Cubsrule
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Overwing Evacuation Question

Mon May 12, 2008 1:31 pm

On aircraft with overwing exits and no slides (e.g. CRJ, DC-9 variants, 737, etc.), if the flaps are not able to be lowered all the way, is it permissible to use the overwing exits anyway?
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A10WARTHOG
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RE: Overwing Evacuation Question

Mon May 12, 2008 1:40 pm

CRJ and ERJ wing roots set low enough it would not be a problem.
 
Cubsrule
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RE: Overwing Evacuation Question

Mon May 12, 2008 1:43 pm



Quoting A10WARTHOG (Reply 1):
CRJ and ERJ wing roots set low enough it would not be a problem.

I figured that, and they might be on -9s (and progeny) too, but they certainly aren't on 737s.
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EMBQA
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RE: Overwing Evacuation Question

Mon May 12, 2008 7:46 pm

Quoting Cubsrule (Thread starter):
if the flaps are not able to be lowered all the way, is it permissible to use the overwing exits anyway?

If you're given a reason to be going out the over wing exit.... trust me... you'll be motivated enough to do what ever it takes to get away from the plane

Quoting Cubsrule (Reply 2):
but they certainly aren't on 737s.

A 737 would be fine as well as the wing is really not that high off the ground. Looking at the drawings on the Boeing web site... and some pictures of people working around a 737 as scale.. I'd say its about 6ft at the trailing edge.

[Edited 2008-05-12 12:59:52]
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Cubsrule
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RE: Overwing Evacuation Question

Mon May 12, 2008 9:14 pm



Quoting EMBQA (Reply 3):

If you're given a reason to be going out the over wing exit.... trust me... you'll be motivated enough to do what ever it takes to get away from the plane

 checkmark But I know that evacuation checklists for pilots have flap extension on them... I'm curious what (if anything) the checklists say if the flaps cannot be extended.
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Markhkg
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RE: Overwing Evacuation Question

Wed May 14, 2008 5:48 am

Incidentally activation of the overwing slide on the B757/B767 automatically lowers the inboard spoilers if they are still deployed in the upright position.
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jetmech
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RE: Overwing Evacuation Question

Wed May 14, 2008 6:01 am



Quoting Markhkg (Reply 5):

Apparently on the 767, the spoiler lowering is accomplished using an explosive squib. I wonder if the 757 is similar?

Regards, JetMech
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pilotpip
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RE: Overwing Evacuation Question

Wed May 14, 2008 6:27 pm

The evacuation route on the ERJ is over the leading edge anyway.
DMI
 
Cubsrule
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RE: Overwing Evacuation Question

Wed May 14, 2008 7:03 pm



Quoting Pilotpip (Reply 7):
The evacuation route on the ERJ is over the leading edge anyway.

The ERJ does have leading edge devices, though, right?
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pilotpip
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RE: Overwing Evacuation Question

Wed May 14, 2008 8:18 pm

Nope.

It has VGs and vortillions but those are well outboard.
DMI
 
Bellerophon
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RE: Overwing Evacuation Question

Wed May 14, 2008 8:41 pm

Cubsrule

...I know that evacuation checklists for pilots have flap extension on them...

Some may, but none of the various passenger jet aircraft I've flown has had any mention of extending flaps on the evacuation checklist!

On most of them, the overwing door slides would have facilitated the egress of the passengers, and one type didn't have any flaps to lower anyway!  Wink

Evacuation checklists generally tend to focus on setting the park brake, shutting the engines down, ordering the evacuation and, should circumstances permit, telling ATC.

EMBQA has it spot on. If it is deemed necessary to evacuate an aircraft, use the nearest available exit, and if that happens to be an overwing exit, don't ignore it just because the flaps aren't fully out.

I can promise you I wouldn't!

Remember that the Captain is always the last flight crew member to leave the aircraft.
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....as I hit the slide ahead of my F/O, he automatically becomes Captain! Big grin


Best regards

Bellerophon
 
EMBQA
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RE: Overwing Evacuation Question

Wed May 14, 2008 9:51 pm



Quoting Bellerophon (Reply 10):
I can promise you I wouldn't!

I was flying cockpit jumpseat once and told during the egress brief..."....if you're slow you'll be a foot stool...."
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Viscount724
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RE: Overwing Evacuation Question

Wed May 14, 2008 11:43 pm

Overwing exits are one thing you don't have to worry about on the BAe146/Avro RJ.  Smile


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They have no window exits, just the forward and rear passenger and galley service doors.
 
