Above flight level 410, which controls must be in NORM?

Above flight level 410, which controls must be in NORM?

• A. Pressurization source buttons only
• B. ECS knob only
• C. Engine bleed buttons only
• D. All three: pressurization source buttons, ECS knob, and engine bleed buttons

Answer: (D)

At very high altitude the cabin needs a reliable supply of bleed air to pressurize and condition the air, and all parts of the system must be in their normal operating mode to work together automatically. The pressurization source selector in NORMAL lets the cabin pressure controller automatically use the appropriate bleed source and regulate cabin pressure. The ECS knob in NORMAL allows the air conditioning packs to operate to condition and distribute air properly. The engine bleed switches must be ON so bleed air from the engines is available to the ECS and pressurization system when needed. If any one of these isn’t in NORMAL/ON, the system may not provide adequate bleed air or automatic regulation, risking loss of cabin pressurization or improper temperature control. Therefore, all three controls should be in their normal positions.

At very high altitude the cabin needs a reliable supply of bleed air to pressurize and condition the air, and all parts of the system must be in their normal operating mode to work together automatically. The pressurization source selector in NORMAL lets the cabin pressure controller automatically use the appropriate bleed source and regulate cabin pressure. The ECS knob in NORMAL allows the air conditioning packs to operate to condition and distribute air properly. The engine bleed switches must be ON so bleed air from the engines is available to the ECS and pressurization system when needed. If any one of these isn’t in NORMAL/ON, the system may not provide adequate bleed air or automatic regulation, risking loss of cabin pressurization or improper temperature control. Therefore, all three controls should be in their normal positions.