Possibility small STOVL carrier USN/USMC

Discuss the F-35 Lightning II
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Thumper3181

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Unread post15 Jul 2009, 02:42

solomon wrote: i got drawn back in because Thumper3181 pinned you like a UFC fighter, pounded your statement like a piece of cold meat and sent your "version" of the facts back to the showers....but like a bad dream you won't let this go! wow...seek help.


Easy buddy. He is entitled to his opinion. This isn't the Key publishing forum. There are many knowledgeable and literate people here. We do not have to resort to name calling to make a point.

Spaz, I think you are missing the point that we are trying to make to you and believe it or not some of us also know a thing or two about naval aviation. You are comparing a much smaller plane with a much smaller payload, yet it is rated at 9G where in peacetime the F-35C is going to be rated at 7.5G. You can only put so much steam in the piston but lets assume that the amount of steam is sufficient that if necessary they could rip the nose gear out of the plane. In other words it is true there is plenty of steam to shoot the plane. It is true that the travel distance on the C-13s is somewhere around 200 feet, roughly double the old cats on your ship. The problem is that MTOW has more than tripled. Although T/W may be better on F-35C I may be wrong but I would guess that wing loading is better on the A-4. I think you are going to have trouble under more conditions with the F-35C at 22 knots than you would the A-4. Please show me where I am wrong.
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Unread post15 Jul 2009, 06:01

Thumper I am happy to answer questions as best I can, and I am only going to claim what I know rather than pretend I know more than that. I still think you have not understood the difference between what is commonly referred to as the Max/Min G loading for an aircraft and apparently the F-35C has a 7.5G limit (maybe the F-35A is different at 9G?). Whatever it is is irrelevant during a catapult shot. I am referring to the horizontal G force down the fore and aft axis of the aircraft. The G force more commonly referred to acts in the vertical plane either on (positive G) or under (negative G). If you know what this horizontal G force is then well and good because I do not.

Working out without the graphs or figures to do so what a JSF-C requires from different USN catapults to be launched at Max All Up Weight is something I cannot do. My stories illustrated the variables involved in any catapult shot calculation. Depending on what the various limits are then something sensible can be said about what various conditions can mean such as the WOD for example. Without these figures we can only guess as you have been doing. I'm not prepared to guess but prepared to educate you about the catapult in a general sense, especially about the horizontal G limit. You cannot make the vertical G limit the horizontal one unless that is fact. The A4G had a 6G limit (in a general sense) but had that much higher 9G limit in the horizontal down the catapult track fore and aft direction.

The physical effect of this G force on the pilot is like being punched in the chest with a closed fist. Breathing is impossible. Every pilot would hold their breath and tense up (as they do for vertical G force) in an effort to stop their breath being punched out of their lungs by the 6G A4G ordinary cat shot. I think the 'war shot' of just under 9G was only ever theoretical because it was likely never used in practice.

Yes extraploting from what one aircraft can achieve via a catapult shot under varying conditions to take that guesswork to another aircraft just compounds the guesswork. So not much point really. However as has been suggested the WOD can be important. My guess would be that the JSF-C has been designed with the catapults in use in mind so that it will not have a problem being catapulted at the maximum all up weight under reasonable conditions (whatever they might be). The story about aircraft being catapulted downwind attempted to highlight that sometimes WOD can be negative or NIL in the case of a catapulted aircraft from a carrier at anchor.

Another story, in the prop era there were several attempts to land aircraft with the straight deck carrier at anchor but hopefully pointed into the wind. I don't believe this silliness was ever attempted in the jet era but one never knows. Mabye Google knows. :-)

Also your figure of 200 feet for one catapult would be I guess a minimum length (without looking up catapult lengths for current nuke USN carriers) I would have thought that these catapults are much longer. The longer the catapult stroke the less the G force longitudinally needs to be to achieve the desired end speed (up to the limit of the groundspeed due to tyre limits). There are simple formulas to observe in mathematics but they are too simple to apply to the real world of the catapult because it is a mechanical device with the power at beginning, that usually starts to taper off somewhere down the stroke. EMALS neatly avoids that issue with computer/electric power tailored for each aircraft in a more refined way than today's methods (which are still good). The sustained application of less G force down the track keeps the aircraft under less stress with EMALS.
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Unread post15 Jul 2009, 06:18

