737 a/c?

[skid]

I was just wondering why is it that when you get on a SWA 737 that the Airconditioning is kicking out nice cool air at a high velocity out of the eye vents even during engine start, and when I ride any other airline it is hotter than heck in the back with no air movement at all even when the engines are not being started. I have noticed this several times on my LAS-SEA commute.

I understand the high draw on the APU for starts to explain no air then but what about the rest of the time. Has SWA put a mod to the APU bleed or packs on the 737's to counter the hot summers in the south or is it just purely a difference in airline operations for starting (aka checklists)?

 

[Hutchman]

If it is blowing hard up front and cold, it means everyone in the back is Freezing and turned off thier individual "Eyeball" vents. Low flow out of eyes up front = vents are all open in back.

 

[StopNTSing]

I was just wondering why is it that when you get on a SWA 737 that the Airconditioning is kicking out nice cool air at a high velocity out of the eye vents even during engine start, and when I ride any other airline it is hotter than heck in the back with no air movement at all even when the engines are not being started. I have noticed this several times on my LAS-SEA commute.

I understand the high draw on the APU for starts to explain no air then but what about the rest of the time. Has SWA put a mod to the APU bleed or packs on the 737's to counter the hot summers in the south or is it just purely a difference in airline operations for starting (aka checklists)?

I guess we're not running -300s on the LAS-SEA route, else you might have a different impression. The -700 air system is WAY more capable than the -300.

 

[TriStar_drvr]

I was just wondering why is it that when you get on a SWA 737 that the Airconditioning is kicking out nice cool air at a high velocity out of the eye vents even during engine start, and when I ride any other airline it is hotter than heck in the back with no air movement at all even when the engines are not being started. I have noticed this several times on my LAS-SEA commute.

I understand the high draw on the APU for starts to explain no air then but what about the rest of the time. Has SWA put a mod to the APU bleed or packs on the 737's to counter the hot summers in the south or is it just purely a difference in airline operations for starting (aka checklists)?

The high airflow out the eyeball vents during engine start is due to the gasper fan being on. SWA encourages it's use during engine start (when the packs are turned off). However, not all airlines equip their 737s with this fan, or choose not to use it.

 

[CesnaCaptn]

Another difference in the way SWA operates their airplane is that they start the right engine first. While starting the right engine you will just be getting air from the recirc fans. After the engine is started they isolate the right a/c system which cools the cabin, then start the left engine. Other 737 operators might start the left engine first and/or don't isolate the right pack system after starting the first engine.

 

[HalinTexas]

Starting the right engine first is Boeing SOP. Only ATA does the left one first. I keep my opinion as to why to myself. It's stupid.

The NG APU's are much better than the classics. They can provide air to both packs simultaneously, and sometimes better than directly engine-pack at idle power. SWA's gasper fan does help.

 

[PhatAJ2008]

Sorry for butting in, but what is a gasper fan?

 

[DiamondZ]

Starting the right engine first is Boeing SOP. Only ATA does the left one first.

Unless its changed recently, I thought CAL SOP was to start the left first.

 

[DiamondZ]

Where's the edit button...anyways, I thought the left was started first to allow loading of late bags on the right.

 

[SWA GUY]

The -700's APU is so good it'll start BOTH motors at the same time.

Er....so I hear...

 

[Lear70]

I believe AAI starts left first as well (bag loading reasoning).

Gasper fan is an ELECTRIC motor fan that draws air out of the supply duct downline of the packs to provide air circulation out of the eyeball outlets in the PSU (passenger service unit over your head) even if there is no source of air conditioning such as an APU or engine bleed providing air.

It's also in the same ducting that the external air plugs into (on most aircraft) so you get that air pumped if it's being supplied to the aircraft.

Lastly, if there's no air conditioning packs running and no external air conditioning hose hooked up, the gasper fan (if on) pulls outside air which, in the summer, brings HOTTER air into the cabin. Obviously a no-no.

 

[Mach 80]

SWA found the benefit of cooling the passengers sooner during the engine start process outweighed the very few times there were late bags. From my non-revving experience I wish some others would do the same. Sometimes the packs get turned off waayyy before engine start and nothing comes back on till after they are both started. Miserable in a full airplane in the summertime.

 

[ERfly]

Everytime I've jumpseated on CAL, I've noticed if they're going out on both engines they crank #1 first. If they're only going out on one engine, they crank #2.

 

[Phrogs4ever]

Engine start sequence at CAL is at the discretion of the Captain. This time of the year it's generally "any late bags on the way? OK, we'll be starting #2 first". Isolate #2, get the AC going, start then start #1. If taxiing on one engine, will still start #2 first, isolate, and run both packs. The APU actually pumps better air on #1 than the engine would.

 

[Alcatraz]

I understand the high draw on the APU for starts to explain no air then but what about the rest of the time. Has SWA put a mod to the APU bleed or packs on the 737's to counter the hot summers in the south or is it just purely a difference in airline operations for starting (aka checklists)?

I think it's mostly due to the recirc and gasper (the eyeball things) fans running irrespective of pack valve position.

It may be a difference in procedure, too. "Packs - OFF" is not a checklist item at SWA, it's part of the FO's flow just prior to start. And I mean just prior... I don't turn that pack(s) off until the Captain says "Turn two." At other operators I could see a Before Start Checklist being run that included shutting the packs off, only to then wait for a push call or late bags or whatever.

 

[Palomino]

some airplanes have better flow than others even though they are all the same model plane.

debris in the ductwork, holes in the ductwork, weak components, tired equipment...etc

if you think the 737 is bad...try a vintage MD80 or EMB-120. Hutchman knows what i'm talking about. i would've gladly shown up to work the Brasilia in a Borat banana hammock if the FOM allowed. sure woulda been a lot cooler!

 

[Captain X]

i would've gladly shown up to work the Brasilia in a Borat banana hammock if the FOM allowed. sure woulda been a lot cooler!

Ahh...the Brasilia Summer weight loss program! Memories!