gasper and humidifier

[Guest alexhn]

just a quick question: the gasper and humidifier - options on the 744 - and i noticed that pmdg have modelled them. What is their purpose? what do they do? etc. Can anyone explain this, or even provide a link to a page of 744 systems info? (and i have already checked the 744 manual which someone posted a while ago - there is nothing on either!)

[744pilot 0]

Hello,The Humidifier is like the name says, it puts humi. in the air.The Gasperfan is there to allow the air to go into the cabin.

[Guest alexhn]

but...1. why would you want to put humidity into the cabin air2. the gasperfan, by putting air into the cabin, wouldn't that accomplish the same thing as the packs or the recirc fans?3. why are these only options, not mandatory?

[Guest alexhn]

also, WHERE DOES TRIM AIR COME FROM? and why is it called trim air!? thanks!

[Guest Babubhai]

1. Air can get very dry in the cabin, humidity levels can drop lower than 5%. And a comfortable ammount of humidity is around 40-50%. Flying long haul flights with virtually no humidity can also result in dehydration and can be uncofortamble.2. A gasper fan can be effective like when the packs are off as cabin air is drawn through the distribution ducts down the risers and into the main mixing chamber where it is blown into the cold air risers and out of the fans. Its an electrical fan to increase presure in the gasper system, which are outlets located above the passenger's seats during circumstances of low supply pressure or on a high cold air demand normally usually during on hot days.3. Because they are not required...

[Guest Babubhai]

Ok basically trim air is used with the packs to control the tempretaure of the different zones in the aircraft cabin .

[Guest Erups]

All the air used in airplanes air conditioning comes from the 8th (if i am not mistaken) stage of the turbine compressor.It is then variously treated to purify it (from kerosene fumes) and cool it (by mixing with external air).Then it is fed to the cabin.The devices accomplishing mixing are the packs (if i am not mistaken).Packs are only few per airplane (two or three, dunno if the 747 has four?) and to differently climatize different zones the trim air is used.

[Guest Babubhai]

The 747 has three packs...

[Chaos81 110]

>>3. why are these only options, not mandatory?Pretty much everything is an option. ;)

[Guest alexhn]

does anyone know a webpage or anything which details 744 systems, or even better, a kind person who is knowledgable in this area and is able to answer my many, many questions? :D

[Guest Babubhai]

Yes me.....feel free to PM me, or ask questions here...

[ChuckB 0]

There is no set stage that bleed air comes from, it is all dependent on the engine manufacturer and model design.ChuckC-130H Flight EngineerDyess AFB, TXAthlon XP 2800+ | ASUS A7N8X-E Deluxe | Antec TruePower 480 PS | 1.0 gig DDR PC2700 | WD 120 gig HD | WD 80 gig HD | Twin WD 160 gig SATA HDDs | SB Audigy 2 | ATI Radeon 9800Pro 128 | CH Products USB Yoke | CH Products USB Pedals | Nostromo n52 | Windows XP Pro SP2http://www.precisionmanuals.com/images/forum/ng_driver.jpg

[CF104 0]

>does anyone know a webpage or anything which details 744>systems, or even better, a kind person who is knowledgable in>this area and is able to answer my many, many questions? :D Hi Alex,Feel free to direct any 747 questions my way as well and I'll try to help.Here is some extra info regarding your first questions from the Boeing 744 AOM.-Gasper SystemThe gasper system supplies recirculated air drawn from the upper passenger cabin area. Gasper air is distributed to the passenger service unit air gasper outlets above each passenger seat.-Temperature Control, Passenger and CombiZone temperatures are controlled by the zone temperature controller (ZTC). Hot trim air from the bleed air system is added through trim air valves in the zone conditioned air supply ducts. The ZTC modulates the zone trim air valves to regulate the temperature of the conditioned air in each zone.The temperature zone requiring the coolest temperature controls pack outlet temperature.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

[Guest alexhn]

thanks john! well, i do have a question :( What is the 4th hydraulic system aux pump used for, and why/when would you use it?

[Guest Babubhai]

It will be used on the ground during engine start, it's an electronic driven pump, to provide pressure for the parking brakes so they can be used.Once the engine driven pump for system 4 has been started, the selector can be moved back to the auto position.