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Can F-15s making 9G turns with payload?



 
 
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  #11  
Old September 18th 03, 10:33 PM
Ed Rasimus
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Chad Irby wrote:

In article ,
"José Herculano" wrote:

Maximum I read regarding the Phantom was a guy in Vietnam pulling 14 G to
get an ass-SAM divergence. The bird held and landed.


I know there were a couple of cases in Vietnam where F-4s made hard
enough turns to rip the ECM pods off...


Gotta wonder about that, since ECM pods were routinely carried in the
Sparrow missile wells. Can't imagine a situation in which the pods
suspension gear would fail. Don't say it couldn't, simply that I doubt
it.

In 250 combat missions, 150 over NVN where high threat evasions were
most likely, I never, not even once, heard of a structural failure nor
of an inadvertent separation of any piece of equipment off an
aircraft. I'm not saying it couldn't have, simply that I doubt it.

YMMV.

Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038
  #12  
Old September 18th 03, 10:34 PM
Gene Storey
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"Ed Rasimus" wrote

"The aircraft G-limits are only there in case there is another flight
by that particular airplane. If subsequent flights do not appear
likely, there are no G-limits."


They even include a chair where you can give it back to the taxpayers
anytime you like...


  #13  
Old September 18th 03, 10:38 PM
Gene Storey
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"Scott Ferrin" wrote

REad of a Skyray pulling 12 Gs and wrinked the wing. Don't know if it
ever flew again. And also of a Tomcat that did a NEGATIVE 8+ (they
didn't have a choice). I think the Tomcat flew again.


Humans aren't rated for -8 G's for over 1 second :-)


  #14  
Old September 18th 03, 10:57 PM
Chad Irby
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In article ,
Ed Rasimus wrote:

Chad Irby wrote:

I know there were a couple of cases in Vietnam where F-4s made hard
enough turns to rip the ECM pods off...


Gotta wonder about that, since ECM pods were routinely carried in the
Sparrow missile wells. Can't imagine a situation in which the pods
suspension gear would fail. Don't say it couldn't, simply that I doubt
it.


The missile well adapter was only held on by four moderate-sized bolts,
and I could see quite a few situations where the whole assembly would
pull right out. I had to swap the MWAs out on a regular basis when I
was at George AFB. They kept launchers in that left-front spot until
the regs forced to exercise with the pods.

I also seem to remember at least one case where one of the hooks on an
MWA cracked, and the pod came back in being held by the rear lug only...

In 250 combat missions, 150 over NVN where high threat evasions were
most likely, I never, not even once, heard of a structural failure nor
of an inadvertent separation of any piece of equipment off an
aircraft. I'm not saying it couldn't have, simply that I doubt it.


Even when the thing was in good shape, I could see one or more bolts
giving way under a hard maneuver, taking the rest of them out too.

--


Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.
  #15  
Old September 18th 03, 11:28 PM
Thomas Schoene
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"Peter Kemp" peter_n_kempathotmaildotcom wrote in message

On Thu, 18 Sep 2003 19:03:03 +0100, "José Herculano"
wrote:


An Argentinian 707 shadowing the British fleet pulled 7 G to
avoid a couple of Sea Dart missiles. She too landed.


The second claim is incorrect. No Sea Dart missiles were ever launched
at the shadowing aircraft. by a British vessel, although at one point
they nearly did, before identifying the aircraft as (IIRC) a Brazilian
charter flight.


No, it's correct. It is true that the British never fired on the 707s that
shadowed the main Task Force on its trip south, and those flights ended for
several weeks after a pointed warning.

However, the Argentines did eventually resume the flights, conducting
reconnaissance against British reinforcements headed south from Ascension.
On 22 May, HMS Bristol and HMS Cardiff each fired a pair of Sea Darts at a
707 belonging to Grupo 1, which took evasive action as desribed above.

Source: _Falklands: The Air War_

--
Tom Schoene Replace "invalid" with "net" to e-mail
"If brave men and women never died, there would be nothing
special about bravery." -- Andy Rooney (attributed)




  #16  
Old September 19th 03, 12:38 AM
Mike Marron
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Ed Rasimus wrote:
Chad Irby wrote:


I know there were a couple of cases in Vietnam where F-4s made hard
enough turns to rip the ECM pods off...


Gotta wonder about that, since ECM pods were routinely carried in the
Sparrow missile wells. Can't imagine a situation in which the pods
suspension gear would fail. Don't say it couldn't, simply that I doubt
it.


In 250 combat missions, 150 over NVN where high threat evasions were
most likely, I never, not even once, heard of a structural failure nor
of an inadvertent separation of any piece of equipment off an
aircraft. I'm not saying it couldn't have, simply that I doubt it.


I doubt it too!

I don't know how much an F-4 ECM pod weighs, but I do know that it
would require a hellacious amount of G's to cause the bolts that
fasten the pod to the airframe to fail. Much more force than the
surrounding airframe structure itself could withstand.

