The GAU-22/A thread

F-35 Armament, fuel tanks, internal and external hardpoints, loadouts, and other stores.
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marsavian

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Unread post30 Jan 2020, 23:43



Thanks for the link

Static Structural and Durability Testing

Activity

• Teardown inspections of the F-35A full scale durability test article (AJ-1) were completed in July 2019 and correlations to the finite element models (FEM) are in progress. The FEM data are used to estimate the structural and durability performance of the original design structure. The program expects the F-35A Durability and Damage Tolerance report to be released in February 2020.

• Teardown inspections of the original F-35B full scale
durability test article (BH-1) were completed in October 2018. The program canceled the third lifetime testing of BH-1 due to the significant amount of discoveries, modifications, and repairs to bulkheads and other structures that caused the F-35B test article to no longer be representative of the wing-carry-through structure in production aircraft. The program secured funding and contracted to procure another F-35B ground test article, designated BH-2, which will have a redesigned wing-carry-through structure that is production representative of Lot 9 and later F-35B aircraft.

• Disassembly and teardown of the F-35C durability test
article (CJ-1) were completed in November 2019. Testing
was stopped during the third lifetime testing in April 2018, following the discovery of more cracking in the Fuselage Station (FS) 518 Fairing Support Frame. The cracking had been discovered near the end of the second lifetime and required repairs before additional testing could proceed. After estimating the cost and time to repair or replace the FS 518 Fairing Support Frame, coupled with other structural parts that had existing damage (i.e., fuel floor segment, bulkheads FS 450, FS 496, FS 556, and front spar repair), the program determined that the third lifetime testing would be
discontinued.

Assessment

• For all F-35 variants, structural and durability testing led to significant discoveries requiring repairs and modifications to production designs, some as late as Lot 12 aircraft, and retrofits to fielded aircraft.

• Based on durability test data, there are several life-limited parts on early production F-35 aircraft which require mitigation. In order to mitigate these durability and damage tolerance shortfalls, the program plans to make modifications to these early production aircraft, including the use of laser shock peening to increase fatigue life for specific airframe parts, e.g., bulkheads. The JPO will also continue to use Individual Aircraft Tracking of actual usage to help the Services project changes in timing for required repairs and modifications, and to aid in Fleet Life Management.

• For the F-35A and F-35C, expected service life will be
determined from the durability and damage tolerance
analyses, once completed. Although the program planned for a third lifetime of testing to accumulate data for life extension, if needed, the program has no plans to procure another F-35C ground test article.

• Procuring and testing a production-representative F-35B ground test article will allow the program to certify the life of the design improvements. Once on contract, program plan dates will be finalized.

• Despite the F-35 program’s FEM-based structural design, static and durability testing, and developmental flight testing, additional structural discoveries requiring repairs and modifications are occurring in the field. For example, the F-35A has gun-related structural problems and the F-35A/C are experiencing longeron (structural component) cracks. The effect on F-35 service life and the need for additional inspection requirements are still being determined.



Gun Testing

Activity

• All three F-35 variants have a 25-mm gun. The F-35A gun is internal; the F-35B and F-35C each use an external gun pod. Differences in the outer mold-line fairing mounting make the gun pods unique to a specific variant (i.e., an F-35B gun pod cannot be mounted on an F-35C aircraft).

• Units flying newer F-35A aircraft discovered cracks in the outer mold-line coatings and the underlying chine longeron skin, near the gun muzzle, after aircraft returned from flights when the gun was employed.


Assessment

• Based on F-35A gun testing to date, DOT&E considers
the accuracy of the gun, as installed in the F-35A, to be
unacceptable. F-35A gun accuracy during SDD failed to
meet the contract specification. Investigations into the gun mounts of the F-35A revealed misalignments that result in muzzle alignment errors. As a result, the true alignment of each F-35A gun is not known, so the program is considering options to re-boresight and correct gun alignments.

• The program has made mission systems software corrections to improve the stability of gun aiming cues. The program also made progress with changes to the gun installation, boresight processes, and hardware. However, testing to confirm the effectiveness of these changes was not yet complete. Until the new hardware and software changes are successfully tested
and verified in operationally representative conditions, the F-35A internal gun system remains unacceptable.

• Due to the recent cracking near the gun muzzle in newer F-35A aircraft, the U.S. Air Force has restricted the gun to combat use only for production Lot 9 and newer aircraft.

• F-35B and F-35C air-to-ground accuracy results to date
with the gun pod have been consistent and meet the contract specifications. The results do not show the accuracy errors of the internal F-35A gun.
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ricnunes

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Unread post30 Jan 2020, 23:54

Yeah, but lets not forget this:
The program has made mission systems software corrections to improve the stability of gun aiming cues. The program also made progress with changes to the gun installation, boresight processes, and hardware. However, testing to confirm the effectiveness of these changes was not yet complete. Until the new hardware and software changes are successfully tested
and verified in operationally representative conditions, the F-35A internal gun system remains unacceptable.


