Forum: General F-35 Forum

spazinsbad - about the highly negative speculation, it was just that, speculation. I don't know how this cable thing wasn't caught sooner, and it seems inconceivable that such a critical design element wasn't tested during the QDR. The allegations of fraud were, as you say, over the top, but the idea that the F-35C may have to be dramatically changed is also an extreme occurance. Personally, I just think that the simulations that they used didn't capture the correct cable dynamics, but I have no evidence for that.

The problem with the tail hook is this: how could such a critical capability for the F-35C not have been caught sooner? We don't know.

My comment about the flight path was this, the F-35C's flight path for a carrier landing may work, I am certainly not qualified to say yes or no. The only issue may be that the tail-hook didn't have the right shape for that approach.

Anyway, to the document, I found this interesting quote on the 5th page: "The basic size of the variants is as large as can be supported by the allowable STOVL performance level ... For the sake of commonality, the other two variants are of the same basic size as the STOVL variant." Once again, the basic premise of my complaint about STOVL is true, the F-35A and C are more variants of the F-35B than the other way around.

My criticisms of the STOVL variant comes from this idea, that the performance of the F-35A and F-35C were limited because of the STOVL variant; the STOVL requirement set the boundary for weight and dimensions, thus making the other two versions sub-optimal. This can be seen with the tail-hook issue. The F-35C's design is clearly on the extreme end of tail-hook positioning, especially compared with current aircraft, and that position was driven by the need to make the F-35B STOVL. If the F-35C wasn't tied to the F-35B's shape, the F-35C may have had a much more optimal tail-hook position, among other attributes.

I didn't notice that document discussing the F-35C's tail hook positioning, it discussed gear locations, aerodynamic requirements, etc.

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Not having read the 1Mb PDF recently I'll assume you are referring to the 'how to design' PDF? From memory you will note that the aircraft is 'designed to the ship'. IF the ship cannot take a differently designed aircraft then the ship is not changed. OK? Yes minor changes might be made on any ship to handle any new aircraft but the ship dictates the design along with the carrier approach requirements. You can take a quote from any source to back up any claim about the F-35 at this point - either good or bad. So no problem. I still make the point that a long time ago it was decided to make the three variants as common as possible. How can the F-35B be blamed. Is it sentient?

And by the way search out your own documents to back up your guessing. As mentioned that small PDF is only one out of many or referenced ad nauseam in the latest version of the "how to deck land" PDF. I realise there is more in that 2GB PDF than could interest most people but it can be 'flicked through' to find what might be relevant to your interest - if any. Maybe if you read some of it you will have more knowledge? But then again I don't claim to know what knowledge you have already to make the claims you have made so far. I'm happy to provide information as I find it but you can contribute also - rather than just your apparently ill-informed guesswork.

arkadyrenko wrote:

spazinsbad - about the highly negative speculation, it was just that, speculation. I don't know how this cable thing wasn't caught sooner, and it seems inconceivable that such a critical design element wasn't tested during the QDR. The allegations of fraud were, as you say, over the top, but the idea that the F-35C may have to be dramatically changed is also an extreme occurance. Personally, I just think that the simulations that they used didn't capture the correct cable dynamics, but I have no evidence for that.

The problem with the tail hook is this: how could such a critical capability for the F-35C not have been caught sooner? We don't know.

My comment about the flight path was this, the F-35C's flight path for a carrier landing may work, I am certainly not qualified to say yes or no. The only issue may be that the tail-hook didn't have the right shape for that approach.

Anyway, to the document, I found this interesting quote on the 5th page: "The basic size of the variants is as large as can be supported by the allowable STOVL performance level ... For the sake of commonality, the other two variants are of the same basic size as the STOVL variant." Once again, the basic premise of my complaint about STOVL is true, the F-35A and C are more variants of the F-35B than the other way around.

My criticisms of the STOVL variant comes from this idea, that the performance of the F-35A and F-35C were limited because of the STOVL variant; the STOVL requirement set the boundary for weight and dimensions, thus making the other two versions sub-optimal. This can be seen with the tail-hook issue. The F-35C's design is clearly on the extreme end of tail-hook positioning, especially compared with current aircraft, and that position was driven by the need to make the F-35B STOVL. If the F-35C wasn't tied to the F-35B's shape, the F-35C may have had a much more optimal tail-hook position, among other attributes.

