in the 600/700 leave the one on, 800/900 left off, right on, at least that what the pilot used when i was in the cockpit, and when i asked they say that they only really need the right one, in the 800.

Ralgh can you descrive in the different stages of flight how they should be set please?

At American we turn them to auto during the first flight of the day preflight and leave them in auto until we shut down after the last flight of the day. It's not an official precedure to shut the left one off to make it quiet, It's just something we do so we can hear eachother better.

Ralgh tanks for the reply :D

Whew, this cleared up some of my doubts, too. Thanks for asking this question.So pretty much the Packs are the Air Conditioner and the Recirc. are like fans?

Whew, this cleared up some of my doubts, too. Thanks for asking this question.So pretty much the Packs are the Air Conditioner and the Recirc. are like fans?

Recirc. is short for Recirculation Fan.

Whew, this cleared up some of my doubts, too. Thanks for asking this question.

You're welcome ;)

in the 600/700 leave the one on, 800/900 left off, right on, at least that what the pilot used when i was in the cockpit, and when i asked they say that they only really need the right one, in the 800.

But the right one in the 800 is the most noisy :(!!!

They are both in the same part of the aircraft, both move air in the main distribution manifold, the only difference in position is that one is on the left, one on the right. Same noise for both fans.Maybe you find it louder because pmdg simulated increased volume if you have already turned on the first fan. If you turn on the right before the left fan, the left one will be louder.However, in the 737 the fans are not too much louder, on other aircrafts there are more noisy conditions... For example the display fan on the CRJs.

One reason to use the recirc fans it to save fuel. They recirculate the old cabin air causing less demad for new air from the packs which get their from the engines. When the packs take air from the engines they take power away from them so the engines have to work a little harder to get a given amount of thrust. I have never seen a number publshed as to how much of a fuel savings it really makes though. The 787 has no engine bleed air so it won't be a problem on that.

The electric pumps on the 787 which replace the bleed air still have to be powered by an engine driven generator. Running the pumps to provide air for the cabin will still consume extra fuel.

They are both in the same part of the aircraft, both move air in the main distribution manifold, the only difference in position is that one is on the left, one on the right. Same noise for both fans.

Maybe you find it louder because pmdg simulated increased volume if you have already turned on the first fan. If you turn on the right before the left fan, the left one will be louder.

However, in the 737 the fans are not too much louder, on other aircrafts there are more noisy conditions... For example the display fan on the CRJs.

Not for me. Just having the right one on is way louder than just having the left one on.

 

Too bad it doesn't really matter whether you turn them off or on (apart from you wanting to be as real as it gets)

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One reason to use the recirc fans it to save fuel. They recirculate the old cabin air causing less demad for new air from the packs which get their from the engines. When the packs take air from the engines they take power away from them so the engines have to work a little harder to get a given amount of thrust. I have never seen a number publshed as to how much of a fuel savings it really makes though. The 787 has no engine bleed air so it won't be a problem on that.

 

The main reason to turn the recircs off on the ground, mainly on hot days, is because the air flows down around to forward cargo compartment on its way back to the mix manifold. On a hot summer day that air is heated when it does this so if the recircs are on you are just pumping warm air back into the plane counteracting the pre conditioned air. Turning them off really does make a noticable difference in the cabin but it could just be my perception but the cockpit feels a lot hotter to me.

 

Hi to everyone,

 

As I'm an engineer on that plane I agree with you! These Recircfans take a small amount of "used" air out of tha cabin and mix it with the airflow from the packs coming. The rest is leaving through the E&E Compartment and the two Cargo's out

of the Outflowvalve. This is to reduce the amount of bleedair what we take from the engines. :Peace:

 

Greetings

Sven Wendel