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HAWK21M
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9G Bulkhead

Sun Apr 30, 2006 4:55 am


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Freighters are Equipped with a 9G bulkhead or 9G net.
Why 9G,not more.How was it decided that 9G resistant would be adequate.
Also the 9G bulkhead needs to be attached to reinforced Floor boards.Are there any other methods of Attachment.
BTW nice photoid number  Smile
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
VC-10
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RE: 9G Bulkhead

Sun Apr 30, 2006 5:15 am

Hawk,

As you say you are a Licensed Engineer I am surprised that you believe that the nets are attached to floorboards. They are attached to main a/c structure as are galley's & seats.
 
A/c train
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RE: 9G Bulkhead

Sun Apr 30, 2006 6:02 am

Hawk, maybe you havn't worked heavy maintenance and have not seen barrel nuts in floor structure, or have not locked a seat to a seat track floor beam. Must admit rather surprsing, I guess it all depends on what maintenance background you have. There are indeed holes for floor bushings in the composite floor boards which may make it seem like they are attached to just the floor boards.
 
ilikeyyc
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RE: 9G Bulkhead

Sun Apr 30, 2006 7:53 am

The aft wall in the CRJ that separates the cabin from the aft cargo is also known as the 9G wall. But since I'm new to Mx, I am curious as to what 9G means and how it got this name. Before this thread, I thought it was a term used only on the CRJ.
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777MechSys
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RE: 9G Bulkhead

Sun Apr 30, 2006 8:04 am

My understanding is that everything bolted, rivetted, screwed, or attached inside of an aircraft must be able to withstand 9Gs of force and not become unattached.

Just my understanding I could be way out in left feild on this one.

-Erick
 
corey07850
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RE: 9G Bulkhead

Sun Apr 30, 2006 8:07 am

Quoting Ilikeyyc (Reply 3):

Unless I'm completely off my rocker, it simply means the barrier is meant to withstand 9 G's (IE 9x the force of gravity)


And for Hawk, I believe they are rated at 9G's and not more simply because if you are experiencing over 9-G's you would be having much more serious problems than cargo passing through the net/wall (non-military aircraft of course)... Your guess is as good as mine as to why they chose the figure of 9
 
ilikeyyc
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RE: 9G Bulkhead

Sun Apr 30, 2006 8:49 am

Quoting Corey07850 (Reply 5):
Unless I'm completely off my rocker, it simply means the barrier is meant to withstand 9 G's (IE 9x the force of gravity)

That is what I inferred from Hawk's post. What had me puzzled is that 9g's of lets say a passenger's bag produces a different force than 9g's of an entire bin filled with bags. So 9g's of what?
Fighting Absurdity with Absurdity!
 
474218
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RE: 9G Bulkhead

Sun Apr 30, 2006 9:57 am

Quoting Ilikeyyc (Reply 6):
That is what I inferred from Hawk's post. What had me puzzled is that 9g's of lets say a passenger's bag produces a different force than 9g's of an entire bin filled with bags. So 9g's of what?

If an overhead bin has a maximum capacity, 60 pounds. It would have to be built to withstand a 540 pound load in the forward direction. 9 X 60 = 540.
 
L-188
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RE: 9G Bulkhead

Sun Apr 30, 2006 12:13 pm

It is simply what the certification standard calls for.
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HAWK21M
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RE: 9G Bulkhead

Sun Apr 30, 2006 11:01 pm

Quoting VC-10 (Reply 1):
As you say you are a Licensed Engineer I am surprised that you believe that the nets are attached to floorboards

Typo error I meant "Floor Beam"  Smile Sorry.Did not realise till I read the replies.

Quoting Corey07850 (Reply 5):
Unless I'm completely off my rocker, it simply means the barrier is meant to withstand 9 G's (IE 9x the force of gravity)

Thats correct.Why 9G not 8G or 10G is puzzling.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Tod
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RE: 9G Bulkhead

Mon May 01, 2006 12:03 am

Quoting Ilikeyyc (Reply 6):
So 9g's of what?

9G of the cargo container immediately aft of the bulkhead with failed restraints.

Quoting HAWK21M (Reply 9):
Why 9G not 8G or 10G is puzzling

Just the number the FAA picked for forward loads.
Forward loads on new seating has been increased to 16g.