Here is a different view of USN catapults:

http://www.fas.org/programs/ssp/man/usw ... riers.html

"From its four catapults, an aircraft carrier can launch an aircraft every 20 seconds. The catapults are about
300 feet long and consist of a large piston underneath the deck. Above the deck, only a small device engages
the aircraft nose gear. The catapult has two rows of slotted, cylindrical piping in the trough beneath the flight
deck. When the planes are ready for takeoff, the aircraft handlers on the flight deck guide the plane onto the
catapult and hook up the catapult to the plane's nose gear. On each plane's nose gear is a T-bar which pulls
the plane down the catapult. This bar on the nosegear of the aircraft attaches to a shuttle protruding from the
flight deck and connects to a pair of pistons in the trough. A holdback device installed on the nosegear holds
the aircraft in place as tension is applied. After a final check, the pilot increases the aircraft engines to full
power. When the engines are steady at full power, the catapult is fired , which accelerates the plane from 0 to
160 knots in under two seconds. On a signal from the catapult safety observer on the flight deck, steam is
admitted to the catapult by opening the launching valves assembly. (The length of time the valves remain open
is determined by the weight of the aircraft and the wind over the deck.) Steam surges into the cylinders,
releasing the holdback and forcing the pistons and shuttle forward while accelerating the aircraft along the 300-
foot deck. A 60,000-pound aircraft can reach speeds in excess of 150 mph in less than two seconds. The
shuttle is stopped when spears on the pistons plunge into waterbrake cylinders. A cable and pulley assembly
then pulls the shuttle back down the catapult for the next launch."
________________________
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from here: http://www.irconnect.com/noc/press/page ... l?d=135057

"Nimitz-class aircraft carriers have four steam-powered catapults that launch aircraft from the flight deck of the carrier. These catapults can propel a 48,000-pound aircraft 300 feet, from zero to 175 miles per hour in two seconds. Northrop Grumman will complete testing on all four of George H. W. Bush's catapults later this year."
______________
&
there are assumptions made in this calculation from: (best to download the doc - I'll make a graphic soon)

https://pumas.gsfc.nasa.gov/files/03_23_02_1.doc

"Exercise 4. Given that the length of the steam catapult (d) is 309 ft (94.2 m), and assuming the aircraft starts from rest and the catapult exerts a constant force on the aircraft, what “g force” does the pilot experience just before takeoff?

Solution: In addition to the length of the catapult, we can use the value for v we calculated in the first exercise, 256.7 ft/s or 78.2 m/s. Acceleration will be constant because force and mass are constant. Using two motion equations we are already familiar with, we can solve a system of two equations with two unknowns:

Dv = a t

And solve for t=2.41s and a=106.64 ft/s2 or 32.5 m/s2. If we divide the aircraft’s acceleration by the acceleration of gravity, we get 3.3 g’s experienced by the pilot in this case, meaning that all the pilot’s body parts and internal organs seem to weigh three times as much as normal. (Which actual hornet pilots confirm is in the right ballpark.)
______________________

The graphic below has been made from the same document above (the text only mangles the formulae) so the graphic is exactly what is seen in the doc. [Bear in mind the G force is the HORIZONTAL G FORCE in the direction of the acceleration down the 'longer' catapult track - shorter track more G force and on and on with other variables.]
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Unread post15 Jul 2009, 06:45

Good 'news item' opinion about EMALS and the RN Carriers: http://www.theregister.co.uk/2009/07/03 ... act_inked/

Go for it. Probably whatever this article implies is always debatable and never fact. The dire straits of the UK economy with not much money for new kit with an incredible squabble going on about it all would be fact though. I believe another inquiry into UK Defence requirements is being held because there is no money available for much.

&
http://navy-matters.beedall.com/cvf1-25.htm
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&
for the USN:

http://www.naval-technology.com/projects/cvn-21/

"General Atomics has been awarded the contract to develop the EMALS electromagnetic aircraft launch system which uses a linear electromagnetic accelerator motor. EMALS demonstrators have been tested at the Naval Air Systems Command (NASC) Lakehurst test centre in New Jersey. It is planned that EMALS will replace the current C-13 steam catapults."
Last edited by spazsinbad on 15 Jul 2009, 10:28, edited 1 time in total.
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Unread post15 Jul 2009, 06:55

Concise explanation about USN catapulting (& other matters) here:

http://navysite.de/cvn/flightdeck.htm

"When the engines are steady at full power, the catapult is fired , which accelerates the plane from 0 to 160 knots in under two seconds. On a signal from the catapult safety observer on the flight deck, steam is admitted to the catapult by opening the launching valves assembly. (The length of time the valves remain open is determined by the weight of the aircraft and the wind over the deck.) Steam surges into the cylinders, releasing the holdback and forcing the pistons and shuttle forward while accelerating the aircraft along the 300-foot deck. A 60,000-pound aircraft can reach speeds in excess of 150 mph in less than two seconds."
_________________________

http://www.tpub.com/content/aviation/14 ... 10_135.htm
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Unread post15 Jul 2009, 23:54

ok, whats your point? four posts and i'm still missing what you're trying to convey. executive summary please.
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Unread post15 Jul 2009, 23:56

solomon, take a hike, the thread started with ELP post, you hijacked and I just followed thumpers incorrect statements & answered his questions and I'll ignore your stupid, very ignorant remarks completely.
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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Unread post16 Jul 2009, 01:55

yeah, i'll take a hike...right into your area of responsibility....what's your point cowboy? you've posted all this information and i want to know...whats your point?
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Unread post16 Jul 2009, 02:25

solomon I know you are incapable of following a thread. My concise answer would be the information about the catapults in use in the USN is for Thumper who thought they were 200 feet. Also you and Thumper have no idea how a catapult works hence the simple explanations etc. Don't bother me again with your crap.
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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Unread post16 Jul 2009, 02:52

you've focused in on the simplest of details in order to attempt to prove a point that continues to elude you. the only crap on here is your line of reasoning.
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Unread post16 Jul 2009, 03:32

Then prove that statement stupid.
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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Unread post16 Jul 2009, 06:02

spazsinbad wrote:I still think you have not understood the difference between what is commonly referred to as the Max/Min G loading for an aircraft and apparently the F-35C has a 7.5G limit (maybe the F-35A is different at 9G?). Whatever it is is irrelevant during a catapult shot. I am referring to the horizontal G force down the fore and aft axis of the aircraft. The G force more commonly referred to acts in the vertical plane either on (positive G) or under (negative G).

Working out without the graphs or figures to do so what a JSF-C requires

Also your figure of 200 feet for one catapult would be I guess a minimum length (without looking up catapult lengths for current nuke USN carriers) I would have thought that these catapults are much longer. The longer the catapult stroke the less the G force longitudinally needs to be to achieve the desired end speed (up to the limit of the groundspeed due to tyre limits).


EMALS neatly avoids that issue with computer/electric power tailored for each aircraft in a more refined way than today's methods (which are still good). The sustained application of less G force down the track keeps the aircraft under less stress with EMALS.



I very well understand the difference in G forces. What I was trying to point out is that the A-4 was probably built to a different standard than the F-35. Forces the nose gear of the A-4 can tolerate the F-35 probably will not.

I agree with you about the C-13, its travel is much longer than 200 feet. Correct as your excellent references show but we are not talking about C-13s. We are talking about what would be fitted to CVF. That catapult would be considerably shorter. Look at the picture at ther URL you gave me below. Fitted with Catapults as shown CVF would not be able to conduct simultaneous take off and landings. In order to do that the #2 catapult would have to be made considerably shorter.
http://navy-matters.beedall.com/cvf1-25.htm

I agree with you about emails. It does promise to be a more efficient, kinder way to launch aircraft.
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Unread post16 Jul 2009, 08:09

Thumper fair enough about now you refer to the new RN carriers. Difficult to know what is being referred to in this thread. Vaguely I recall that the 'beedall' page was referring to the C-13s anyway; but that is moot because they are not going to be fitted. Perhaps in the future an EMALS will be fitted for future aircraft after the JSF-B. I do not see any point in speculating other than that.

"Officials from both competing CVF teams made it clear during 2002 that given the development risks still associated with EMCAT technology, steam catapults in the form of the C13 system employed in all current US Navy carriers represented the only proven, reliable, low-risk solution for CVF at Main Gate. "Steam exists, and the C13-2 catapult is the launch system against which the JSF CV variant is being built," said a senior member of the BAE Systems ship/air interface team. "Its performance characteristics are going to be matched around that technology". A Thales source concurred. "Today's steam-catapult technology is very, very reliable. There are still a lot of unknowns concerning EMCAT technology, such as pulse effects on other ship systems." (from the 'beedall ' reference given above)

The A-4 was NOT towed by the nose gear, I guess this would allow the higher horizontal / fore and aft G force for the catapult. All the strain was taken by two catapult hooks under the main frame alongside but inside the main wheels. One reason why the Skyhawk disappeared quickly from the USN was the changeover to the new way of launching aircraft. The pic below attempts to show arrangements.

I am not concerned with the CVF with catapults because it is not happening (for now). Sadly perhaps none or only one will be built - due to the lack of finances. How any catapults would theoretically be fitted (despite the rough sketch) my guess would be that the bow cat would still be usable for simultaneous arrests and cats on the CVF. [HMAS Melbourne was too small for those ops - the landing foul line went over the beginning of the catapult as it seems to do in the rough CVF sketch - depending on accuracy etc.]

To get back to the JSF-C on USN carriers. I would imagine that all the parameters are known given that the C-13 steam catapult is in use. My guess would be that the JSF-C can be catapulted at max all up weight (for the catapult) while doing that in normal conditions will not be a problem. The formula is a simple way to determine that but in practice computer simulations would be done with baseline data and then trials ashore at Lakehurst I think (EMALS is being tested/developed there also).

Now that we agree anyway that a JSF-C will be going down a 300 foot catapult in the USN, then the G forces are not going to be too dramatic, the JSF-C will be OK on USN carriers. AND this thread started to discuss ELP's notion of a small ski-jump equipped JSF-B carrier so why do we discuss catapults and JSF-Cs? I have no idea but it has been fun.
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Unread post17 Jul 2009, 02:25

spazsinbad wrote:"Officials from both competing CVF teams made it clear during 2002 that given the development risks still associated with EMCAT technology, steam catapults in the form of the C13 system employed in all current US Navy carriers represented the only proven, reliable, low-risk solution for CVF at Main Gate.

EMALS may have been the higher risk but it is going to get done. Steam is no longer an option for the Navy. If there are problems money will be thrown at it and heads will roll. EMALS was not going to work for the RN from the start because there is not enough spare generating power in the power plant they chose and the flight deck arrangements are all wrong. Simply put Thales botched the design.

spazsinbad wrote:I am not concerned with the CVF with catapults because it is not happening (for now). Sadly perhaps none or only one will be built - due to the lack of finances.

You are right but this was a self inflicted wound. Tranche 3 should not happen and the A400 dumped. Rather than building the Thales monstrosity they could have built 3 or 4 to the Italian, Spanish or Japanese designs or they could have modified the LHA to take the RR Gas turbines so it has a decent turn of speed and cost about 20 percent less than the Thales design to build.

spazsinbad wrote:Now that we agree anyway that a JSF-C will be going down a 300 foot catapult in the USN, then the G forces are not going to be too dramatic, the JSF-C will be OK on USN carriers. AND this thread started to discuss ELP's notion of a small ski-jump equipped JSF-B carrier so why do we discuss catapults and JSF-Cs? I have no idea but it has been fun.

I never had any doubt that F-35C could be launched at full load from a C-13. We got off on a tangent because I tried to point out to you that when you take a really good look at the CVFs and you look at the politics, catapults were never and will never be an option for them.

As for ELP, well lets just say that he has an equally bad understanding of modern project management, macro economics and now naval aviation. The following is for ELP’s benefit.

First, modern PM lesson. It makes no sense to test excessively with your prototypes when you have vetted models, component testing procedures, simulations and test beds. You can eliminate much of the early flight testing and with it much of the development cost.

Second the Macro Economics lesson. Due to the fact that the US dollar remains the world’s reserve currency and that is not changing anytime too soon, Obama can simply print money. The risk he runs is not bankruptcy but inflation. ELP likes to trot out the fact that the Chinese are bank rolling the US deficient when in fact all they are doing is keeping costs in the US low by soaking up debt. They are stuck in a “dollar trap” The hold trillions in paper and in return we got trillions in goods. Who has the better of the deal? If they dump their notes the value of the dollar goes down and they hurt themselves. Not going to happen. We can keep doing this until there is a nation with the natural resources, domestic market, relative stability and economic prowess that exceeds that of the US. Not going to happen anytime soon.

Third, the naval aviation lesson. Why would I want to use the least capable, most costly model of F-35 for power projection? Why would I want to base them on a relatively slow ship with little combat endurance when compared to a CVN? Why would I want to base them on a ship that cannot embark it’s own fixed wing AEW or air refueling? Study after study has found that the large deck CVN is the most cost effective and flexible platform for naval aviation. Fitting a ski ramp and neutered (relatively speaking) F-35 to a gator boat is not cost or combat effective when you have the luxury of 11 CVNs in your fleet.
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Unread post17 Jul 2009, 03:03

Thanks for the ending to get us back on track thumper. Perhaps ELP did not pose the question correctly. I would have thought that the USMC would run a dedicated small ski jump carrier (with all the grunt required) using JSF-Bs so that the USMC own and control the whole package (I guess the Navy run the ship) with the aircrew/maintainers and Command & Control being Marine to go and do what the Marines require. Of course I'm only dreaming.

I guess until the RN carriers are built using JSF-Bs there are going to be some unknowns. Personally I would be confident that the RN FAA will get the best out of what they are given - to surprise some of us anyway. Remember the Falklands War.
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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