User avatar
nitepilot79
Posts: 783
Joined: Tue May 20, 2008 9:10 pm

Why So Few Exits?

Tue Jul 14, 2009 7:42 am

I just saw a picture of an Air Canada 762; and happened to notice that it had 6 total exits . 2 over-wing and 4 full-size exits. My question is: why on earth does the 734 have 2 more exits with less passenger capacity? Perhaps safety standards changed as the 734 is a bit younger than the 762, even still, the 732 has the same # of exits as the 762. Seems to me the increase of pax capacity(762) should have warranted more exits than a on 732. PS- Not trying to cry over spilled milk, just curious.  eyebrow 
 
LY777
Posts: 2269
Joined: Fri Nov 25, 2005 6:58 pm

RE: Why So Few Exits?

Tue Jul 14, 2009 8:07 am



Quoting Nitepilot79 (Thread starter):
I just saw a picture of an Air Canada 762; and happened to notice that it had 6 total exits . 2 over-wing and 4 full-size exits. My question is: why on earth does the 734 have 2 more exits with less passenger capacity? Perhaps safety standards changed as the 734 is a bit younger than the 762, even still, the 732 has the same # of exits as the 762. Seems to me the increase of pax capacity(762) should have warranted more exits than a on 732. PS- Not trying to cry over spilled milk, just curious

I aked myself the very same question, and in fact, there are 2 main reasons:

- the 762 has 2 aisles, so evacuation would be easier
- the doors of the 767 are much wider than the 737

Hope this helps!
Flown:A3B2,A320,A321,A332,A343,A388,717,727,732,734,735,738,73W,742/744/748,752,762/2ER/763/3ER,772/77E/773/77W,D8,D10,L
 
UAL747
Posts: 6725
Joined: Mon Dec 13, 1999 5:42 am

RE: Why So Few Exits?

Tue Jul 14, 2009 8:12 am

Wider doors, twin aisle aircraft. Basically, it's two RJ's wide. One a CRJ and one an ERJ on either side of the aisle, with bigger doors.

All of these evacuations have been timed and are in full compliance with safety standards. You won't find manufacturers putting on any more doors than they need because of the weight.

The 763 with only 2 doors and 2 over wing exits is a bit of a stretch to me personally, but I guess it works the same way.

UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Why So Few Exits?

Tue Jul 14, 2009 8:48 am

Evactuation Tests are carried out to determine the speed of the Evacuation of the main pax cabin.If not within the permissible timeframe,the regulatory authority would insist addition of exits to fulfill that requirement prior to certification.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
BMI727
Posts: 11099
Joined: Mon Feb 02, 2009 9:29 pm

RE: Why So Few Exits?

Tue Jul 14, 2009 7:16 pm



Quoting LY777 (Reply 1):
- the 762 has 2 aisles, so evacuation would be easier

Aren't the certification tests done using the exits on only one side of the aircraft?
Why do Aerospace Engineering students have to turn things in on time?
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Why So Few Exits?

Tue Jul 14, 2009 7:47 pm



Quoting BMI727 (Reply 4):

Aren't the certification tests done using the exits on only one side of the aircraft?

Technically, with only 50% of the exits operable....Airbus chose to disable all of the slide packs on one side for the A380 evacuation test  Wink They could have just as easily randomly chosen which exits would have worked and which ones didn't and been in full compliance of the letter of the law. The test subjects, however, can't know what's going on, IIRC...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Why So Few Exits?

Tue Jul 14, 2009 8:05 pm



Quoting KELPkid (Reply 5):
The test subjects, however, can't know what's going on, IIRC...

Didn't Airbus gather a bunch of college students and offer some kind of monetary bonus if they all get out in time for the A380 tests? A stroke of brilliance, if you ask me. They could improve the times even further if a few hundred kegs of beer and swimsuit models were awaiting the college kids.

2H4
Intentionally Left Blank
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Why So Few Exits?

Tue Jul 14, 2009 11:14 pm



Quoting BMI727 (Reply 4):
Aren't the certification tests done using the exits on only one side of the aircraft?

50% are supposed to be randomly deactivated.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
BMI727
Posts: 11099
Joined: Mon Feb 02, 2009 9:29 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 12:51 am



Quoting KELPkid (Reply 5):
....Airbus chose to disable all of the slide packs on one side for the A380 evacuation test

This seems like it might be the most realistic scenario for having fewer exits available, like having a fire on one side or something.

Quoting 2H4 (Reply 6):
They could improve the times even further if a few hundred kegs of beer and swimsuit models were awaiting the college kids.

