F-35C nose gear issues

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quicksilver

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Unread post24 Mar 2017, 15:22

"If you can decrease the initial slope of the ramp up to speed on the shot you might eliminate the problem."

In effect, that's part of what they've done. They changed the shuttle preload (and consequential compression of the nose strut) just before the RRHB (repeatable release holdback bar) releases.
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Unread post24 Mar 2017, 18:54

quicksilver wrote:"If you can decrease the initial slope of the ramp up to speed on the shot you might eliminate the problem."

In effect, that's part of what they've done. They changed the shuttle preload (and consequential compression of the nose strut) just before the RRHB (repeatable release holdback bar) releases.


I am not a Naval Aviator, nor do I play one on TV. I likely suffer the same blind spots as the good General ...

But I`m not going to let that keep me from pontificating... There seems to be a critical cross over point with this issue.

First can it be handled without mods? It seems likely with adjustments here and adjustments there.

However, carrier ops is filled with safety procedures to avoid bad results. I imagine you can get so many of these cued up that you guarantee a human error will happen. They rename the "Super Hornet" to"Rhino" so SH`s don`t launch/land into the water, and Hornets don`t get ripped apart, due to wrong weight settings. etc.

I`d be a little nervous if the answer here is ....
Once you get below a certain weight, wave a purple card at the deck crew, turn your flight suit inside out. Once that`s done and your boots are laced back up, wave both hands back and forth and wait for the sailor to do a boogie spin left, boogie spin right dance, before the next Cat launch..

I mean they can probably do it for a 9-5 DT checkout. But what about ...
You get roused from the rack in the middle of the night, after 2 hours sleep, during a typhoon, and told to launch ASAP in the bird they are rapid turning from the previous sortie, at half fuel and A-A weapons only, and you have to go save Iceman! and all you can think about is whether you will actually be able to land in a typhoon, after you save Iceman, ... and suddenly.... if you think about it at all, ... you go, "Sh**! I forgot my purple card! " and wave frantically at the deck crew .... Yeah ... that`s gonna work ...

At some point this gets to be a formula for disaster with an 18 year old sailor in the loop.

No?

Just asking, Spaz? Others?
BP
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quicksilver

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Unread post24 Mar 2017, 19:45

"First can it be handled without mods? It seems likely with adjustments here and adjustments there."

Short answer is maybe. You know from your own program experience with "Red Teams" and such that they are going to take a systems engineering approach to identification of all the potentialities wrt RCCA. Once they've done that (they have), then they start testing with the low hanging fruit -- like (in this case) adjusting the shuttle pre-load and hold back tension (which they are doing, and which require no technical mods to the jet nor changes to SOPs). If that proves to be unsatisfactory then they will move on to more complex, time consuming, and expensive alternatives. The Super Hornet had this same issue in DT; it was fixed in the fashion suggested by their current approach for F-35.

Everyone should remember that the program is at the stage where very very few things rise to the level of 'major crisis.' Most issues, regardless of the severity assigned, are very subjective assessments; the difference of opinion between the DT and Fleet guys is emblematic. They'll do some more shore-based work in the near-term before they go to sea again.
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Unread post24 Mar 2017, 20:21

https://news.usni.org/2017/03/23/f-35c- ... 92e82094bc

Bogdan: F-35C Tests Offer Proposed Fixes to Catapult Problem; Carrier Trials to Continue This Fall
By: Sam LaGrone
March 23, 2017 1:13 PM •
Updated: March 24, 2017 10:12 AM


WASHINGTON, D.C. – The Navy has completed testing on potential solutions to solve a ‘must fix’ catapult launch problem on the carrier version of the Lockheed Martin F-35 Lighting II Joint Strike Fighter, the head of the JSF joint program office said on Wednesday. Now the service and the JPO are set to test the fixes during the next set of underway carrier trials for the fighter in the fall, Air Force Lt. Gen. Christopher Bogdon said during the McAleese/Credit Suisse defense conference.
During F-35C testing on USS George Washington (CVN-73) late last year, pilots were buffeted in the cockpit when after launch the fighter would excessively bob up and down on the nose gear as the JSF was catapulted down the flight deck.
“This is a very stiff airplane, even though the oscillations about the same magnitude as you would see in a Super Hornet, it beats the pilot up pretty good,” Bogdan said. “He’s hurting after doing three or four of these [launches] and in some instances even banging his half-a-million dollar helmet on the canopy. That’s not good for the canopy or the helmet. So we knew we had an issue there.”

