Nov 13, 2020

Cabine temp hot NNC - why 290 kts at level off?

Hi folks,

For Cabin temp hot NNC at step 24 there is written: “Maintain 290 knots minimum. Flight deck and passenger cabin temperature can increase rapidly at speeds below 290 knots.”

Any idea why? Previous steps were to switch PACK OFF (L or R depending where is hot), Trim Air off... Ram Air door closes with Pack OFF so in what way 290 kts helps keep temperature lower?


1 answer1 reply

Hi Jakub,

The step 24 "Maintain 290 knots" is tied with the following QRH steps to ensure increased cooling.

At steps 26-28 you depressurise the aircraft (both PACKs OFF). As the airplane cabin is not air-tight (leaks around doors and opened outflow valve) you can to some extent ventilate the cabin. The faster you fly the more ventilation you will get (Venturi Effect).

I hope this helps:)

- Petr

Nov 25, 2020

Now I see! Great thanks Petr :)