F-35 Cancelled, then what ?

[Finnpog]

I was just thinking about you, JF, and your detailed and informative posts on ski-jump ramps when I read Spaz's post just above.

Interesting point about both the camber on the ramp and also the differences in main gear configuration.

You would assume that the nose gear was designed with a ski-jump in mind as there might not be the weight allwance to 'swap in' the C-model version.

[John Farley]

Finnpog

There are several points to consider for the F-35B ramp

The ramp max nose leg load case. I would guess this might be up to 3 times that standing stationary at whatever weight you are considering for takeoff (but I would expect the nose gear strength to be set by VL loads not ramp loads because with a VL overstress the oleo will probably not have time to compress and the strut can be considered almost as a rigid structure).

The max time on the ramp (the longer the time the further the nose oleo will be compressed for a given load and you don't want it to bottom as this will involve a shock load. (On the ramp the oleo has plenty of time to shorten despite its damping unlike with a heavy VL)

The profile. Obviously affects the nose leg loads. Dunno why they are talking of the need for a very accurate profile on the QE class. John Fozard always reckoned the tyres could accommodate even sudden changes like a lip of 1/8 inch where sections joined. This though may have been because the Harrier tyre pressures were low compared to may fast jets. What is very important is the exit profile which is needed to unload the nose leg from its very compressed state. Without that the shock loading as the leg suddenly shoots out to full length as you leave the ramp is again a nasty shock load. Could apply to the mains as well although this was not a problem with the Harrier main leg that I can recall.

[SpazSinbad]

Daytime VL DT-II

DAYTIME VL VIDEO ONLY:

F-35B Lightning ll - YouTube

[Engines]

Finn,

The F-35B gear was designed with a range of loading conditions in mind, including ramp work. However, (at least a few years ago) the ramp launch was not the stressing manoeuvre. If it became one, LM had the fix ready, which was an adjustment to the oleo metering system.

The 'C' model nose gear is a completely different beast and would not be considered for ski-jump work.

The ramp angle quoted here (12.5 degrees) is interesting, and indicates that the team are seeking to get the maximum available 'delta' from the ramp. The explanation of the advantages the ramp provides is very good, the only thing it misses is the fact that it also reduces pilot workload and improves safety.

As I've posted before, the ski-jump is the nearest I've ever seen to providing 'something for nothing', and the big 'something' is a massive improvement in launch payload. Give any aircraft designer a way of taking off with another 20% payload with no additional strengthening, easier handling and improved safety, and they would offer to have your babies. It's just another great RN invention for maritime aviation.

Great to see the team pressing forward at speed with the clearances - eight landings in one night is going some.

And for Killface - no one said that there aren't any thermal effects on the deck. It's whether they are acceptable or not that matters, and that's why the BAE team have been working the issue with LM for around 12 years now, using a mix of full scale tests, rigs and computer simulation. The fact that the test team are back on the ship doing large numbers of landings to the deck shows that they understand the issue and can cope with it. JF's comment is an excellent one to consider.

Best Regards as ever to the team actually doing the business,

Engines

[Finnpog]

Thanks folks.
Very informative once again. I appreciate the detail.

(I was slightly tongue in cheek about the C-Model. That's obviously hewn from the centre of the earth for CATOBAR dynamic forces.)

[Engines]

John,

Sorry, didn't see your post before I posted back to Finn.

As ever, you are bang on the money. It's not nose leg loads (they are set by max rate VLs) but rate of oleo closure while on the ramp, and the need to avoid bottoming the strut.

I'd suggest that concern over QE ramp profile was due to issues with one of the CVS's ramps that was not built as precisely as one would have wanted, and that led to limits on SHAR launch weight from that ship. You are also quite correct that the Harrier's very soft front tyre limited some of the issues. However, F-35's is a mite higher in pressure.

And finally, yes, the need to manage leg extension on ramp exit has been noted, and the team have been modelling and testing that since around 2002. Incidentally, the landing gear team at Fort Worth were quite the nicest bunch of people you could ever have wished to work with - great boss and very talented engineers working in a highly specialised field. They had very good assistance from the BAE team at Farnborough (all ex Dunsfold people) on all matters to do with ramps.

Best Regards as ever

Engines

[Courtney Mil]

Thanks, guys, for the informed postings here. All very interesting and encouraging. It clearly flies well and the airframe is doing what it should. Please, does anyone have any equally reliable encouragement about the systems?