According to a December Pentagon’s director, Operational Test & Evaluation report,
“fleet pilots reported that the oscillations were so severe that they could not read flight critical data, an unacceptable and unsafe situation during a critical phase of flight. Most of the pilots locked their harness during the catapult shot which made emergency switches hard to reach, again creating, in their opinion, an unacceptable and unsafe situation.”
The report said the Navy had told the JPO the problem was a “must fix,” deficiency. In an evaluation of the pilot discomfort following 105 test launches on George Washington (CVN-73), 74 resulted in moderate pain, 18 caused severe pain, reported Inside the Navy in December.

In February, Bogdon told Congress the Navy would test potential fixes at Joint Base McGuire-Dix-Lakehurst, N.J. at the Navy’s land-based test catapults. “What we wanted to try and figure out was do we need a complete redesign of the nose gear or can we do other things? Well, the testing at Lakehurst has shown us that there are a couple of things we can do to mitigate this problem,” Bogdon said. Those were changes on securing the pilot in the cockpit and adjusting the tension of the pull back bar on the catapult that compresses the strut of the nose gear. “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. “We’ve proven that out. Whether that reduces that enough, I don’t know. We have to take that out to the field and check it out. If [it doesn’t work] we have to take it back to the drawing board and structurally look at what else we need to do.” The Navy and the JPO will tests the fixes at sea later this year. If they don’t work the Pentagon and Lockheed may have to begin an estimated years-long effort to redesign the nose gear.

"Jul 12, 2011

NAVAL AIR SYSTEMS COMMAND, PATUXENT RIVER, Md. – Using F-35C test aircraft CF-2, the F-35 integrated test force based at Naval Air Station Patuxent River collaborated with the aircraft launch and recovery engineering team at Joint Base McGuire-Dix-Lakehurst to complete the first jet blast deflector (JBD) testing July 8....Future carrier suitability testing is scheduled for later this summer, including JBD testing with two aircraft, catapult launches and arrestments in preparation for initial ship trials in 2013."

....so what gives???, are these just "whiners" are what??...the testing at Lakehurst was completed years ago, and I would have doubt they brought an entire ordinance load to test "catting"...sounds to me like someone forgot to tell the cvn test guys to loosen (no adjustments/ no feedback from the flight crews) the hold backs...an operating squadron would get this fixed by simple gripes,,,,not redesigning the nosegear....wheres grampa pettibone??????????

:oops:
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Unread post24 Mar 2017, 20:32

Oh 'cmon man' with the drama... The recent election should be instructive about what one chooses to believe in almost anything reported in the public domain.

They're not redesigning anything yet.
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Unread post24 Mar 2017, 21:37

Beats me why peeps cannot thread read before these questions about 'what happened in the past'. F-35C test pilots wrote up the problem from beginning (not reported then publically obviously) when it was noted as 'worse at lightweights'. Any solution I guess was put on backburner. Fast Forward to recent past when FLEET pilots now experience for 1st time F-35C catapulting at lightweights such as those during Carrier Qualifying. HORROR - they rightly complain - so USN says this is a 'must fix problem' to JPO. JPO goes into 'must fix' mode - JPO thinks they fixed it - USN requires testing. Big deal? Nope.

On page ONE this thread - post from 'talkitron': viewtopic.php?f=58&t=52644&p=359512&hilit=Documentation#p359512
"Documentation dating back to November 2014 reveals the developmental test community raised concerns about the F-35C catapult launch. For example, a deficiency report issued in December 2015 that aggregated data from six previous reports acknowledged the catapult was suitable to continue developmental testing but would not be acceptable by fleet standards. VFA-101's at-sea testing last August was the first time fleet aviators could evaluate the catapult shot."


