Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
User avatar
LaunchDetected
Topic Author
Posts: 319
Joined: Fri Jul 13, 2012 4:42 pm

Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Mar 04, 2020 7:55 am

Hi everyone,

In an A320, a fraction (≈ 30-50%) of "dirty" air coming from the cabin is reinjected into the Mixer Unit to be sent back into cabin again. Just before the mixer unit, this "dirty" air flows through HEPA filters.

Those filters are often described as "Hospital-Grade Filters" but I also have those kind of filters on my vacuum cleaner and I would not clean an operating room with it.

This brochure indicate:
"[...] remove more than 99.97 percent of airborne particles both larger and smaller than 0.3 micron"
(https://www.donaldsonaerospace-defense.com/library/files/documents/pdfs/F112273-ENG-Air-Purification-System-Airbus.pdf)

Given the general madness around Covid-19, do you think an airline can introduce higher-grade filters as a marketing argument like "our planes are safer for your lungs"?
Caravelle lover
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Mar 04, 2020 8:50 am

I don't think airlines really can do much. Recirculated air not the problem. The level of pathogens surviving is negligible. The risk is person to person transmission in the cabin. Air doesn't go directly from a person to be recirculated, and someone next to you can easily cough or sneeze and send stuff flying.

Your vacuum cleaner may have HEPA filters, but it is not an operating theatre grade filtering system.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
VSMUT
Posts: 4470
Joined: Mon Aug 08, 2016 11:40 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Mar 04, 2020 11:53 am

LaunchDetected wrote:
Given the general madness around Covid-19, do you think an airline can introduce higher-grade filters as a marketing argument like "our planes are safer for your lungs"?


Exactly, it is madness, and that is why they shouldn't do it. It's a total waste of money and resources.

If they want to try their hands at profiteering from the fear, they should just market the already fitted filters and bleed air systems instead. Most travelers are of the mistaken assumption that all the air in the cabin is just what was in there when the doors were closed, and that it gets recycled throughout the entire flight.
 
flybaurlax
Posts: 621
Joined: Sun Oct 05, 2008 12:34 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Mar 04, 2020 5:38 pm

There is guidance from the OEMs to actually use the recirc fans consistently. In fact, the guidance tells us that the not using the recirc fans is worse than using them. The reason is the HEPA filters. These filters actually work better the "dirtier" they are. The only reason why they are changed is due to restricted flow rate over time, not because they are inefficient.

The airlines are actively working with the CDC and OEM guidance. There aren't any recommendations to change any mx programs or introduce different filters. The existing filters should be effective in capturing this virus.
Boilerup! Go Purdue!
 
bhill
Posts: 1835
Joined: Thu Sep 13, 2001 8:28 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Mar 04, 2020 6:52 pm

I always thought the first stage of bleed air is rather hot....and those bugs do not do well in that type of environment.
Carpe Pices
 
User avatar
Horstroad
Posts: 524
Joined: Thu Apr 08, 2010 8:19 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Thu Mar 05, 2020 12:30 am

bhill wrote:
I always thought the first stage of bleed air is rather hot....and those bugs do not do well in that type of environment.

Hot bleed air from the engines or APU goes to the PACKs where it gets cooled down. Some of the hot bleed air bypasses the PACKs and rejoins the cooled air to get the desired temperature. This fresh conditioned air is sent to the cabin. To increase efficiency on the engines we want to reduce the amount of air needed in the cabin. So we recycle some of the cabin air. There are recirculation fans which take (potentially contaminated) cabin air and mix it with the freshly cooled air from the PACKs. There is an air filter in front of the recirc fans to catch any dust particles and other contamination. The effectiveness of these air filters which should clean the recirculating, recycled cabin air is discussed in this thread.
 
smartplane
Posts: 1508
Joined: Fri Aug 03, 2018 9:23 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Fri Mar 06, 2020 10:44 pm

Starlionblue wrote:
I don't think airlines really can do much. Recirculated air not the problem. The level of pathogens surviving is negligible. The risk is person to person transmission in the cabin. Air doesn't go directly from a person to be recirculated, and someone next to you can easily cough or sneeze and send stuff flying.

Your vacuum cleaner may have HEPA filters, but it is not an operating theatre grade filtering system.

There are 10 grades or aircon filter, rated one (protect the equipment from FOD) to 10 (operating theatres and other sterile environments).

Recirculating cabin air in an aircraft reduces hourly flying costs. Almost 100% of cabin air on a 787 is recirculated. Unlike an operating theatre, where a blocked filter triggers an alarm, on an aircraft the filter is bypassed (like the oil filter in your car). Aircraft are fitted with a range of filter types. If high number types only were used, they would block quickly. Usually filters are in a cartridge, containing say a Type 1, 3 and 5, and then another containing a 6 and 7 or 8.

