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Buyantukhaa
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Pros And Cons Of 737NG Overwing Exit Design

Thu May 21, 2009 11:55 pm

This came up in another thread - it seems to me that the 737NG hatch-type overwing emergency exit design is much safer, as it does not require one to lift a 25kg door in a life-or-death situation, probably works much faster and might thus save lives.

On the other hand, this type of door might not be a plug-type door, risking accidental opening in flight. Was there ever such an issue with this door type in practice?

(meanwhile I read http://www.airliners.net/aviation-forums/tech_ops/read.main/167414/ on the 737NG lock mechanism)

So I wonder, if accidental opening is not an issue with this door, the safety gains are obvious (even if there presumably is a slight weight penalty) and perhaps this type of door should be made mandatory from now on? As overwing exits may not always have FAs sitting next to them, this would reduce the passengers' survival on the skills of whoever sits there (even if they have been properly selected and briefed by the crew).

What are your thoughts on this?
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tdscanuck
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RE: Pros And Cons Of 737NG Overwing Exit Design

Fri May 22, 2009 12:26 am



Quoting BuyantUkhaa (Thread starter):

On the other hand, this type of door might not be a plug-type door, risking accidental opening in flight.

Although this is a risk that a plug-type door doesn't have, most cargo doors aren't plug-type, so we've already accepted, and mitigated, that risk as far as aircraft design goes.

Quoting BuyantUkhaa (Thread starter):
This came up in another thread - it seems to me that the 737NG hatch-type overwing emergency exit design is much safer, as it does not require one to lift a 25kg door in a life-or-death situation, probably works much faster and might thus save lives.

I'm not sure that it really translates to increased safety. In the adrenaline of a life-or-death situation, I don't think anyone who's allowed to sit in an exit row will have any problem with the door weight. Your major risk, I suspect, is panic/freeze-up of the person by the door, but that will impact you no matter what type of door you have.

Tom.
 
m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Fri May 22, 2009 12:34 am

I think its a great safety improvement. All you have to do is pull down on the handle (almost anyone can do that) and the exit is already open, in the proper open position, and ready for use. No more throwing it out of the aircraft or trying to toss it over a row of seats in a crowded, hectic, cabin where people are likely to be screaming at you and crowding your space trying to get out. Exit row procedures on non 737NG aircraft IMO are incredibly flawed. More than half the people that sit there don't read the safety card, ignore F/A safety instructions, and don't know what to do. Not only that, on aircraft with round rafts, pax seated at the exits would be required to get everyone out of the aircraft, retrieve the raft from the overhead bin or ceiling compartment, drag it out onto the wing, and deploy it.

The new 737NG exit is a step in the right direction but more needs to be done about exit rows. Thank God there hasn't been a life threatening emergency evacuation of a CRJ or ERJ with only 1 F/A recently. That sole F/A has no way of opening both doors and then fighting their way down the aisle to assist at the over wing exits, which are the closest exits for about 75% of passengers. Quick opening of the exit is also extremely important on these types of aircraft since there are no aft exits and if the over wing area starts on fire, the passengers in the back of the plane would be trapped. So, in a dream world all over wing window exits would be converted to the type found on the 737NG.
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PGNCS
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sat May 23, 2009 3:25 am



Quoting Tdscanuck (Reply 1):
Quoting BuyantUkhaa (Thread starter):

On the other hand, this type of door might not be a plug-type door, risking accidental opening in flight.

Although this is a risk that a plug-type door doesn't have, most cargo doors aren't plug-type, so we've already accepted, and mitigated, that risk as far as aircraft design goes.

Of course passengers don't have access to the controls for cargo doors in flight, either.

Quoting Tdscanuck (Reply 1):
I'm not sure that it really translates to increased safety. In the adrenaline of a life-or-death situation, I don't think anyone who's allowed to sit in an exit row will have any problem with the door weight. Your major risk, I suspect, is panic/freeze-up of the person by the door, but that will impact you no matter what type of door you have.

I think you are correct that panic and freezing up are much bigger contributors to the evacuation than the specifics of the exits. For an eminently readable new book germane to the subject, I highly recommend Amanda Ripley's "The Unthinkable."

Incidentally, I know there are people here who specialize on the maintenance end of the 737 world who insist that the 737NG overwing exit actually is a plug door. I only flew the 737 classic, so I have no specifics about the NG door, so confirmation of this would be welcome.