Search on GO! - use 'nose + gear' and ALL TEXT selected in the F-35 Forum Ffsake:

viewtopic.php?f=22&t=52843&p=363910&hilit=nose+gear#p363910
then: OMG
Navy to Test Fix for F-35C Catapult Problem viewtopic.php?f=61&t=52822&p=362876&hilit=USNI+Nose%2A#p362876

This is why having MANY THREADS about the same topic/issue is very helpful - especially for those forgetful & why I search constantly, as anyone else here can emulate.

FULL 'talkitron' article via 'Dragon029': viewtopic.php?f=62&t=16223&p=360354&hilit=nose+gear#p360354
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Unread post05 Apr 2017, 21:47

Potential Fixes for F-35C Oscillation Problem to Be Tested Later This Year
04 Mar 2017 Jon Harper

"NATIONAL HARBOR, Md. – The Defense Department has identified potential fixes to a major problem with the F-35C joint strike fighter, and there are plans to test them out later this year, a Lockheed Martin executive said April 4. In its latest annual report to Congress, the Pentagon’s operational test and evaluation office noted difficulties that aviators have had during developmental testing of the aircraft.

“Vertical oscillations during F-35C catapult launches were reported by the pilots as excessive, violent, and therefore a safety concern during this critical phase of flight,” the report said. “The program is still investigating alternatives to address this deficiency.”

A U.S. government-sponsored “red team” has been looking at potential fixes at Naval Air Engineering Station Lakehurst, New Jersey, said Jack Crisler, head of F-35 strategy and business development at Lockheed. “We just finished testing up at Lakehurst,” he told reporters on the sidelines of the Navy League Sea-Air-Space conference. The red team has completed its analysis, he said.

“They’re submitting their recommendation,” Crisler said. “We’ll probably want to take that out to the carrier for carrier [qualifications] in the third quarter of this year if the recommendation is accepted.” “We’re satisfied with … the solution set going forward,” he added.

Crisler declined to state what the potential fixes are [see quote block from elsewhere], saying he didn’t want to get out ahead of the red team. But he did note that the ones being looked at would not entail a redesign of the front landing gear assembly. If that were required, it could prevent the aircraft from reaching initial operating capability as scheduled....

...Crisler expressed confidence that the oscillation problem would be resolved. “It’s just like everything else in the program,” he said. “We identify these things and then we put in place the fix, and then we take it out and test it and then we retire the risk.”..."

Hornet fleet still stinging
04-10 Apr 2017 LEIGH GIANGRECO

"...A report from the Pentagon’s top weapon tester late last year detailed issues with the F-35C’s stiff landing gear struts, particularly the nose gear, which caused “excessive jarring” that often required pilots to stop taxiing. Pilots described vertical oscillations during catapult launches as excessive and violent, according to the report.

Lockheed recently completed tests at NAS Patuxent River, Maryland, and determined that the aircraft did not require a new nose gear. Gigliotti says the holdback bar behind the nose gear has been detuned to a lower release, which results in slightly less strut compression on the initial catapult release.

“That has seen some improvement there in the response of the aircraft going down,” he says. “We’ve also looked at some techniques the pilot uses in the airplane to firmly strap yourself in, but please keep in mind that any catapult is an inherently violent evolution anyway.”

Both Lockheed and the F-35 Joint Programme Office maintain the oscillation issues occur only with very low fuel weights, such as when the navy conducts initial carrier qualifications when pilots carry low fuel, and not during typical fleet operations...."