OEM interest is in demonstrating the lowest possible operating costs to potential customers, not the cleanest air to passengers, so the OEM filter replacement cycle is meaningless for passengers and crew.

The cleanliness of cabin air depends on the number and grades of filters used, the frequency of replacement (and whether replaced with new, or cleaned and re-used old ones), the percentage of outside air admitted compared to recirculated, cabin volume, number of passengers and crew, and the rate of circulation.

Like restaurant health compliance grades, airline cabins should be graded, or required to make this information available when booking, as should cruise ship operators.

A relative owned a business making very specialised HEPA filters for a range of industries.
 
brilondon
Posts: 3158
Joined: Sun Aug 21, 2005 6:56 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Jul 15, 2020 9:29 pm

bhill wrote:
I always thought the first stage of bleed air is rather hot....and those bugs do not do well in that type of environment.

Yeah, they do.
Rush forever Closer To My Heart
 
GalaxyFlyer
Posts: 6078
Joined: Fri Jan 01, 2016 4:44 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Jul 15, 2020 10:13 pm

Bizjets are installing ionizers in addition to the filters. How well that works, I can’t say but engineers insist it’s another layer of protection. The main vector is the coughing person next to you, not the recirc air.
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Thu Jul 16, 2020 12:13 am

brilondon wrote:
bhill wrote:
I always thought the first stage of bleed air is rather hot....and those bugs do not do well in that type of environment.

Yeah, they do.


These aren't "hot day" temperatures. We're talking 200-250 degrees C. Way hotter than any known organism can survive.

Note this is the "new" bleed air, not the recirculated air.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Dalmd88
Posts: 3139
Joined: Fri Jul 28, 2000 3:19 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Fri Jul 17, 2020 12:00 am

The air exchange rate in even the worst aircraft is about 10 times better than most public buildings. Air flows in a cellular profile through the cabin. Air enters the cabin from the middle of the ceiling and the gasper vents above the seats and flow directly down to return air vents at the bottom of the sidewalls. The studies have shown there is very little airflow between the rows.
 
GalaxyFlyer
Posts: 6078
Joined: Fri Jan 01, 2016 4:44 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Fri Jul 17, 2020 12:20 am

Dalmd88 wrote:
The air exchange rate in even the worst aircraft is about 10 times better than most public buildings. Air flows in a cellular profile through the cabin. Air enters the cabin from the middle of the ceiling and the gasper vents above the seats and flow directly down to return air vents at the bottom of the sidewalls. The studies have shown there is very little airflow between the rows.


There ya go, letting facts get in the way of good rumor from the peanut gallery
 
889091
Posts: 209
Joined: Sat Apr 06, 2019 7:56 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Fri Jul 17, 2020 9:05 am

Starlionblue wrote:
brilondon wrote:
bhill wrote:
I always thought the first stage of bleed air is rather hot....and those bugs do not do well in that type of environment.

Yeah, they do.


These aren't "hot day" temperatures. We're talking 200-250 degrees C. Way hotter than any known organism can survive.

Note this is the "new" bleed air, not the recirculated air.


When the 787 was first introduced into service, this was one of the marketing points that Boeing/the airlines used - bleedless air for the 787. Combined wit the CFRP fuselage, the humidity of the cabin air could be adjusted so that it is not that dry, technically you should arrive at your destination more refreshed, etc.

Is it safe to assume that the 787 relies purely on filters to try and catch the virus and it doesn't zap them with heat before filtering them out?
 
Dalmd88
Posts: 3139
Joined: Fri Jul 28, 2000 3:19 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Fri Jul 17, 2020 1:51 pm

GalaxyFlyer wrote:
Dalmd88 wrote:
The air exchange rate in even the worst aircraft is about 10 times better than most public buildings. Air flows in a cellular profile through the cabin. Air enters the cabin from the middle of the ceiling and the gasper vents above the seats and flow directly down to return air vents at the bottom of the sidewalls. The studies have shown there is very little airflow between the rows.


There ya go, letting facts get in the way of good rumor from the peanut gallery

During one of the recent online Delta employee town hall event. One of the Vp's talked about the air quality testing and surface contamination they had done on the planes recently.

He through out some numbers. all very low, but to make them meaningful he compared them to random out of company testing they had done.