As anyone who knows my views realizes I am not a promoter of the 737, but in this case it does seem to me that the NG design is a major improvement over other overwing doors, perhaps at the expense of added complexity (again, a MX type could clarify that issue.) I do think the NG door is a step in the right direction; I understand it was required by the British as a requirement for certification. (If so then jolly good job!) I have no problem giving credit where credit's due, and it seems that Boeing deserves the credit here.
 
Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 1:37 am

Overwing plug style doors have been plagued with human factors problems since their creation. But as they say sarcastically in the industry, it takes a tragedy for change to happen.

One key incident is the Manchester Air Disaster, when it took 45 seconds at one exit for it to be opened. The woman seated there did not know how to intuitively use the exit, and attempted to pull the armrest. Worse, when the OWE was finally opened, it fell onto the passenger who was not aware of its weight. Strikingly, a passenger ended up dying in the same OWE when he got lodged in it -- something that a gullwing-style exit probably wouldn't have been able to solve either.

http://www.aaib.gov.uk/cms_resources/8-1988%20G-BGJL.pdf

The new, self-disposing style exits have some great benefits:
- The cabin crew briefing is much shorter because it is far more intuitive. "Pull down on the Red Handle and let go", versus having to explaining far more steps
- There is no need to worry about the heavy weight of the exit or the bulkiness of the hatch
- There is no need to worry about disposing the hatch. The hatch interfering with exiting (laying on the floor, on the wing, etc.) is a constant concern for regulators so they do impede exits.

I've had to open one for training and it was pretty awesome. The only downside from a rescue point of view is that for ARFF crews they better know to put their leg in front of them or they could get a hatch into the face while trying to open the hatch.

In fact, the EASA is so impressed with the self-disposing design they may make it mandatory. The FAA may also follow in making it required. The C-Series Bombadier aircraft will use a self-disposing design in response to these new requirements.

http://www.flightglobal.com/articles...-easa-with-aircraft-exit-rule.html

http://www.aviationweek.com/aw/gener...?channel=comm&id=news/BOM03249.xml

From a real-world perspective though, we haven't had a real chance to see if the overwing exit design has made a huge difference on a major accident. The Turkish airlines crash didnt't have a post-crash fire. As far as I can tell, all passengers on the China Airlines 120 Flight left by slides and not the overwings (Good decision, by the way!). I'm pretty confident that the self-disposing type will make a big difference in a future emergency, but thankfully we haven't seen it in full use yet.
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AirframeAS
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 4:16 am

Not to hijack the thread, but it would be real nice of Airbus would put the same type of overwing exits that the 737NG's feature on the A320 family.
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Ps76
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 11:26 am

Hi,

Apologies if slightly off topic but was just wondering if the exit does open outwards is it locked from the flight deck or automatically? What is there to stop it being accidentally opened during flight?

Any info welcome.

Many thanks,

Pierre.
 
Tristarsteve
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 11:52 am



Quoting AirframeAS (Reply 5):
Not to hijack the thread, but it would be real nice of Airbus would put the same type of overwing exits that the 737NG's feature on the A320 family.

Agreed. But the old grandfather rights raise their head again. A320 certified with throw out exits and can keep them for ever.

Same applies to the B737. The four doors have no emergency opening bottles, and manually attached escape slides. Both features were made redundant around 1980, but new B737 still have them.
With most doors, opening them in emergency mode is easier than in normal. On the B737 its harder. As you manually push the door open (which is hard anyway!) you have to pull the escape slide out of its canister.
 
tdscanuck
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 3:27 pm



Quoting TristarSteve (Reply 7):
On the B737 its harder. As you manually push the door open (which is hard anyway!) you have to pull the escape slide out of its canister.

How's that work? The 737 doesn't have a girt bar?

Tom.
 
Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 5:26 pm

The B737 is one of the few modern "next generation" narrow body aircraft that doesn't have a power assist on the floor level exits, which is what TSS was getting at. The 737 has a girt bar, but no electrical or pneumatic emergency assist unlike the A320 , the E-170, etc. So it's all you as you attack the door with your body weight to push it open.

