Launched directly from hangar

[archipeppe]

In the very first years of aircraft carriers development both English and Japanese envisioned launch of their aircrafts directly from the hangar. This result was usually achieved through an opening in the bow, at the hangar level, and a catapult that launched aircraft in the ship's direction, like the deck ones one floor above.

Interestingly, during WWII U.S. Navy needed so badly more catapults that they thought to place them even on the ship's side, launching directly the aircraft fighters and recce from the hangar.

In this optic, even if generally less knows, the first 6 Essex class ships were equipped with side catapults (they should be USS Essex, USS Yorktown, USS Intrepid, USS Hornet, USS Franklin, USS Lexington).



Trials happened during 1944 involving aircraft like F6F and TBF-1, obviously the catapults itself was shorter than the ones present on the flight deck, furthermore they didn't launched in the ship motion direction, with general poor performances (let's imagine the pilot's joy....).


A F6F-3 Hellcat ready to be launched by the USS Hornet (CV-12).


A Grumman F6F-3 Hellcat of VF-15, launched by USS Hornet (CV-12) on 12 February 1944 when the ships was located in Chesapeake Bay.


The same aircraft as above during its side launch.


A Grumman TBF-1 Avenger of VT-5 launched by the USS Yorktown (CV-10).

Even if the concept itself proven feaseble, at the end of 1944 trials the whole thing was judged too complex or at least unsatisfactory and it was abandoned.
By the end of 1944 all the side catapults on the Essex class aircraft carriers were removed.

 

[TomcatViP]

@archipeppe : Having seen this last picture (TB-1) long ago, this is the first time I am given the chance to understand it. Many thanks.

 

[EwenS]

Some additional info on the cross deck catapult in the USN.

The cross deck catapult on the hangar deck goes back to the early 1930s and the design of the USS Ranger CV-4, albeit that they were never fitted to her as an economy measure. Subsequently Yorktown CV-5, Enterprise CV-6 & Hornet CV-8 each received a hangar deck H-2 model catapult as well as two of the same model on the flight deck. Wasp CV-7 received 2 such hangar catapults as well as 2 on the flight deck. At that time catapults were little used as aircraft were relatively light weight but even less use was made of those on the hangar deck (Enterprise used hers 3 times in 1941 out of 21 catapult launches total). On 17 Feb 1942 their removal was authorised, and by June 1942 that had been done on Enterprise and Hornet. Yorktown retained hers when sunk. I don’t know about Wasp, but she did receive a short refit in May/June1942 before departing for the Pacific so their removal is possible.

The Essex class were designed in 1939/40 with an H4A cat on the flight deck and an H4B on the hangar deck. Equipment shortages saw Essex complete with none. She received a flight deck catapult only before deploying to the Pacific in mid-1943. Lexington CV-16 also only got the flight deck cat at completion.

The 6 that received the hangar deck catapult were Yorktown CV-10, Intrepid CV-11, Hornet CV-12, Franklin CV-13, Bunker Hill CV-17 and Wasp CV-18. As these ships came in for refits and damage repairs in 1944/45 the hangar deck catapults were removed and a second cat installed on the flight deck, so bringing them into line with later completions.

Those Essex class completing from the beginning of 1944 had the hangar deck cat replaced with a second flight deck cat.

As aircraft weights increased the hangar deck cats were found to be of less and less use since there was no additional benefit from the wind over the deck generated by the ship’s speed through the water to aid the launch. Hornet CV-12 was the last to lose her hangar deck cat in her Jun-Sept 1945 refit.

In the pre-war British (Furious, Courageous and Glorious) and the Japanese Akagi and Kaga) there were no catapults at hangar deck level to assist aircraft in taking off. All takeoffs from the hangar deck level in these ships were unassisted. As aircraft grew in size and weight this became impossible. So the Japanese rebuilt their ships to eliminate the feature in the mid1930s.

In C&G the lower flight deck wasn’t used after 1935 and the doors welded shut. Furious’s forward hangar opening was plated in as part of her 1938/39 refit.

Incidentally no Japanese Carrier was equipped with a catapult.

Catapults only reached RN carriers with the completion of the conversion of Courageous in 1928. Of the earlier carriers only Argus ever received one before being either sunk or retired.

 

[Tzoli]

No Japanese carrier equipped with catapult remained with such catapults equipped. At least Kaga but maybe Akagi as well were equipped experimental catapults but these were removed when they were modernized.

 

[GTX]

Another view showing one of the catapults:

Source

 

[EwenS]

No Japanese carrier equipped with catapult remained with such catapults equipped. At least Kaga but maybe Akagi as well were equipped experimental catapults but these were removed when they were modernized.

Are you sure about this? I’ curious, do you have a source?

The Warship articles I have by Hans Lengerer published back in the 1980s make no mention of this installation on either ship.

