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9G Bulkhead  
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Posted (8 years 4 months 3 weeks 2 days 21 hours ago) and read 4615 times:


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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


Think of the brighter side!
21 replies: All unread, jump to last
 
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3701 posts, RR: 34
Reply 1, posted (8 years 4 months 3 weeks 2 days 21 hours ago) and read 4610 times:
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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.


User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 2, posted (8 years 4 months 3 weeks 2 days 20 hours ago) and read 4591 times:

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.

User currently offlineIlikeyyc From United States of America, joined Dec 2003, 1373 posts, RR: 20
Reply 3, posted (8 years 4 months 3 weeks 2 days 18 hours ago) and read 4566 times:

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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User currently offline777MechSys From United States of America, joined Apr 2006, 350 posts, RR: 3
Reply 4, posted (8 years 4 months 3 weeks 2 days 18 hours ago) and read 4562 times:
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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


User currently offlineCorey07850 From United States of America, joined Feb 2004, 2527 posts, RR: 5
Reply 5, posted (8 years 4 months 3 weeks 2 days 18 hours ago) and read 4560 times:

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


User currently offlineIlikeyyc From United States of America, joined Dec 2003, 1373 posts, RR: 20
Reply 6, posted (8 years 4 months 3 weeks 2 days 17 hours ago) and read 4545 times:

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!
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 7, posted (8 years 4 months 3 weeks 2 days 16 hours ago) and read 4527 times:

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.


User currently offlineL-188 From United States of America, joined Jul 1999, 29799 posts, RR: 58
Reply 8, posted (8 years 4 months 3 weeks 2 days 14 hours ago) and read 4501 times:

It is simply what the certification standard calls for.


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User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 9, posted (8 years 4 months 3 weeks 2 days 3 hours ago) and read 4462 times:

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



Think of the brighter side!
User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 10, posted (8 years 4 months 3 weeks 2 days 2 hours ago) and read 4458 times:

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]

User currently offlineLotsamiles From United States of America, joined May 2005, 323 posts, RR: 0
Reply 11, posted (8 years 4 months 2 weeks 6 days 16 hours ago) and read 4378 times:

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


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1651 posts, RR: 1
Reply 12, posted (8 years 4 months 2 weeks 6 days 12 hours ago) and read 4351 times:

<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.


User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 13, posted (8 years 4 months 2 weeks 6 days 4 hours ago) and read 4318 times:

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


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 14, posted (8 years 4 months 2 weeks 3 days 21 hours ago) and read 4242 times:

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



Think of the brighter side!
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 15, posted (7 years 2 months 2 weeks 3 days 21 hours ago) and read 4068 times:

Do any Freighters have a higher 9G + Bulkhead or net Installed.Anyone aware.
regds
MEL



Think of the brighter side!
User currently offline113312 From United States of America, joined Apr 2005, 572 posts, RR: 1
Reply 16, posted (7 years 2 months 2 weeks 3 days 21 hours ago) and read 4063 times:

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.

User currently offlineDeltaGuy From , joined Dec 1969, posts, RR:
Reply 17, posted (7 years 2 months 2 weeks 3 days 21 hours ago) and read 4057 times:

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


User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 18, posted (7 years 2 months 2 weeks 3 days 2 hours ago) and read 3999 times:

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


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 19, posted (7 years 2 months 2 weeks 2 days 8 hours ago) and read 3923 times:

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



Think of the brighter side!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 20, posted (7 years 2 months 2 weeks 2 days 2 hours ago) and read 3907 times:

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."
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 21, posted (7 years 2 months 2 weeks 2 days 1 hour ago) and read 3901 times:

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

Exactly.
regds
MEL



Think of the brighter side!
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