Actually the BAe-146 is kind of famous for having incredibly difficult doors to open in the R2/L2 when it's on an angle. Again, no power assist. I'm trying to find a citation on this but it I think this problem was identified during an actual evacuation.
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Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 5:39 pm

Here's a case where a BAe-146 aircraft had difficulty with the rear doors because of the hinged towards-rear opening design.
http://www.haverikommissionen.se/virtupload/news/rl2006_20e.pdf
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Tristarsteve
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 5:54 pm



Quoting Tdscanuck (Reply 8):
Quoting TristarSteve (Reply 7):
On the B737 its harder. As you manually push the door open (which is hard anyway!) you have to pull the escape slide out of its canister.

How's that work? The 737 doesn't have a girt bar?

Tom.

Sorry I put it badly.
The brand new B737 has a girt bar, but the cabin crew must kneel down and attach it to the floor.
In emergency, the door is opened as usual, but now the girt bar has the slide attached to it. So the force to open the door is greater than normal, until the slide has left the canister and dropped out. There was an incident on Ryanair a few years ago when the cabin crew tried to open the door, met the increased force, and gave up thinking the door was jammed!
Just about every other airliner has less force when opening the door in emergency, because there is some sort of air powered assistance, or in the case of the Tristar and B767 the door whizzes up into the ceiling as the weight of the slide is removed.
 
AirframeAS
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 24, 2009 6:47 pm



Quoting TristarSteve (Reply 7):
Agreed. But the old grandfather rights raise their head again. A320 certified with throw out exits and can keep them for ever.

The Enhanced A320 can add these types of exits and still maintain the type certificate and still grandfather it over.
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Buyantukhaa
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RE: Pros And Cons Of 737NG Overwing Exit Design

Mon May 25, 2009 11:40 am



Quoting Markhkg (Reply 4):
In fact, the EASA is so impressed with the self-disposing design they may make it mandatory. The FAA may also follow in making it required.

Very interesting. So that confirms my original thought, that this design has such safety advantages that regulators may make it mandatory.

The most recent EASA document I could find is this one:

http://www.easa.eu.int/ws_prod/r/doc/NPA/NPA%202008-04.pdf

It says "In addition, instead of the conventional Type III exit design incorporating a removable hatch, an Automatically Disposable Hatch (ADH), is required for aeroplanes with a passenger seating configuration of 41or more."

Quoting AirframeAS (Reply 5):
Not to hijack the thread, but it would be real nice of Airbus would put the same type of overwing exits that the 737NG's feature on the A320 family.

I agree. Given that the 737 and 320 series are the most popular passenger jets, having this type of exit on both would already have quite an impact on the total aircraft population (over time, of course).
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BEG2IAH
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RE: Pros And Cons Of 737NG Overwing Exit Design

Tue May 26, 2009 1:35 am

I had two questions regarding the overwing exits.

I have recently flown multiple times on CO B738s sitting in the exit row (12). One time it was really cold next to that exit. Is it possible that there was a very small air leak, enough to make the immediate surroundings pretty cold?

And second question - on the latest flight as we descended and ambient temps increased there was a lot of moisture coming down from the top of the emergency exit. I would say the leak was worth a full cup. And it wasn't raining outside.   Are these exits tightly closed?

It amazes me that you're aloud to put your smaller carry-on luggage below the seat in front of you, although it's the exit row. I wasn't allowed to have a small (4"x5") case in my hands on Air France A319 earlier this month (exit row, I think it was 10), let alone anything below the seat in front of me.

BEG2IAH

[Edited 2009-05-25 18:38:00]
 
tdscanuck
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RE: Pros And Cons Of 737NG Overwing Exit Design

Tue May 26, 2009 3:28 am



Quoting BEG2IAH (Reply 14):

I have recently flown multiple times on CO B738s sitting in the exit row (12). One time it was really cold next to that exit. Is it possible that there was a very small air leak, enough to make the immediate surroundings pretty cold?

It's possible there was a small leak (no airliners are airtight) but, if there way, it wouldn't make it colder. The pressure differential would ensure that any air was moving out through the exit, not in, so you'd still be getting ambient cabin air.

That said, the exit wall is often cold because, thanks to the structure to support the exit, there's less insulation in there. I've gotten frost on the inside wall near an exit before.

Quoting BEG2IAH (Reply 14):
And second question - on the latest flight as we descended and ambient temps increased there was a lot of moisture coming down from the top of the emergency exit. I would say the leak was worth a full cup. And it wasn't raining outside. Are these exits tightly closed?

