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| An F-35C test aircraft successfully catches a wire during testing at Naval Air Station Patuxent River, Md., in December 2013. |
Something is screwy with this tailhook story. Check out this blurb from USNI News on the tailhook
Lockheed and the Joint Strike Fighter program office ultimately traced the problem back to the shape of the hook and a faulty wire dynamics model supplied by the Naval Air Systems Command. The solution was to reshape the hook point and adjust the system’s hold-down damper, which helps prevent the hook from bouncing around upon touchdown.NAVAIR isn't that sloppy. Meanwhile check this out from the X-47 program which also experienced a faulty tailhook...
The team at FRCSW did not hesitate when asked to redesign this instrumental X-47B component. Within a few weeks of receiving the initial request from the UCAS team, the FRC signed a formal work order July 10, anticipating theThe X-47 experienced a similar issue and the problem was solved in a couple of months.
manufacturing and shipping process would take up to one month.
The UCAS and FRC teams worked together to overcome a series of complications to ensure the hook points were completed as quickly as possible. For example, machining the first steel part took longer than expected. As a result, the FRC made an investment in a more efficient machine to decrease cycle times.
In less than two months, despite the design challenges, the UCAS team received the completed parts from FRCSW in early August, avoiding costly delays and allowing the team to proceed with aircraft testing. Since then, the X-47B successfully engaged the arresting gear with the redesigned hook point during three separate roll-in arrestment tests.
The issue with the F-35 has lingered for almost a year and we still aren't sure if its solved.
Of course I could be reading all this wrong.
Check out the USNI News story here.
Read the NAVAIR X-47 story here.
If you watch the latest Tailhook Conference videos from a few months back, they admitted fault there too.
ReplyDeleteAs to the timelines, manned fighters always take longer to test than drones.
I noticed that the F-35C required a damper & hook and the X-47 only mentions a new hook. Also, the X-47 bit only mentions a roll-in test which the F-35C did MANY months ago soon after the problem was discovered.
DeleteThe F-35C did full arrested landings with the hook only many moths ago too. The latest tests (and the pic above shows) were full arrested landings with the hook and new damper for the F-35C.
In other words, the F-35C is demonstrating the final solution while the news on the X-47 is only an interim step.
i don't think thats valid. the X-47 had arrestor issues, NAVAIR came up with fixes, they were implemented and the plane got out to the ship in less than a year. the F-35C can't say that. as a matter of fact i refuse to believe that it will get on the water before middle 2015...at earliest.
DeleteWhere are those Tailhook Association vids anyway? Does CodeOne have them up, and if not, why not?
DeleteHere is the link to the 2013 Tailhook Convention. As to why LM does not have them, why would they? The vids cover the entire conventions, not just the F-35.
Deletehttp://new.livestream.com/wab/tailhook
I am by no means an apologist for F-35C, but I think the program is pretty confident that they know the issues, and have solved the problem - at least the ability to grab a wire. They knew the wire data used to design the arrestment system for both aircraft was flawed, and based on the X-47B experience, knew the initial roll-in tests for the F-35C were not going to go well. The X-47B program is very small, and there were not a lot of competing priorities for test aircraft. They could modify the the hook design pretty fast, and they also don't have to worry about signature (the hook is stored in an open bay - not very stealthy.) For the F-35C, there is a huge test bureaucracy with different priorities to navigate. Scheduling an aircraft to modify probably took some time, more time than it took to design a solution, and then scheduling the modified aircraft for retests. Apparently, an interim design did some successful roll-in tests at Lakehurst over the summer, then a successful fly-in test at Pax last Christmastime (nice present.) It's unclear whether the fly-in test was the interim design, or the final. It is also unclear if any of the new designs alter outer mold lines, or have even been tested for RCS effects. The other thing I find weird is what is wrong with the Lakehurst test setup? It's supposedly undergoing some mods, which is why the December tests took place in Maryland. I don't want to sound conspiratorial, but I hope they're not trying to make things too easy. Anyway, what we do know (via the DOTE,) that a new hook added 125lbs or so to the F-35C, and later this summer, we'll see if it works on the boat.
ReplyDeleteHey, I'm late to the party - just saw the USNI article about 30+ roll-in grabs in early January. More fly-in tests scheduled for back at Pax over the next 4 months, then to the boat late in the year. Still not sure why they split the fly-ins / roll-ins tests the way they do, but maybe they are working on the EMALS system at Lakehurst. Who knows.