Thanks again.

[John Farley]

Engines

Thanks. Especially the info re one of the CVS ramps.

As to me not remembering the Harrier main leg being a prob off the end of the ramp - wot a prat I am. Of course it wasn't a problem on extension as the main leg was selfshortening and had no rebound. Doh!

JF

[Killface]

And for Killface - no one said that there aren't any thermal effects on the deck. It's whether they are acceptable or not that matters, and that's why the BAE team have been working the issue with LM for around 12 years now, using a mix of full scale tests, rigs and computer simulation. The fact that the test team are back on the ship doing large numbers of landings to the deck shows that they understand the issue and can cope with it. JF's comment is an excellent one to consider.

You misunderstand me. I posted the picture of the F-22 takeoff in afterburner to show the F-35C afterburner picture Low Observable is trying to make a mountain from a molehole of, is quiet normal.

It was also Low Observable who said:

Cool pic, Spaz - though maybe "cool" isn't quite the word. No thermal effects on the deck there, nosiree Bob!

you have to forgive him, a lot of people have been counting on the F-35B to fail thanks to that heat, and he is extremely disappointed (and responding with immaterial snark) about the F-35B succeeding in an area he hoped it would fail. just as you point out no one said "no thermal effects" what they said is that the thermal effects wouldn't lead to issues.

Clearly there is heat effects on the deck, as there is with the Harrier and Osprey but its obviously within tolerances. (just as people said it would be)

Just to elaborate further this has been a huge bone of contention with Bill Sweetman:

U.S. Navy Details Ship Mods Required For F-35

"The changes confirm that Lockheed Martin and the Marine Corps issued erroneous statements in early 2010 regarding the environmental effects of the F-35B’s exhaust. At that time, a company spokesman said that “extensive tests” had shown that “the difference between F-35B main-engine exhaust temperature and that of the AV-8B is very small, and is not anticipated to require any significant CONOPS changes for F-35B.”

As he tried to paint any changes as "significant." which is of course a relative term. You will also remember that Bill Sweetman predicted exploding concrete that has yet to come to fruition as well.

I actually had a very snarky comment lined up for LO's original post myself, but decided to be civil and simply respond with a picture trying to show that stealth aircraft in burner on takeoff doesn't seem to effect them on their missions. And he should know this with his:

30+ years of open source research and analysis on stealth. Tracking JSF and its direct predecessors since 1986.

http://www.pprune.org/military-aircr...ml#post7848457

[NoHoverstop]

ski-jumping advanced STOVL

Following on from the undercarriage/ramp interaction discussion, another area where the F-35B designers have to be pretty savvy is how the flight control laws cope with finding themselves suddenly in the sky but in a situation where sustained flight is not instantaneously possible. We never did ski-jump take-offs with the VAAC Harrier's experimental FCS engaged (for real that is to say. We did do lots in simulation), because the margins for recovery from a yaw channel (read as nose-wheel steering in this context) runaway of VAAC's simplex (and sometimes just plain wrong!) control laws were just too small for comfort. However, prior to that assessment we did all the other work to allow for ski-jumps including letting the FCS know what was going on in this "special case", so that it would not try to fly straight away on leaving the ramp but instead get the correct priorisation and blending of accelerations. In our case the logic to let the monitoring software back-off temporarily to let the control laws get on with it was triggered by a combination of weight-on-wheels and airframe movement that could only happen on the ramp during a ski-jump. As I said, we never got to try it for real, so it will be truly a "great leap forward" for STOVL technology when an F-35B does it for the first time.

For what TJSF and the ITF have achieved so far

[LowObservable]

For a few of the slower learners around here:

As for Spaz's F-35C photo, I was not talking about the afterburner.

http://www.jsf.mil/images/gallery/sd...5testb_164.jpg

"Spalling" concrete was predicted by Navy engineers. This prediction is reflected in specs for VL landing pads that are being built today. So far, too, every VL we have seen is on such pads, or concrete protected by AM-2, or on steel decks.

Likewise, concern about ship-deck impact was also first raised by Navy engineers, giving rise to an ONR/DARPA effort to look at cooling schemes.

None of these things were invented by the media, oddly enough.

