Saab-Scania Ab (Saab) 340B N344SB

Summary

On 17 November 1995 at about 14:45 local time, a Saab-Scania Ab (Saab) 340B registered N344SB, operated by Simmons Airlines, was involved in an incident near Corsicana, Texas, United States. 33 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

17 November 1995 at 14:45

Classification

Incident

Location

Corsicana, Texas, United States

Coordinates

Not recorded

Aircraft

Saab-Scania Ab (Saab) 340B

Registration

N344SB

Category

Airplane

Engines

2

Operator

Simmons Airlines

Operating rule

Part 121: Air Carrier

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Corpus Christi → Dallas/Ft Worth

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

FTW96IA045

Nobody was injured.

Total loss of power in the left engine from ice ingestion; and failure of the left-engine auto-relight system caused by an open fuse in the Digital Electronic Control Unit (DECU), which prevented an automatic relight of the left engine. Factors relating to the incident were: inadequate design of the engine air inlet anti-ice system, which allowed ice/slush accumulation; inadequate action by the FAA to ensure compliance with certification requirements regarding inlet ice accumulation; and an inadequate procedure in the flight manual concerning use of the engine synchrophaser during single-engine operation.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

During descent, after exiting light icing conditions, the left engine lost power, & power fluctuations of the right engine were noted. The flightcrew declared an emergency, diverted to the nearest airport, & made an uneventful landing. There were indications of engine ice ingestion, but no engine damage. During ground runups, the right engine performed normally. The left engine ran normally, except its auto-ignition & overspeed protection were inoperative due to an open fuse in the Digital Electronic Control Unit (DECU). The open fuse would have prevented an automatic relight after a flameout. The Saab 340 fleet has a history of power losses associated with in-flight icing, dating back to 1985. The manufacturer (Saab) had determined that ice/slush could accumulate on the rear wall of the inlet protective device (bird catcher) & shed from the 'splitter lip' into the engine airflow path. As a preventive measure, Saab had developed an auto-ignition system to provide automatic relighting of the engine. Also, Saab was testing an improved heating system to prevent ice/slush from accumulating on the splitter lip. Title 14 CFR Part 25 requires that airplanes be designed so that engine inlet ice that would adversely affect engine operation cannot accumulate. During flight tests with the left engine inoperative & the propeller synchrophaser engaged, multiple power fluctuations of the right engine occurred. Instructions to turn the synchrophaser 'off' were not included in the engine failure checklist.

Quoted verbatim from the NTSB record.