Document
OAS-43A (12/12)
Interagency Aviation
Accident Prevention Bulletin
No. IAAPB 23-06 September 25, 2023 Page 1 of 1 Subject: Bell Medium Helicopter operations with Simplex Model 304 Fire Attack System Area of Concern: Emergency Jettison of water load Distribution: Exclusive Use and Call When Needed Bell Medium contracts with Simplex Model 304 Fire Attack System Discussion: A recent event uncovered a potential hazard when attempting to perform emergency jettison procedures in helicopters configured with the Simplex Model 304 Fire Attack System.
In the event of an emergency, the Simplex system provides two options for jettisoning the liquid load.
The first method requires the Master ON/OFF switch located on the Cockpit Display Box (CBD), to be placed in the “OFF” position. This procedure will remove power to the door actuators allowing the drop doors to open so that all liquid can exit the tank. The second method is to place the DOORS OPEN switch located on the Cyclic Control Box to the DOORS OPEN position and hold for 3-5 seconds. Power to the door actuators will be removed allowing the drop doors to open, enabling all liquid to exit the tank.
In the event of a CCB (Cyclic Control Box) malfunction when flying from the left seat or when 3-5 seconds to jettison is inadequate time to respond to the specific flight circumstances or emergency, the pilot may have difficulty maintaining controlled flight while moving their right hand from the CYCLIC to turn the MASTER switch off, due to the CDB’s location in the center pedestal.
As with other Emergency Procedures, it is imperative that pilots commit to memory the emergency jettison procedures for the aircraft and equiptment configuration they are flying. Rehearse procedures in those configurations in a safe environment, especially if it requires removing the right hand from the cyclic to complete the emergency jettison.
/s/ /Keith Raley /s/ Lori Clark Keith Raley Lori Clark Chief, Aviation Safety, Program Evaluation, Branch Chief - Aviation Safety and Quality Management Management Systems DOI, Office of Aviation Services USDA, Forest Service