They should be drip-tight. It's much more likely that you were getting condensation from the inside surface of the skin, rather than outside moisture.

Tom.
 
DfwRevolution
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RE: Pros And Cons Of 737NG Overwing Exit Design

Tue May 26, 2009 3:30 am



Quoting BEG2IAH (Reply 14):
I have recently flown multiple times on CO B738s sitting in the exit row (12). One time it was really cold next to that exit. Is it possible that there was a very small air leak, enough to make the immediate surroundings pretty cold?

No, a leak would be a very serious problem. What is likely the case is the emergency hatch lacks the same insulation as the standard blankets located behind the cabin trim for normal seating rows.
 
BEG2IAH
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RE: Pros And Cons Of 737NG Overwing Exit Design

Tue May 26, 2009 3:37 am



Quoting Tdscanuck (Reply 15):
That said, the exit wall is often cold because, thanks to the structure to support the exit, there's less insulation in there.



Quoting DfwRevolution (Reply 16):
No, a leak would be a very serious problem. What is likely the case is the emergency hatch lacks the same insulation as the standard blankets located behind the cabin trim for normal seating rows.

Thanks, guys. This makes perfect sense.

BEG2IAH
 
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HAWK21M
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RE: Pros And Cons Of 737NG Overwing Exit Design

Tue May 26, 2009 7:52 am



Quoting BEG2IAH (Reply 14):
It amazes me that you're aloud to put your smaller carry-on luggage below the seat in front of you, although it's the exit row. I wasn't allowed to have a small (4"x5") case in my hands on Air France A319 earlier this month (exit row, I think it was 10), let alone anything below the seat in front of me.

As long as its not in the way to delay/prevent an emergency evacuation.
Out here no luggage on the floor near the EE seats.

regds
MEL.
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BEG2IAH
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RE: Pros And Cons Of 737NG Overwing Exit Design

Tue May 26, 2009 2:46 pm



Quoting HAWK21M (Reply 18):
As long as its not in the way to delay/prevent an emergency evacuation.
Out here no luggage on the floor near the EE seats.

Maybe it has to do with the fact that there is far more space in the exit row on CO's compared to AF's aircraft. Could be eating habbits in this country.  Smile

BEG2IAH
 
m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sat May 30, 2009 9:11 pm

What commands do F/As give to exit row passengers in the event of an unplanned emergency evacuation? All the F/A training videos i've seen show nothing about yelling or shouting commands to exit row passengers in the event of an unplanned evac.

I think the airline industry is relying to much on able bodied passengers instead of trained professionals for safety. Personally, I think that 1F/A for 50 pax is way to low. It should be 1F/A for 40 pax like Canada and Australia require with at least one seated in the vicinity of the over wing exit rows. There were only six F/As required on AF358 when it crashed in Toronto but because of the service required on that flight nine F/As were onboard. The accident report stated that had their only been six F/As on that plane, which would have required some F/As to be responsible for two exits, the outcome probably wouldn't have been as good as it was. TWA 843 also was only required to have 6 F/As but there were a total of 14 F/As onboard because there were IIRC five F/As dead heading. The FAA said that if there hadn't been so many F/As onboard the evacuation probably wouldn't have been so successful. I'm getting off topic here but I thought this was important information.
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Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 31, 2009 1:02 am



Quoting M11Stephen (Reply 20):
What commands do F/As give to exit row passengers in the event of an unplanned emergency evacuation

As usual, it depends on carrier to carrier, but I have heard, "YOU AT THE EXIT ROW! OPEN THOSE EXITS!" As you noted, many carriers do not have specific commands and instead rely on the preflight briefing.

One major US carrier has the available F/A get out the jumpseat, approach the overwings shouting "OUT OF MY WAY" , followed by "OPEN THAT EXIT" and then "OUT OF THOSE SEATS".

I saw a video of a Delta Flight Attendant commanding a passenger on how to open the overwing. It's in a cute youtube video of a Time news writing going to Flight Attendant school.

http://www.youtube.com/watch?v=ICabEHU5_VY&feature=channel_page

Quoting M11Stephen (Reply 20):
The FAA said that if there hadn't been so many F/As onboard the evacuation probably wouldn't have been so successful.

