Forum: F-35 Lightning II

Composites Machining for the F-35 Article From: Modern Machine Shop , Peter Zelinski, Senior Editor Posted on: 8/3/2010 [Long article]

http://www.compositesworld.com/articles ... r-the-f-35

"Lockheed Martin’s precision machining of composite skin sections for the F-35 provides part of the reason why this plane saves money for U.S. taxpayers. That machining makes the plane compelling in ways that have led other countries to take up some of the cost. Here is a look at a high-value, highly engineered machining process for the Joint Strike Fighter aircraft....

....The F-35 features “supportable” VLO. That is, the VLO on this plane comes with very low maintenance cost.

Stealth aircraft of the past couldn’t make that claim. Because radar detects sharp edges, even small mismatches between exterior parts on past VLO planes were smoothed out using epoxy. The epoxy would dry, harden and separate in the field—meaning it had to be frequently inspected and replaced.

By contrast, adjacent parts of the F-35 match so fluidly and precisely that no epoxy is needed. The trouble with previous stealth aircraft has disappeared...."
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OLD PR about 'affordable stealth' reminder [March 18th, 2008]:

F-35C STEALTH ON THE CARRIER DECK MEANS HIGH PERFORMANCE, LOW MAINTENANCE
http://www.lockheedmartin.com/news/pres ... rrier.html

"...technicians have spent the last decade perfecting the aircraft’s stealth design and materials to ensure they stand up to harsh carrier-deck and combat conditions with very little upkeep.
“The F-35C’s stealth will bring a profound increase in capability to the Navy’s fighter fleet. What it will not bring is increased maintenance,” said Steve O’Bryan, a former carrier fighter pilot and director of F-35 Domestic Business Development for Lockheed Martin. “The Lightning II is a 5th generation fighter with supportable stealth that was designed into the aircraft from the very beginning. It will endure extreme abuse without degrading its stealth radar-signature performance....”

...The F-35 achieves its Very Low Observable stealth performance through its fundamental design, its external shape and its manufacturing processes, which control tolerances to less than half the diameter of a human hair. Special coatings are added to further reduce radar signature.

The package is designed to remain stealthy in severe combat conditions, and tests have validated that capability. After obtaining baseline radar cross section (RCS) measurements from a highly detailed, full-scale Signature Measurement Aircraft (SigMA), a team of Lockheed Martin and Northrop Grumman engineers intentionally inflicted extensive damage – more than three dozen significant defects – on the model. The damage represented the cumulative effect of more than 600 flight hours of military aircraft operations. RCS measurements taken after the damage showed that the stealthy signature remained intact.

“Even operating in harsh carrier-deck conditions, the F-35C will require no special care or feeding. In fact, its stealth adds very little to the day-to-day maintenance equation,” O’Bryan said. “We’ve come a long way from the early stealth airplanes, which needed hours or even days of attention and repair after every flight. The F-35 not only avoids that intensive level of upkeep, it will require significantly less maintenance than the nonstealth fighters it is designed to replace....”

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Interesting stuff and they seem extremely confidant that affordable and low maintenance stealth qualities can be achieved, which is something which I and i'm sure many others were very sceptical about.

I'm beginning to think they have actually cracked it now though.

Salute!

Thanks, Spaz.

SHAPE IS EVERYTHING!!!!! No secrets there. Go see Skunk Works ref's about the F-117 prototype. Ben Rich's book is a good one. The problem was figuring out the optimum shape for the expected attack profile. So the "diamond" shape of the Have Blue prototype achieved the goal. Further tweaking reduced the RCS even more. Way back in the late 40's the Northrop flying wing ( YB-49, I believe) was very hard to see when coming straight toward the ground radar station. Hmmmmm.....

All should remember that we're talking about RCS less then 0.001 meter squared.

You don't have to have the Romulan cloaking device. You just have to be able to get within strike distance before the other guy in the air or on the ground can do anything to stop you from launching.

Gums sends ...

One can only surmise what the DoD beancounters based their estimates on how much it would cost to maintain the F-35's stealth?

Sorry if I'm little sceptical to this, the "affordable" stealth jet is the subject of acrimonious debate in the aerospace community worldwide. The more so as its development has been delayed and prices for early deliveries are climbing.

While Professional Engineers and the technologists charged with developing the JSF have been struggling with a myriad of challenges of their making, the marketing and PR strategies of the JSF Program and their authors have built up a mythology centred around “a total indifference to what is real” which what we all know as “Bullshit”.

One of the larger forms of “a total indifference to what is real” resides in the claim that “Affordability is the cornerstone of the JSF Program”, as the following APA analysis shows:

http://www.ausairpower.net/APA-NOTAM-190209-1.html

Lockheed Martin claimed the F-22 to be affordable, so how can we believe them now? Smile

thg wrote:

Sorry if I'm little sceptical to this, the "affordable" stealth jet is the subject of acrimonious debate in the aerospace community worldwide. The more so as its development has been delayed and prices for early deliveries are climbing.

While Professional Engineers and the technologists charged with developing the JSF have been struggling with a myriad of challenges of their making, the marketing and PR strategies of the JSF Program and their authors have built up a mythology centred around “a total indifference to what is real” which what we all know as “Bullshit”.

One of the larger forms of “a total indifference to what is real” resides in the claim that “Affordability is the cornerstone of the JSF Program”, as the following APA analysis shows:

http://www.ausairpower.net/APA-NOTAM-190209-1.html

Lockheed Martin claimed the F-22 to be affordable, so how can we believe them now? Smile

You claim it is all BS, but then cite an APA article? That is just funny all by itself.

