# NTSB LAX97IA180: Saab-Scania 340B, N313AE, San Luis Obispo, CA, May 13, 1997 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: May 13, 1997, 06:05 local (13:05 UTC) - Place: San Luis Obispo, CA - Coordinates: 35.249809, -120.620056 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.2498&lon=-120.6201&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 21 uninjured - Status: Completed, report January 28, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 29646 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX97IA180 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29646/pdf - Page: https://openairdocs.org/ntsb/LAX97IA180 ## Probable cause Compressor stalls of both engines due to in-service compressor contamination. Factors in the compressor stall of the right engine were an atmospheric temperature inversion and a transient fuel flow condition produced when the constant thrust on takeoff (CTOT) system was disabled by the pilot's inadvertent movement of the right engine power lever during execution of the emergency procedure. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(partial) - nonmechanical, takeoff - initial climb - 2 engines - misc,engine compressor stall/surge - compressor assembly - contamination (cause) - powerplant controls - inadvertent use, pilot in command - other system - disengaged (contributing factor) - weather condition - temperature inversion (contributing factor) - Forced landing, descent - emergency - Miscellaneous/other, emergency landing ## Analysis The flight crew reported that all pretakeoff checks were normal and that prior to setting takeoff power the Constant Thrust on Takeoff (CTOT) computer was set to 100-percent engine torque for takeoff. The ensuing takeoff was normal through liftoff and gear retraction; however, during initial climb the left engine experienced compressor stalling and lost power. As the crewmembers were executing the engine failure checklist, the right engine first increased power in Automatic Power Reserve (APR) and then began to similarly stall and lose power. After about 20 seconds the engines recovered sufficient power to enable the flight crew to remain airborne and return for landing on the departure runway. Review of the digital flight data recorder (DFDR) output and internal examination of each engine revealed that the engines had compressor stalled due to accumulated dirt and contaminants on the compressors. A review of the right engine DFDR data revealed that, while the left engine was stalling, the flight crew had retarded the right engine power lever past the 64-degree power lever angle position which tripped off the CTOT system. The resulting transient in fuel flow, in company with an atmospheric temperature inversion, reduced the stall margin of the right engine. ## Factual narrative HISTORY OF FLIGHT On May 13, 1997, at 0605 hours Pacific daylight time, Wings West Airlines, Inc. Flight 3319, a Saab 340B, N313AE, experienced a temporary loss of power on both engines while at 200 feet agl on departure climbout from McChesney Field, San Luis Obisbo, California. The aircraft was not damaged and the 2 cockpit crew, the 1 cabin crewmember, and 18 passengers were not injured. The scheduled, domestic passenger flight was operated under 14 CFR Part 121 by Wings West Airlines, Inc., and was departing San Luis Obispo destined for Los Angeles, California. The flight was operating on an instrument flight rules flight plan and visual meteorological conditions prevailed. The flight crew reported the incident as compressor stalls in both engines. The flight crew stated that the flight was routine through takeoff and initial climb. The takeoff was made at 100 percent torque with Constant Torque on Takeoff (CTOT) on and Automatic Power Reserve (APR) armed. During the initial climb, approximately 200 feet agl, there was a "loud hammering noise," accompanied by loss of torque on the left engine. The first officer (the pilot flying) initiated the engine failure memory items and by the time the crew had identified the left engine, the right engine began to similarly lose power. At this point the rate of climb was zero, both engines were "erratic," and the left and right over temperature lights were flashing. The crew was preparing for an off-airport landing when the right engine resumed producing (more) power. The flight crew left the power levers in a reduced power position and was able to return for landing on the departure runway. A passenger reported to the flight attendant that flames were seen coming from the exhaust of both engines and this information was passed on to the cockpit crew. Postflight reduction of stored engine computer data confirmed that the left engine had a power loss and exceeded ITT temperature limits for 7 seconds. The right engine went into APR mode at 104.4 percent torque, and then it had a power loss and exceeded ITT temperature limits for 17 seconds. A Powerplants Group was formed to examine powerplant issues related to the incident. Their report is attached. PERSONNEL INFORMATION The captain and first officer were on the third day of a 3-day schedule flying together. They had remained overnight in San Luis Obispo and this was the first flight of the day for them. The first officer was the flying pilot. The captain upgraded to the Saab 340 in January, 1997, and had accumulated 170 hours in the type aircraft. He had 7,500 hours total time and for the previous 5 years was a BAE Jetstream captain for Wings West. The first officer was hired by Wings West in January, 1995, and had been a Saab 340 first officer the entire time. He had 3,300 hours total time and 1,100 hours in the Saab 340. He is not type rated in the Saab. Flight Crew Interviews The flight crew was interviewed separately at the Safety Board's regional office in Gardena, California, on June 19, 1997. Notes from the interview are attached to the Powerplants Group report. According to the captain, the crew went to the aircraft at 0530. The first officer did the external inspection and the captain did the cockpit checks. The dispatch release was reviewed and the maintenance log checked where they found that the left engine was on derivative