There are a lot of similarities between this accident and the L-1011 TWA Flight 843, which had like 5 deadheading flight attendants on board in addition to the usual complement. Fascinating website by one of the flight attendants who was on that flight: http://www.twaflight843.com/

Cranfield University in a hallmark study involving competitive evacuation showed that one key factor in timely evacuation is assertive cabin crew. Cabin crews help prevent flow problems, bottlenecks, re-direct passengers to dried up exits and increase overall evacuation speed.
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m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 31, 2009 1:54 am



Quoting Markhkg (Reply 21):
Cranfield University in a hallmark study involving competitive evacuation showed that one key factor in timely evacuation is assertive cabin crew. Cabin crews help prevent flow problems, bottlenecks, re-direct passengers to dried up exits and increase overall evacuation speed.

Definitely, F/As have proven that time and time again they are the key factor to a successful evacuation. I still doubt that 2 F/As can successfully evacuate 100 pax within 90 seconds and supervise the opening of six exits. (I'm using the E190 as an example) It would be interesting to see what the evacuation time of an aircraft would be with some F/As responsible for 2 exits like a typical 737 has vs. an evacuation with one F/A seated in the vicinity of the over wing exit rows and each door manned by an F/A.

On US1549, the F/A in the back was responsible for two exits (I'm not blaming the F/A in the back) and because there was only one F/A back there a passenger attempted to open an exit door that shouldn't have been opened because the door was below the water line. This may have been a contributing factor to the back of the airplane sinking so quickly. I can't help but think that this situation may have been averted had there been two F/As in the back, one for each doors. But, unfortunately, like many other things in the airline industry, money is more important than safety so I doubt that the 1F/A per 50 pax rule will ever change. If anything we may start seeing two F/As for 150pax...

Thank you Mark for the information concerning exit rows, I never knew about F/As yelling commands. I also never knew cabin safety could be so interesting!  Smile
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WNCrew
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 31, 2009 2:15 am

At the carriers I've worked for the OWWE was always a "secondary exit. You open the doors first as the pax flow-rate is higher there... then if you're able you move to the OWWE. Once there we either open the exit, or direct pax to do so and then command: COME THIS WAY- THIS WAY OUT- LEAVE EVERYTHING- STEP OUT!

I highly doubt that a FA, on a single-aisle aircraft, would ever make it from the front of the aircraft to the OWWE during an evacuation (in our case there are two FA's up front) and be able to open the exits AFTER having initiated an evac, opened their own primary exits etc. Pax will likely have already opened the exits.
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Viscount724
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 31, 2009 2:34 am



Quoting M11Stephen (Reply 20):
TWA 843 also was only required to have 6 F/As but there were a total of 14 F/As onboard because there were IIRC five F/As dead heading. The FAA said that if there hadn't been so many F/As onboard the evacuation probably wouldn't have been so successful.

That also reminds me of the Overseas National Airways DC-10-30 crash at JFK in 1975. It struck a flock of seagulls during the takeoff roll on a positioning flight to JED via FRA (they were probably operating Hajj charters). The #3 engine ingested some of the seagulls and disintegrated causing a fire. Takeoff was rejected but the aircraft overran, the gear collapsed, and the fire spread quickly. All 139 on board were trained ONA crewmembers. The report said that may have been a factor in the successful evacuation. There were only 2 serious injuries and a few minor. It may well have been much worse with a full load of regular passengers.
http://aviation-safety.net/database/record.php?id=19751112-1


 
Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 31, 2009 8:35 am



Quoting M11Stephen (Reply 22):
I also never knew cabin safety could be so interesting

If I may suggest a book to read. "Just In Case" by Daniel A. Johnson ISBN 0-306-41576-3
It's a little dated (1984...the most advanced aircraft in the book the A300...) but the information is fascinating. It's written by a researcher that worked for the Douglas Company, who later started an aircraft safety card company (Interaction Safety Corp). I actually wrote to him with a question one time and he very kindly responded.

The book is filled with great anecdotes of emergency research he did during his time at the Douglas Company.
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m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sun May 31, 2009 6:45 pm



Quoting Markhkg (Reply 25):
If I may suggest a book to read. "Just In Case" by Daniel A. Johnson ISBN 0-306-41576-3

I just ordered it off Amazon, thanks for the recommendation, I can't wait to read it!