He said before they cleaned it his own personal cell phone was like 1000 time worse than the airplane galley surfaces they had tested. Then they cleaned it with the same methods for the galley and it was in line with the airplane results. For the air tests they did some random 'secret shopper' style testing around places like local grocery stores. The stores were about 10x worse than the plane during a regular 60% loaded plane in cruise.

The airplane air quality has always been much better than most public buildings. People just have this conception that it has to be bad since you are crammed in a tube for hours with strangers. Most of the issues that people attribute to bad air in planes is really caused by the dryness of the air. That was one of the goals that Boeing set out to improve with the 787 system.
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 19, 2020 2:02 pm

GalaxyFlyer wrote:
Dalmd88 wrote:
The air exchange rate in even the worst aircraft is about 10 times better than most public buildings. Air flows in a cellular profile through the cabin. Air enters the cabin from the middle of the ceiling and the gasper vents above the seats and flow directly down to return air vents at the bottom of the sidewalls. The studies have shown there is very little airflow between the rows.


There ya go, letting facts get in the way of good rumor from the peanut gallery

Except for it doesn't answer the question. Would droplets with infection go the full loop and be efficiently spread across the cabin through the middle of the ceiling and the gasper vents above the seats? That's why question is asked about filters.
How would it work in less traditional settings - e.g. 777 without personal vents? I flew in one of those early this year - there was zero airflow over my seat. In such a situation, flow between tows should be as efficient as in any office.
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 19, 2020 2:05 pm

kalvado wrote:
GalaxyFlyer wrote:
Dalmd88 wrote:
The air exchange rate in even the worst aircraft is about 10 times better than most public buildings. Air flows in a cellular profile through the cabin. Air enters the cabin from the middle of the ceiling and the gasper vents above the seats and flow directly down to return air vents at the bottom of the sidewalls. The studies have shown there is very little airflow between the rows.


There ya go, letting facts get in the way of good rumor from the peanut gallery

Except for it doesn't answer the question. Would droplets with infection go the full loop and be efficiently spread across the cabin through the middle of the ceiling and the gasper vents above the seats? That's why question is asked about filters.
How would it work in less traditional settings - e.g. 777 without personal vents? I flew in one of those early this year - there was zero airflow over my seat. In such a situation, flow between tows should be as efficient as in any office.


Droplets would be caught in the HEPA filters if they entered the ventilation system. They would not come back out.

Aircraft without personal vents still have the same amount of air circulation. It just isn't always obvious since you don't have a personal vent.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 19, 2020 2:34 pm

Starlionblue wrote:
kalvado wrote:
GalaxyFlyer wrote:

There ya go, letting facts get in the way of good rumor from the peanut gallery

Except for it doesn't answer the question. Would droplets with infection go the full loop and be efficiently spread across the cabin through the middle of the ceiling and the gasper vents above the seats? That's why question is asked about filters.
How would it work in less traditional settings - e.g. 777 without personal vents? I flew in one of those early this year - there was zero airflow over my seat. In such a situation, flow between tows should be as efficient as in any office.


Droplets would be caught in the HEPA filters if they entered the ventilation system. They would not come back out.

Aircraft without personal vents still have the same amount of air circulation. It just isn't always obvious since you don't have a personal vent.

HEPA filter is a very good argument. However a few responces here seem to come directly through marketing material and don't address the issue - if not outright misleading.
As for total flow.. reminds me about 36.6 average patient temperature in the hospital (including those in morgue).
There was no flow OVER MY SEAT. 777 is an old enough design to assume flow throughout the cabin was guesstimated, not modelled, so a few dead spots are more than likely. Those would be perfect for virus spread,
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 19, 2020 3:08 pm

Dalmd88 wrote:
The air exchange rate in even the worst aircraft is about 10 times better than most public buildings. Air flows in a cellular profile through the cabin. Air enters the cabin from the middle of the ceiling and the gasper vents above the seats and flow directly down to return air vents at the bottom of the sidewalls. The studies have shown there is very little airflow between the rows.

And now some numbers:
Waters, M. A., et al. "Measurements of indoor air quality on commercial transport aircraft." Proceedings of indoor air (2002): 782-787.
Carbon dioxide concentrations in coach averaged over both front and rear locations and over the entire flight period ranged from 874-2328 ppm (mean 1387 ppm, sd=351 ppm). The lowest 5-minute TWAs over the duration of the flight averaged 1021 ppm. Some flights never had CO2 concentrations lower than 1556 ppm. The highest gate-to-gate 5-minute TWAs averaged 2216 ppm, with single values at one location ranging as high as 4902 ppm CO2.

How high that is? Quote from elsewhere:
1,000 - 2,000 ppm: level associated with complaints of drowsiness and poor air.
2,000 - 5,000 ppm: level associated with headaches, sleepiness, and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present.