I didn't notice that document discussing the F-35C's tail hook positioning, it discussed gear locations, aerodynamic requirements, etc.

I think that it is clear that the requirements of the STOVL variant placed limitations on the designs of the CTOL and CV versions.

maus92 - getting other people here to accept that fact is like pulling teeth... Its obvious, it was set at the core of the program, and yet no one wants to accept it? But, I'm not going to speculate why.

As to the problems with the landing sequence, I read most of the documents, websites, etc. And, the only answer I can give is that we'll see if the new hook design works or not. I presume that the F-35C's approach is the optimal approach for the aircraft and the carrier, and I presume that a proper hook geometry will work with that approach, but as this is the shortest tail hook design in recent memory, both in terms of weight of aircraft and length from rear wheels to tail hook, the success of the hook will be notable.

And, as the STOVL variant was sized to fit a LHA, the Carrier variant should by all reason fit the CVN. Though, the carrier has taken a wide range of aircraft sizes, and the F-18 has a bigger footprint, without wing folding, compared to the F-35C.

Last edited by spazsinbad on Dec 17, 2011 - 04:07 AM; edited 3 times in total

Differences of opinion/fact can be quite different. I can happily accept that the F-35B requirements affected the other variants. But I don't get crankily emotional about it. "IF this and IF that were not true." But That's Life.

[edit] My method of seeing is this: that the requirement for STOVL replacement gave eventually reason for the three variants (by Congressional act] with all the benefits - and yes some disadvantages - all that entails. Why whine about it though?

arkadyrenko I don't follow your last sentences "...And, as the STOVL variant was sized to fit a LHA, the Carrier variant should by all reason fit the CVN. Though, the carrier has taken a wide range of aircraft sizes, and the F-18 has a bigger footprint, without wing folding, compared to the F-35C." I don't see any suggestion that the F-35C will not 'fit' the CVNs. Is that what you meant?

On that very topic from the PDF [http://handle.dtic.mil/100.2/ADA399988] here is the table with ship size parameters:
(having no luck uploading attachments today so photobucket it is - this point is emphasised because moderators have requested all attachments be uploaded and not hotlinked).

http://i98.photobucket.com/albums/l261/ ... nStats.gif

While I too am disappointed about the lack of testing for the F-35C and how long it took to discover this tailhook problem I'm still optimistic that this isn't a "deal breaker" and can be fixed. If the YF-17 could be redesigned into the F/A-18 (albeit with McDonnel Douglas experience with carrier aircraft) and the T-45 could be developed from the British Hawk which also is a land based aircraft (and interestingly enough, also with McDonnel Douglas input) I believe that the F-35C is fixable. Just my Two Cents

The question shouldn't be whether they can get the C to trap but rather what exactly will it take to do that? It's possible they can find a fix within the current structure or they might need a significant redesign of the C. In other words how much time and money is required?

Last edited by spazsinbad on Dec 17, 2011 - 10:49 PM; edited 2 times in total

The attached PDF is an heavily edited version of the original here:

http://www.globalsecurity.org/military/ ... /14310.pdf (5.6Mb)

In good text and graphic detail the 'nuts & bolts' of current USN arrest/recovery and catapult equipment is explained.... No can upload so the above URL is the place to get the whole thing.

"General Error
Could not connect to FTP Server: 'attach.high-g.net'. Please check your FTP-Settings."

Thanks to mods - file attachment upload problem fixed Cheers

FlightDreamz wrote:

While I too am disappointed about the lack of testing for the F-35C and how long it took to discover this tailhook problem I'm still optimistic that this isn't a "deal breaker" and can be fixed. If the YF-17 could be redesigned into the F/A-18 (albeit with McDonnel Douglas experience with carrier aircraft) and the T-45 could be developed from the British Hawk which also is a land based aircraft (and interestingly enough, also with McDonnel Douglas input) I believe that the F-35C is fixable. Just my Two Cents

Don't forget that the first F-35C didn't roll out of the factory until July 29, 2009. So they discovered the tail hook problem pretty quickly all things being considered.

