F-35C nose gear issues

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johnwill

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Unread post10 Jul 2017, 05:40

In the first post of this thread we were told the function of the holdback bar is " with the hold back bar restraining the aircraft from forward movement due to engine thrust" That's true, but it is not the primary function of the holdback, which is to prevent launch unless the catapult force plus engine thrust is enough to successfully launch the airplane. Catapults are not 100% reliable, and it sometimes happens that steam pressure is less than required. That's called a cold cat. Without a properly set holdback, the airplane would simply roll off the bow and into the water.

Let's say the airplane weighs 70,000 lb, requiring a catapult launch force of 200,000 lb. The holdback will not release until the actual launch force reaches 200,000 lb. The next airplane up for launch weighs only 50,000 lb and requires a 170,000 lb launch force. Here the holdback is set to release when the launch force reaches 170,000 lb. Fifty years ago, as on F-111B, the holdbacks had a link calibrated to fail at a certain load. Those links were stamped with the gross weight of the airplane to be launched. Today's holdbacks seem to have an adjustable mechanism to vary the release force. Reducing holdback force for lighter airplanes has been standard procedure for a long time, but Gen Bogdan seems not to know that:

“We were pulling that down to the max load of the airplane, not recognizing that was causing the biggest oscillations and you can actually launch this thing at low weight with a lot less tension on that catapult bar,” Bogdon said.

I don't fault him for not knowing that since he is USAF, but some USN person should have told him, unless they did not know themselves.
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spazsinbad

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Unread post10 Jul 2017, 06:03

'johnwill' we do not know the details of an F-35C catapult setting for CarQual Carrier Qualifications. A long ago example was that the catapult (similar to what is seen for the Phantom above) for an A4G FIRST CATAPULT usually after their FIRST ARREST was set way higher than the actual carqual weight of the A4G to ensure - if anything went amiss - that the aircraft had a good chance of flying well off the lightweight catapult. Two A4G catapults examples spring to mind.... Perhaps the first F-35C carquallers were catapulted with more force than necessary - just in case - as per....

The very first catapult of an A4G (after the refit to HMAS Melbourne to enable A4G/S2E ops) went awry when the radar screen unit in the front panel came out of the housing to land in the lap of the pilot forcing the control column to the left. 'Luckily' the cat shot end speed was more than necessary for the A4G weight at that time (a tradition of sorts) ensuring the A4G had plenty of flying speed at the end of the stroke. Our pilot LCDR John Da Costa (had trained in the USofA on the A-4 and had carqualled there with another instructor pilot) was able to skillfully fly the aircraft - with some difficulty - on trim alone, making a high speed landing into the short field gear at NAS Nowra. The USN were able to theorise now why some A-4s were lost off the catapult (as seen in the video) without any other information (pilot dead, does not speak on radio & aircraft lost at sea).

A second example was a sprog/nugget pilot in the early 1980s who had not carqualled earlier was ferried out to HMAS Melbourne to be catapulted for the first time in an A4G. However he forgot to lower the catapult hand grip and tighten the throttle friction to full so that holding the grip handle and the throttle at same time, the throttle would not move.

You guessed it - during the short catapult stroke - 100 feet in less than two seconds - the throttle went to the idle position despite the pilot best efforts. Thankfully in a jet engine that does not mean the RPM goes to idle - it just starts down that path; however power is dramatically reduced. Once out of the throes of the transeverse catapult G force our lucky pilot placed the throttle at full. Sinking noticeably though (lack of full power) with extra airspeed because it was first catapult he was able to survive to fly another day. What happens with the F-35C in a NON TEST environment but CarQual? Dunno.

A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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johnwill

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Unread post10 Jul 2017, 11:33

You're right of course. I certainly don't know the details of launch settings. I only know what Gen Bogdon was reported to have said. He didn't seem to know the fundementals of cat system operation.