For example, a standard AN6 bolt (3/8-inch diameter shank) has
a shear strength of approx. 8700 lbs. IIRC. And there is probably
more than just one of these or similiar types of bolts securing the
ECM gear to the belly of an F-4.

-Mike (A&P mech) Marron



  #17  
Old September 19th 03, 12:45 AM
Tarver Engineering
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"Mike Marron" wrote in message
...
Ed Rasimus wrote:
Chad Irby wrote:


I know there were a couple of cases in Vietnam where F-4s made hard
enough turns to rip the ECM pods off...


Gotta wonder about that, since ECM pods were routinely carried in the
Sparrow missile wells. Can't imagine a situation in which the pods
suspension gear would fail. Don't say it couldn't, simply that I doubt
it.


In 250 combat missions, 150 over NVN where high threat evasions were
most likely, I never, not even once, heard of a structural failure nor
of an inadvertent separation of any piece of equipment off an
aircraft. I'm not saying it couldn't have, simply that I doubt it.


I doubt it too!

I don't know how much an F-4 ECM pod weighs, but I do know that it
would require a hellacious amount of G's to cause the bolts that
fasten the pod to the airframe to fail.


How could you possibly know that?


  #18  
Old September 19th 03, 05:13 AM
Chad Irby
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Mike Marron wrote:

Chad Irby wrote:


I know there were a couple of cases in Vietnam where F-4s made hard
enough turns to rip the ECM pods off...


I don't know how much an F-4 ECM pod weighs, but I do know that it
would require a hellacious amount of G's to cause the bolts that
fasten the pod to the airframe to fail. Much more force than the
surrounding airframe structure itself could withstand.

For example, a standard AN6 bolt (3/8-inch diameter shank) has
a shear strength of approx. 8700 lbs. IIRC. And there is probably
more than just one of these or similiar types of bolts securing the
ECM gear to the belly of an F-4.


The only problem is that the missile well adapter isn't held in by the
full strength of 4 brand-new bolts... it's held in by the bolt
*threads*. You're not working with the shear strength of a 3/8"
diameter piece of metal - you're dealing with the actual (not
theoretical) tensile strength of the *threads* of that bolt *and* the
nut plate.

Yep - the four bolts run straight up into the fuselage, making all of
the stress rest on the four bolts, through their four nut plates. That
shouldn't be a problem, since correct installation would give you full
strength. Except...

That's the problem with thoretical and design limits. After a few
months of actual (mis)use, those numbers change. A *lot*. The spec
says that someone should replace those nut plates and bolts each time
you swap out the launcher for the MWA. Nobody did that, of course.
Took too long, cost too much.

Sure, the four bolts, when new, should have been able to hold a total of
almost 35,000 pounds. But then you add in the preload from torquing it
in (at least 600 pounds per bolt, maybe more) plus the 6000 pounds it
would have been carrying with a 600 pound pod at ten times the force of
gravity (maybe higher), and you have a load of at least 8400 pounds, on
a system that is not evenly loaded, in six kinds of vibration modes,
loading and unloading like mad.

I figure one semi-catastrophic failure over a quarter century is pretty
good, considering.

--


Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.
  #19  
Old September 19th 03, 07:17 AM
Scott Ferrin
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On Thu, 18 Sep 2003 16:45:14 -0700, "Tarver Engineering"
wrote:


"Mike Marron" wrote in message
.. .
Ed Rasimus wrote:
Chad Irby wrote:


I know there were a couple of cases in Vietnam where F-4s made hard
enough turns to rip the ECM pods off...


Gotta wonder about that, since ECM pods were routinely carried in the
Sparrow missile wells. Can't imagine a situation in which the pods
suspension gear would fail. Don't say it couldn't, simply that I doubt
it.


In 250 combat missions, 150 over NVN where high threat evasions were
most likely, I never, not even once, heard of a structural failure nor
of an inadvertent separation of any piece of equipment off an
aircraft. I'm not saying it couldn't have, simply that I doubt it.


I doubt it too!

I don't know how much an F-4 ECM pod weighs, but I do know that it
would require a hellacious amount of G's to cause the bolts that
fasten the pod to the airframe to fail.


How could you possibly know that?



Math.
  #20  
Old September 19th 03, 08:51 AM
Chad Irby
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In article ,
Scott Ferrin wrote:

On Thu, 18 Sep 2003 16:45:14 -0700, "Tarver Engineering"
wrote:


"Mike Marron" wrote in message
.. .


I don't know how much an F-4 ECM pod weighs, but I do know that it
would require a hellacious amount of G's to cause the bolts that
fasten the pod to the airframe to fail.


How could you possibly know that?


Math.


....and a near-religious faith that new bolts are just as strong as old
bolts, while corrosion never happens and flightline troops never make
mistakes.

Film at 11.

--


Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.
 




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