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HAWK21M
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RE: Overwing Evacuation Question

Thu May 15, 2008 6:17 am



Quoting JetMech (Reply 6):
Apparently on the 767, the spoiler lowering is accomplished using an explosive squib. I wonder if the 757 is similar?

No such Mechanism on the B752.
regds
MEL
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longhauler
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RE: Overwing Evacuation Question

Thu May 15, 2008 1:41 pm



Quoting Bellerophon (Reply 10):
Some may, but none of the various passenger jet aircraft I've flown has had any mention of extending flaps on the evacuation checklist!

The B737 and the E190 series aircraft I have flown include it in the checklist, no others.

Not just the evacuation drill, but also the rejected takeoff drill.
In fact, in any occurrence where an evacuation is a possibility, the First Officer is expected to extend the flaps.
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roseflyer
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RE: Overwing Evacuation Question

Thu May 15, 2008 2:30 pm



Quoting EMBQA (Reply 3):
A 737 would be fine as well as the wing is really not that high off the ground. Looking at the drawings on the Boeing web site... and some pictures of people working around a 737 as scale.. I'd say its about 6ft at the trailing edge.

The drop from a 737 is the maximum distance permissable by the FAA and various regulatory agencies. The 737 engines cowling does not have a circular outer diameter because the engine is so low to the ground. It needed the extra clearance by not being circular. Boeing has looked at going to a taller gear, but that would require evacuation sildes from the overwing exit, which would definitely add weight and that's not something that Boeing wants to do at all since all that equipment would be hundreds of pounds. A taller gear would also require a lot of modifications expecially in the forward wheel well since the pressure bulkhead would have to be moved. So the 737 is at the max allowed now.
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BAE146QT
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RE: Overwing Evacuation Question

Thu May 15, 2008 5:41 pm



Quoting RoseFlyer (Reply 15):
The drop from a 737 is the maximum distance permissable by the FAA and various regulatory agencies.

I agree with EMBQA though. Imagine you're on a decapitated 747 slewed off the runway at Tenerife.

"But the FAA says we can't do this!"
"The who now? Oh. Um, yeah... you've got a point there. Guess we better burn then. Still at least it's warm."

To be fair, the OP asks whether it is permissable, not, "is it permissable as part of certification". And on a crashed aircraft, absent an instruction by the crew I'd be using that overwing exit as a last resort, not knowing the state of the engines or fuel tanks.
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PGNCS
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RE: Overwing Evacuation Question

Thu May 15, 2008 6:13 pm



Quoting Markhkg (Reply 5):
Incidentally activation of the overwing slide on the B757/B767 automatically lowers the inboard spoilers if they are still deployed in the upright position.

The 767 does have this feature; the 757 does not.
 
Cubsrule
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RE: Overwing Evacuation Question

Thu May 15, 2008 6:56 pm



Quoting BAe146QT (Reply 16):
To be fair, the OP asks whether it is permissable, not, "is it permissable as part of certification".

Well, AFAIK, normal flap operation is assumed as part of the evacuation tests... all 'functional' exits are functioning normally. Whether or not that's a good test is a different question.
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BAE146QT
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RE: Overwing Evacuation Question

Thu May 15, 2008 8:09 pm



Quoting Cubsrule (Reply 18):
Well, AFAIK, normal flap operation is assumed as part of the evacuation tests... all 'functional' exits are functioning normally. Whether or not that's a good test is a different question.

Exactly, Cubs. I wasn't saying that Rose was wrong, just that the real world doesn't have the damned common courtesy to act like FAA tests expect. Manchester airport probably has a few ghosts who feel the same.

Isn't there someone here whose .sig block says something like, "regulations are made of paper and do a poor job of preventing flesh from meeting the earth"?
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KELPkid
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RE: Overwing Evacuation Question

Thu May 15, 2008 8:33 pm



Quoting BAe146QT (Reply 19):
Isn't there someone here whose .sig block says something like, "regulations are made of paper and do a poor job of preventing flesh from meeting the earth"?

Close  Wink
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KELPkid
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RE: Overwing Evacuation Question

Thu May 15, 2008 8:39 pm



Quoting Cubsrule (Reply 18):
Quoting BAe146QT (Reply 16):
To be fair, the OP asks whether it is permissable, not, "is it permissable as part of certification".

Well, AFAIK, normal flap operation is assumed as part of the evacuation tests... all 'functional' exits are functioning normally. Whether or not that's a good test is a different question.

I've heard, more than once, that in quite a few real-world evacuations, the overwing exits were never opened...it would be interesting if anyone has compiled statistics on that.