They could better simulate typically stupid pax by making them take the beer and models out of the overheads and carry them out with them.  Smile
Why do Aerospace Engineering students have to turn things in on time?
 
Viscount724
Posts: 18971
Joined: Thu Oct 12, 2006 7:32 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 1:47 am



Quoting Nitepilot79 (Thread starter):
I just saw a picture of an Air Canada 762; and happened to notice that it had 6 total exits . 2 over-wing and 4 full-size exits.

Some 762s operated by charter carriers with very high-density seating configurations were built with 4 over-wing exits to meet evacuation requirements, for example those ordered by Britannia Airways which had very tight 8-abreast seating with about 29 inch seat pitch and probably at least 100 more seats than the typical 7-abreast mixed-class 762 operated by most scheduled airlines. Not sure if any other carriers ordered 762s with the 4 overwing exits. Photos of two Britannia 762s with the additional over-wing exits below. (Britannia is now Thomson Airways and they no longer operate 762s.)


View Large View Medium
Click here for bigger photo!

Photo © Koksy
View Large View Medium
Click here for bigger photo!

Photo © Jordi Grife - Iberian Spotters

 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Why So Few Exits?

Wed Jul 15, 2009 2:23 am



Quoting 2H4 (Reply 6):
Didn't Airbus gather a bunch of college students and offer some kind of monetary bonus if they all get out in time for the A380 tests?

That probably wouldn't have passed certification...the passengers used in the evacuation test are supposed to be a representative sample (age, size, fitness, gender, etc.). Just because 850+ money-starved college students can get out of an A380 in time doesn't mean a real passenger load could.

Tom.
 
Markhkg
Posts: 838
Joined: Mon Dec 05, 2005 4:13 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 3:22 am



Quoting KELPkid (Reply 5):
Airbus chose to disable all of the slide packs on one side for the A380 evacuation test

Actually, Airbus doesn't get to choose I believe - the monitoring regulatory agencies specify which exits are to be "deactivated". However I find that for whatever reason most of the evacuation certifications are done with "right" or "left" side only. In fact there are some mumblings that if you attempted to block off all the floor level exits on the A320 or B737-800 and made people go through all the overwings, they couldn't make the 90 second time limit even though all 4 overwings would still count as 50% of exits if the four Type I doors are blocked. I don't think an evacuation certification has ever attempted this.

Quoting 2H4 (Reply 6):
Didn't Airbus gather a bunch of college students and offer some kind of monetary bonus if they all get out in time for the A380 tests

No, competitive evacuations are not used during evacuation certification. Cranfield University conducted their own research after the Manchester Air Disaster using monetary compensation but it is unrelated to certification.
Release your seat-belts and get out! Leave everything!
 
Markhkg
Posts: 838
Joined: Mon Dec 05, 2005 4:13 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 3:27 am



Quoting Nitepilot79 (Thread starter):
4 full-size exits

To give you an idea of how dual lane versus single lane doors result in:

The Boeing 737 has a type I door. The FAA allows for 45 passengers per one pair of Type I doors.

The Boeing 767 has a type A door. The FAA allows for 110 passenger per one pair of Type A doors.

This is described in FAR 25.807
Release your seat-belts and get out! Leave everything!
 
User avatar
Starlionblue
Posts: 17079
Joined: Fri Feb 27, 2004 9:54 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 3:45 am



Quoting MarkHKG (Reply 11):
Cranfield University conducted their own research after the Manchester Air Disaster using monetary compensation but it is unrelated to certification

They used monetary compensation to make people more motivated. It was thought that this more accurately modeled real conditions, since of course if the plane is in a real emergency people are more motivated to get out than in a simulated one.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 3:50 am



Quoting Starlionblue (Reply 13):
They used monetary compensation to make people more motivated. It was thought that this more accurately modeled real conditions, since of course if the plane is in a real emergency people are more motivated to get out than in a simulated one.

That's what I thought. It makes sense...the cost of motivational compensation pales in comparison to the cost of treating all the burns and settling all the lawsuits when utilizing fully realistic motivational techniques.  Wink

2H4
Intentionally Left Blank
 
Markhkg
Posts: 838
Joined: Mon Dec 05, 2005 4:13 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 6:36 am

Quoting 2H4 (Reply 14):
treating all the burns and settling all the lawsuits when utilizing fully realistic motivational techniques.

To be clear, Airbus did not use monetary bonus incentives for the A380 evacuation. The only compensation was 60 Euros and a free lunch.

