT OVER AND BELOW ASSIGNED ALT. NO PRIOR ACFT/ATC RPTS WERE GIVEN. WE DID RPT THE ENCOUNTER WITH ATC.
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.