"Investigators Find Crew's Halon Extinguisher Use Ineffective on Overheating Oven"

Investigators discovered that the crew's attempt to control an overheating oven using halon extinguishers was ineffective. This revelation sheds light on potential safety lapses aboard the vessel and underscores the importance of proper fire management protocols. The findings highlight a critical oversight in emergency response procedures and prompt a reevaluation of firefighting strategies to ensure crew and passenger safety in similar scenarios.

Boston Brand Media brings you the latest news - Investigators from the Dutch Safety Board discovered that the oven had been loaded with a meal-tray carrier that had a perforated but mostly closed rear face, significantly prolonging the oven's heating time and disrupting its airflow. This led to a higher temperature behind the oven, affecting its control circuits. Consequently, the heating elements remained on, causing the temperature to escalate until smoke emerged from the oven. 

Prior to the incident, a safety device had been damaged but not replaced, rendering it unable to disconnect power to the oven. Although no flames were observed, the cabin crew interpreted the significant amount of smoke as indicative of a fire, prompting them to discharge six halon extinguishers into the oven, with a seventh prepared for use. The aircraft, which had 13 halon extinguishers onboard, lacked a cooling effect from halon, exposing the gas to oven temperatures surpassing its decomposition threshold of 482°C. Consequently, the halon decomposed into toxic by-products including hydrogen bromide, hydrogen chloride, hydrogen fluoride, free halogens, and small quantities of carbonyl halides. Moreover, halon discharge can deplete oxygen levels. As a result, twelve passengers and three cabin crew members experienced breathing difficulties or dizziness.

Boston Brand Media also found that the prolonged overheating of the oven eventually caused the heating elements to malfunction, resulting in a significant drop in temperature. This enabled the control circuits to resume proper functioning, instructing the heating elements to turn off and halting the overheating incident.

According to the inquiry, all heat damage was confined to the interior of the oven and did not extend to its surroundings, although some components, such as the aluminium fan, melted.

However, the safety board highlights that electrical power to the malfunctioning oven remained connected throughout the incident and the remainder of the flight. There was no verification of the correct position of the galley area main power button by checking other galley electrical equipment.

The inquiry further notes that the cabin crew did not pull the circuit breaker of the oven nor were they instructed to do so as per the oven smoke or fire procedure.

Investigators discovered that the cabin crew's training emphasized the importance of not manipulating circuit breakers, leading to a general understanding that pulling a circuit breaker was prohibited, even in the presence of fire or smoke from electrical equipment.

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Source: flightglobal‍