Quoting WNCrew (Reply 23):
I highly doubt that a FA, on a single-aisle aircraft, would ever make it from the front of the aircraft to the OWWE during an evacuation (in our case there are two FA's up front)

I have a ExpressJet ERJ Safety Card and it says "In the event a crew member cannot make it to your row in the event of an emergency evacuation you may need to open the exit." As I was reading that I was like no s**t the sole F/A won't be able to make it past 30+ panicked passengers blocking the single aisle.
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m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Wed Jun 03, 2009 11:24 pm

I read an article about CO1404 and apparently a "bottle neck" was created because to many people were attempting to use the overwing exits. Luckily, an off-duty pilot was seated in the vicinity of the overwing exits who directed passengers to the full size doors.
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Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Thu Jun 04, 2009 6:49 am

It must have been so disorientating once the pax stepped onto the wing. Which way is front? Back? Which side do I slide off? Even though the exit path is painted on, the darkness/ice/smoke probably didn't help. One of the advantages I think the A320 and B-767 has is that overwing slide ramp that forces people down the correct side...


I keep hearing of stories of passengers evacuating towards the wingtips, and then realizing that winglet to ground distance isn't what the safety card was telling them to do. (Injuries result when people jump from the wingtips.)
Release your seat-belts and get out! Leave everything!
 
m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Thu Jun 04, 2009 5:19 pm



Quoting Markhkg (Reply 28):
It must have been so disorientating once the pax stepped onto the wing. Which way is front? Back? Which side do I slide off? Even though the exit path is painted on, the darkness/ice/smoke probably didn't help. One of the advantages I think the A320 and B-767 has is that overwing slide ramp that forces people down the correct side...


I keep hearing of stories of passengers evacuating towards the wingtips, and then realizing that winglet to ground distance isn't what the safety card was telling them to do. (Injuries result when people jump from the wingtips.)

Theres also the danger with turbo-props that passengers will attempt to jump off the wing to close to a prop if its still running and get injured. The same holds true for a jet still running. In that FR accident back in 2000 I think it was, a bunch of pax evacuated onto a wing with an engine burning and only went back and found another exit cause a fire fighter told them to do so.

My point is we need to stop relying on a 20 second briefing and a safety card that the majority of pax don't look to instruct pax on how to operate window exits. F/As are to far away in the event of an emergency to help pax at the over wing exits and during the panic and caos of it all they are likely to either freeze or open an exit when its unsafe or a "bottle neck" will be created because to many passengers will attempt to use them. These are all problems that an F/A seated at the over wing exit rows could help with.
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Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Thu Jun 04, 2009 8:47 pm

Evacuation dynamics are so interesting...humans are really the weakest link. Like how passengers will try to evacuate out the door which they came in. Or how people will hesitate at the slide or try to sit down first. Ultimately, the most important cabin safety feature on board aircraft is the flight attendant.
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m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Fri Jun 05, 2009 3:15 am



Quoting Markhkg (Reply 30):
Evacuation dynamics are so interesting...humans are really the weakest link. Like how passengers will try to evacuate out the door which they came in. Or how people will hesitate at the slide or try to sit down first. Ultimately, the most important cabin safety feature on board aircraft is the flight attendant.

Yeah, as the ONA accident proved, when everyone onboard is a F/A or when they're are an abundance of F/As onboard things go a lot smoother. Id love to know your opinion on this but 1 F/A per 50 Passengers, especially with a lot of them responsible for 2+ exits, isn't enough. All the extremely successful post-accident evacuations have had more than the minimum required amount of F/As or dead heading crew on board. AF358 had 9, TWA 843 had 9 plus 5 dead headers, and CO1404 had 3 plus a couple of dead heading flight crew.

Yes, US1549 was successful but doors were opened that shouldn't have been and lots of passengers were exiting without flotation devices. Also, if the aircraft hadn't been so close to land the slide/rafts would have been even more important meaning those at the rear doors would have had to been relocated to the forward doors and since those slides weigh close to 100lbs I'm sure at least 3 F/As would have been required... The three ladies on that flight did the best they could especially considering one of them was badly injured but I'm sure more F/As on that flight would have been extremely helpful.

I haven't been able to find a report of a regional jet or turbo prop being evacuated probably because there haven't been to many serious accidents involving those. Another danger with regional jets is that on a lot of them, 1/2 of the exits are located over fuel filled wings meaning those passengers in the back of the plane will have to go through the fire and exit with the rest of the passengers at the two forward exits. I know I'm being pessimistic and what if-ing but this is how future accidents are prevented. When AA had F100s with an identical exit and F/A seating configuration to CRJs and ERJs, F/As referred to it as the "Dutch Oven" and some F/As refused to fly on them because of the unsafe exit configuration.
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Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Fri Jun 05, 2009 8:48 pm



Quoting M11Stephen (Reply 31):
Id love to know your opinion on this but 1 F/A per 50 Passengers, especially with a lot of them responsible for 2+ exits, isn't enough.