Source: FLIGHT International 4-10 April 2017


Source: http://www.nationaldefensemagazine.org/ ... px?ID=2474
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Unread post24 Apr 2017, 20:21

DOD Needs to Complete Developmental Testing Before Making Significant New Investments [GAO Report]
24 Apr 2017 GAO

"...F-35C catapult launches:
In 2016, officials identified issues with violent, uncomfortable, and distracting movement during catapult launches. Specifically, officials stated that the nose gear strut moves up and down as an aircraft accelerates to takeoff, which can cause neck and jaw soreness for the pilot because the helmet and oxygen mask are pushed back on the pilot’s face during take-off. This can be a safety risk as the helmet can hit the canopy, possibly resulting in damage, and flight critical symbology on the helmet can become difficult to read during and immediately after launch due to the rotation of the helmet on the pilot’s head. Officials evaluated several options for adjusting the nose gear to alleviate the issue, but determined that none of the options would significantly affect the forces felt by the pilot. Officials subsequently assembled a team to identify a root cause and a redesign. According to officials, adjustments to the catapult system load settings are being considered to address this issue, and a design change to the aircraft may not be required. But flight testing of the proposed changes is required to confirm this solution...."

Source: http://www.gao.gov/assets/690/684207.pdf (2.1Mb)
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Unread post24 Apr 2017, 20:44

spazsinbad wrote:
DOD Needs to Complete Developmental Testing Before Making Significant New Investments [GAO Report]
24 Apr 2017 GAO

"...F-35C catapult launches:
This can be a safety risk as the helmet can hit the canopy, possibly resulting in damage, ...

Source: http://www.gao.gov/assets/690/684207.pdf (2.1Mb)


Damage to wot? The canopy? Or the $400,000 helmet?

Is it not uncommon during high-G maneuvers / roll reversals / scissors and other I-gotta-jink-NOW-or-I'm-dead maneuvers for the pilot to get "tossed" a bit about the cockpit and have the helmet bash into the canopy? Me thinks the canopy and helmet would be designed for this maneuvering violence? Or am I missing something?
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 post24 Apr 2017, 20:58

steve2267 wrote:Damage to wot? The canopy? Or the $400,000 helmet?

Is it not uncommon during high-G maneuvers / roll reversals / scissors and other I-gotta-jink-NOW-or-I'm-dead maneuvers for the pilot to get "tossed" a bit about the cockpit and have the helmet bash into the canopy? Me thinks the canopy and helmet would be designed for this maneuvering violence? Or am I missing something?

It's the force due to the rapid up/down movement that makes it dangerous.

During high-G maneuvers there is indeed a lot of stress on the components but they are not changing as fast as with the "bumpy" carrier launch. In one of the DT video's you can clearly see that during launch one of the pilots visor is flipped up due to this force, I can understand why this is deemed unwanted and possibly dangerous.

Check this video to see the forces at play:

Last edited by botsing on 24 Apr 2017, 21:02, edited 2 times in total.
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Unread post24 Apr 2017, 21:00

Operative word is 'possibly'. Methinks - I'm guessing - the HELMET is at risk. The canopy will be robust - remember the chicken cannon? Chickenman... He's everywhere - He's everywhere....

The backseater in TA4G could not resist the side of the helmet bashing the canopy during rapid rolls - it was unstoppable. Permanent white helmet paint marks/scratches on that spot most of the time. Of course one warned the sprog in front not to be so violent - 720 degrees per second rolling at best roll IAS 250 KIAS is not to be trifled with. :mrgreen:




Last edited by spazsinbad on 24 Apr 2017, 21:12, edited 2 times in total.
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Unread post24 Apr 2017, 21:10

spazsinbad wrote:The canopy will be robust - remember the chicken cannon? Chickenman... He's everywhere - He's everywhere....

The backseater in TA4G could not resist the side of the helmet bashing the canopy during rapid rolls - it was unstoppable. Permanent white helmet paint marks/scratches on that spot most of the time. Of course one warned the sprog in front not to be so violent. :mrgreen:

Poor sod with his helmet milk-marks. :P

As for the chicken cannon: That force is projected to the front of the canopy which would structurally wise be stronger (also due to shaping).