Additional load requirements per 14CFR25.561:

Upward, 3.0g
Sideward, 3.0g on the airframe; and 4.0g on the seats and their attachments.
Downward, 6.0g
Rearward, 1.5g


Tod

[Edited 2006-04-30 17:09:45]
 
lotsamiles
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RE: 9G Bulkhead

Wed May 03, 2006 10:35 am

Quoting HAWK21M (Thread starter):
Also the 9G bulkhead needs to be attached to reinforced Floor boards.Are there any other methods of Attachment.

The 9G barrier is typically attached to a shear plate mounted to the floor beams that carries the load out to the fuselage skin. At the top there are fittings that carry loads out to doublers either inside or outside the skin, or sometimes stringers. The floorbeams are not able to take much in the way of fore/aft loads.

The cargo system restraints are rated for 3G so the 9G is intended to protect the crew in a very hard landing when the cargo system fails and everything moves forward into the barrier.

Best regards,
Lotsamiles
 
ThirtyEcho
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RE: 9G Bulkhead

Wed May 03, 2006 2:28 pm

<8G or 10G is puzzling.>>

That is because the most overbuilt aircraft of the post-WWII era, the Luscombe 8E, was certified to plus 9 or negative 3 Gs. It seemed to be the most stringent G loading requirement possible.

I soloed in an 8E, and it seemed like the only way to get to 9 Gs was to dive it into the ground, nosefirst. It was a lot of fun and I learned how to loop, spin and roll before my first solo.

Rumor has it that I did a loop in the traffic pattern on my first solo. Not true.
 
Tod
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RE: 9G Bulkhead

Wed May 03, 2006 10:04 pm

Quoting Lotsamiles (Reply 11):
At the top there are fittings that carry loads out to doublers either inside or outside the skin, or sometimes stringers.

Intercostals between multiple frames are also common structural attachments for rigid bulkheads.

Tod
 
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HAWK21M
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RE: 9G Bulkhead

Sat May 06, 2006 5:41 am

A Reason conveyed was that no human can survive beyond 9G,hence no point going higher.I don't know if that is true.
Anyone aware.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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HAWK21M
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RE: 9G Bulkhead

Thu Jul 05, 2007 4:46 am

Do any Freighters have a higher 9G + Bulkhead or net Installed.Anyone aware.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
113312
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RE: 9G Bulkhead

Thu Jul 05, 2007 4:57 am

I believe that 9G was an arbitrary value that the FAA and other certifying authorities applied many decades ago for stress on most attach points including seats and cargo restraints. However, experience has proven this number to be inadequate and now most seat structures and mounts are designed for greater crash-worthiness. The official standard for cargo barriers has not changed. A net at the forward end of a cargo compartment is a secondary restrain as most cargo is loaded into containers and those are locked to the floor with locks that have greater strength. Also, many all cargo aircraft use a rigid forward cargo barrier rather than the net systems.
 
DeltaGuy
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RE: 9G Bulkhead

Thu Jul 05, 2007 5:30 am

Quoting HAWK21M (Reply 14):
A Reason conveyed was that no human can survive beyond 9G,hence no point going higher.

People survive over 9 G's...question is, do they stay awake.

If 9G's was so deadly why would there be a coveted club for those who have reached it?  Wink

DeltaGuy
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Tod
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RE: 9G Bulkhead

Fri Jul 06, 2007 12:38 am

Quoting DeltaGuy (Reply 17):
People survive over 9 G's

 checkmark 

When considering G loads on people you also have to factor in the duration.

People have endured over a 100 G for milliseconds with less harm than 9 G for a few seconds.

Tod
 
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HAWK21M
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RE: 9G Bulkhead

Fri Jul 06, 2007 6:22 pm

Quoting DeltaGuy (Reply 17):
People survive over 9 G's...question is, do they stay awake.

If 9G's was so deadly why would there be a coveted club for those who have reached it



Quoting Tod (Reply 18):
When considering G loads on people you also have to factor in the duration

Why 9G, & not 10G,11G,12G.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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Starlionblue
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RE: 9G Bulkhead

Sat Jul 07, 2007 12:23 am

Quoting HAWK21M (Reply 19):

Why 9G, & not 10G,11G,12G.

Why not 7? The aircraft breaks earlier than that. But pulling Gs on the plane and impact on the net are not the same.

I guess they had to come up with a number and figured beyond that would be too expensive.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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HAWK21M
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RE: 9G Bulkhead

Sat Jul 07, 2007 12:59 am

Quoting Starlionblue (Reply 20):
But pulling Gs on the plane and impact on the net are not the same

Exactly.
regds
MEL
I may not win often, but I damn well never lose!!! ;)

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