​​On February 1, 1994, at 2140 central standard time, Simmons Airlines/Arnerican Eagle flight 3641, a Saab 340B, registration N349SB, operating under Title 14 Code of Federal Regulations, Part 121, sustained substantial damage during a forced landing at False River Air Park, New Roads, Louisiana. Of the 23 passengers, 2 flightcrew, and I flight attendant aboard the airplane, there was one minor injury to the flight attendant during evacuation. There was no postcrash fire. ​

​We detem1ined that the probable causes of this accident were the captain's movement of the power levers below flight idle in flight, the inadequate certification requirerments and consequent design of the airplane's power levers that permitted them to be moved below the flight idle position into the beta range, either intentionally or inadvertently, while in flight, and the inadequate action taken to require a positive rneans to prevent beta operation on airplanes for which such operation is prohibited. 

​As a result of this investigation, we reiterated a safety recommendatoin and urges early rulemaking action:

To the Federal Aviation Administration:

• ​Issue an airworthiness directive applicable to Ssaab 340 airplanes that would require installation of a system that prevents the power levers from moving aft of the flight idle stops into the beta range in flight regardless of pilot action. Until the system is installed, cockpit placards should be installed in Saab 340 airplanes to warn pilots not to move the power levers into the beta range while in flight.(A-94-061) (supersedes safety recommendations a-88-105 and a-90-182)
  
• Revise Title 14 Code of Federal Regulations Parts 25.1155 and 23.1155 to require a positive means to prevent operation of the propeller in the beta mode while in flight, unless the airplane is certified for such use. (A-94-062)
  
• ​Review all other turbopropeller airplane designs to determine whether in-flight engine operation in the beta range should be prohibited. issue appropriate airworthiness directives applicable to those airplanes to install a system to prevent movement of power levers into the beta range, and require appropriate warnings in airplane operating manuals and on cockpit placards to warn pilots not to move power levers into the beta range in flight, unless the airplane is certificated for such use. (A-94-063) (supersedes safety recommendations a-88-105 and a-90-182)