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B737-700 flight crew experiences fluctuating N1 on the left engine climbing through 11;000 feet. Auto thrust is turned off with no change then the thrust is reduced until stability returns at about 70 percent N1. The right engine also experienced brief N1 fluctuations and the crew returns uneventfully to the departure airport.
| Attributes | |
| ACN | 1084017 |
| Time | |
| Date | 201304 |
| Place | |
| Locale Reference | ZZZ.TRACON |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb |
| Component | |
| Aircraft Component | Turbine Engine |
| Person 1 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 215 |
| Person 2 | |
| Function | Pilot Flying First Officer |
| Experience | Flight Crew Last 90 Days 220 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe |
Narrative:
Our flight departed and was climbing through 11;000 feet when the Number1 engine began to surge. N1 was fluctuating between 100-70 percent. As you would expect; this caused substantial aircraft yaw. The first officer (pilot flying) immediately recognized the condition and executed the QRH memory items for engine surge by disconnecting the autothrottles and pulling back the thrust levers to about mid range. Simultaneously the number 2 engine began to fluctuate but to a lesser degree of approximately 95-80 percent. After about 15-30 seconds with the thrust levers in the reduced position; both engines stabilized at approximately 70% N1. Our flight was approximately 20 miles northeast of the departure airport when this event started and the weather was clear with unlimited visibility. We quickly determined that returning would be our safest course of action. ATC gave us vectors back to the field and we landed without further incident. On landing roll; both number 1 and number 2 engine control lights illuminated. Upon arrival at the gate; maintenance was notified and the aircraft was subsequently taken out of service.
Original NASA ASRS Text
Title: B737-700 flight crew experiences fluctuating N1 on the left engine climbing through 11;000 feet. Auto thrust is turned off with no change then the thrust is reduced until stability returns at about 70 percent N1. The right engine also experienced brief N1 fluctuations and the crew returns uneventfully to the departure airport.
Narrative: Our flight departed and was climbing through 11;000 feet when the Number1 engine began to surge. N1 was fluctuating between 100-70 percent. As you would expect; this caused substantial aircraft yaw. The F/O (Pilot Flying) immediately recognized the condition and executed the QRH memory items for engine surge by disconnecting the autothrottles and pulling back the thrust levers to about mid range. Simultaneously the Number 2 engine began to fluctuate but to a lesser degree of approximately 95-80 percent. After about 15-30 seconds with the thrust levers in the reduced position; both engines stabilized at approximately 70% N1. Our flight was approximately 20 miles northeast of the departure airport when this event started and the weather was clear with unlimited visibility. We quickly determined that returning would be our safest course of action. ATC gave us vectors back to the field and we landed without further incident. On landing roll; both Number 1 and Number 2 ENG CONTROL lights illuminated. Upon arrival at the gate; Maintenance was notified and the aircraft was subsequently taken out of service.
Data retrieved from NASA's ASRS site as of July 2013 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.