So poor air quality and lack of ventilation in the cabin is not a myth but a scientific fact.
Thanks for making me look it up!
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 19, 2020 3:45 pm

And sorry for flooding the thread..
https://www.nejm.org/doi/pdf/10.1056/NEJMoa031349
After one flight carrying a symptomatic person and 119 other persons, laboratory-con-firmed SARS developed in 16 persons, 2 others were given diagnoses of probable SARS,and 4 were reported to have SARS but could not be interviewed
....
illness reported in 8 of the 23 persons who were seated in the threerows in front of the index patient, as compared with 10 of the 88 persons who were seated elsewhere (relative risk, 3.1; 95 percent confidence interval, 1.4 to 6.9).

Although paper talks about 777-300, looks like it was a 737-300:
https://en.wikipedia.org/wiki/Air_China_Flight_112
Although there are other papers looking at similar situations where transmission was not detected. But this event shows that row-to-row isolation is not that great.
 
brilondon
Posts: 3158
Joined: Sun Aug 21, 2005 6:56 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 12:55 pm

Remember that pilots breath the same air so all you specialists can think about that.
Rush forever Closer To My Heart
 
brilondon
Posts: 3158
Joined: Sun Aug 21, 2005 6:56 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 12:55 pm

Remember that pilots breath the same air so all you specialists can think about that.
Rush forever Closer To My Heart
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 1:02 pm

brilondon wrote:
Remember that pilots breath the same air so all you specialists can think about that.


They don't breathe the same air. The cockpit does not get recirculated air. It is all from the bleeds.

Mind you, it has nothing to do with disease risk. As mentioned, the HEPA filters deal with that just fine. But in case there is smoke in the recirculation system you really don't want the pilots becoming incapacitated by it.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 1:49 pm

Starlionblue wrote:
brilondon wrote:
Remember that pilots breath the same air so all you specialists can think about that.


They don't breathe the same air. The cockpit does not get recirculated air. It is all from the bleeds.

Mind you, it has nothing to do with disease risk. As mentioned, the HEPA filters deal with that just fine. But in case there is smoke in the recirculation system you really don't want the pilots becoming incapacitated by it.

Would that mean that cockpit humidity is lower than in the back? I am not sure how much moisture sources in the cabin - such as exhaled moisture - would contribute; probably at least to some extent..
 
brilondon
Posts: 3158
Joined: Sun Aug 21, 2005 6:56 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 2:15 pm

kalvado wrote:
Starlionblue wrote:
brilondon wrote:
Remember that pilots breath the same air so all you specialists can think about that.


They don't breathe the same air. The cockpit does not get recirculated air. It is all from the bleeds.

Mind you, it has nothing to do with disease risk. As mentioned, the HEPA filters deal with that just fine. But in case there is smoke in the recirculation system you really don't want the pilots becoming incapacitated by it.

Would that mean that cockpit humidity is lower than in the back? I am not sure how much moisture sources in the cabin - such as exhaled moisture - would contribute; probably at least to some extent..


Yes, they do breath the same air. A pilot told me so. I thought they had a difference between the cockpit and the cabin, but his explanation seemed to make sense. The cockpit is a very small space and when you open the door, there is no difference. It's not sealed. The air is circulating throughout the aircraft. Why do you question things you don't know about?
Rush forever Closer To My Heart
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 3:59 pm

brilondon wrote:
kalvado wrote:
Starlionblue wrote:

They don't breathe the same air. The cockpit does not get recirculated air. It is all from the bleeds.

Mind you, it has nothing to do with disease risk. As mentioned, the HEPA filters deal with that just fine. But in case there is smoke in the recirculation system you really don't want the pilots becoming incapacitated by it.

Would that mean that cockpit humidity is lower than in the back? I am not sure how much moisture sources in the cabin - such as exhaled moisture - would contribute; probably at least to some extent..


Yes, they do breath the same air. A pilot told me so. I thought they had a difference between the cockpit and the cabin, but his explanation seemed to make sense. The cockpit is a very small space and when you open the door, there is no difference. It's not sealed. The air is circulating throughout the aircraft. Why do you question things you don't know about?