power. The passengers boarded at 0545, the crew received their ATC clearance and, winds being calm, taxied to runway 29 for departure. The tower was still closed. They ran the first flight of the day checklists and everything checked normal. Visual meteorological conditions prevailed but there was low fog west and northwest of the airport and low fog at the departure end of the runway. The crew completed the checklist and the first officer determined that a 100 percent torque takeoff was required. On the runway the captain advanced the power levers to 80-85 percent, actually 82 percent, and called "set power." The CTOT was set to "APR" by the first officer and power came up to 100 percent. There was nothing unusual. At 80 knots the first officer took the flight controls and everything was routine through V1 (takeoff decision speed) and Vr (takeoff rotation speed). The first officer called "positive rate, gear up" and the captain retracted the landing gear. Seconds later they heard banging and felt shaking on the left side of the aircraft that felt and sounded like "a washing machine out of balance." The captain said that he had never experienced anything like this before. They didn't know what was wrong but saw the torque on the left engine drop to 20-40 percent. The first officer called "confirm left engine failed and positive autocoursen" which the captain confirmed. The first officer started the engine fail checklist memory items. The captain identified the left power lever and the first officer confirmed the captain's selection. The captain pulled the left power lever to flight idle and identified the left condition lever in preparation for feather of the propeller. As he was pointing to the left condition lever, the right engine started the same banging and shaking. Both sides were the same and both torque gauges fell to 20-40 percent. The captain told the first officer to fly the aircraft. They were over the fog bank now and the first officer identified a clear spot straight ahead in anticipation of an off-airport landing. According to the captain, he didn't know what was happening and so he moved the right and left power levers 2-3 inches with no effect. The over temperature lights were flashing. The captain turned the CTOT off for 1 or 2 seconds, which had no effect so he turned it back on again. Eventually the power came back on one engine and the first officer called "straight ahead or turn." The captain said turn. More power came back in the turn and both engines were delivering partial power on downwind leg. The crew ran the checklists and made a normal landing. In response to a question about which crewmember operated which controls during the flight, the captain said that at the start of the takeoff roll his left hand was on the tiller and his right hand was on the power levers. The first officer, the pilot flying, usually would have had his right hand on the yoke and his left hand near the CTOT switch. The captain brought the power up to 80-plus (80/81) percent power and called "set power." The first officer, with his left hand, moved the CTOT to "APR" position with his right hand on the yoke. At 80 knots the captain called "your aircraft." At this point the captain's left hand was idle and his right hand was on the power levers. The captain said that he did not rest his hand heavily on the levers but rather applied a light pressure. The first officer's right hand was on the yoke and the left may have been backing up the power levers. The captain next called V1 and removed his right hand from the power levers leaving both hands idle. The first officer had both hands on the yoke. The captain called Vr and the first officer then called "positive rate, gear up." The captain raised the gear using his right hand. When the banging started the first officer had both hands on the yoke and the captain had both hands in his lap. The first officer called "confirm left engine fail and positive autocoursen." The captain's hands were in his lap. The first officer called "identify left power lever." The captain placed the index finger of his right hand on the left power lever, and, after confirmation by the first officer, the first officer called "flight idle" and the captain, using his index finger only, pulled the left power lever to flight idle. The first officer called "identify left condition lever" and the captain placed his right hand index finger on the left condition lever. The captain never moved the conditi ## Aircraft - Registration: [N313AE](https://openairdocs.org/aircraft/N313AE), registered now, S/N 340B-313 (OpenAirDocs) - Reported make and model: Saab-Scania AB (Saab) 340B - Registry model: [Saab-Scania SAAB 340B](https://openairdocs.org/model/saab-scania-saab-340b) (registry code 7860101) (OpenAirDocs) - Registry engine: [GE CT7-SER series](https://openairdocs.org/engine/ge-ct7-ser-series) (registry code 30031, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 340B-313 - Airframe hours: 9594 - Engines: GE CT7-9B 1750 horsepower turbo prop - Damage: No damage - Flight: Part 121 - Operator: Wings West Airlines, Inc, doing business as American Eagle - Registered owner: Flagship Airlines, Inc. - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, March 25, 1997, 308 hours before - Departed: SBP - Destination: LAX, LOS ANGELES, CA - Flight plan: IFR - Airport: SBP, San Luis Obispo County, runway 29, 4,799 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 42; airline transport, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 7,600 total, 120 in this make and model, 6,500 as pilot in command, 120 in the last 90 days, 60 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 15 statute miles - Lowest ceiling: none - Temperature: 48 °F, dew point 45 °F - Altimeter: 29.00 inHg - Observed at: SBP, 1 nm away ## Other investigations on N313AE (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB FTW97IA305](https://openairdocs.org/ntsb/FTW97IA305), Aug 12, 1997: Saab-Scania 340B (N313AE), Lafayette, LA, incident, minor damage. Probable cause: The failure of the AC generator due to the failure of the anti-drive end bearing. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.