It's pretty interesting since Transport Canada requires 1 flight attendant for every 40. But there is now talk about increasing it to 1:50 to meet "international standards". It's pretty sobering to think that after Air Canada Flight 797, the aviation world realized how important those 90 seconds before flashover occured. And Flight 797 wasn't even a full flight! As time has progressed, these lessons I think are sometimes being forgotten for economics.

Quoting M11Stephen (Reply 31):
US1549 was successful but doors were opened that shouldn't have been and lots of passengers were exiting without flotation devices

I am looking forward to reading the final NTSB report. There is a lot of speculation right now if the L1 door was damaged on impact, if there was a crazed passenger who tried to open it, or something. What I'm curious about is the configuration. Was the rear F/A in a swivel seat facing front or in an aft facing seat? (Might have changed the dynamics of stopping people from using those rear exits). Did anyone have problems opening the overwings? (There doesn't seem to be anything in the news regarding this. For whatever reason, I haven't heard of as many problems with the Airbus overwing hatches as I have with the MD-80s or Boeing Series).

I think it was pretty fortunate the slide ramps deployed - they're not designed to fill properly if they inflate under the water line- but they provided a nice platform away from the cold water. I don't think anyone thought to use the ditching lines, probably wouldn't have made a difference.

Quoting M11Stephen (Reply 31):
the rear doors would have had to been relocated to the forward doors

I have never heard of any emergency in which they were able to do this. I'm just stunned that the FAA still requires this as part of training. It's so unlikely to be used - and the danger of inflating a slide/raft during transport from one end of the aircraft to the other could be terrible. The process is also surprisingly involved...(even with those stenciled instructions). Definitely not something the crew will usually think to do when the engines stop turning.

Quoting M11Stephen (Reply 31):
I haven't been able to find a report of a regional jet or turbo prop being evacuated probably because there haven't been to many serious accidents involving those.

Not so much to do with evacuations but I think one really interesting case was Robin Fech on ASA Flight 529 (a EMB-120). Just one flight attendant was able to brief 26 passengers in under 7 minutes before the impact - she checked every single passenger could adopt the brace position and was yelling her commands till impact. And then she went into rescue mode. A true class act.
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Markhkg
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RE: Pros And Cons Of 737NG Overwing Exit Design

Fri Jun 05, 2009 9:35 pm



Quoting MarkHKG (Reply 32):
L1 door was damaged on impact

Whoops, I meant L2. Pardon the typo!
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m11stephen
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RE: Pros And Cons Of 737NG Overwing Exit Design

Sat Jun 06, 2009 7:09 am



Quoting MarkHKG (Reply 32):

Not so much to do with evacuations but I think one really interesting case was Robin Fech on ASA Flight 529 (a EMB-120). Just one flight attendant was able to brief 26 passengers in under 7 minutes before the impact - she checked every single passenger could adopt the brace position and was yelling her commands till impact. And then she went into rescue mode. A true class act.

She is truly a hero. She also helped rescue people on the ground even though she was badly injured herself. She showed what a HUGE responsibility single F/As on RJs and turbo props have... and how to successfully execute that responsibility.


In regards to US1549, the rear F/A was seated in the aisle swivel seat facing forward. I also thought that it was "creative" of the passengers to use the off-wing slide ramps... All exits above the waterline should be considered usable in a ditching, not just those with slide rafts at them. I know its ideal to get directly into a raft but when an aircraft is filling with water quickly, passengers should get out anyway they can and the diagram on safety cards should reflect that. I don't know if this is possible but I wonder if there could be some way to "mod" the over wing exit slides to allow them to be disconnected post ditching... There should also be a raft in the forward part of the cabin since the aft doors with slide rafts are most likely not going to be usable and therefore shouldn't be counted towards the aircraft's total slide raft requirement. As you stated, F/As are not going to have time or the strength to haul a 100 pound raft up through a sinking plane and deploy it from a usable door.

I know I'm way off subject here, and I apologize to the original poster for that lol.
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