Notice it wasn't even painted at the roll out ceremony.

alloycowboy That's a very valid point thanks for pointing out the time of the factory rollout (nice pic to illustrate the point too). I've griped about the lack of testing for the F-35C on other threads, not going to revisit it here (I mean after the STOL F-35B, the C is the hardest to develop why wasn't it run through more tests)? Oh wait, I remember, computer testing was going to solve all the problems (-SIGH!-)! Still maintaining an optimistic view that this can be fixed with too much time and expense.

maus92 wrote:

arkadyrenko wrote:

spazinsbad - about the highly negative speculation, it was just that, speculation. I don't know how this cable thing wasn't caught sooner, and it seems inconceivable that such a critical design element wasn't tested during the QDR. The allegations of fraud were, as you say, over the top, but the idea that the F-35C may have to be dramatically changed is also an extreme occurance. Personally, I just think that the simulations that they used didn't capture the correct cable dynamics, but I have no evidence for that.

The problem with the tail hook is this: how could such a critical capability for the F-35C not have been caught sooner? We don't know.

My comment about the flight path was this, the F-35C's flight path for a carrier landing may work, I am certainly not qualified to say yes or no. The only issue may be that the tail-hook didn't have the right shape for that approach.

Anyway, to the document, I found this interesting quote on the 5th page: "The basic size of the variants is as large as can be supported by the allowable STOVL performance level ... For the sake of commonality, the other two variants are of the same basic size as the STOVL variant." Once again, the basic premise of my complaint about STOVL is true, the F-35A and C are more variants of the F-35B than the other way around.

My criticisms of the STOVL variant comes from this idea, that the performance of the F-35A and F-35C were limited because of the STOVL variant; the STOVL requirement set the boundary for weight and dimensions, thus making the other two versions sub-optimal. This can be seen with the tail-hook issue. The F-35C's design is clearly on the extreme end of tail-hook positioning, especially compared with current aircraft, and that position was driven by the need to make the F-35B STOVL. If the F-35C wasn't tied to the F-35B's shape, the F-35C may have had a much more optimal tail-hook position, among other attributes.

I didn't notice that document discussing the F-35C's tail hook positioning, it discussed gear locations, aerodynamic requirements, etc.

I think that it is clear that the requirements of the STOVL variant placed limitations on the designs of the CTOL and CV versions.

As did the CV requirements. Commonality was king and the jet got as heavy as it is because the Navy drove the range/radius and internal weapons requirements and commonality also drove CV structural/loads consequences into the CTOL and STOVL variants. In fact, the Navy was the odd man out; the USAF was URF constrained -- it wanted F-16 replacement in numbers sufficient to replace existing force structure. The bigger and heavier the jet got, the more that need was compromised because it became more expensive. Rule of thumb at the time was $1500/lb. Do the math. Albeit for different reasons, 'bigger and heavier' is anathema to STOVL jets. F-35 got fatter (fineness ratio) and heavier due to CV requirements.

I quote from Chapter 3 of one of Sweetman's books -- "Ultimate Fighter" (Zenith Press, 2004) -- "The F-35 has four tails because it has to land on an aircraft carrier...The hard fact is, though, that the four tail layout is not the lightest or most efficient layout for the STOVL or CTOL airplanes." And later from the same chapter speaking of design requirements for commonality -- "...The goal is to reduce or eliminate 'scar weight,' which is the extra weight of a component that is needed to withstand CV loads but is still carried on the CTOL and STOVL versions without sacrificing too much commonality. It is a complex process, in which simplicity and commonality, and hence cost, must be traded against weight...".

I just want to reiterate that it was the US Congress that forced the services down this path.
Q: How many of them will now stand up and take responsibility for these problems?
A: None. It's everyone's fault but theirs.

To add to 'quicksilver's' comments here is some old text from an old 1990 GAO report to Congress about NATF which gives some more indication about carrier aircraft requirements in general. Probably similar text in the F-35 Design Consideration Influences PDF?...

