What effect does turning off AC packs have on takeoff weight?

What effect does turning off AC packs have on takeoff weight?

• A. It can allow a higher maximum allowable takeoff weight.
• B. It decreases takeoff weight
• C. It has no effect on takeoff weight
• D. It makes takeoff unsafe

Answer: (A)

Turning off AC packs reduces the bleed-air load on the engines. With packs on, some engine power is diverted to supply conditioned air for the cabin, which slightly limits the thrust available for takeoff. When the packs are off, that bleed-air demand drops, freeing more engine thrust for the takeoff and improving performance margins. As a result, you can meet takeoff performance requirements at a higher takeoff weight, so the maximum allowable takeoff weight can be increased. This option doesn’t imply an unsafe condition by itself when used within approved procedures, and it does change performance versus leaving the packs on.

Turning off AC packs reduces the bleed-air load on the engines. With packs on, some engine power is diverted to supply conditioned air for the cabin, which slightly limits the thrust available for takeoff. When the packs are off, that bleed-air demand drops, freeing more engine thrust for the takeoff and improving performance margins. As a result, you can meet takeoff performance requirements at a higher takeoff weight, so the maximum allowable takeoff weight can be increased. This option doesn’t imply an unsafe condition by itself when used within approved procedures, and it does change performance versus leaving the packs on.