richiemo
Topic Author
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737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 4:49 am

I notice some of Continental's 739s have a small door mid-aft of the wing, and some don't. Why is that. Somoene said the extended range has the door. But why is that. I thought additional doors were required when you had more passengers. Don't extended range jets have fewer seats (less weight?)
 
elbandgeek
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 4:53 am

The ER has a higher maximum seating capacity than the standard which is limited to 189 (the same max as the 800) because of the exist configuration. The ER added the extra set of doors and flattened the rear bulkhead to fit in more seats, but because CO doesn't configure theirs with more than 189, they were given the option of plugging those doors to save weight.
 
tdscanuck
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 5:17 am

Quoting richiemo (Thread starter):
Don't extended range jets have fewer seats (less weight?)

The usual way to extend range is to increase fuel capacity or increase MTOW (allow more fuel to be loaded with an equivalent payload). ER models are rarely lighter or carry less payload.

Tom.
 
Boof
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 10:56 am

Remember that originally the 739 series was built for payload rather than range, hence the 189 seat limit and the lack of need for the extra exits. When Boeing launched the 739ER with the greater fuel capacity, winglets and extra seating capacity (to 215 in single class) the extra door was required for the emergency exit certification to comply with the 90 second evacuation rule.

CO don't require the aft wing exit to be activated as they use the 739ER for the extra payload/range and have less than 189 seats in 2 class layout hence the cabin layout is the same on CO regardless of if its a 739 or 739ER.

Quoting elbandgeek (Reply 1):
they were given the option of plugging those doors to save weight.

You can see the plug here:
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Photo © Andrew Compolo



As compared with the standard exit door here:
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Photo © Paul Spijkers



View the large photos to get a better look at them.

Cheers,

Boof
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eraugrad02
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 8:15 pm

So did CO add a fuel tank to the "ER" they've ordered? Or was only added range from AFB winglets which they've added to non-ER so does that mean the range are the same if CO didn't add the 1 of 2 extra fuel tanks that can be added to "ER"?

Desmond in ILM,
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LH422
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 8:40 pm

Quoting Boof (Reply 3):
When Boeing launched the 739ER with the greater fuel capacity, winglets and extra seating capacity (to 215 in single class) the extra door was required for the emergency exit certification to comply with the 90 second evacuation rule.

I don't quite get it. Why does a 739ER need more exits than a 772 or an A333?
 
harleydriver
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 8:52 pm

I am curious as to why you would plug an available exit? If it's there and built into the airframe then a door with the required slide wouldnt be that much extra weight then just the plug. Its just one more option passengers and crew have to depart the aircraft should something unfortunate happen.
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star_world
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 9:04 pm

Quoting LH422 (Reply 5):
I don't quite get it. Why does a 739ER need more exits than a 772 or an A333?

One aisle vs. two is probably the simplest reason...
 
bohica
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 9:10 pm

Quoting HarleyDriver (Reply 6):
I am curious as to why you would plug an available exit? If it's there and built into the airframe then a door with the required slide wouldnt be that much extra weight then just the plug.

CO's 739's have less than 189 seats so it's simply not needed and it complies with FAA regulations. A plug weighs much less than a door, slide, handles, hinges, etc. and it requires less maintenance.

UA used to have some 722's which originally came with an extra exit just forward of the wing. The intention was to use them on high density routes. I don't know if they ever did though. They were plugged and you could not tell it was even there from the inside.
 
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AA777223
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 9:32 pm

Quoting bohica (Reply 8):
UA used to have some 722's which originally came with an extra exit just forward of the wing. The intention was to use them on high density routes. I don't know if they ever did though. They were plugged and you could not tell it was even there from the inside.

Have any pics of this?
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tullamarine
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 9:38 pm

The 739ER added the extra door so LCCs could carry more than the 189 pax the 737 was certified for. Without the extra door a LCC could carry no more pax on a 739 than on a 738.

Quoting LH422 (Reply 5):
Why does a 739ER need more exits than a 772 or an A333?

It is because of the size of the main exits. A 772 or A332 have doors that are rated as being able to handle 2 pax at the same time whereas the less wide 737 doors are one at a time.
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Renfro747
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 10:16 pm

 
nws2002
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 10:43 pm

Quoting LH422 (Reply 5):
I don't quite get it. Why does a 739ER need more exits than a 772 or an A333?

Because the 737 exits are much smaller and have a lower flow rate compared with the 777 or A330 exits.
 