Navy’s Participation in Air Force’s Advanced Tactical Fighter Program
March 1990 GAO Report

http://archive.gao.gov/t2pbat11/141083.pdf (2Mb)

Chapter 3
Basing and Mission Differences Affect Aircraft Design

Carrier Suitability
A key factor contributing to the design differences between the ATF and NATF is their different basing requirements. The ATF is designed to operate from land bases, whereas the NATF must operate from the pitching and rolling deck of an aircraft carrier at sea. To be suitable for carrier operations, the NATF must have, among other things, a stronger structure than the ATF to withstand carrier launches and recoveries; excellent lowspeed flying qualities tailored to carrier approaches and landings; and size, weight, configuration, and environmental compatibility with carrier operations.

Carrier Launch and Recovery
Carrier launch and recovery requires that an aircraft be equipped with a strong landing gear, an arresting tail hook, and a reinforced structure to withstand the high stress of catapult takeoffs and arrested landings. The acceleration, deceleration, and impact forces encountered by carrier-based aircraft are substantially greater than those experienced by land-based aircraft. For example, because land-based aircraft do not use catapults for takeoffs, they are not equipped with a nose landing gear suitable for catapulting or subjected to the substantial acceleration forces experienced during catapult takeoffs. Similarly, land-based aircraft do not routinely make arrested landings. Therefore, they are not equipped with a fully capable tail hook or normally subjected to the deceleration forces of arrested landings. The deceleration force experienced in arrested carrier landings is 24 times greater than that experienced by land-based aircraft, and the vertical impact force is over 3 times the level encountered by land-based aircraft.

Accordingly, a land-based aircraft’s landing gear, wings, and fuselage must be strengthened with additional materials and/or redesigned structure to enable the aircraft to withstand the stress of catapult launches and arrested landings. Air Force and Navy program officials estimate that, to accommodate these and the other Navy requirements, the empty weight* [*Empty weight includes the weight of an aircraft’s structure, engines, hydraulic and electrical systems, and avionics. It does not include such items as fuel and armament.] of the NATF will have to be about 4,000 pounds heavier than the ATF.

Low-Speed Flying Qualities
To ensure a safe carrier approach and landing, the NATF must be capable of a lower landing speed and more precise flight control during landings than required for the ATF. The low approach speed is necessary to stay within the structural load limits of the arresting gear aboard both the aircraft and the carrier. If approach speeds are too high, damage or failure of the aircraft’s or carrier’s arresting equipment is a risk. In addition, a carrier-based aircraft’s design must provide unusually good aerodynamic performance at these low speeds for the precise flight control needed during carrier approach and landing.

Size, Weight, and Configuration Compatibility
Although carrier-based aircraft tend to have heavier structures to withstand catapult launches and arrested landings, they must not exceed certain size and weight limits imposed by carrier operations.

The physical constraints associated with handling an aircraft above and below decks on an aircraft carrier pose strict limits on an aircraft’s size, weight, and configuration that are not normally imposed on land-based aircraft. The need to park and maneuver a large number of aircraft while avoiding obstructions, not only limits the aircraft’s length and width but also necessitates folding the aircraft’s wings, (See fig. 3.1.) Similarly, aircraft weight is limited by the capacity of the carrier’s elevators, catapults, and arresting equipment. For example, the carriers from which the NATF will operate have an elevator load capacity of 130,000 pounds and dimensions of 70 feet by 52 feet. Because the Navy has a design goal of lifting two NATFS on an elevator simultaneously, the Navy has limited the NATF'S size with wings folded to basically that of the F-14 and has limited its takeoff gross weight goal to 65,000 pounds.

The NATF must also be configured to accommodate carrier use and safe Carrier approaches and landings. The need for stability while maneuvering an aircraft on a pitching, rolling deck to prevent tipping to the side or back constrains landing gear placement. Further, main landing gear placement is also limited to allow for adequate wheel clearance from the edge of the carrier deck during catapult launch.

