 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Crj-900 flight crew reported descended from assigned altitude of FL370 when they were unable to maintain speed because of downdrafts.
| Attributes | |
| ACN | 1340075 |
| Time | |
| Date | 201603 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZ.ARTCC |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | Regional Jet 900 (CRJ900) |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Person 1 | |
| Function | Pilot Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Person 2 | |
| Function | Pilot Not Flying First Officer |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence Inflight Event / Encounter Loss Of Aircraft Control |
Narrative:
During cruise flight at our planned cruising altitude of FL370; we encountered mountain wave and up/downdrafts. During the hour or so in cruise at FL370 leading up to the event; we were constantly changing the power; attempting to maintain our filed cruise speed of M.77. At one point; the airspeed started to drop towards M.74. I selected the climb detent. Instead of increasing; the airspeed started decreasing. At about M.72 I selected maximum power (apr thrust). I told my first officer (first officer) to ask ATC for a lower altitude. ATC said it would be 3 minutes before they could grant a descent clearance. The airspeed continued to decrease; even though we were still set at apr thrust. Once the speed decreased to approximately M.705 and showed a negative trend vector; I started approximately 1;000FPM descent and instructed my first officer to inform [center] that we were in a descent. Within about 600 feet descent; we were able to regain our normal airspeed and returned to a normal flight profile at FL350 with an amended ATC clearance. Flying at a lower altitude than our planned cruising altitude during times of strong jetstream winds and mountain wave would give us a greater margin to recover airspeed lost due to a downdraft.
Original NASA ASRS Text
Title: CRJ-900 flight crew reported descended from assigned altitude of FL370 when they were unable to maintain speed because of downdrafts.
Narrative: During cruise flight at our planned cruising altitude of FL370; we encountered mountain wave and up/downdrafts. During the hour or so in cruise at FL370 leading up to the event; we were constantly changing the power; attempting to maintain our filed cruise speed of M.77. At one point; the airspeed started to drop towards M.74. I selected the climb detent. Instead of increasing; the airspeed started decreasing. At about M.72 I selected MAX POWER (APR thrust). I told my First Officer (FO) to ask ATC for a lower altitude. ATC said it would be 3 minutes before they could grant a descent clearance. The airspeed continued to decrease; even though we were still set at APR thrust. Once the speed decreased to approximately M.705 and showed a negative trend vector; I started approximately 1;000FPM descent and instructed my FO to inform [Center] that we were in a descent. Within about 600 feet descent; we were able to regain our normal airspeed and returned to a normal flight profile at FL350 with an amended ATC clearance. Flying at a lower altitude than our planned cruising altitude during times of strong jetstream winds and mountain wave would give us a greater margin to recover airspeed lost due to a downdraft.
Data retrieved from NASA's ASRS site 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.