1. I am not questioning anything, I am asking for a smaller detail.
2. After hanging out on this site for well over 10 years, one thing I can say for sure - I am not impressed by overall qualification of posters who pose to be industry professionals. Not sure if many "747 captains" are still in high school, or it is just that "professionals" are at the line personell at botom of the feeding chain.
3. Looking up some data, it looks like that AT LEAST 737, and AT LEAST IN SOME CONFIGURATION - when left pack is on - has bleed-only cockpit air.
Image
4. See why I am saying (2)?
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Jul 21, 2020 4:41 pm

And on 320 things seem to be more democratic:
Image

Emergency ram air is an interesting detail, though...
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Jul 22, 2020 12:39 am

I haven't flown either type, but neither the 737 nor the A320 diagram seem very "precise". More like idealised representations.

Note on this 737 diagram how the cockpit is split off separately from the manifold.

Image

The A320, however, does seem to be "democratic" as mentioned.

Image

brilondon wrote:
kalvado wrote:
Starlionblue wrote:

They don't breathe the same air. The cockpit does not get recirculated air. It is all from the bleeds.

Mind you, it has nothing to do with disease risk. As mentioned, the HEPA filters deal with that just fine. But in case there is smoke in the recirculation system you really don't want the pilots becoming incapacitated by it.

Would that mean that cockpit humidity is lower than in the back? I am not sure how much moisture sources in the cabin - such as exhaled moisture - would contribute; probably at least to some extent..


Yes, they do breath the same air. A pilot told me so. I thought they had a difference between the cockpit and the cabin, but his explanation seemed to make sense. The cockpit is a very small space and when you open the door, there is no difference. It's not sealed. The air is circulating throughout the aircraft. Why do you question things you don't know about?


Types will vary, but as far as I can tell from the systems diagrams, on the A330 and A350 cockpit air coming out of the vents is only "fresh". Obviously it isn't a sealed compartment so there is some exchange with the cabin, especially if you open the door.

I don't think that it makes a meaningful difference to humidity.

On the other end of the air path so to speak, lavatory and galley air is not recirculated. Again, obviously there is some exchange since these are not sealed compartments.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Wed Jul 22, 2020 1:02 am

Starlionblue wrote:
Note on this 737 diagram how the cockpit is split off separately from the manifold..

I wouldn't say 737 got a separate split from the manifold on this diagram. The way I understand it, cyan and red flows are outside air going into the manifold from the left pack which is shown, and part of that flow is directed to cockpit. Right pack - which should be on top of the chart - doesn't supply cockpit directly. IF left pack doesn't supply air, flow from the manifold backstreams into cockpit - now with recirculated air mixed in, but ventilation is still there.
Actually diagram I posted earlier shows the same thing.

On a separate note - I also came across similar diagram for DC-10, and it doesn't show any recirculation. I wonder if that is actually the case.
 
ALTF4
Posts: 1228
Joined: Tue Jul 13, 2010 5:01 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Thu Jul 23, 2020 6:24 pm

brilondon wrote:
A pilot told me so.


Well, case closed folks! Second-hand information from a pilot (who knows what type), seals the deal!

I'd much prefer information from those on here backing their information up with sources, and not your mindless blathering. I'm a pilot, too - so keep in mind, everything I say is correct as well by your standards.
The above post is my opinion. Don't like it? Don't read it.
 
brilondon
Posts: 3158
Joined: Sun Aug 21, 2005 6:56 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Thu Jul 23, 2020 9:53 pm

Starlionblue wrote:
I haven't flown either type, but neither the 737 nor the A320 diagram seem very "precise". More like idealised representations.

Note on this 737 diagram how the cockpit is split off separately from the manifold.

Image

The A320, however, does seem to be "democratic" as mentioned.

Image

brilondon wrote:
kalvado wrote:
Would that mean that cockpit humidity is lower than in the back? I am not sure how much moisture sources in the cabin - such as exhaled moisture - would contribute; probably at least to some extent..


Yes, they do breath the same air. A pilot told me so. I thought they had a difference between the cockpit and the cabin, but his explanation seemed to make sense. The cockpit is a very small space and when you open the door, there is no difference. It's not sealed. The air is circulating throughout the aircraft. Why do you question things you don't know about?


Types will vary, but as far as I can tell from the systems diagrams, on the A330 and A350 cockpit air coming out of the vents is only "fresh". Obviously it isn't a sealed compartment so there is some exchange with the cabin, especially if you open the door.

I don't think that it makes a meaningful difference to humidity.

On the other end of the air path so to speak, lavatory and galley air is not recirculated. Again, obviously there is some exchange since these are not sealed compartments.


I have sat by a lav and no the air does not get heppa filtered.
Rush forever Closer To My Heart
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Thu Jul 23, 2020 11:07 pm

brilondon wrote:
Starlionblue wrote:
I haven't flown either type, but neither the 737 nor the A320 diagram seem very "precise". More like idealised representations.

Note on this 737 diagram how the cockpit is split off separately from the manifold.