Over at Combined Fleet, usually one of the more reliable sources when it comes to Japanese warships, the comment is that while the catapult seatings were installed in Kaga in a May-Nov 1940 refit, it is not clear whether the 3 air-propelled catapults themselves were installed or not.

Kaga

 

[DWG]

An unmentioned issue so far is hangar deck catapults mean you need to keep a whole section of the hangar out of use for the other things supposed to be happening in the hangar. Remove that usage and it frees up a fairly significant area of space for aircraft storage/maintenance/warming up. It's possibly a smaller issue for the forward launching designs as they needed very short take off runs and could use the unenclosed bow for that - ISTR the RN spent a significant period only using hangar deck launch for the lightweight Flycatchers, not for the heavier strike and reconnaissance aircraft.

 

[Jemiba]

, obviously the catapults itself was shorter than the ones present on the flight deck, furthermore they didn't launched in the ship motion direction, with general poor performances (let's imagine the pilot's joy....).

The Hellcat, not to mention the Avenger, are a different class of aircraft, compared to the Supermarine Walrus, being
about half the weight. But, not to forget, about double the installed power, too.
And the Walrus was launched from a number of RN ships (King George-V class BB, County class CA), from a catapult
maybe not that different to the US type, in exactly the same direction, as a standard type of use.
(Photo via reddit,

https://www.reddit.com/r/Warthunder/comments/230bxr

View: https://www.reddit.com/r/Warthunder/comments/230bxr/a_supermarine_walrus_amphibian_airplane_being/
)

 

[Tzoli]

No Japanese carrier equipped with catapult remained with such catapults equipped. At least Kaga but maybe Akagi as well were equipped experimental catapults but these were removed when they were modernized.

Are you sure about this? I’ curious, do you have a source?

The Warship articles I have by Hans Lengerer published back in the 1980s make no mention of this installation on either ship.

Over at Combined Fleet, usually one of the more reliable sources when it comes to Japanese warships, the comment is that while the catapult seatings were installed in Kaga in a May-Nov 1940 refit, it is not clear whether the 3 air-propelled catapults themselves were installed or not.

Kaga

For Kaga here:

https://www.secretprojects.co.uk/threads/ijn-post-taiho-fleet-carrier-plans.32387/#post-388563

https://www.secretprojects.co.uk/threads/ijn-post-taiho-fleet-carrier-plans.32387/#post-388564

and

https://pbs.twimg.com/media/CTvA3UiUwAAenqb?format=jpg&name=large

 

[Tzoli]

Only Kaga received Catapults as the images shows, Akagi did not but I suspect it was considered as well.
When Oyodo was still in the hybrid phase of Cruiser-Carrier design it featured catapults (likely the widely used gunpowder type)

(Images are from Japanese carrier oriented magazines)

I wonder what was the technical difficulties of developing a Hydraulic catapult similar to what the RN and USN used but the IJN were not figured out?

 

[Brickmuppet]

When Oyodo was still in the hybrid phase of Cruiser-Carrier design

Whut?

Oyodo was at one point conceived as flight deck cruiser?
Given the Japanese preliminaries for the Shokaku and the role of the Oyodo this makes sense, but I'd never heard anything about it. (Not that I have ever paid much attention to the Oyodo) Do you have any citations or stats on the ship in that design phase? 8000 tons is awfully small for a carrier landing.

 

[Tzoli]

Oyodo started it's life in 1938 as a small cruiser of 5.000tons with 4x2 12,7cm Type 89 this enlarged to 6.600tons but armament unchanged and possibly reflecting the change as the E16A Paul grew in size (Both designed to carry 6 floatplanes)
By late 1938 Oyodo grew to it's almost final size: 8.200tons 2x3 155mm 4x2 10cm still 6x floatplanes
The Cruiser-Carrier design was W-105 which looks like had the same hull size as the Oyodo but displacement doubled to 16.600tons (Had to re-check my sources) and 20 aircrafts

 

[EwenS]

, obviously the catapults itself was shorter than the ones present on the flight deck, furthermore they didn't launched in the ship motion direction, with general poor performances (let's imagine the pilot's joy....).

The Hellcat, not to mention the Avenger, are a different class of aircraft, compared to the Supermarine Walrus, being
about half the weight. But, not to forget, about double the installed power, too.
And the Walrus was launched from a number of RN ships (King George-V class BB, County class CA), from a catapult
maybe not that different to the US type, in exactly the same direction, as a standard type of use.
(Photo via reddit,

https://www.reddit.com/r/Warthunder/comments/230bxr

View: https://www.reddit.com/r/Warthunder/comments/230bxr/a_supermarine_walrus_amphibian_airplane_being/
)

The catapults on the flight deck and hangar deck, although different model numbers, are of the same length, or almost so. The hangar deck cat had extensions at both ends that folded upwards when not in use, which brings its overall length up to that of the flight deck cat.

