Conversion of V/STOL aircraft-carriers for CAT/STOBAR operations ?

[F.L.]

This idea came to me when I read the story of HTMS Chakri Naruebet. Since 2006, it has had no air group following the withdrawal of the Thai Navy's AV-8S Harriers and the failure to purchase AV-8B or Sea Harriers.
Would it be possible to convert an S/VTOL aircraft carrier for STOBAR operations with aircraft such as the Sea Gripen, Rafale M or Kızılelma for countries who are not able to purchase F-35B ?
Given that some vessels of this type already have a skijump (Chakri, Anadolu, Canberra), the main modification would be to add arresting gear.
Given that some of these ships are designed to operate few aircraft (6 on Chakri), the bolter is less a problem than on the old straight-deck aircraft carriers.

 

[Temeraire]

Probably not the Chakri Naruebet, due to it’s small size the arrestor engines most likely wouldn’t fit and they’d have to make so many adjustments it would be more economical to purposely build a STOBAR ship.
The other ship you show NAM Atlântico (formerly HMS Ocean) is a definite no she cannot even operate STOVL aircraft with any real capability as she lacks a ski jump. Her aft lift is also in the way of any arrestor gear.

 

[CV12Hornet]

It would require a significant rebuild to backfit arresting gear, given that it involves so much belowdecks infrastructure. I won't say it can't be done, but it is expensive enough that just buying new has to get serious consideration.

Many of these carriers are straight up too small for STOBAR takeoffs anyway.

 

[F.L.]

And Anadalu with Kızılelma ? The NAM Atlantico also will be converted for drones operations.

 

[F.L.]

Brazilian Navy NAM Atlântico A140 is now a multipurpose aircraft carrier

Brazilian navy has reclassified its PHM Atlântico (A140) landing platform helicopter ship as a multipurpose aircraft carrier under the name of NAM Atlântico

navyrecognition.com

 

[F.L.]

The only VTOL carrier to have been converted to STOBAR is the Admiral Gorshkov (ex-Baku), transformed into the Vikramaditya for the Indian Navy.
But in fact, the Kiev-class carrier were much bigger (displacement of 44,490 tons loaded) than those mentioned at the start of the thread (11,486 tons full load for Chakri, 21,500 t for Atlantico & 27,436 tons for Anadolu), and much easier to convert, also because of their angled deck.

 

[CV12Hornet]

And Anadalu with Kızılelma ? The NAM Atlantico also will be converted for drones operations.

Anadolu is probably too small as well, but I think she's a maybe rather than a definitely not.

The only VTOL carrier to have been converted to STOBAR is the Admiral Gorshkov (ex-Baku), transformed into the Vikramaditya for the Indian Navy.
But in fact, the Kiev-class carrier were much bigger (displacement of 44,490 tons loaded) than those mentioned at the start of the thread (11,486 tons full load for Chakri, 21,500 t for Atlantico & 27,436 tons for Anadolu), and much easier to convert, also because of their angled deck.
View attachment 707477View attachment 707478

And also because the Indian Navy needed to pay for major ship surgery one way or another. This was a full-on rebuild.

 

[Scott Kenny]

Would it be possible to convert an S/VTOL aircraft carrier for STOBAR operations with aircraft such as the Sea Gripen, Rafale M or Kızılelma for countries who are not able to purchase F-35B ?

I don't believe that the Kizilelma would be able to operate off any ship smaller than a Kiev-class, it's using 2x F100 or F110s so it's roughly F22 sized(!)

 

[helmutkohl]

I don't believe that the Kizilelma would be able to operate off any ship smaller than a Kiev-class, it's using 2x F100 or F110s so it's roughly F22 sized(!)

Kizilelma is using one engine, I believe a Ukrainian one.
You are probably thinking of Kaan.

 

[F.L.]

I don't believe that the Kizilelma would be able to operate off any ship smaller than a Kiev-class, it's using 2x F100 or F110s so it's roughly F22 sized(!)

The Turkish want to navalise it.

 

[F.L.]

Given that the NAM Atlantico has been reclassified as an aircraft carrier, would it be possible that it is to operate navalised EM-312/314 Tucano ?
Would this be possible ?
A bit like the OV-10 Bronco on amphibious assault ships.

 

[BlackBat242]

I don't believe that the Kizilelma would be able to operate off any ship smaller than a Kiev-class, it's using 2x F100 or F110s so it's roughly F22 sized(!)