The NATF must provide the pilot with adequate visibility in addition to low-speed flying qualities to make a safe carrier approach and landing. Steep approach angles, required for carrier landings, demand that the aircraft’s cockpit and front fuselage design provide the pilot with an unobstructed view of the carrier deck and stern. This degree of over-the-nose visibility is unnecessary for a land-based aircraft. Consequently, the ATF cockpit, canopy, and front fuselage structure will likely be redesigned to provide the NATF pilot with an increased forward field of view...."

quicksilver wrote:

maus92 wrote:

arkadyrenko wrote:

spazinsbad - about the highly negative speculation, it was just that, speculation. I don't know how this cable thing wasn't caught sooner, and it seems inconceivable that such a critical design element wasn't tested during the QDR. The allegations of fraud were, as you say, over the top, but the idea that the F-35C may have to be dramatically changed is also an extreme occurance. Personally, I just think that the simulations that they used didn't capture the correct cable dynamics, but I have no evidence for that.

The problem with the tail hook is this: how could such a critical capability for the F-35C not have been caught sooner? We don't know.

My comment about the flight path was this, the F-35C's flight path for a carrier landing may work, I am certainly not qualified to say yes or no. The only issue may be that the tail-hook didn't have the right shape for that approach.

Anyway, to the document, I found this interesting quote on the 5th page: "The basic size of the variants is as large as can be supported by the allowable STOVL performance level ... For the sake of commonality, the other two variants are of the same basic size as the STOVL variant." Once again, the basic premise of my complaint about STOVL is true, the F-35A and C are more variants of the F-35B than the other way around.

My criticisms of the STOVL variant comes from this idea, that the performance of the F-35A and F-35C were limited because of the STOVL variant; the STOVL requirement set the boundary for weight and dimensions, thus making the other two versions sub-optimal. This can be seen with the tail-hook issue. The F-35C's design is clearly on the extreme end of tail-hook positioning, especially compared with current aircraft, and that position was driven by the need to make the F-35B STOVL. If the F-35C wasn't tied to the F-35B's shape, the F-35C may have had a much more optimal tail-hook position, among other attributes.

I didn't notice that document discussing the F-35C's tail hook positioning, it discussed gear locations, aerodynamic requirements, etc.

I think that it is clear that the requirements of the STOVL variant placed limitations on the designs of the CTOL and CV versions.

As did the CV requirements. Commonality was king and the jet got as heavy as it is because the Navy drove the range/radius and internal weapons requirements and commonality also drove CV structural/loads consequences into the CTOL and STOVL variants. In fact, the Navy was the odd man out; the USAF was URF constrained -- it wanted F-16 replacement in numbers sufficient to replace existing force structure. The bigger and heavier the jet got, the more that need was compromised because it became more expensive. Rule of thumb at the time was $1500/lb. Do the math. Albeit for different reasons, 'bigger and heavier' is anathema to STOVL jets. F-35 got fatter (fineness ratio) and heavier due to CV requirements.

I quote from Chapter 3 of one of Sweetman's books -- "Ultimate Fighter" (Zenith Press, 2004) -- "The F-35 has four tails because it has to land on an aircraft carrier...The hard fact is, though, that the four tail layout is not the lightest or most efficient layout for the STOVL or CTOL airplanes." And later from the same chapter speaking of design requirements for commonality -- "...The goal is to reduce or eliminate 'scar weight,' which is the extra weight of a component that is needed to withstand CV loads but is still carried on the CTOL and STOVL versions without sacrificing too much commonality. It is a complex process, in which simplicity and commonality, and hence cost, must be traded against weight...".

Wow, quick and I actually agree to some extent Smile

The F-35B design is the largest practical size for a STOVL jet, and forced the other variants to be single engine aircraft - not a big deal for a land based aircraft, but a big concession for the Navy who had been working to rid their decks of single engine aircraft. The CV version is a considerably larger aircraft than the others (for the reasons you mention) and has different internal structure - like a keel - to deal with the unique loads associated with carrier aviation. In hindsight, it looks like it may have been smarter to develop a separate twin engined naval aircraft with the same avionics systems as JSF, but the Navy was stuck with the political situation at the time. But the Navy may get lucky....

...forced the Navy variant to be single engine. Propulsion was/is part of the USAF URF constraint, and they will also tell you (with statistical justification) that modern single engine jets are safer than those with two.

Forum: General F-35 Forum

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