Image

The A320, however, does seem to be "democratic" as mentioned.

Image

brilondon wrote:

Yes, they do breath the same air. A pilot told me so. I thought they had a difference between the cockpit and the cabin, but his explanation seemed to make sense. The cockpit is a very small space and when you open the door, there is no difference. It's not sealed. The air is circulating throughout the aircraft. Why do you question things you don't know about?


Types will vary, but as far as I can tell from the systems diagrams, on the A330 and A350 cockpit air coming out of the vents is only "fresh". Obviously it isn't a sealed compartment so there is some exchange with the cabin, especially if you open the door.

I don't think that it makes a meaningful difference to humidity.

On the other end of the air path so to speak, lavatory and galley air is not recirculated. Again, obviously there is some exchange since these are not sealed compartments.


I have sat by a lav and no the air does not get heppa filtered.

You understand that HEPA refers to particle filtration and does nothing to odors, right?
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Fri Jul 24, 2020 4:38 am

Plus that lav aroma comes from air exchange within the cabin. Lav air is normally dumped overboard.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
brilondon
Posts: 3158
Joined: Sun Aug 21, 2005 6:56 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 26, 2020 2:07 pm

Starlionblue wrote:
Plus that lav aroma comes from air exchange within the cabin. Lav air is normally dumped overboard.


I hope it's flushed into a tank. Not dumped overboard.
Rush forever Closer To My Heart
 
mmo
Posts: 2059
Joined: Thu Apr 18, 2013 3:04 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sun Jul 26, 2020 3:56 pm

brilondon wrote:
Starlionblue wrote:
Plus that lav aroma comes from air exchange within the cabin. Lav air is normally dumped overboard.


I hope it's flushed into a tank. Not dumped overboard.


The lav air is handled by the lav/galley vent system. It is essentially collected in a manifold and just vented overboard to ensure there are no odors that escape into the cabin.
If we weren't all crazy we'd all go insane!
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 12:39 am

brilondon wrote:
Starlionblue wrote:
Plus that lav aroma comes from air exchange within the cabin. Lav air is normally dumped overboard.


I hope it's flushed into a tank. Not dumped overboard.


We are talking about lav air. Not toilet juice. 8-)
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
shamrock137
Posts: 367
Joined: Mon Jul 25, 2005 7:10 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 1:32 am

Interesting policy from United. It sounds like instead of connecting ground air, theyll be running the packs during boarding and deplaning. Not really sure how this would help though... Instead of bringing in 100% outside air through the external air cart and PC air connection, they'll recirculate using the packs? Unless this means that with the PC air connected, the recirculation fans will be left on to force more air through the help filters.

Anyone have any more insight on this one?
Time to spare? Go by air!
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 3:15 am

shamrock137 wrote:
Interesting policy from United. It sounds like instead of connecting ground air, theyll be running the packs during boarding and deplaning. Not really sure how this would help though... Instead of bringing in 100% outside air through the external air cart and PC air connection, they'll recirculate using the packs? Unless this means that with the PC air connected, the recirculation fans will be left on to force more air through the help filters.

Anyone have any more insight on this one?


I can see the logic. Even at ports with high-quality ground air, the supply is nowhere near as powerful as the APU bleed and the packs. By using the bleed and packs you get much more airflow, and thus faster air exchange. The recirculated air goes through the HEPA filters so all good.

You can't use low-pressure ground air and the bleeds at the same time. The bleed/pack supply is so powerful it would probably blow the external hoses off.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
battlegroup62
Posts: 50
Joined: Mon Jul 03, 2017 5:05 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 3:25 am

I think it may have to do with the capacity of the PC air systems in terms of airflow and filtering. The aircraft can circulate more air than most PC air units unless you use one from an A380 on a 737, and the air would be filtered with HEPA filters vs unknown filters on the PC air. Plus I have heard that on really hot days the PC air units can barely maintain temperature on a 737, and can't bring an aircraft down from ambient. I could also be a cost saving measure, I'm sure the airports charge to use the air units. It may be cheaper to pay for a 100-200 pounds of fuel versus the connection fee albeit slightly less environmentally friendly.
We have to keep planes airworthy. That doesn't mean they have to fly.
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 3:53 am

battlegroup62 wrote:
I think it may have to do with the capacity of the PC air systems in terms of airflow and filtering. The aircraft can circulate more air than most PC air units unless you use one from an A380 on a 737, and the air would be filtered with HEPA filters vs unknown filters on the PC air. Plus I have heard that on really hot days the PC air units can barely maintain temperature on a 737, and can't bring an aircraft down from ambient. I could also be a cost saving measure, I'm sure the airports charge to use the air units. It may be cheaper to pay for a 100-200 pounds of fuel versus the connection fee albeit slightly less environmentally friendly.