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calpsafltskeds
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RE: 737-900: Mid-aft Door, Why And Why Not

Wed Jan 12, 2011 11:38 pm

Quoting eraugrad02 (Reply 4):
So did CO add a fuel tank to the "ER" they've ordered? Or was only added range from AFB winglets which they've added to non-ER so does that mean the range are the same if CO didn't add the 1 of 2 extra fuel tanks that can be added to "ER"?

To my knowledge CO did not take the extra tanks, which is probably why they pulled them off LAX-HNL. With headwinds, payload would have to be reduced to make the trip with full tanks. Maybe the aux tanks would only be needed on Hawaii flights?

The standard 739ER has 6,875 gallons (46,063 lbs), same as the 738, 739 and 73G.

The 739ER has the option of one optional tank at 515 gallons (3,450 lbs.) and a second one at 447 gallons (2,995 lbs.) With both, it's 962 gallons (6,445 lbs.) more.

My load planning days are long past, but I'm wondering how often CO's 738s go out with full fuel as it looks to me like a 738 has 38,137 lbs. available for payload with full tanks. For 160 pax that would be an average of 230 lbs. per pax plus bags, or less per pax if cargo is being boarded.

A comparable 739ER would have 43,142 lbs. available payload, an average of 249 lbs. per pax (173 pax & bags).
With one aux tank, the payload would be 36,697 lbs. , lowering the average to 212 lbs. (173 pax & bags).
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Starlionblue
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RE: 737-900: Mid-aft Door, Why And Why Not

Thu Jan 13, 2011 2:06 am

Quoting HarleyDriver (Reply 6):
I am curious as to why you would plug an available exit? If it's there and built into the airframe then a door with the required slide wouldnt be that much extra weight then just the plug. Its just one more option passengers and crew have to depart the aircraft should something unfortunate happen.

An exit costs money in maintenance of the exit itself and the slide.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Viscount724
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RE: 737-900: Mid-aft Door, Why And Why Not

Fri Jan 14, 2011 12:20 am

Quoting HarleyDriver (Reply 6):
I am curious as to why you would plug an available exit? If it's there and built into the airframe then a door with the required slide wouldnt be that much extra weight then just the plug. Its just one more option passengers and crew have to depart the aircraft should something unfortunate happen.

British Airways, KLM, Cathay Pacific and one other carrier I've forgotten (possibly Thai), sealed up the overwing doors on their 747-100/200/300s and added additional seats in those areas. That was a controversial change as it significantly increased the distance from that part of the cabin to the nearest exit as well as increasing the number of passengers, but it was obviously permitted by the regulatory authorities at the time. Not sure if the rules were changed as it was never done on the 747-400. I believe CX, at least, later reactivated those doors, but I don't believe BA or KL did.

Photos of the same BA/CX/KL 742s before and after the overwing doors were deactivated.


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Photo © pkaviation
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Photo © Tim Rees


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Photo © Mick Bajcar
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Photo © Tim Rees


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Photo © Ed Groenendijk
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Photo © Udo K. Haafke



[Edited 2011-01-13 16:24:07]
 
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bikerthai
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RE: 737-900: Mid-aft Door, Why And Why Not

Fri Jan 14, 2011 3:07 pm

Quoting HarleyDriver (Reply 6):
I am curious as to why you would plug an available exit?

Along with the reason already stated by others . . .

Exist doors are notoriously noisy and cold. With a plug you get better sound and heat insulation, a plus for the passenger.

bikerthai
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
Viscount724
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RE: 737-900: Mid-aft Door, Why And Why Not

Sat Jan 15, 2011 12:00 am

Quoting AA777223 (Reply 9):
Quoting bohica (Reply 8):
UA used to have some 722's which originally came with an extra exit just forward of the wing. The intention was to use them on high density routes. I don't know if they ever did though. They were plugged and you could not tell it was even there from the inside.

Have any pics of this?
Quoting Renfro747 (Reply 11):
Quoting AA777223 (Reply 9):
Have any pics of this?

Right here...

The 2nd of those UA 722s in the links above before and after the extra exit was deactivated.


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Photo © Howard Chaloner
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Photo © Frank J. Mirande



If memory correct, Eastern was the only original customer to order their 720s with 2 overwing exits per side. Other 720s only have one per side, except a few 720Bs later acquired by charter carriers with high-density seating which had the 2nd exit installed to permit another 30 or so passengers to be carried. I think Eastern had planned to use their 720s in a high-density layout but don't believe they ever did.

Eastern 720 with the extra overwing exits.


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