Aeroplane Equipment and Instruments — Page 78, Lesson 121

I want to walk you through the aeroplane equipment and instruments requirements that apply to first aid oxygen and emergency break-in markings. Let's start with the oxygen rules for pressurized aeroplanes. An operator cannot operate a pressurized aeroplane above 25 000 ft when a cabin crew member is required to be carried, unless the aeroplane is equipped with a supply of undiluted oxygen for passengers who, for physiological reasons, might need oxygen after a cabin depressurization. "Undiluted" means pure oxygen — not mixed with cabin air. The amount of oxygen must be calculated using an average flow rate of at least three litres per minute per person, measured at STPD — that stands for Standard Temperature Pressure Dry. STPD is a reference condition that removes the effects of temperature, pressure, and water vapour so the volume measurement is consistent. The oxygen supply must be sufficient for the remainder of the flight after the cabin depressurization, but only for the portion where the cabin altitude exceeds 8 000 ft and does not exceed 15 000 ft. And it must cover at least 2% of the passengers carried, but in no case less than one person. So if you have 100 passengers, you need oxygen for at least two people; if you have 30 passengers, 2% is 0.6, so you round up to one person minimum. There must also be a sufficient number of dispensing units — the masks or cannulas that deliver the oxygen — but in no case less than two. And there must be a means for cabin crew to use the supply. The dispensing units may be of a portable type, meaning they don't have to be fixed to the seat structure. Now, paragraph (b) says the amount of first aid oxygen required for a particular operation must be determined on the basis of cabin pressure altitudes and flight duration, consistent with the operating procedures established for each operation and route. So it's not a one-size-fits-all number — it depends on the specific flight profile. Paragraph (c) specifies the performance of the oxygen equipment itself. The equipment provided must be capable of generating a mass flow to each user of at least four litres per minute, STPD. But means may be provided to decrease that flow to not less than two litres per minute, STPD, at any altitude. So the minimum design capability is 4 L/min, but you can have a regulator that turns it down to 2 L/min if needed. Let's move to break-in markings. Areas of the fuselage suitable for break-in by rescue crews in an emergency must be marked by red or yellow lines. If necessary, those lines are outlined in white to contrast with the background. The idea is that rescue crews can quickly identify where to cut into the fuselage to reach passengers. If the corner markings are more than 2 m apart, intermediate lines measuring 9 cm by 3 cm are inserted so that there is no more than 2 m between adjacent markings. So the pattern ensures that no gap between markings exceeds 2 m. The intermediate lines are small rectangles — 9 cm long and 3 cm wide. Now, means of emergency evacuation. Where the sill height of an emergency exit is more than 1.83 m — that's 6 ft — above the ground with the landing gear extended, or 1.83 m above the ground after an undercarriage collapse, the exit must be fitted with a means to enable passengers and crew to reach the ground safely. So if the exit is too high to jump safely, you need something like an evacuation slide or a rope to get people down. The excerpt cuts off there, but that's the core requirement.