And then there's this:
Due to the recent cracking near the gun muzzle in newer F-35A aircraft, the U.S. Air Force has restricted the gun to combat use only for production Lot 9 and newer aircraft


So from what I read, this means that the gun cracking problem only affect older pre-Lot 9 F-35s and not the most recent/newer ones.
“Active stealth” is what the ignorant nay sayers call ECM and pretend like it’s new.
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marsavian

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Unread post31 Jan 2020, 00:03

I am not sure if there is a grammatical error in that report as what you quoted does not tie in with this earlier quote*. Regardless the gun is not essential especially for a stealth aircraft and the structural stuff is just growing pains revealed by testing and deployment and no doubt will be sorted in the future. It's nice to get the facts quickly rather than just the sensational reporting that dogs the F-35. As long as the sensors, bombs and missiles work that's good enough for IOC especially when retrofits can fix the other issues. Concurrency in action !

*
Units flying newer F-35A aircraft discovered cracks in the outer mold-line coatings and the underlying chine longeron skin, near the gun muzzle, after aircraft returned from flights when the gun was employed.
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quicksilver

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Unread post31 Jan 2020, 00:27

Structural discovery will likely be a recurring issue, just as it has been periodically for every aircraft type. NAVAIR chased harmonics all over the AV-8B and every time a stiffener or other reinforcement was applied, the harmonic ‘moved’ somewhere else. Hornet had to structurally reinforce the verticals and add a LEX fence to deal with excess loads on the verticals from vortex generation off of the LEX. Later there were center barrel replacements.

An unfortunate but common reality.

https://www.navy.mil/submit/display.asp?story_id=10068

http://www.asipcon.com/proceedings/proc ... 0_Rose.pdf
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8DCAD310-E9DD-4936-8B31-0EF7CF151718.jpeg
5B1717A4-221C-4E91-998B-B4591D5EBE5D.jpeg
Last edited by quicksilver on 31 Jan 2020, 00:40, edited 2 times in total.
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Unread post31 Jan 2020, 00:38

Went looking for the '40 year old' gun accuracy article that was posted here years ago (not found yet) to find this:

viewtopic.php?f=22&t=24483&p=284421&hilit=accuracy+spazsinbad#p284421 [from 'smsgtmac']
"The F-35 Operational Requirements Document (ORD) currently requires the gun system to have an accuracy of < 3.1 miliradians and it must have a Probability of Kill (Pk) of .35 against lightly armored and thin-skinned vehicles at 9,000 feet of slant range. In layman’s terms, this means the gun system must have an accuracy of approximately 3 feet for every 1000 feet of range from the target. At 9,000 feet of slant range this means the gun must be accurate to within approximately 27 feet. Additionally, the JSF is required to have a fully integrated, cockpit programmable fire control system that accounts for the effects of wind and aim wander on long-range air to ground employment opportunity. Within the DoD’s Joint Munitions Effectiveness Manual (JMEM), a publication that deals with data and methodologies for conventional weapons, it is suggested that lightly armored and thin-skinned vehicles be targeted using a .35 Probability of Kill. By performing a 30-45 degree High Angle Strafe (HAS) attack at 9000 feet of slant range, the JSF will be able remain above small arms fire while achieving the desired Probability of Kill against these types of targets."

Source via the footnotes was: Joint Strike Fighter Operational Requirements Document (Joint Strike Fighter Program Office, March 2000)
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ricnunes

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Unread post31 Jan 2020, 00:51

marsavian wrote:I am not sure if there is a grammatical error in that report as what you quoted does not tie in with this earlier quote*.

*
Units flying newer F-35A aircraft discovered cracks in the outer mold-line coatings and the underlying chine longeron skin, near the gun muzzle, after aircraft returned from flights when the gun was employed.



Yes, indeed it's quite possible that that the part/phrase of the report that I quoted isn't well placed (IMO, that is). Perhaps it was meant that the newer F-35A aircraft (Lot 9 and newer) will only be able to use the gun in combat situations (thus the "restricted the gun to combat use only" part) and not during training for example in order not to wear "unnecessarily" the gun.

As odd as this might look, this can actually be a "not so bad" news (IMO again) for the F-35A because and in case it only affects the newer aircraft and not older ones (pre-Lot 9) then this could probably mean a defective part or parts on the gun or gun assembly on newer aircraft which in this case it would be a matter of finding the defective part or parts and correct them.
“Active stealth” is what the ignorant nay sayers call ECM and pretend like it’s new.
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Unread post31 Jan 2020, 05:33

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charlielima223

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Unread post31 Jan 2020, 10:00

Now we're going to read on the interwebs that the gau-22 is tearing the F-35 apart :bang:
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Unread post31 Jan 2020, 23:20

Based on F-35A gun testing to date, DOT&E considers the accuracy of the gun, as installed in the F-35A,
to be unacceptable. F-35A gun accuracy during SDD failed to meet the contract specification


This phrasing has always (it's verbatim from 2018 report) struck me as odd.
Contract specifications can be and often times have to be more stringent than what's in the ORD.

