I have been flying the 737-900 more and more as it replaces the beloved 757's on many of my DL routes. I have NEVER see another plane type where the Cabin air is so weak. ITs bothersome, and I always find myself extremely hot and therefor less comfortable on these planes.

I'm hoping perhaps a Mechanic can help answer why this is the case on this 1 plane type

Thank you in advance.

I've noticed it as well. There's probably some money-saving explanation as to why the "cute" new gaspers have a pinhole though which to blow air, but it's awful waiting to depart DAB on a July day on a 739. Ask me how I know.

good point, those are horrible little valves to begin with, I didn't realize that the valve itself might be constricting the air (doh)

It also takes away that lovely sounds of pressurized air full blast which we hear on every other plane, and to me helps enhance the relaxation experience of the flights.

Bigger airplane, probably same volume of air. Just wait for the -10...

arcticcruiser wrote:

Bigger airplane, probably same volume of air. Just wait for the -10...

I’d say you’re close but off just a bit. Bigger plane so more volume of air to have to circulate but the same number of recirculating fans and highly likely to have to same PACK system as the -800 or even -700.

Another thought is some times pilots turn off the recirculating fans during Preflight since they had a huge amount of noise on he flight deck. They’ve been known (including myself) to occasionally forget to turn them back on for entire flights.

NWADTWE16 wrote:

I have been flying the 737-900 more and more as it replaces the beloved 757's on many of my DL routes. I have NEVER see another plane type where the Cabin air is so weak. ITs bothersome, and I always find myself extremely hot and therefor less comfortable on these planes.

I'm hoping perhaps a Mechanic can help answer why this is the case on this 1 plane type

Thank you in advance.

The 737 is one of the oldest aircraft around in terms of design....lengthened to make the -900. Boeing was trying to squeeze in as many butts as possible so comfort was bound to suffer.

But the 757 200 and 300 models are bigger, especially of course the 300 and then the A330, 747, A380 all of which push air hard thru the cabin, its noticeable and until you stop at the gate your in it. This to me makes the 737-900 stand out very oddly. Possibly Boeing extended an old airframe and this causes it but then wouldn't the 757 have the same issue?

kjeld0d wrote:

NWADTWE16 wrote:

I have been flying the 737-900 more and more as it replaces the beloved 757's on many of my DL routes. I have NEVER see another plane type where the Cabin air is so weak. ITs bothersome, and I always find myself extremely hot and therefor less comfortable on these planes.

I'm hoping perhaps a Mechanic can help answer why this is the case on this 1 plane type

Thank you in advance.

The 737 is one of the oldest aircraft around in terms of design....lengthened to make the -900. Boeing was trying to squeeze in as many butts as possible so comfort was bound to suffer.

As well as almost every other manufacturer and airline. But in regards to the question, it is because of both the small nozzles, and the lengthening of the aircraft w/o an equivalent upgauge in amount of bleed air for the AC Packs. It does help quite a bit when the pilots turn the Pack switches to high flow instead of the normal "auto" setting. But as this setting is pretty much never used for takeoff (for the performance hit), most crews will never turn them to High flow when on the ground taxiing, as it's one more thing they'd have to change in the before-takeoff checks. If you think about it, packs get shut off for engine-start, in order to re-route the bleed air from the APU to the engines to start them. After engine start, they get turned back on and bring in bleed air from the engines instead of the APU. But as soon as taxi starts, or even before taxi starts, the pilots usually start preparing the aircraft configuration for takeoff. The airflow is much better in the cockpit, than in the cabin. So unfortunately, most crews never even think twice to turn the packs on High Flow when on the ground before take off. Hope this makes sense. Other aircraft aren't as prone to this, as in the case of the 757/767, they have much more bleed air coming into the AC system. Heck, on the 747, since it has 3 packs, they can even leave one of them on during engine start to provide some air to the cabin.

thank you ual763! That's exactly the kind of response I was looking for. I knew there was some explanation and that makes sense. It's a shame Boeing made that "flaw" id say, because for those of us that fly all the time, this is just another reason to not like one of their aircraft. The 737 900 is a sweet airplane with now two annoying flaws

Yeah no problem! I misspoke slightly above. Boeing actually reduced the nozzle size in an effort to actually try and increase the pressure, as the smaller the opening the air is forced through, the higher the pressure. However, the little amount of bleed air from the engine isn't nearly enough to make any difference really. Have to keep in mind also, that the -900 has had troubles meeting it's performance goals. It has trouble climbing above FL330 occasionally when full. In an effort to get everything they can muster out of the engines, they do it at the expense of the bleed air. This should get much better on the new MAXs coming out. As I'm sure you've noticed on the -800s, they're also much better than the -900s in this regard.

Older 737 have a gasper fan in addition to the recirc fans to provide airflow to these little vents. The 800-900 don't have gasper fans.

Last night I was lead FA on a B737-800 flying a full house LPA-OSL. Halfway enroute a guy became quite drunk and began farting profusely, stinking down half the cabin and many pax loudly complained as the useless gasper vents on the BSI hardly release any air. The pilots switched to fresh air only to try to replace the cabin air but it took a good half hour to clear the fart-filled air. The pax was reseated to last row as he became a bit obnoxious and my poor colleagues in the aft galley nearly fainted from the smell as he kept on farting until we parked at the gate...

Let's hope the MAX gasper vents are better.

ilovelamp wrote:

arcticcruiser wrote:

Bigger airplane, probably same volume of air. Just wait for the -10...

I’d say you’re close but off just a bit. Bigger plane so more volume of air to have to circulate but the same number of recirculating fans and highly likely to have to same PACK system as the -800 or even -700.

Another thought is some times pilots turn off the recirculating fans during Preflight since they had a huge amount of noise on he flight deck. They’ve been known (including myself) to occasionally forget to turn them back on for entire flights.

I believe the 800/900 have one more recirculation fan than the 600/700 does. There are differences in the air conditioning system between the 700 and 800. The 900 is mostly identical to the 800.

CRJ900 wrote:

Last night I was lead FA on a B737-800 flying a full house LPA-OSL. Halfway enroute a guy became quite drunk and began farting profusely, stinking down half the cabin and many pax loudly complained as the useless gasper vents on the BSI hardly release any air. The pilots switched to fresh air only to try to replace the cabin air but it took a good half hour to clear the fart-filled air. The pax was reseated to last row as he became a bit obnoxious and my poor colleagues in the aft galley nearly fainted from the smell as he kept on farting until we parked at the gate...

Let's hope the MAX gasper vents are better.

The cabin air would have completely changed over multiple times in 30 minutes. I think you flight probably had more problems than farts.

I beg to differ. In my opinion it's quieter than what other planes offer. Mind you that 737 is not exactly quiet either, but every decibels count. And in my opinion those gasper vents have sufficient power to blow air to my face. I like it more, because it's more diffuse than what they put on the other planes, and it does not hit my face as hard.

There is a range of 737-900 line numbers that have issues in the mid cabin (rows 6-11) or so. There is a flow issue that Boeing is aware of and is still investigating the issue. These -900s are recent deliveries within the last 2 years or so.

flybaurlax wrote:

There is a range of 737-900 line numbers that have issues in the mid cabin (rows 6-11) or so. There is a flow issue that Boeing is aware of and is still investigating the issue. These -900s are recent deliveries within the last 2 years or so.

Delta, unfortunately, has quite a few of those.