ReplyDeleteWe weren't given the whole story. The corrective action obviously went beyond reshaping the hook and adjusting the damper. The fix added 139 pounds to the aircraft and is now called the "redesigned arresting hook system."
ReplyDeleteFrom the recent report:
Other risks include the potential gouging of the flight deck after a missed cable engagement (due to an increase in weight of 139 pounds) and the potential for sparking from the tail hook across the flight deck because of the increased weight and sharper geometry of the redesigned hook.
Okay, the hook is heavier, but not 139 pounds heavier.
I caught that one too Don, if it is a simple redesign of the hook, why the 139 pound increase? Why the extra time?
DeleteWhen you look at how close the weight margins are, 139 pounds is a lot!
And then you couple that with the time factor, as Solomon did --
Deletenews report-
A Pentagon Concurrency Quick Look Review (QLR) of November 2011 says that all eight run-in/rolling tests undertaken at NAS Lakehurst in August 2011 to see if the F-35C could catch a wire with the tail hook have failed.
30 months (and counting) vs. 2 months for UCAS
JTF=WTF
The basic problem of course is the geometry of the hook placement.
ReplyDeleteimage -- F-35C v. F-18
http://www5.picturepush.com/photo/a/8828858/img/Anonymous/f-35-c-f-35c-f-a-18-j-15-naval-stealth-fighter-jet.jpg
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ReplyDeleteJust an idea of what the F-35C might face during testing....
ReplyDeleteUnnatural Acts of Landing - Patuxent River Naval Air Museum Association - The Kneeboard Mag'n Spring 2012
-“For most people, the idea of flight testing means seeing how fast an airplane can go or how quickly it can maneuver. While answering these questions may be part of a flight test program, there is more to flight testing than speed and agility. Navy carrier aircraft must also withstand the stressful loads of re-peated arrested landings (traps) that can exceed 6 Gs on the aircraft.
The landing gear must:
- Survive thousands of landing shocks
- Reduce the loads reaching the aircraft structures and crew
- Allow the pilot to stay in control of the aircraft’s behavior
Ground Loads Testing shows that an aircraft structure can withstand carrier operations at maximum takeoff and landing weights. Normal landings at these conditions are no problem. But testing must also show that an aircraft can absorb these loads when:
- Its sink rate (how fast it descends) is high (as much as 26 feet per second!)
- Its wings are not level when it lands
- Its tailhook catches an arresting cable to the side of the center line
- The carrier deck pitches and heaves...
...During Super Hornet development, Ground Loads Testing required 125 test flights, 370 catapult launches, 471 traps, & 3 years to complete. Incidents included blown tires & various air-plane parts (other than the wheels & tailhook) hitting the deck."
http://api.ning.com/files/8OBnZkm85rrIMYQKeV*ggLdFOJeVqjQZZd6TVym3edKjcGDND6Xeiz4Pmo1qdQel3UuSwHY4oOAYEPGPr3FYJaGwJlDafX1q/KneeboardSpring2012.pdf
There has been a cover-up in the F-35C program.
ReplyDeleteThe F-35C tailhook problem continues, now with a significant coverup. The initial 2011 diagnosis of a problem isolated to the hook itself was expanded to include the damper, requiring merely a hook redesign and a damper adjustment. Then in 2012 a much more significant structural problem was found. testing revealed higher than predicted loads, impacting the upper portion of the arresting hook system, referred to as the “Y frame,” where loads are translated from the hook point to the aircraft) and hold down damper.
Now in 2014 after a significant F-35C delay we get the DOT&E report and it doesn't mention any structural load problem leading to a significant F-35C redesign. The report doesn't mention the “Y frame." But the report does say, without explanation, that there has been an F-35C weight gain of 139 pounds. That's a significant weight increase on a plane where weight is critical. It strongly implies major structural changes in an attempt to correct a serious stress failure(s).
The Quick Look Review back in November 2011, which first reported the tailhook problem as it was known then, was prescient. "With corrective action still in development, the AHS is considered an area of major consequence. If the proposed redesigned components do not prove to be compatible with MK-7 arresting gear, then significant redesign impacts will ensue."
http://www.documentcloud.org/documents/274217-dod-quick-look-ahern-report.html