Cranfield University on the other hand, has used a system of monetary bonuses to increase competitive behavior in some of their studies. One study design for a 737 mockup involved the first 50% passengers off the study aircraft getting 5 British pounds. (Some studies later involved the first 75% passenger off). The results were somewhat horrendous: the addition of the monetary money resulted in bottlenecks at the bulkhead partitions and people getting stuck in the Type III overwing exits, while non-competitive (i.e. no bonus money) evacuation trials did not demonstrate this behavior.

And all for just 5 pounds!

[Edited 2009-07-14 23:36:58]
Release your seat-belts and get out! Leave everything!
 
FlyingColours
Posts: 2202
Joined: Fri Dec 26, 2003 3:13 am

RE: Why So Few Exits?

Wed Jul 15, 2009 10:12 am



Quoting MarkHKG (Reply 15):
Quoting 2H4 (Reply 14):
treating all the burns and settling all the lawsuits when utilizing fully realistic motivational techniques.

To be clear, Airbus did not use monetary bonus incentives for the A380 evacuation. The only compensation was 60 Euros and a free lunch.

Cranfield University on the other hand, has used a system of monetary bonuses to increase competitive behavior in some of their studies. One study design for a 737 mockup involved the first 50% passengers off the study aircraft getting 5 British pounds. (Some studies later involved the first 75% passenger off). The results were somewhat horrendous: the addition of the monetary money resulted in bottlenecks at the bulkhead partitions and people getting stuck in the Type III overwing exits, while non-competitive (i.e. no bonus money) evacuation trials did not demonstrate this behavior.

And all for just 5 pounds!

I believe that was after the Manchester Air Disaster of 1985, they wanted to conduct a study into evacuations since so many people lost their lives in that accident due to not being able to get out before being overcome by smoke & fumes before the cabin flashed over 90 or so seconds later.

Quoting Viscount724 (Reply 9):
Some 762s operated by charter carriers with very high-density seating configurations were built with 4 over-wing exits to meet evacuation requirements, for example those ordered by Britannia Airways which had very tight 8-abreast seating with about 29 inch seat pitch and probably at least 100 more seats than the typical 7-abreast mixed-class 762 operated by most scheduled airlines.

At one point we operated 3 ex BY 767-200s, G-SATR, G-BNYS & G-BOPB, all were fitted with 290 seats and 4 main exits and 4 overwings. I wouldn't say the seating was too cramped, sure on a long haul flight (BGI-LGW - I did it once, because a 763 went tech) it would be unbearable but it's not as bad as some would think, though if you are 6 feet tall then it's a different story....

A bit of history here, TR became a freighter years ago (incidentally it clipped a Bmi Baby 737 tail at Manchester), YS went to Air Seychelles and was supposed to be coming back to us in the winter, but due to our bankruptcy did not and has now been scrapped. "Papa Bravo" as the company preferred it to be called (we preferred "Pile 'O B&llocks" spent many months stored after XL's Bankruptcy but is now operating for Yemen Air (in our full colours), I believe alongside the ex Silverjet birds in their old liveries (incidentally all ex BY machines).

Quoting MarkHKG (Reply 11):
block off all the floor level exits on the A320 or B737-800 and made people go through all the overwings, they couldn't make the 90 second time limit even though all 4 overwings would still count as 50% of exits if the four Type I doors are blocked.

Not mumblings there, its true, one main benefit of the large doors is that an evacuation if handled correctly by crew (crowd control) will be able to flow through the doors at a rate of one passenger per second, overwings do not offer this as huge bottlenecks occur both at the exits and in the cabin as all the exits are in the same area of the aircraft. To add to that passengers would have to step out of the aircraft and either stay on the wing or come off the wing depending on the evacuation (water or land).

Phil
FlyingColours
Lifes a train racing towards you, now you can either run away or grab a chair & a beer and watch it come - Phil
 
dynamicsguy
Posts: 442
Joined: Tue Jul 08, 2008 9:24 am

RE: Why So Few Exits?

Wed Jul 15, 2009 11:56 am



Quoting MarkHKG (Reply 15):
And all for just 5 pounds!

My old boss used to work in the area and knew some of the people who ran that study. Apparently they were originally going to offer a larger sum, but discovered that 5 quid is really all the motivation people needed.

I wonder if any commercial airliner would pass the certification tests if they were done with such a motivation. I've seen footage of some of the above-mentioned study, and it was truly chaotic (and frightening).
 
Markhkg
Posts: 838
Joined: Mon Dec 05, 2005 4:13 pm

RE: Why So Few Exits?