Really hot days can be an issue, but it depends on the port. Some places just have more powerful ground air, especially in the tropics where temperatures can be high year-round.

As you say also cost is a factor. Same with APU vs ground power. In some places, ground power is so expensive that company policy is to use the APU instead.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 12:03 pm

Starlionblue wrote:
battlegroup62 wrote:
I think it may have to do with the capacity of the PC air systems in terms of airflow and filtering. The aircraft can circulate more air than most PC air units unless you use one from an A380 on a 737, and the air would be filtered with HEPA filters vs unknown filters on the PC air. Plus I have heard that on really hot days the PC air units can barely maintain temperature on a 737, and can't bring an aircraft down from ambient. I could also be a cost saving measure, I'm sure the airports charge to use the air units. It may be cheaper to pay for a 100-200 pounds of fuel versus the connection fee albeit slightly less environmentally friendly.


Really hot days can be an issue, but it depends on the port. Some places just have more powerful ground air, especially in the tropics where temperatures can be high year-round.

As you say also cost is a factor. Same with APU vs ground power. In some places, ground power is so expensive that company policy is to use the APU instead.

I expected last phrase to read "APU still burns expensive fuel while ground air runs on grid"...
So basically jetway/stairs is the only thing connected in such locations? I mean, water and lav service also have to be pricey with such policy?
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 12:49 pm

kalvado wrote:
Starlionblue wrote:
battlegroup62 wrote:
I think it may have to do with the capacity of the PC air systems in terms of airflow and filtering. The aircraft can circulate more air than most PC air units unless you use one from an A380 on a 737, and the air would be filtered with HEPA filters vs unknown filters on the PC air. Plus I have heard that on really hot days the PC air units can barely maintain temperature on a 737, and can't bring an aircraft down from ambient. I could also be a cost saving measure, I'm sure the airports charge to use the air units. It may be cheaper to pay for a 100-200 pounds of fuel versus the connection fee albeit slightly less environmentally friendly.


Really hot days can be an issue, but it depends on the port. Some places just have more powerful ground air, especially in the tropics where temperatures can be high year-round.

As you say also cost is a factor. Same with APU vs ground power. In some places, ground power is so expensive that company policy is to use the APU instead.

I expected last phrase to read "APU still burns expensive fuel while ground air runs on grid"...
So basically jetway/stairs is the only thing connected in such locations? I mean, water and lav service also have to be pricey with such policy?


It would depend on what each individual item costs at the port in question. The reason we know about APU, ground power and ground air at a port specifically is that the cockpit has the APU, ground power and bleed controls. We have no way of knowing from the cockpit whether potable water tanks are being refilled, or whether the poo lorry is draining the waste tank. All this stuff is more in the purview of the station manager and turnaround coordinator.

BTW as you say ground air runs on grid (unless it is a ground air cart), and from an environmental perspective running the APU instead of getting ground power and air is probably not ideal. But cost is cost. Same discussion as fuel tankering, basically.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kalvado
Posts: 2854
Joined: Wed Mar 01, 2006 4:29 am

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 1:00 pm

Starlionblue wrote:
kalvado wrote:
Starlionblue wrote:

Really hot days can be an issue, but it depends on the port. Some places just have more powerful ground air, especially in the tropics where temperatures can be high year-round.

As you say also cost is a factor. Same with APU vs ground power. In some places, ground power is so expensive that company policy is to use the APU instead.

I expected last phrase to read "APU still burns expensive fuel while ground air runs on grid"...
So basically jetway/stairs is the only thing connected in such locations? I mean, water and lav service also have to be pricey with such policy?


It would depend on what each individual item costs at the port in question. The reason we know about APU, ground power and ground air at a port specifically is that the cockpit has the APU, ground power and bleed controls. We have no way of knowing from the cockpit whether potable water tanks are being refilled, or whether the poo lorry is draining the waste tank. All this stuff is more in the purview of the station manager and turnaround coordinator.

BTW as you say ground air runs on grid (unless it is a ground air cart), and from an environmental perspective running the APU instead of getting ground power and air is probably not ideal. But cost is cost. Same discussion as fuel tankering, basically.