During Teknofest 2022, Baykar announced that there will be at least 3 variants of Kızılelma with different engine configurations. The engines are produced by the Turkish-Ukrainian joint venture Black Sea Shield.[32][33][34] Kızılelma-A will be capable of near-supersonic speeds, being powered by the AI-25TLT engine. Kızılelma-B will fly at supersonic speeds, powered by a single Ukrainian AI-322F engine.[35][36] The Kızılelma-C will incorporate two AI-322F engines.

• Powerplant: 1 × Ivchenko-Progress AI-25TLT Turbofan engine, 16.9 kN (3,790 lbf) thrust - no afterburners (Kızılelma-A).
• Powerplant: 1 × Ivchenko-Progress AI-322F Turbofan engine, 24.5 kN (5,510 lbf) thrust dry, and 9,900 lbf (44 kN) with afterburner (Kızılelma-B).
• Powerplant: 2 × Ivchenko-Progress AI-322F Turbofan engines, 49 kN (11,020 lbf) thrust dry, and 19,800 lbf (88 kN) with afterburner combined (Kızılelma-C).

Each F100 or F110 produces 15,000 lbf - 18,000 lbf dry and 24,000 lbf - 32,000 lbf... 50% more than 2 AI-322Fs!

So even the "large" Kızılelma has total engine thrust equal to one F404 - making it about the size of the F20 or the Gripen.

 

[Dilandu]

Would it be possible to convert an S/VTOL aircraft carrier for STOBAR operations with aircraft such as the Sea Gripen, Rafale M or Kızılelma for countries who are not able to purchase F-35B ?

Possible... but costly. You would need to add at least a small angle deck extention to make sure that your aircraft would not land along the main deck. And this would be a reasonable headache with stability issues.

Also, I'm not sure that most of those carriers have enough deck lenght to launch fully-loaded STOBAR aircraft. Definitely not long enough to put them one after another for quick takeoff.

P.S. I wonder, maybe a fuel-air catapult installation would be more practical solution?

 

[helmutkohl]

some US company proposed a conversion of a the 22,000 ton Izumo stovl carrier to a catobar

 

[F.L.]

some US company proposed a conversion of a the 22,000 ton Izumo stovl carrier to a catobar

Very interesting ! Nice find !

 

[F.L.]

Thank you, @helmutkohl, this gives us some basis for comparison.
The Izumo have a displacement of :
- 26,000 tons at full load,
- 19,500 tons standard.
And she is 248m long.
That seems to me to make the Atlantico's possible conversion a bit more feasible.

 

[riggerrob]

Let’s review deck length. The latest USN super carrier Gerald Fore is 1,000 feet long with an angled flight deck roughly 750 feet long and forward catapults about 300 feet long. Her flight deck is 256 feet wide.
Yes, you can combine the two on a shorter hull if you overlap them.
Mind you current doctrine - and current USN air craft - require an angled landing deck so that - in the event of a missed wire (aka. bolter) - the airplane can continue straight ahead and circle around for a second landing attempt.
While straight landings and mid-ships crash barriers (nets) might have been survivable at WW2 landing speeds, they would kill modern pilots and spray schrapnel all over the forward half of a modern ship.

The other problem with angled flight decks is that they require a wide beam (256 feet on Gerald Ford). Perhaps a retrofit could cheat by adding an external elevator to the starboard side of the stern and a second external elevator extending off the port thwart amidships.

 

[F.L.]

Mind you current doctrine - and current USN air craft - require an angled landing deck so that - in the event of a missed wire (aka. bolter) - the airplane can continue straight ahead and circle around for a second landing attempt.
While straight landings and mid-ships crash barriers (nets) might have been survivable at WW2 landing speeds, they would kill modern pilots and spray schrapnel all over the forward half of a modern ship.

Given that the ships in question carry few aircraft, it might be possible to leave the forward part of the straight decks clear in the event of a bolter.

 

[F.L.]

Given that the ships in question carry few aircraft, it might be possible to leave the forward part of the straight decks clear in the event of a bolter.

Like that :

 

[EwenS]

Given that the ships in question carry few aircraft, it might be possible to leave the forward part of the straight decks clear in the event of a bolter.

And that defeats part of the reason for having the angled deck in the first place - to speed up flight operations. To keep the forward part of the deck clear, means striking each aircraft down into the hangar as it lands and before the next one arrives.

Back in the 1930s that was why the crash barrier was developed, to keep aircraft just landed safe in the forward deck park area from those following.

 

[F.L.]