It makes sense to me, actually, since in 99% of all airliners, the wing is a huge fuel tank, and in probably 70-80% of those, underneath those fuel tanks is a really good source of heat, and in the case of an accident, probably open flame too  flamed  I could see where the cabin crew, at least, would be hesitant to open the overwing exits unless absolutely necessary.

You've got to love the exit row passenger safety cards, that say, in Ikeaspeak (you know, the iconographic language used on your new coffee table or bookshelf purhased at Ikea  Wink ), look for fire and wreckage outside the window before popping the emergency exit  Smile
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roseflyer
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RE: Overwing Evacuation Question

Thu May 15, 2008 10:18 pm



Quoting BAe146QT (Reply 19):

Isn't there someone here whose .sig block says something like, "regulations are made of paper and do a poor job of preventing flesh from meeting the earth"?

As someone who designs airplane parts and works around planes for a living, the regulations are what we build to. The certification requirements for an airplane don't just set guidelines, but are requirements. I acknowledge that if someone is able to jump 6ft and get away from the plane, then they probably won't break both legs and be paralyzed if they have to jump 6ft 1inch, but those are the regulations and we follow them. Without some overarching policy, then we would have nothing to design towards. I know that there's no super pilot out there who is going to stomp on the brakes with 150lbs of force, but they still have to be designed to take that load, but don't worry because no one will ever exert 151lbs of force on the rudder pedals.

Now parts are also designed for reality. We don't follow rules like the Titanic by not having enough equipment to save everyone, but things are designed with safety in mind. FMEA is done on most parts to evaluate the associated risks.
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KELPkid
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RE: Overwing Evacuation Question

Thu May 15, 2008 11:33 pm

Quoting RoseFlyer (Reply 22):
I know that there's no super pilot out there who is going to stomp on the brakes with 150lbs of force, but they still have to be designed to take that load, but don't worry because no one will ever exert 151lbs of force on the rudder pedals.

I could do it, but only on one pedal at a time   I'd have to stand up and put all my weight on the pedal...

I'd hate to see the results of a 302 lb. pilot standing up and putting his entire weight on both brakes  Wow!

Of course, I'm sure that RoseFlyer, being a good engineer, probably erred on the side of caution and designed the parts to 110% of the specified force... 

EDIT: along these lines, I've heard from a former US customs pilot that in the Convair 580, holding rudder against a dead engine in an engine-out requires every single once of strength from both the captain and the first officer.

[Edited 2008-05-15 16:36:33]
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roseflyer
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RE: Overwing Evacuation Question

Fri May 16, 2008 12:04 am



Quoting KELPkid (Reply 23):
Of course, I'm sure that RoseFlyer, being a good engineer, probably erred on the side of caution and designed the parts to 110% of the specified force...

Nope, we don't design parts for 110% of specified force. We design them for the requirements. There isn't a cushion built in. If there was a 10% cushion on all the parts, think of how much extra weight you'd be flying around. Airplanes don't have tolerances like that. If the part is supposed to have an ultimate tensile strength of 150lbs, then we'll get as darn close to 150lbs as possible while making sure that 95%, 98.7%, 99.8% (or whatever spec you are using) of the parts will meet the requirement.

Now, for wing loading for example needs to be 150% of maximum load. Theh 777 wing made it to 154% of maximum load before it failed. Extra tolerance is not done. If we did, you wouldn't get off the ground.
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BAE146QT
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RE: Overwing Evacuation Question

Fri May 16, 2008 5:01 pm



Quoting KELPkid (Reply 20):
Close Wink

Ahh, thank you.  Smile

Quoting RoseFlyer (Reply 22):
As someone who designs airplane parts and works around planes for a living, the regulations are what we build to.

I absolutely understand - really I do, because yours is not the only industry to do so. And as you point out, the reasons are obvious - you build to be safe and legally compliant, yet efficient. Those rules will be determined partly by operating costs, partly by material tolerances, partly by political lobbying and partly by averaging out what people can take, I should think. As I said in Post 19, you can make a regulation, and you can build to it, but people have a fascinating habit of defying regulations when they have to.

One last note: Hopefully the Pinto is something that can't happen again.

Quoting RoseFlyer (Reply 24):
If the part is supposed to have an ultimate tensile strength of 150lbs, then we'll get as darn close to 150lbs as possible

Did you know that the US DOH&HS has guidelines for exactly how much cattle faeces and insect remains are allowed to be present in ground beef? There used to be a rumour that the chop-shops employed QA inspectors to ensure that exactly that amount of crap and bugs were present. Obviously I don't believe that.
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