[JSFfan]

For a few of the slower learners around here:
As for Spaz's F-35C photo, I was not talking about the afterburner.
http://www.jsf.mil/images/gallery/sd...5testb_164.jpg

as a slow learner, I still don't know what you were talking about, here is a f-22 with vortex
http://i1.ytimg.com/vi/PyKYw_p1Hrc/h...jpg?feature=og

[SpazSinbad]

F-35B 'BlowTorch' Night Vertical Landing Videos :-)

Two F-35B Lightning II Jets Begin Developmental Testing II Aboard USS Wasp

Two F-35B Lightning II Jets Begin Developmental Testing II Aboard USS Wasp - YouTube

F-35B Accomplishes First Night Vertical Landing Aboard USS WASP

You Tube

[SpazSinbad]

Sung to the tune of 'FireStarter' (NOT F-35B) Video

The Prodigy - Firestarter - YouTube

[glad rag]

No Spaz. You just don't get that Prodigy song, do you!

[SpazSinbad]

My Preferred 'FireStarter' Youtube Video

Yeah this version is more to my liking.... even though these are Kiwi KAHUs there are ex-A4Gs there in the mix - probably. All single seat ex-A4Gs gone to KAHUs with one exception are in USofA today with DRAKEN.

RNZAF A4K Skyhawk and P3 Orion Firestarter 99.mpg

RNZAF A4K Skyhawk and P3 Orion Firestarter 99.mpg - YouTube

[SpazSinbad]

F-35Bs 40 STOs & 41 VLs as of 18 Aug 2013 USS Wasp

F-35B Accomplishes First Night Vertical Landing Aboard USS Wasp 20 Aug 2013

"...As of August 18, the two F-35Bs participating in DT-II, known as BF-1and BF-5, had completed a total of 40 short takeoffs and 41 vertical landings...."

Lockheed Martin · F-35B Accomplishes First Night Vertical Landing Aboard USS Wasp

[SpazSinbad]

VIDEO Twilight F-35B Ops WASP

F-35B Twilight Operations on the USS Wasp

"Published on Aug 21, 2013
The Integrated Test Force operates F-35B test aircraft aboard the USS Wasp at twilight in August 2013. The tests were a part of Developmental Test Phase Two for the F-35B short takeoff/vertical landing variant."

F-35B Twilight Operations on the USS Wasp - YouTube

[SpazSinbad]

F-35B FRP $110 Million - 22% Drop Op/Sup Costs Bogdan

F-35 Support Costs Fall 22%, Pentagon Manager Estimates 21 Aug 2013 Tony Capaccio

"A fleet of Lockheed Martin Corp. (LMT)’s F-35 fighters will cost $857 billion over 55 years to operate and support, 22 percent less than previously estimated, according to the head of the Pentagon office developing the plane.

The new estimate reflects the aircraft’s performance in 5,000 test flights over 7,000 hours, Air Force Lieutenant General Christopher Bogdan, the Defense Department’s program manager for the F-35, told the Senate Armed Services Committee in written answers last month that haven’t been made public until now.

“The previous cost estimate did not factor in this new knowledge,” Bogdan said.

Operating costs include expenses from spare parts to repairs and fuel. Officially, the Pentagon’s estimate remains $1.1 trillion, a two-year-old projection developed by the Pentagon’s independent cost-assessment office....

...Bogdan estimated that basic production costs, including engines, for the three variations of the aircraft will fall as much as $35 million per plane by fiscal 2018, when full-rate production is scheduled to begin.

If current trends hold and production rates increase, Bogdan said, the Marine Corps version will fall to $110 million a plane from $153 million under the fifth production contract signed in December.

The Navy’s version will drop to $100 million from $140 million and the Air Force’s to $85 million from $120 million, he said...."

F-35 Support Costs Fall 22%, Pentagon Manager Estimates - Bloomberg
_________________________

F-35 operating cost drops below $1 trillion -source 21 Aug 2013

"Aug 21 (Reuters) - The U.S. government now estimates it will cost $857 billion to operate and maintain a fleet of more than 2,000 Lockheed Martin Corp F-35 fighter jets over 55 years, a drop of more than 20 percent from the previous estimate of more than $1 trillion, according to a senior defense official.

The new estimate reflects actual data about the airplane's performance and revised assumptions about how it will be used in combat...."

F-35 operating cost drops below $1 trillion -source | Reuters

[Rhino power]

IF current trends hold and production rates increase, Bogdan said, the Marine Corps (and RAF/RN's) version will fall to $110 million a plane

Only $110m per copy? Bargain!...

-RP