And that defeats part of the reason for having the angled deck in the first place - to speed up flight operations. To keep the forward part of the deck clear, means striking each aircraft down into the hangar as it lands and before the next one arrives.

Taking into account that a ship of this type carries 6/8 aircraft, the aircraft can be parked on the side of the deck.

 

[EwenS]

Taking into account that a ship of this type carries 6/8 aircraft, the aircraft can be parked on the side of the deck.

And you know that your crashing aircraft will continue in a nice straight line up the deck? Just how wide is your deck? Much less (but doesn’t eliminate) of a problem with an angled deck if it deviates from straight.

I think you would also need to position your arrester gear further forward than your “landing” aircraft appears to indicate. The objective is to keep the landing spot as close to midships as is practicable to minimise the effects of vertical stern movements in heavy weather. Otherwise the risk of deck accidents is increased. Note the location of the landing area (blackened with tyre marks) on Charles de Gaulle




And the Gerald S Ford





Even on a supercarrier vertical deck movements in heavy seas can be a problem, let alone the smaller vessels being considered here.

 

[F.L.]

In any case, there were some studies for CATOBAR sea control ship with straight deck. I think the problem of crash landings and aircraft parking was solved.

https://www.secretprojects.co.uk/threads/sea-control-ship-scs-and-vstol-support-ship-vss.7635/page-3

https://www.secretprojects.co.uk/threads/cvn-77-cvx-and-cvn-21-design-studies.809/page-2

3D Warehouse

3D Warehouse is a website of searchable, pre-made 3D models that works seamlessly with SketchUp.

3dwarehouse.sketchup.com

 

[Scott Kenny]

some US company proposed a conversion of a the 22,000 ton Izumo stovl carrier to a catobar

(image deleted for space)

Slide is from General Atomics Electromagnetics division (IIRC the guys who make the cats and arresting gear for the Ford class).

The port catapult is completely in the way of the angled deck, so only usable when there aren't any planes landing.

Even the starboard cat/JBD is not completely clear. I think the starboard cat would need to move about 10ft/3m outboard to clear the angled deck. At least the breech end of the cat needs to move outboard, the muzzle end does not have to; this would angle the starboard cat like the port cat.

 

[archipeppe]

Some months ago I spottend on Fincantieri's website a drawing resembling the CATOBAR version of the Cavour....

 

[Scott Kenny]

In any case, there were some studies for CATOBAR sea control ship with straight deck. I think the problem of crash landings and aircraft parking was solved.

https://www.secretprojects.co.uk/threads/sea-control-ship-scs-and-vstol-support-ship-vss.7635/page-3

https://www.secretprojects.co.uk/threads/cvn-77-cvx-and-cvn-21-design-studies.809/page-2

3D Warehouse

3D Warehouse is a website of searchable, pre-made 3D models that works seamlessly with SketchUp.

3dwarehouse.sketchup.com

View attachment 707564

The only issue with that is that you cannot launch and recover aircraft at the same time. If you're only launching one E2 every 4-6 hours and everything else is VTOL, that's fine.

 

[F.L.]

Some months ago I spottend on Fincantieri's website a drawing resembling the CATOBAR version of the Cavour....

@archipeppe, can you post it ?

 

[F.L.]

The only issue with that is that you cannot launch and recover aircraft at the same time. If you're only launching one E2 every 4-6 hours and everything else is VTOL, that's fine.

However, I believe that these ships were also to have F/A-18.

I find Lazarus.S's 3d model on the 3d Warehouse really cool.

 

[Scott Kenny]

However, I believe that these ships were also to have F/A-18.

No, they were supposed to have something like the Rockwell XFV-12 VSTOL supersonic fighter or some Harriers, a couple of VSTOL AWACS planes, and then a bunch of ASW helicopters. Modern day escort carriers, basically, to protect the convoys going to Europe in case of a war.

 

[TomS]

Slide is from General Atomics Electromagnetics division (IIRC the guys who make the cats and arresting gear for the Ford class).

The port catapult is completely in the way of the angled deck, so only usable when there aren't any planes landing.

Even the starboard cat/JBD is not completely clear. I think the starboard cat would need to move about 10ft/3m outboard to clear the angled deck. At least the breech end of the cat needs to move outboard, the muzzle end does not have to; this would angle the starboard cat like the port cat.

Yeah, this feels like GA having a lark more than a serious proposal. Aside from the layout issues, I'd question whether the Izumo class as currently built have enough electrical power generation to drive EMALS.

 

[F.L.]