Wed Jul 15, 2009 2:36 pm



Quoting Dynamicsguy (Reply 17):
with such a motivation

I always thought German people angrily shouting "RAUS RAUS RAUS" would be motiviation enough. Big grin

Seriously though, I think it has to be said that evacuation trials do generate motiviation of a different sort - a team mentality - to get off the plane as quickly as possible. I remember watching videos during the Boeing 777 trial in which one pax tries to help with opening one of the main doors - and has to be pushed back since he could have fallen out of the exit before the slide deployed. Then again, the same trial had one participant who was also so scared she refused to jump onto the slide...
Release your seat-belts and get out! Leave everything!
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Why So Few Exits?

Wed Jul 15, 2009 2:49 pm



Quoting 2H4 (Reply 6):
Didn't Airbus gather a bunch of college students and offer some kind of monetary bonus if they all get out in time for the A380 tests? A stroke of brilliance, if you ask me. They could improve the times even further if a few hundred kegs of beer and swimsuit models were awaiting the college kids.

2H4

One of the ways I used to get flying money in college was to volunteer as a test subject for psychology dept. experiments  Wink (sure beat selling blood plasma...).
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
dynamicsguy
Posts: 442
Joined: Tue Jul 08, 2008 9:24 am

RE: Why So Few Exits?

Thu Jul 16, 2009 6:48 am



Quoting Markhkg (Reply 18):
Seriously though, I think it has to be said that evacuation trials do generate motiviation of a different sort - a team mentality - to get off the plane as quickly as possible.

That was sort of my point (though I didn't express it very clearly). An evacuation trial creates that sort of motivation - to work as a team to meet the goal. There's no genuine danger and there's no benefit for you to get out sooner than the next person in front of you, so everyone's working to get everyone off.

The 5 pound incentive provides a more realistic motivation - to get yourself out of the plane as quickly as possible for the individual rather than the team. I think the latter is more representative of a real life evacuation, and I'm not sure that a planeful of people working as individuals like that would get out in 90 seconds.
 
zappbrannigan
Posts: 231
Joined: Wed Oct 01, 2008 7:41 am

RE: Why So Few Exits?

Thu Jul 16, 2009 10:18 am



Quoting Dynamicsguy (Reply 20):
That was sort of my point (though I didn't express it very clearly). An evacuation trial creates that sort of motivation - to work as a team to meet the goal. There's no genuine danger and there's no benefit for you to get out sooner than the next person in front of you, so everyone's working to get everyone off.

The 5 pound incentive provides a more realistic motivation - to get yourself out of the plane as quickly as possible for the individual rather than the team. I think the latter is more representative of a real life evacuation, and I'm not sure that a planeful of people working as individuals like that would get out in 90 seconds.

Agreed. They all know they're in an evac test, and what sort of "behaviour" is expected. And I'm sure they all want to do the right thing by the aircraft manufacturer - i.e. help them pass the test wherever possible. In addition, there's no real stress - no actual fear of injury or death, and no fight-or-flight response.

In my experience in various other areas, when you add actual stress into the equation, to a group of subjects who are not trained in a specific response to that stress (unlike, say, a pilot responding to an emergency with a procedural, trained response to stimuli under stress), the results will be a lot more chaotic. I imagine offering cash to the first X percent off would generate a similar response.
 
Ditzyboy
Posts: 289
Joined: Thu Feb 28, 2008 5:15 am

RE: Why So Few Exits?

Tue Aug 11, 2009 12:29 pm

The 767s have dual-lane slides at both the doors and off-wing. The 737s have only single lane slides.
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Why So Few Exits?

Tue Aug 11, 2009 3:15 pm

A search of the TCDS would have revealed the following:

The number and type of doors determines the maximum number of passengers .

255 for a 767-200 equipped with 2 pair Type A and 1 pair Type III doors.

290 for a 767-200/300 equipped with 2 pair Type A and 2 pair Type III doors.

290 for a 767-300 equipped with 3 pair Type A and 1 pair Type III doors.

351 for a 767-300 equipped with 3 pair Type A and 1 pair Type 1 doors.

375 for a 767-400
 
Tod
Posts: 1709
Joined: Sat Aug 28, 2004 6:51 am

RE: Why So Few Exits?

Tue Aug 11, 2009 5:35 pm

For other Type Certificate Data Sheets, see the link below:

http://www.airweb.faa.gov/Regulatory...keModel.nsf/MainFrame?OpenFrameSet

Tod

Who is online

Users browsing this forum: Google [Bot] and 7 guests