For something as inherently quantitative as gun accuracy, it's a strangely qualitative assessment.
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neptune

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Unread post01 Feb 2020, 00:07

charlielima223 wrote:Now we're going to read on the interwebs that the gau-22 is tearing the F-35 apart :bang:


.....having glanced over the 9 pages here, I have two questions...

1- how does this issue(s) with the GAU-22A compare to the M61A2 of the other LM stealth aircraft?
2- with the imminent upgrade of the Tech Refresh 3, and with the IR tracking and targeting systems and the ISAR radar capabilities and the signal merging capability of the mission computer; has there been or will there be an algorithm to follow and target/ place the bullets and tracers from the gun on the target aircraft/ strafing point (ps: not OTH!!) which should account for windage, etc.

My understanding that by the time the aircraft is in gun range, the target should have been identified (maybe to the squadron) and thus should identify "ON" the target the prime areas for gun damage, or not??

Thank You,
Neptune
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Unread post05 Feb 2020, 05:49

Newer F-35As cracking due to gun use
03 Feb 2020 Pat Host

"Key Points
• Lot 9 and newer F-35As have developed cracks after gun use
• The aircraft variant's gun inaccuracy has stumped the programme for years


The Pentagon has restricted gun use on Lot 9 and newer Lockheed Martin F-35A Lightning II Joint Strike Fighter (JSF) conventional variants to combat-only after discovering cracks in the aircraft after gun operation.

Robert Behler, director of operational test and evaluation (DOT&E), said in his fiscal year 2019 (FY 2019) report released on 30 January that units flying these newer F-35As discovered cracks in the outer mold-line coatings and the underlying chine longeron skin, near the gun muzzle, after the gun was used. F-35A Lot 9 aircraft were delivered in 2017....

a F-35B gun pod cannot be mounted on a F-35C aircraft. Lockheed Martin spokesperson Brett Ashworth said on 1 February that the B- and C-models carry a low observable belly gun pod mounted on the centreline.….

Ashworth said that the F-35 programme has made significant progress on the F-35A gun since the data used for the DOT&E report. The programme has implemented software updates and installed a field gun alignment aid to ensure proper gun barrel position."

Source: https://www.janes.com/article/94071/new ... to-gun-use
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Corsair1963

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Unread post05 Feb 2020, 07:01

spazsinbad wrote:
a F-35B gun pod cannot be mounted on a F-35C aircraft. Lockheed Martin spokesperson Brett Ashworth said on 1 February that the B- and C-models carry a low observable belly gun pod mounted on the centreline.….




What??? The B and C model use a different Gun Pod??? I assume they meant the F-35A not the F-35C???
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Unread post05 Feb 2020, 07:32

It had been previously stated on this forum (some wheres) that the Bee and Cea use different gunpods. I forget what the differences are exactly... something to do with how they mate the fuselage, if memory serves.
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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steve2267

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Unread post05 Feb 2020, 07:43

neptune wrote:
1- how does this issue(s) with the GAU-22A compare to the M61A2 of the other LM stealth aircraft?


The muzzle energy / blast of the GAU-22A cannon (25mm) is substantially higher than that from the M61A2 Vulcan (20mm). I think it is fair to say, then, that the dynamics / stresses of the structure at / near / around the muzzle of the F-35 gun are higher than the structure in the vicinity of the F-22's cannon muzzle. ("Dynamics are higher..." is a bit of a nebulous statement, not very technically accurate, but hopefully the point is made. Maybe the simpler statement is better: to wit, F-35 gun is bigger, so has higher stresses. Bigger boom => higher stress.)
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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Unread post05 Feb 2020, 07:54

steve2267 wrote:It had been previously stated on this forum (some wheres) that the Bee and Cea use different gunpods. I forget what the differences are exactly... something to do with how they mate the fuselage, if memory serves.

Aren't I naughty - here are the full appropriate paragraphs. Always best to read FULL article - I'm only allowed 50% or so.
"...All three variants have a 25 mm gun. The F-35A gun is internal while the F-35B short take-off and vertical landing (STOVL) model and the F-35C aircraft carrier variant each use an external gun pod.

Differences in the outer mold-line fairing mounting make the gun pods unique to a specific variant. For example, a F-35B gun pod cannot be mounted on a F-35C aircraft. Lockheed Martin spokesperson Brett Ashworth said on 1 February that the B- and C-models carry a low observable belly gun pod mounted on the centreline…."
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