The APA team does have an open agenda (as does the JSF team) but that does not mean that their data is bad.

Forum Veteran Joined: Apr 16, 2005 - 03:16 PM Posts: 800

It's not sure that affordable stealth is impossible. Stealth is for the most part faceting. The SH is not very faceted and has an RCS in the order of 0.1sqm.

Just by using the same type of material and RAM coatings as the SH on a faceted airframe you can reduce its RCS by several orders of magnitude and get in the VLO range.

And the SH costs 42 million flyaway after 500 produced.

Viperalltheway wrote:

It's not sure that affordable stealth is impossible. Stealth is for the most part faceting. The SH is not very faceted and has an RCS in the order of 0.1sqm.

Just by using the same type of material and RAM coatings as the SH on a faceted airframe you can reduce its RCS by several orders of magnitude and get in the VLO range.

And the SH costs 42 million flyaway after 500 produced.

With due respect, I don't think the Super Bug is a good example of a stealth platform or the cost associated with stealth.

I've been impressed with they've been able to accomplish with the basic airframe, especially since Lockheed has long insisted that stealth cannot be 'bolted on'. But at the same time, the Super Bug's L/O credentials only hold for the clean airframe. It can't do much that is useful in this configuration. Bolt on a couple of pylons and things that go boom and it's RCS balloons.

I think internal carriage of weapons is a big part of a tactical stealth design. The design and production cost for that feature has got to be pretty significant.

I think the Silent Eagle might be a more interesting comparison. If Boeing has been able to give that aircraft the same treatment it gave the Super Bug, with internal carriage, it might qualify as a useful stealthy tactical aircraft. From general interest readings, I'm curious as to how successful they've been. There obviously isn't a sharp chine around the craft, the engine faces still look very exposed (radar blockers aren't a perfect fix), the canopy still appears to be framed, and I wonder what they've done with the radar bulkhead.

Forum Veteran Joined: Apr 16, 2005 - 03:16 PM Posts: 800

You don't get my point. I say that if you took the same level of composite material and RAMs as on the F-18 and used that on a completely faceted aircraft you would already have a VLO aircraft.

The difficulty is to make an aircraft with a VLO shape that can fly well. Once you have that a faceted aircraft with internal bays and a large fuselage is more expensive but not necessarily MUCH more expensive. Why would it be much more difficult to build something faceted than something not faceted?

Viperalltheway wrote:

You don't get my point. I say that if you took the same level of composite material and RAMs as on the F-18 and used that on a completely faceted aircraft you would already have a VLO aircraft.

The difficulty is to make an aircraft with a VLO shape that can fly well. Once you have that a faceted aircraft with internal bays and a large fuselage is more expensive but not necessarily MUCH more expensive. Why would it be much more difficult to build something faceted than something not faceted?

Isn't it a bit of a truism to say that putting the right materials on the right shape will get you most of the ways to stealth?

The materials don't only have to be stealthy; they have to meet the performance and maintenance requirements of the aircraft. The materials don't just have to work well; they have to play well adjacent materials to prevent corrosion. There have been problems on the B-2 and the F-22 in this regard.

The shape doesn't just have to be faceted; that faceting is affected by the performance of the aircraft shape. The planform and panel edge alignment angles on the -22 for example are dictated by the sweep angle of the nose and wings. The shape has to have an adequate volume to carry the mission load. Dynamic loads and load paths associated with the structure change with open and closed weapons doors.

I take your point that stealth itself likely doesn't have to be as expensive as it has been. Have Blue was done on a relative shoe string and the technology should get cheaper with experience. Part of the reason that recent stealth programs have been much more expensive has been because of other requirements (e.g., blistering performance on the -22; interoperability on the -35).

Forum Veteran Joined: Apr 16, 2005 - 03:16 PM Posts: 800

Yes of course I don't disagree with that. The biggest challenge is to find a shape that can give you the specifications you want. If you can't find it too bad forget it if you can you're in business.

The F-22 and B-2 use a more advanced combination of materials and RAMs because they have the lowest RCS possible but the JSF doesn't have such drastic requirements. That's why the F-35 is faceted but less. And because of that it may have an even better aerodynamics than the F-22 because the shape of the F-22 is very angular.

thg wrote:

Sorry if I'm little sceptical to this, the "affordable" stealth jet

Lockheed Martin claimed the F-22 to be affordable, so how can we believe them now? Smile

Had they purchased the original 750 they would have been affordable.. duhhhhh Just what did you expect the price to be when they go from planning to buy 750 to 187 and only buying 20 per year as well????????

Beazz

Beazz wrote:

Had they purchased the original 750 they would have been affordable.. duhhhhh Just what did you expect the price to be when they go from planning to buy 750 to 187 and only buying 20 per year as well????????

Beazz

Because in opposite land buying more expensive things saves you money!!

The unit cost might have gone down, making each jet relatively more affordable, but the program cost would have still gotten bigger.

Beazz wrote:

Had they purchased the original 750 they would have been affordable.. duhhhhh

Affordable? The F-22 Raptor, is too delicate to deploy and has never been used in combat, fearing the plane’s advanced avionics and radar-avoiding capabilities could fall into enemy hands. The F-22 Raptor and the F-35 Joint Strike Fighter have run up so high that the government cannot afford to purchase significant numbers of either of them.

Forum: F-35 Lightning II

How F-35 Affordable Stealth Obtained