As for the respective aircraft weights I’m not following you. Maybe something has been lost in translation.

Walrus - empty 4,900lbs gross 7,200lb max t/o 8,050.
Hellcat - empty 9,414lb, loaded 12,647lb
Avenger - empty 10,843lb loaded 18,250lb

So both the Avenger and Hellcat are heavier empty than a Walrus at max take off weight.

 

[archipeppe]

In any case even German and Italian battleships and battlecruisers had catapults for their Arado Ar-96 or IMAM Ro-43 and Reggiane Re 2000.

 

[Tzoli]

When Oyodo was still in the hybrid phase of Cruiser-Carrier design

Whut?

Oyodo was at one point conceived as flight deck cruiser?
Given the Japanese preliminaries for the Shokaku and the role of the Oyodo this makes sense, but I'd never heard anything about it. (Not that I have ever paid much attention to the Oyodo) Do you have any citations or stats on the ship in that design phase? 8000 tons is awfully small for a carrier landing.

I was correct with the displacement.
Here is the page from Eric Lacroix's book:

 

[Brickmuppet]

Wow! Thanks! Thats really interesting.

 

[Tzoli]

Wow! Thanks! Thats really interesting.

Welcome, if you have questions on any other class feel free to ask

 

[Tzoli]

Regarding the matter of laucnh from hanger, the British proposed such carriers in the 1950's and 60's where there were catapults leading from the Hanger on an angled ramp, will post the drawings later when I find them.

 

[Dilandu]

A question; where there any attempts to put rotating catapult on carrier? So it could be used to launch planes in any wind direction?

 

[Tzoli]

I know no such realised ideas but again the same carrier I've mentioned for the RN a different one featured something like that
But remember rotating catapults are required for surface ships to launch the aircrafts out from the shadows and nuisance of the hull structures. The carreir is basically a floating airfield, plenty of space to take off of.

 

[Dilandu]

I know no such realised ideas but again the same carrier I've mentioned for the RN a different one featured something like that
But remember rotating catapults are required for surface ships to launch the aircrafts out from the shadows and nuisance of the hull structures. The carreir is basically a floating airfield, plenty of space to take off of.

Hm, I always though that main advantage of rotating catapult was the ability to launch into wind regardless of the ship's own heading.

 

[Tzoli]

yes but while a carrier could turn into wind easily and it does not matter if it's in a pursuit or actively searching as it has long striking range via the aircraft for a cruiser or battleship that would make a possible pursuit or search less efficient as sometimes the wind blows from the aft of the ship and making a full 180 degree turn just to launch an aircraft is not too optimal (if you lack rotating catapults). In case of the British that is compensated by the longer catapult length as they were usuall full cross deck length.

 

[Tzoli]

Here is the HMS Warrior envisioned with catapults.
And the two Hanger Catapult launch carrier design of the RN

 

[Ivan Culjak]

I know no such realised ideas but again the same carrier I've mentioned for the RN a different one featured something like that
But remember rotating catapults are required for surface ships to launch the aircrafts out from the shadows and nuisance of the hull structures. The carreir is basically a floating airfield, plenty of space to take off of.

Hm, I always though that main advantage of rotating catapult was the ability to launch into wind regardless of the ship's own heading.

In theory ( and in practice) yes, but with a disadvantage at throwing power.. Actually, turntables were first widely used catapults, in commercial service with Lufthansa,

Aircraft template

As said, the others, USA, GB, were using or planning to do turntable. But as said, throwing power was the reason to abandon them.
Here is a patent, https://patents.google.com/patent/US1960264
There was a good discussion:

Why didnt Kriegsmarine have aircraft carriers? - Page 7 - Axis History Forum

'In May of 1933 an eight-ton Dornier Do J II “Wal” flying boat made the first catapult launch from the Westfalen, a 428-foot steamer with a massive fixed catapult occupying most of her foredeck. (The plane had landed alongside the ship and had been hoisted aboard.) Regular service began in February of 1934. By abandoning the turntable catapult, with its limited throw-weight, and acquiring dedicated catapult ships, Lufthansa had greatly increased the permissible size of its planes and the distance and reliability of their service. Eventually the 110-foot catapults accelerated four-engine, 38,691-pound Blohm und Voss Ha 139B floatplanes and 44,092-pound Dornier Do 26 flying boats, machines eight times as heavy as the scout planes then being handled by the U.S. Navy’s turntables."

 

[Dorknought]

The USN had a catapult barge (ACV-1)

Aircraft Catapult Barge (AVC)

 

[Ivan Culjak]

The USN had a catapult barge (ACV-1)

Aircraft Catapult Barge (AVC)

As said there,
"Only the prototype was built, and after catapult trials it served as a static test article at Philadelphia until stricken in June 1944."
But anyway, if you have something more on trials of these type or other catapult concepts, welcome. But it seems that everything was still until Commander C. C. Mitchell.