No, they were supposed to have something like the Rockwell XFV-12 VSTOL supersonic fighter or some Harriers, a couple of VSTOL AWACS planes, and then a bunch of ASW helicopters. Modern day escort carriers, basically, to protect the convoys going to Europe in case of a war.

Yes, but I'm sure I read somewhere that F-18s were also part of a possible air wing.

 

[helmutkohl]

The old INS Viraat/Hermes technically could have done this?

It has a ski jump, arrestor cables, and an angle deck.. just not at the same time.

granted if the kept the wires and angle deck, and added the ski jump.. landing and take off would have to be at different times given how narrow/close the landing lane is with the take off lanem

 

[F.L.]

The old INS Viraat/Hermes technically could have done this?

It has a ski jump, arrestor cables, and an angle deck.. just not at the same time.

granted if the kept the wires and angle deck, and added the ski jump.. landing and take off would have to be at different times given how narrow/close the landing lane is with the take off lanem

Yes, if the hull hadn't been so old, they could have converted it for use with the MiG-29K once the Shars have been deactivated.
Or they could have done it back in the 90s to complement them with early MiG-29K.

 

[F.L.]

I tried to make a 3d of what could be the Chakri Naruebet after the addition of an angled deck.
I was surprised at the amount of space this added, and therefore the number of aircraft that could be parked on the deck.

 

[GTX]

Providing the weights and balances were managed...

 

[H_K]

@F.L. That angle deck is too big… would not be manageable from a seakeeping / stability perspective.

Back in the day I drew up a Principe de Asturias-sized CATOBAR carrier based on Bazan’s SAC 200/220 designs, but shrunk to 185 meters. It was as small as I dared make it! But that would have been a new build, not a conversion.

BSAC-185
22,000t CTOL carrier with 20 Sea Gripen, 3 Alize AEW & 4-5 helos

I shortened the carrier to 187m (613ft) waterline, exactly the same length as tiny Principe de Asturias! So it's now "SAC-185" I guess. This makes it 20 feet shorter than Invincible and a good 40ft shorter than Colossus! Displacement would still be 22,000t though due to the wider 92ft hull needed to support the flight deck (vs. 80ft for PdA &Colossus & 90ft for Invincible).

Airgroup of 20 Sea Gripen, 3 Alize AEW and 4-5 helos. Pretty impressive for the size. If fuel & munitions capacity stay the same as in the smaller PdA (1,367 tons av. fuel, ~250t munitions), that would still be good enough for 40-50 sorties per day for 5-6 days.

Note that I chose the Alize AEW because of its smaller wingspan and because I generally like its fairly aerodynamic design which gives it good endurance and speed versus the S-2 Tracker. It should be able to do the job just as well as S-2 Tracker AEW as long as you install a modern, uprated engine. For example, compared to the Alize's old Dart Rda.7, ta new 3,000ehp PW-127G provides 50% more power and burns 30% less while weighing 10% less! Enough space in back for two radar operators, plus the co-pilot who could be the mission commander. However, obviously returning a few Alize airframes to flyworthy status would be a feat! (Though perhaps no more than for an S-2?)

Reverting back to an S-2 Tracker AEW instead of Alize would have little impact though - just move the safety line outboard by 8-10 feet or so like on my previous drawing.

 

[F.L.]

Back in the day I drew up a Principe de Asturias-sized CATOBAR carrier based on Bazan’s SAC 200/220 designs, but shrunk to 185 meters. It was as small as I dared make it! But that would have been a new build, not a conversion.

Beautiful and super interesting, @H_K, I'm thinking of trying to redesign my Chakri with a smaller angled deck similar to your SAC-185 drawing.

 

[H_K]

P.S. It’s been 10+ years since that drawing… Sea Gripen is no longer an option and steam catapults also probably increasingly hard to source.

So if I was to refresh that drawing today, I would go with a ski jump, 18x Rafale STOBAR, and Merlin AEW.

I’d possibly also experiment with a slimmed down island, moved all the way back (where the aft elevator is) and diesel propulsion with waterline exhausts to eliminate the uptakes and improve the deck/hangar flow.

 

[F.L.]

I've managed to improve my 3d STOBAR Chakri with a much smaller but equally effective angled deck.
Modifications to the Chakri would also include the transformation of the side elevator to allow the use of Sea Gripens, following the disappearance of the rear one.
I like to imagine Thailand selling the Chakri to Brazil and then upgrading it to a STOBAR configuration with Sea Gripens as stopgap before arrival of of a nationally-built carrier.
Here it is !

 

[F.L.]