All Grounded F-35 Test Jets to Return to Flight

All Grounded F-35 Test Jets to Return to Flight

After weeks of being grounded the three late model F-35 Lighting II Joint Strike Fighter test jets have been cleared to fly. The jets’ return to flight comes after program officials tweaked maintenance procedures which had led to the failure of two generators and an oil leak during a test flight of an F-35A on March 9.

A March 25 email from the Pentagon’s F-35 office states:

Flight clearance was reinstated after an investigation and test data indicated a maintenance procedure resulted in excess oil remaining within the [alternate engine starter/generator] lubrication system. Previous maintenance procedures could allow a small amount of extra oil to remain within the generator following servicing. Under some conditions, the extra oil that is churning inside a narrow air gap within the AES/G could cause internal temperatures to increase. It was assessed that high temperatures led to the generator failures. Maintenance documents have been amended to provide improved engine starter/generator servicing procedures.”

The problem only impacts F-35s built relatively recently.

The backup generator kicked in during the March flight of an Air Force test F-35 known as AF-4, allowing the plane to safely return to Edwards Air Force Base in California.

The two most recent production F-35s have also been cleared to fly and the grounding did not have a “significant” impact the JSF’s development or production, according to the e-mail.

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A supposedly dual redundant system with a single point of failure isn’t a maintainence issue it’s a design flaw.


Oblat, this single point of failure you speak of is shared by every jet engine in the world.

Someone did not read the most recent version of the maintenance manual and over serviced the engine’s accessory gearbox. Too much oil makes for too much resistance (heat). Simple stuff and easily fixed, just make sure that in the future all the wrench turners know to put the proper amount of oil into the engine.

The aircraft making it back to base on only its #3 generator is a vindication for the survivability of the design.

yes its true
If we make a aircraft which needs only one time starting fuel thats a new FUTURE

A no doubt if it had crashed it would have been a vindication of design of the ejection seat.

Since the old generators do not suffer from this problem they obviously traded off safety to get the 40% extra performance they needed in the redesign of the generators.


Let us hope that those seats will not need to be tested anytime soon.

I have as much apprehension as the next skeptic about the cost and program management of the JSF. Having said that, to go off and use a human error (over filling the engine gearbox with oil) as a reason why the program is doomed is a non-starter in my opinion.

I think Lockheed have tried pushing the design envelop with the F-35 a bit too much and this is one of the problems with the program. Another is that the F-35A and F-35C variants of the F-35 should have been designed to use the Pratt & Whitney F119 engine that used in the F-22 Raptor as this would allow the F-35A/C to be capable of super-cruise and even more maneuverable with the thrust vector.

I’m curious; if LM will re-develop the generators as two independent devices similar to these non-independent devices, you think??

For the first time in history, USA have build one plane who reduce his overall capability and ruined the defense budget.
Don’t will see the next…

Not gone happen. The F135 has more power than a F119, so super-cruise is out. The F135 is basically a F119 configured for a single engine aircraft unless you use two, its not going to make a big difference.

Having the generator and the backup in the same unit means its NOT actually a redundant backup system.

This is engineering 101 stuff and No not every other fighter uses this setup.

The F-35 in question was lucky to get home, and that wonderful Honeywell IPP has got its own design issues.

Aside from an engine powered generator what other options are there for a modern fighter aircraft’s power needs?

F-35 power system redundancy in this case worked fine. It prevented a loss of aircraft, A dual generator fault caused switching to the next backup generator, which kept power on and kept charging the A/C batteries (the last chance backup) until the A/C returned to base. Fault did not occur in the generators per se, but in their lubrication system, and it was maintenance induced.
Make it as redundant as you want. There’s no such thing as ‘Maintenance OR Operator Proof’: a design can only be somewhat ‘resistant’.
Oh bla dee Oh bla on dat Oblat. Methinks thou speaks as ye hast ne’er turned a fair w®ench in thy life.

I’d believe that if there was in fact an actual maintenance manual to use…

The reason I say that is because when I was on the program, we mostly worked to the blueprints. The manuals were still being developed and revised and were not cleared for use, I would say 80%, of the maintenance actions. Since they are LRIP A/C, each bird has subtle design changes to it when it comes off the line. Wich means maintenace on each A/C may be slightly different in some areas. So I can see how it may have been a maintenace issue, but I doubt that it was if they were going by what the instructions told them to do.

Aux powerplants and ram air turbines.

ALL aircraft have “mechanicals”. Ask the pilots of the F-15 who punched out over Libya…

isn’t there a cia brief stating, that a mig-25 was involved?

also there is a good story posted on the ARES blog.

explaining why it failed (on the f-35)

Maybe it’s too much oil and maybe it’s not. I’ve done investigations on this type of equipment. You are almost never 100% sure even after thorough review of data. I have seen people jump to the first possible answer only to find out there is more to the story. That said, I hope they are right , this aircraft has sucked up more resources that it ever deserved. Unfortunately is is still poised to suck up even more…

“The backup generator kicked in during the March flight of an Air Force test F-35 known as AF-4, allowing the plane to safely return to Edwards Air Force Base in California.”

That is funny. Most all naysayers claim one of the biggest problems with the F-35 is that it does NOT push the design envelope…

The F135 is a BETTER engine for the F-35 than the F119. The F-35/F135 has/have notable different design intent from the F-22/F119. Cruising @ >Mach 1.5 without afterburner is not necessary for the F-35 — THAT is what the F-22 is for.

