6 26 fcom sa227 fire protection

AIRCRAFT SYSTEMS FIRE PROTECTION

SA227‐ SERIES/FCOM/VTM

6.26.1

FIRE DETECTION AND PROTECTION SYSTEMS

Fire protection systems installed on SA227 aircraft consist of engine and wing overheat detection and engine fire extinguishing. Wing overheat detection incorporates heat sensors located in critical areas of the wings and engines. The heat sensors react to higher than rated temperatures and complete an electric circuit that illuminates cockpit warning lights on the annunciator panel and fire extinguisher control assembly. An annunciator Press to Test switch confirms continuity of the engine fire/wing overheat detectors and illuminates the lights on the annunciator panel and the fire lights on the Fire Extinguisher Control Panel.

FIRE PROTECTION CONTROLS AND INDICATORS

Figure 6.26‐1

Revision: Original Aug 1,2013

GO/FCOM/SA227‐SERIES/VTM

AIRCRAFT SYSTEMS

FIRE PROTECTION SA227‐ SERIES/FCOM/VTM 6.26.2 ENGINE FIRE DETECTION

Four heat sensors located in each engine compartment provide overheat information to the cockpit annunciator panel. Three of the sensors are rated at 450°F and one at 600°F. If any of the sensors detect a temperature equal to their rated value, a signal will be transmitted to the fire extinguisher control panel. The red FIRE light will illuminate when an overheat situation is detected.

Figure 6.26‐2 Engine fire Warning Sensor Location

ENGINE FIRE EXTINGUISHER CONTROL

The control assembly contains a logic control module, two control indicators, and a test switch. The two control indicators (one for each bottle) contain three indicator lights, and a firing switch.

Pushing the lens of the indicator lights activates the fire switch. Since the system is powered from both essential buses through isolation diodes, pushing the switch will fire the bottle if power is on the buses.

The lens is covered by a clear plastic spring‐loaded guard to avoid accidental firing.

A red FIRE light, an amber E (empty) light, and a green OK light comprise the three indicator lights. The lights are operated by the logic module. The fire extinguisher test switch is located between the two control indicators on the instrument panel.

Pressing the annunciator panel test switch will test the engine fire warning system for continuity as well as illuminate the red FIRE light on the control indicator. On SA227 aircraft prior to AC 535 and AT 538 the annunciator fire warning lights are disconnected when this system is installed. Should the fire detectors on the engine sense an overheat condition, the FIRE light will illuminate.

Normally, no lights on the control indicator are illuminated. When the bottle is thermally discharged, the amber E light will illuminate. If the bottle is fired from the cockpit, the E light will illuminate and the FIRE light will remain illuminated until the fire is extinguished. When the fire extinguisher test switch is pressed, all three lights on both control indicators will illuminate unless the bottle has been discharged.

The green OK light will not illuminate when the test switch is pressed if one of the bottles is discharged.

Revision: Original Aug 1,2013

GO/FCOM/SA227‐SERIES/VTM

AIRCRAFT SYSTEMS

FIRE PROTECTION SA227‐ SERIES/FCOM/VTM 6.26.3 ENGINE FIRE EXTINGUISHING

Engine fire extinguishing consists of one 86 cubic inch bottle containing freon (Bromotrifluromethane) CBrF3 located on the right side of each engine nacelle aft of the firewall. Each bottle has a single outlet which feeds three spray nozzles. The nozzles are located in the engine compartment. Each bottle is activated by 28.5 VDC through a switch located on the Fire Extinguisher Control panel. A pressure gauge on each bottle indicates internal pressure. Each bottle is also equipped with a red thermal relief indicator that will blow out if internal bottle temperature exceeds a preset limit.

Figure 6.26‐3 Fire Extinguisher Bottle

Revision: Original Aug 1,2013

GO/FCOM/SA227‐SERIES/VTM

AIRCRAFT SYSTEMS

FIRE PROTECTION SA227‐ SERIES/FCOM/VTM 6.26.4 WHEELWELL AND WING OVERHEAT WARNING SYSTEM

A wheelwell and wing overheat warning system is provided. Red L WING OVHT and R WING OVHT warning lights are located on the annunciator panel. Two warning modes are incorporated, STEADY and FLASHING.

 A steady warning takes precedence over a flashing warning. It is the more critical of the two warnings. A steady illumination indicates an overheat condition in the wheelwell and/or the conditioned air duct. A wheelwell overheat can be caused by a bleed air leak, overheated brakes or a brake/tire fire.

 A flashing illumination indicates an overheated condition in the leading edge cavity caused by a bleed air leak or an electrical problem. Refer to EMERGENCY PROCEDURES section for procedures to be followed in the event the lights illuminate. The steady illumination Emergency Procedure addresses both modes.

TEST SWITCH

The test switch for the wheelwell and wing overheat warning system is the same test switch used to test all annunciator panel lights.

Revision: Original Aug 1,2013

GO/FCOM/SA227‐SERIES/VTM

AIRCRAFT SYSTEMS

FIRE PROTECTION SA227‐ SERIES/FCOM/VTM 6.26.5 WHEELWELL AND WING OVERHEAT DETECTION

A 250°F thermal switch is located within each wing leading edge cavity inboard of the engine. The thermal switch is in contact with the generator wires, and secured in place by a clamp. If the temperature in this area exceeds 250°F the switch will close and energize a flasher unit, causing the red WING OVHT light in the annunciator panel to flash.

A 350°F thermal switch is located in each wheel well just below and forward of the bleed air flow control valve. If the temperature in this area exceeds 350°F, the switch will close, causing the red WING OVHT light in the annunciator panel to illuminate steadily.

A 450°F thermal switch is located in the air duct where the duct enters the cabin. It will detect a failure of an air conditioning turbine. If the turbine should fail, the temperature in this duct will rise above 450°F and actuate the switch, causing the red WING OVHT light in the annunciator panel to illuminate steadily.

Figure 6.26‐4 Wing Overheat Sensor Location

Revision: Original Aug 1,2013

GO/FCOM/SA227‐SERIES/VTM

AIRCRAFT SYSTEMS

FIRE PROTECTION SA227‐ SERIES/FCOM/VTM 6.26.6 HAND HELD FIRE EXTINGUISHER

Two hand held fire extinguishers are provided in each aircraft. One is located directly behind the copilot’s seat and the other is located on the side wall, immediately aft of the passenger entrance door.

The extinguishers are usable at temperatures of –40°F through +120°F for use on liquid, grease, and electrical fires. Both units are Halon 1211 (Bromochlorodifluoromethane) liquid chemical, nitrogen filled.

When actuated, the vapor pressure causes the agent to expand so that the discharge stream is a mixture of liquid droplets and vapor. The extinguishers have a horizontal stream range of 9 to 15 feet.

Deep seated Class A fires may need to be broken apart to be completely extinguished. On Class B fires, the discharge is applied in a side‐to‐side motion gradually progressing toward the back of the fire. The extinguisher should be initially discharged from not closer than 8 feet to prevent splashing.

Figure 6.26‐5 Portable Fire Extinguisher

Revision: Original Aug 1,2013

GO/FCOM/SA227‐SERIES/VTM