I think the weakest link here is the human neck/spine and the electronics in the helmet, both are something you should handle with care.
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Unread post09 Jul 2017, 23:03

The three page PDF attached & the GIF graphic could have gone elsewhere on the forum where 'chains and planes and tie-downs' are mentioned but it goes here to illustrate 'catapulting nose gear naval aircraft' was NEVER EASY but who 'noes' nose/knows what lies in wait for a CARqualling nugget F-35C pilot of the future - FANTOMS ROOL - F-4B/F-4J all the way.
F-4B/F-4J Plane Captains' Handbook
01 Jan 1970 McDonnell Douglas/USN

PNEUMATIC SYSTEM PRESSURE MINIMUMS FOR CARRIER QUALIFICATION FLIGHTS
"...CAUTION
THE MINIMUM PRESSURES ARE TO BE USED DURING CARRIER QUALIFICATIONS ONLY. DO NOT LAUNCH THE AIRCRAFT IF THE PNEUMATIC SYSTEM PRESSURE IS BELOW THE MINIMUM REQUIRED FOR THE LAUNCH GROSS WEIGHT.

NOTE
DURING CARRIER QUALIFICATIONS, THE REPEATED NOSE STRUT EXTENSIONS PLACE SUCH A HEAVY LOAD ON THE PNEUMATIC SYSTEM THAT SYSTEM PRESSURE CAN NOT BE BUILT BACK UP TO NORMAL. ALTHOUGH 2750 PSI IS THE NORMAL MINIMUM PRESSURE FOR NOSE STRUT EXTENSION, THIS MINIMUM MAY BE LOWERED AS GROSS WEIGHT DECREASES FOR CARRIER QUALIFICATION PURPOSES. THIS CURVE SPECIFIES THE MINIMUM PNEUMATIC SYSTEM PRESSURE FOR A SPECIFIC GROSS WEIGHT. SATISFACTORY NOSE STRUT EXTENSIONS CAN BE OBTAINED AT THESE MINIMUMS. HOWEVER, THERE IS A DECREASE IN ANGLE OF ATTACK ON TAKEOFF...." [oops]

Source: https://www.filefactory.com/file/r6ij0h ... ndbook.pdf (129Mb)
Attachments
Catapult NoseGear & TIEDOWNS F-4B, F-4J Plane Captains' HandbookEDpp3PRNbw.pdf
(568.31 KiB) Downloaded 186 times
Catapult NoseGear F-4B, F-4J Plane Captains' Handbook.gif
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neptune

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Unread post10 Jul 2017, 05:17

spazsinbad wrote:.. to illustrate 'catapulting nose gear naval aircraft' was NEVER EASY ...]


....looks like "anything" that hooks on to the "cat" will benefit from these studies....
typical mechanical system issues; being made more complex of the "one" pressure setting, by adding in the weight and balance for fuel and ordinance (load) for "multiple" pressure settings, nose strut; for all a/c from Cod to X-47B!
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Unread post10 Jul 2017, 05:20

spazsinbad wrote:...- FANTOMS ROOL - F-4B/F-4J all the way.
F-4B/F-4J Plane Captains' Handbook
01 Jan 1970 McDonnell Douglas/USN

...
THE MINIMUM PRESSURES ARE TO BE USED DURING CARRIER QUALIFICATIONS ONLY. DO NOT LAUNCH THE AIRCRAFT IF THE PNEUMATIC SYSTEM PRESSURE IS BELOW THE MINIMUM REQUIRED FOR THE LAUNCH GROSS WEIGHT.

NOTE
DURING CARRIER QUALIFICATIONS, THE REPEATED NOSE STRUT EXTENSIONS PLACE SUCH A HEAVY LOAD ON THE PNEUMATIC SYSTEM THAT SYSTEM PRESSURE CAN NOT BE BUILT BACK UP TO NORMAL....AT THESE MINIMUMS. HOWEVER, THERE IS A DECREASE IN ANGLE OF ATTACK ON TAKEOFF...." [oops]


Doh! Death spiral! They will never sell a single plane more than ... 5,195 ... or so ... of those pigs! <sarc OFF>
:D :D :D
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