Only in your (& other naysayers’) dreams.


I don’t think half the commenters on here have ever turned a wrench in anger on any Mil-Spec A/C judging by what they say…

I gotta hard time visualizing a true stealth design using RAM air turbines. Just saying.…

Probably so; but I for one have turned many a wrench — both in the military and in civilian life. I’ve worked in industries that if you turned the wrench the wrong way, you blew up not only yourself but the entire plant! And in other jobs, I had a small wrench, but the laptop was the judge. So don’t underestimate the knowledge of the civilian posters here. I knew you didn’t anyway — just say’n…

The F-15 is getting so old — I’d believe anything! The sad fact is that any slightly modern aircraft with a composite structure is going to be almost impossible to rebuild. I feel it is smarter to develop better technology to make composite manufacturing processes more modular, so we can hope to return to a day at least similar to the airframe of the B-52 that can be rebuilt forever. In my opinion, the manufacturers have used stealth technology as an excuse to built in obsolescence. This, I feel is still just an excuse to fleece the taxpayer.

There is no excuse not to build modern F-15(etc.) structures using today’s kiln technology so we can save a butt load of money!! I reiterate the same for more modern designs.

You guys must work on this bird, why don’t you all get together and solve this problem?.….I mean, I’am just saying!

JSF Is a Total Waste of Funding. NO GUN on-board for Air-Air Combat, Afterburning engine for IRST recognition, NO Communications with F-22 or any legacy platforms and NO Creditable BFT-CID for Fratricide on Stealth Platform. What do you say!!! Let’s talk to Lockheed Martin and the 200 General’s they have working at Fort-Worth…. The Damn thing cannot even take out a Bridge without hanging Pylon’s not to mention that our AIM-120 A/A Weapon has a PK Rate of less than 20%. We need additional connectivity, longer range A/A Missile’s and Stand-off weapons. NOT another 15 Years of Hell on a Platform that is useless!!!!!!!!!!!!!!!!!!!!!!!! Get a Grip!!!!!!!!!!!!!!!!!!!! LOL… The APU Runs all the time on a JSF??? LOL.… Most APU’s have a automatic start in the event of a Fame Out or Engine Malfunction. This piece of garbage has an APU that Runs the entire flight on purpose…LOL…

No wonder is lemon has a one engine and a price tag of $150,000,000.00 each, times 2600. The President needs to fire, Gates, and all the rest of the senior staff at the Pentagon for allowing this piece of Garbage to be funded. This has been in WORK since 1994, 1995, and here we are… in the same old Lockheed Martin Wall Street Money Pit!!!!!!!!!!! Someone at the Pentagon needs to grow up and Flush this Program down the Drain!!!

I’m no fan of the F-35 program either, but at least get your facts straight before going on a tirade.

“NO GUN on-board for Air-Air Combat,“
Partly true. The Air Force variant (the A model) has an internal cannon. The Marine Corps (B) and Navy © variants have provisions for a reduced-radar cross-section gunpod mounted on the centerline pylon. The actual radar observability performance is yet to be seen for the gunpod.

“Afterburning engine for IRST recognition, “
Modern IRST sensors will pickup aircraft regardless of whether or not they use afterburning engines.

“The Damn thing cannot even take out a Bridge without hanging Pylon’s“
Actually the F-35 can carry two 500, 1000, or 2000 pound bombs internally. I’m not sure how many Small Diameter Bombs it can carry internally, but I believe the F-35 can carry about eight.

“not to mention that our AIM-120 A/A Weapon has a PK Rate of less than 20%.“
Wrong. The AIM-120 has a 90% pk rate with mid-course updates. Without the mid-course updates the pk falls to about 50% when fired from beyond the range of the AIM-120’s onboard monopulse radar. Some NATO allies purchased the AIM-120 without the mid-course updates option. American AIM-120’s are capable of datalinking with other aircraft (to include the E-3 Sentry aka “AWACS”) to receive midcourse updates from them.

“longer range A/A Missile’s“
The AIM-120D has 50% greater range over the AIM-120C-7, which puts it closer in maximum range to the AIM-54C Phoenix missile. However the maximum range of missiles are dependent on a variety of factors to include: relative heading between belligerent aircraft (head-to-head, tail-chase, deflection shot), relative altitudes, relative speeds, and speed of launching aircraft (higher aircraft speed and higher relative altitude provides greater initial starting energy, thereby increasing range).

“and Stand-off weapons.“
The AGM-154 Joint Standoff Weapon can be carried by the F-35A (I’m not sure if the B and C variants are capable of carrying it). The AGM-158 Joint Air-to-Surface Standoff Missile is still being developed, and the F-35 is one of the aircraft that it is planned to be carried by.

“The APU Runs all the time on a JSF??? LOL.… Most APU’s have a automatic start in the event of a Fame Out or Engine Malfunction. This piece of garbage has an APU that Runs the entire flight on purpose…LOL… “
I don’t have access to the technical information to dispute this. But based on your previous statements, this is tidbit has no credibility. If it is true, it’s likely that it’s not actually running operationally as it is running in a standby mode, where a dead-start would be too violent and would have a high chance of material failure with the internal components. Other aircraft do this with certain components, such as hydraulically-run emergency electric generators. In any case, this shouldn’t be considered a severely negative point unless the component fails excessively.… and that would be a a relative term since F-15 JFS’ (Jet Fuel Starter) are changed frequently for failures, particularly on aircraft launch.


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