Cost is cost - although sometimes it just has to be eaten. Like with filters upgrade.
And shouldn't captain be aware of everything that happened with the ship, or it is just "ready to fly" statement form the company and a walkaround + controls check?
I am thinking about it somewhat in connection with JT MAX crash, where pilots were likely unaware of previous day issues...
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Mon Jul 27, 2020 1:12 pm

kalvado wrote:
Starlionblue wrote:
kalvado wrote:
I expected last phrase to read "APU still burns expensive fuel while ground air runs on grid"...
So basically jetway/stairs is the only thing connected in such locations? I mean, water and lav service also have to be pricey with such policy?


It would depend on what each individual item costs at the port in question. The reason we know about APU, ground power and ground air at a port specifically is that the cockpit has the APU, ground power and bleed controls. We have no way of knowing from the cockpit whether potable water tanks are being refilled, or whether the poo lorry is draining the waste tank. All this stuff is more in the purview of the station manager and turnaround coordinator.

BTW as you say ground air runs on grid (unless it is a ground air cart), and from an environmental perspective running the APU instead of getting ground power and air is probably not ideal. But cost is cost. Same discussion as fuel tankering, basically.

Cost is cost - although sometimes it just has to be eaten. Like with filters upgrade.
And shouldn't captain be aware of everything that happened with the ship, or it is just "ready to fly" statement form the company and a walkaround + controls check?
I am thinking about it somewhat in connection with JT MAX crash, where pilots were likely unaware of previous day issues...


If anything is amiss that would affect the safe conduct of the flight, we'd see it from the cockpit, whether from the instruments or written up in the tech log. By contrast, if the poo lorry hasn't drained the tank, it is an inconvenience at most. In an airline operation, you can't see everything. You have to trust that the ground engineer did his/her job, and the cabin manager did his/her job. The engineer signs the aircraft off as ready to fly and the cabin manager says "cabin ready". But again, if anything is affecting safety, we will see it.

With the JT MAX, that sort of issue would be (should be!) in the tech log, and the crew would review it as part of the preliminary cockpit prep. The captain goes through any outstanding issues and then reviews the tech log's past few days or dozen sectors for anything of note. The first officer (and any relief crew) are included in this process. That way you know if there are any niggles, MEL items, history. If needed you'd expand the briefing to review contingencies.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Sokes
Posts: 1646
Joined: Sat Mar 09, 2019 4:48 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Aug 04, 2020 3:46 pm

smartplane wrote:
There are 10 grades or aircon filter, rated one (protect the equipment from FOD) to 10 (operating theatres and other sterile environments).

Recirculating cabin air in an aircraft reduces hourly flying costs. Almost 100% of cabin air on a 787 is recirculated. Unlike an operating theatre, where a blocked filter triggers an alarm, on an aircraft the filter is bypassed (like the oil filter in your car). Aircraft are fitted with a range of filter types. If high number types only were used, they would block quickly. Usually filters are in a cartridge, containing say a Type 1, 3 and 5, and then another containing a 6 and 7 or 8.

If I need my coffee fast, I just cut a hole in the filter paper.
Why can't the world be a little bit more autistic?
 
Sokes
Posts: 1646
Joined: Sat Mar 09, 2019 4:48 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Tue Aug 04, 2020 3:53 pm

Starlionblue wrote:
Types will vary, but as far as I can tell from the systems diagrams, on the A330 and A350 cockpit air coming out of the vents is only "fresh". Obviously it isn't a sealed compartment so there is some exchange with the cabin, especially if you open the door.

I don't think that it makes a meaningful difference to humidity.

On the other end of the air path so to speak, lavatory and galley air is not recirculated. Again, obviously there is some exchange since these are not sealed compartments.

Not that I'm qualified to judge, but I guess cockpit has little higher, toilet little lower pressure than main cabin.
Why can't the world be a little bit more autistic?
 
stratclub
Posts: 1372
Joined: Fri Jan 05, 2018 10:38 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sat Aug 08, 2020 6:43 am

How about infrared lights for sterilization of the air in the return ducts and fresh air masks plugged into the gasper system? The mask and hose could be rented for the flight like earphones are on some flights. A sterile air supply at every seat.
 
User avatar
Starlionblue
Posts: 20032
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Air Recirculation Filters against Covid-19? (ATA 21)

Sat Aug 08, 2020 12:21 pm

stratclub wrote:
How about infrared lights for sterilization of the air in the return ducts and fresh air masks plugged into the gasper system? The mask and hose could be rented for the flight like earphones are on some flights. A sterile air supply at every seat.


Infrared just heats. You may be thinking of ultraviolet.

Lots of airliners today don't have gasper vents.

While giving people individual air supplies is vaguely plausible, the advantages over everyone simply wearing a mask are probably slim to none.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

Who is online

Users browsing this forum: EAARbrat, pcosta and 15 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos