CV-18 Fujian/003 CATOBAR carrier thread

[AndrewS]

I don't know anything about US EMALS's inability to isolate faulty catapult. It sounds like they don't have a switch to cut it off from the bus which is unimaginable by me.

My understanding is that the Ford only has a single on/off switch for all 4 of the catapults

 

[Intrepid]

My understanding is that the Ford only has a single on/off switch for all 4 of the catapults

I understand it like this: the crew has to select three catapults, connect each of them to an energy storage device, then the system is booted up and the launch phase begins.

If there is a problem, the entire launch phase will end, the system will shut down and the problem will be fixed, or the fourth catapult will be selected instead.

The system is then booted up again and the launch phase is continued.

So it was 2015 to ? ... I would be interested to know if it's still like this or if the arrangement has changed.

 

[Intrepid]

For catapult testing the ship has to be turned:



In 2016 - after three years fitting out - CVN 78 was turned to show her stern to the open river for pier side testing of the precision approach landing system:

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[JamesRed]

Not very good with photoshop but I got ~135,000 pixels for the flight deck of the Fujian and ~141,000 pixels for the flight deck of Ford. The Fujian is 5% shorter than the Ford but the main portion of the deck of the Fujian seems to be at least as wide. In comparison to the estimated 80,000 tons vs 100,000 tons, which is 20% smaller - the flight deck is only 4% smaller.

 

[enroger]

I understand it like this: the crew has to select three catapults, connect each of them to an energy storage device, then the system is booted up and the launch phase begins.

If there is a problem, the entire launch phase will end, the system will shut down and the problem will be fixed, or the fourth catapult will be selected instead.

The system is then booted up again and the launch phase is continued.

So it was 2015 to ? ... I would be interested to know if it's still like this or if the arrangement has changed.

So there is no way to operate/maintain the catapults independently whatsoever? There has got to be a good reason for this seemingly cumbersome design

 

[antiterror13]

According to some commentators type 003 uses capacitors. Is using DC better than AC?

Interesting, capacitors is the future but more difficult and more advanced

MVDC is definitely better than MVAC, but very difficult for ship, but it seems China has managed to overcame the technical difficulties (Circuit breaker, etc)

 

[antiterror13]

AC is better option in long distance delivery for civilian uses while DC is better if delivery distances aren't long.

Thats the other way around ... Extremely high voltage DC like in China is to transport huge electricity from Western to the Eastern, and very long distance

HVDC has much lower losses than HVAC

read this

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.

 

[taxiya]

Except in that analogy the lamp is the catapult/motor and the energy store is the AC mains connected to the busbar inside your breaker panel.

So please correct me if wrong - if we were to apply the faulty lamp analogy to the US EMALS, it'd be like there's no on/off switch on the lamp, so you can't replace the light bulb without shocking yourself.

How so? How could the catapult motor (linear motor) and the energy store have no switch in the first place? Any device that engage or disengage them is acting as a switch regardless the name. How would you even be able to trigger the launch if you can not engage the storage and the motor to the bus? If you can not disengage them you would keep them constantly connected and the motor would be fed with electricity all the time, then your motor will get stuck at the end of the launch rail and melt.

I don't know how you picture this in your mind, it seems that something big is missing. Anyway, it is too far out of topic, I will stop here.

 

[taxiya]

My understanding is that the Ford only has a single on/off switch for all 4 of the catapults

That is really weird design to me. I need to see their diagram.
[edit]
A wild guess is like following.

bus -> switch -> 4 control cabinets -> 4 launch motors

Each cabinet is doing the work to excite the coils of one motor. Inside the control circuitry there is a power electronic component to engage and disengage the excitation of the coils. That component acts as a switch. However, even when this switch is off disconnecting the motor, the cabinet is still hot. It is impossible to do a repair on a faulty set when other cabinets are still hot.

Anyway, let's move on to CV-18 and go to the dedicated EM launcher thread for further discussion on EMALS if we can find more information.

 

[Michaelsinodef]

Not very good with photoshop but I got ~135,000 pixels for the flight deck of the Fujian and ~141,000 pixels for the flight deck of Ford. The Fujian is 5% shorter than the Ford but the main portion of the deck of the Fujian seems to be at least as wide. In comparison to the estimated 80,000 tons vs 100,000 tons, which is 20% smaller - the flight deck is only 4% smaller.

Do note, the 003 is 80k+ tons, not 80k tons.

So it could be anywhere from 80k to 89k tons.