Steam Catapults in Eagle/CDG/Clemenceau Class Carriers compared to Essex Class

Hi aschachter!

I just stumbled on your post.
I am in no way an expert so
i’ll limit myself to handing you
those links from my bank.
Hope you find something you like,

http://www.globalsecurity.org/military/systems/ship/cv-design.htm

and

http://www.flightglobal.com/pdfarchive/view/1955/1955%20-%200425.html

and

http://usmilitary.about.com/library/milinfo/navycarriers/blhistory-6.htm

and this dicussion elsewhere

http://www.strategypage.com/militaryforums/9-3569.aspx

Good reading and good day.:)

The “simultaneous launch & recovery” was only really needed because of the large size of the USN supercarriers’ air wings, and only possible because of the size of the ships.

The smaller air wings could not muster enough operational aircraft to sustain truly continuous flight operations, so there was always time to shift between portions of the cycle.

However, the large air wings could keep pairs or quads of aircraft launching & recovering on a steady basis… thus requiring separate launch & recovery areas.

This was enabled by the number of deck-edge elevators and the large deck area, allowing “up” aircraft stored in the hangar to be brought up to replace returning aircraft with malfunctions that would then be struck down, and for aircraft movements to be accomplished… all while air ops were still continuing.

The small deck area of the Brit/French ships meant there wasn’t room to do more than one thing well and another poorly at the same time, much less the “all 3 well at once” of the supercarriers.

The Essex class conversions recieved their catapults before the angled deck was approved for installation. The SCB-27A programme was for axial decked ships, with two H-8 Hydraulic catapults installed forward. The follow on SCB-27C programme was intended to be along the same lines but with the first US Steam Catapults in place of the Hydraulic ones. Halfway through the programme the descision to incorporate the angled deck was taken (SCB-125), and this was done on the last three ’27C ships before they left dock. The other ’27Cs and all but one of the 27As recieved their angled decks at their next refit. The Midway class were undergoing similar upgrades and recieved their angled decks along with their steam catapults. Because their refits were slightly later, they were a little better thought out, and being larger ships they were able to incorporate a third steam catapult on the angled deck. Midway and FDR had their portside deck edge lift at the forward edge of the angle as in the Essex class and the new Forrestals, but operational experience showed this made the lift useless during flying ops, so the third Midway class refit (Coral Sea) had her portside lift moved aft of the port catapult (similarly the follow on ‘Improved Forrestal’ or Kitty Hawk class also moved the port lift aft, as did all later US CV/CVNs).

The RN’s postwar carriers were all wartime designs updated, and initially all had their catapults whether hydraulic or steam mounted forward side by side as in the Essex class. When Eagle was reconstructed between 1959 and 1964, operational experience with angled deck carriers was enough to suggest moving one of the catapults from the foredeck to the angled deck, as the foredeck (Fly 1) was mostly required for deck parking. Just being able to leave several aircraft there during flying ops relieved a lot of pressure on the deck crew. Ark Royal recieved this modified flight deck layout during her 1967-70 modernisation. The French Clemenceau class were built with this layout from the start. So the evolution of flight deck procedure for the British and French Navies primarily was that the portside of the deck was for flying ops and the starboard side was for deck parking (mostly). This worked fine for the smaller decks of the these Navies, the USN with larger decks had more options available to them. The new generation of the RN carriers (CVA-01 class, 3 ships planned) was the result of further studies into carrier operations, which determined that if the forward catapult was moved to starboard then simltaneous launch and recovery became possible. Also, the angled deck would move completley over to port to become the ‘Parallell deck’ creating more deck parking space to staboard. In fact the wide deck wwas divided into three areas, Landing runway and waist cat to port, deck parking to starboard and outboard of the island even further to starboard there was a deck edge lift aft serving a wide ‘Alaska Highway’ and leading to the starborad forward catapult, so aircraft could be brought up from the hangar and launched without disturbing the deck park or interrupting recoveries.

On the existing British and French carriers, simltaneous launch and recovery was never truly possible, but was not considered particularly important either. during flight operations the ship was either launching, recovering or respotting aircraft on deck, all of which was carefully planned in advance. Aircraft were flown in packages throughout the day, eg four Phantoms and four Buccaneers together with a Gannet would be launched, then a flight of Sea King would be ranged on deck and launched. After that the next package would be spotted ready for launch, perhaps a couple of Bucc tankers or a recce Bucc and a relief Gannet etc. Once these were off the deck would be readied for the return of the first package, which would be spotted at fly one on recovery then if needed struck down to the hangar decks. In practice the deck crew could change from ‘Flying stations’ to recovery stations in a couple minutes, as long as it took to re spot any unlaunched aircraft clear of the runway. Returning aircraft did not turn up unexpectedly demanding to land on, Flyco would always have enough time to ready the deck for recovery. Even the crash Barrier needed between two to ten minutes to rig (depending on how well the deck crew were practiced) should the returning aircraft have an emergency. The ability to simltaneouly launch and recover aircraft is ‘nice to have’ but certainly not essential to carrier ops. More it is the fact that it implies a better thought out and generally larger deck that comes with it.

It should therefore be taken that the flight deck configuration of the modernised Essex class CVs should not be seen as contemporary with Ark Royal/Eagle post modernisation and the Clemenceaus, but with the earlier configurations of the RN carriers in the 50s as well as the Centaurs and Victorious.