Thanks for the sad history lesson. I wonder why the radar problem wasn't found during ground based roll out launches.
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Unread post10 Jul 2017, 13:22

Thought the radar in lap during catapult accident had been told in detail here before but it seems not (must have been in other forums). Story mentioned here earlier & I'll continue to search this forum: viewtopic.php?f=58&t=27306&p=291183&hilit=radar+catapult+A4G+#p291183

Attached is a 12 page PDF about this 'first A4G catapult almost accident/loss'. Skyhawk was side number 887 which is flying today with DRAKEN after being sold to the RNZAF then upgraded to KAHU etc. Short story about 'radar in lap' was that first maintainers had been trained in USofA ashore with the Skyhawk aircraft 'probably' not going to see much - if at all - other USN squadrons carqualled or embarked. Anyway the maintainers would not 'properly' secure the radar unit into the front instrument panel, the unit would stay there in ordinary flight ops. However if that 'non-NATOPS' practice was carried over with embarked Skyhawks being catapulted then.... disaster. This is the short story. The PDF explains how the problem was fixed in the RAN FAA - how it was fixed in the USN I have no idea. Initially the embarked squadron VF-805 would carry a very large screwdriver to ensure the radar unit was secure. Then the 'LUG' solution was devised and it was easy to check the LUGS were properly positioned along with the BIG LUG in the cockpit. :mrgreen:

In the graphic below the EXTRA LUGS are shown via RED ARROWS (the yellow rectangle just shows the radar red screen overlay for night time use lug).
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RADAR 1st CATAPULT RAN FAA Skyhawk A4G 887 pp12.pdf
(7.7 MiB) Downloaded 299 times
A4GlugsRADARcatapultSecure.jpg
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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Unread post12 Jul 2017, 06:40

Further to the previous page post about FANtom catapulting issues particularly with nose gear, diagram shows info for the F-4B variant from the PlainSpekeCapitanHandbook: https://www.filefactory.com/file/36uynv9fwh4h/F-4(B,C)_Plane%20Captains'%20Handbook.pdf (186Mb) SINGLE PDF page of same - but original - graphic attached now also.
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Catapult F-4B Plane Captains' HandbookTIF.gif
Catapult F-4B Plane Captains' Handbook PRNbw.pdf
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A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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Unread post07 Sep 2017, 23:19

One would guess that this event is about F-35C nose gear testing during catapulting for HMDS III fixes I suppose...

F-35C being test aboard aircraft carrier USS Abraham Lincoln 08 Sep 2017
viewtopic.php?f=57&t=53429&p=375826&hilit=Beuller%3F#p375826
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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Unread post08 Sep 2017, 00:11

The program’s adjusted the helmet display, Winter said. It’s also retrained pilots and made minor adjustments to fix the intense vibration during catapult take-offs (“cat stroke”). There’s no need for a costly and time-consuming redesign of the aircraft’s nose landing gear, as some had thought.

Two Navy F-35C squadrons (VFA-101 and VFA-125) now have both sets of fixes and are going through carrier qualifications with them aboard the USS Abraham Lincoln, Winter said. This isn’t a test specially arranged for the F-35 program, he emphasized. It’s pilots going through their routine training, using the improved gear and providing feedback on it.


http://breakingdefense.com/2017/09/jpo- ... dm-winter/
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Unread post08 Sep 2017, 00:22

Yeah good one. I'll highlight the OBOGS issues (warning light tweaked).
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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Unread post08 Sep 2017, 00:34

spazsinbad wrote:Yeah good one. I'll highlight the OBOGS issues (warning light tweaked).



The Luke AFB issues were a bit more involved :)

in this summer’s incidents at Luke in particular, the problem was a combination of brutal temperatures and inexperienced pilots. While pilots who know an aircraft well can jump in the cockpit, run through their checklists, and get in the air ASAP, the F-35 is a new plane and most of its pilots are still mastering it. The result was pilots spending half an hour on the runway in the baking Arizona sun and 100-plus degree heat, all the while sitting in the carbon monoxide from their own jet exhaust. That’s enough to make anyone woozy. Fixing this problem requires new training and procedures rather than modifications to the aircraft.
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Unread post08 Sep 2017, 01:56

I think we had already 'dinged' the USAF pilotes for NOT WEARING THEIR FREAKIN' MASKS when they sit in the cockpit! :doh:
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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