Aircraft Carriers II (Closed to posting)

airsuperiority · Nov 15, 2012

randomness of the day: 2 of the most powerful types of warships in the history of navies have the tamest names: aircraft carrier and submarines

bd popeye · Nov 15, 2012

The big problem was that, since the flight deck was the strength deck, holes (lifts, etc.) had to be kept to a minimum, so the internal hangar concept immediately translated into fewer and smaller lifts - compromising the ability to launch and recover aircraft.

Huh? I'm missing something. USN carriers since the Forrestal class have four aircraft elevators. The Ford class will have three. Although USN CVN carry only 62-70 aircraft these days because of precision guided munitions and budget constraints they are well capable of carrying 90 aircraft.

delft · Nov 15, 2012

Pointblank said:
It was not the discontinuation of wood in the flight deck that caused a switch to using the flight deck as the strength deck (wood usage in the flight deck was discontinued due to the increasing size of carrier aircraft, and the introduction of jet aircraft to the carrier air wing), it was the growing size of aircraft carriers, which caused problems with structural strength and stability.

USN carrier design practice pre-WWII and during was to design a carrier with an external hangar, that is, the hangar is located outside the ship's girder while the the RN practice was to design a carrier with an internal hangar; that is, the hangar is contained within the ship's girder. In short, USN practice was to make the flight deck part of the superstructure, while RN practice was to make the flight deck a part of the hull.

However, with the introduction of the Forrestal class carriers, the size of the carriers meant that stress requirements forced the abandonment of the external hangar and hangar deck as strength deck concepts. A shallow hull of that size is a design impracticality. In the Forrestal and after, the flight deck is the strength deck.

An external hangar offers large side openings so that aircraft can be warmed up on the hangar deck, loading and unloading aircraft is made easier, underway replenishment becomes easier and safer and, most importantly, flight deck damage and hangar deck fires are outside the main hull and therefore of less structural consequence. Deck edge lifts are also very easy to install as a result due to the already existing large openings along the side, and there are no major structural issues with placing lifts or holes in the side that would affect structural strength.

An internal hangar is contained within the ship's girder and is enveloped by the ship's hull. It is easier to protect, has better access to machinery shops and maintenance facilities and offers much better protection for the aircraft against bad weather. Deck edge lifts are difficult to install, of questionable value and have serious structural implications.

In structural terms, having an external hangar means that the upper strength deck is the hangar deck. This then means that the hull girder is shallower and thus more highly stressed. The best way to offset this is to thicken up the hangar deck so protection (armor) here grows naturally out of the design concept. If the flight deck is to be armored, that armor has to be in addition to the hangar deck protection.

It is not often realized that Midway started life as a parallel design to Essex, intended to explore the effect of that extra protection on the Essex design. On 27,000 tons, it was found that deck protection had a disastrous effect on airgroup capacity (as few as 60 aircraft rated capacity at a time when Essex was rated at 110). This bought protection against 250 pound bombs. After 1940, the Midway design went its own way, becoming a quite different program to the Essex class. Note though, that the hangar deck remained the strength deck.

The advantage of the internal hangar was that, by using the flight deck as strength deck, the British carriers had a much deeper hull girder, so the designers could use substantially lighter hull structural members, giving them a larger carrier for a given displacement. The big problem was that, since the flight deck was the strength deck, holes (lifts, etc.) had to be kept to a minimum, so the internal hangar concept immediately translated into fewer and smaller lifts - compromising the ability to launch and recover aircraft.

That is just what I meant. If you don't use the flight deck as a strength deck the hull, seen as a beam under bending stress, has less height and thus the strength deck below the hangar and the bottom of the hull will have to carry a higher load than when the strength deck is the flight deck, as it was already with the British carriers in the thirties with their steel flight decks. This became possible when the US abandoned wooden flight decks and it would have been absurd not then to use that steel flight deck as a strength deck.

bd popeye · Nov 15, 2012

Note.. those flight decks were not all wood on the Essex class. I served on one. USS Hancock (CVA 19). There was steel about 1.5 inches thick that those wood beams were placed upon. It was not armored.

Jeff Head · Nov 15, 2012

Pointblank said:
An internal hangar is contained within the ship's girder and is enveloped by the ship's hull. It is easier to protect, has better access to machinery shops and maintenance facilities and offers much better protection for the aircraft against bad weather. Deck edge lifts are difficult to install, of questionable value and have serious structural implications.

The advantage of the internal hangar was that, by using the flight deck as strength deck, the British carriers had a much deeper hull girder, so the designers could use substantially lighter hull structural members, giving them a larger carrier for a given displacement. The big problem was that, since the flight deck was the strength deck, holes (lifts, etc.) had to be kept to a minimum, so the internal hangar concept immediately translated into fewer and smaller lifts - compromising the ability to launch and recover aircraft.

To the contrary, with the Forrestal class and onward, the US Navy has had four very large (not smaller, and not fewer) deck edge elevators.

The elevators in the middle of the deck were no longer present, but they had actually gone away when the Midway and older Essex class carriers that were taken through their major overhauls to turn them into modern angle decked carriers. That is when the large deck edge elevators were installed and the decks completely reconfigured at the time fro new catapaults, including closing in the bow and stern of the vessels. It would be interesting to know, from an engineering perspective, if in those two year long overhauls, in essence, they created a strength deck out of the flight decks.

Either way, they most certainly did create complete strength decks with the Forrestals and onward, and the result was not fewer and smaller elevators on the deck edges, and it was not fewer aircraft.

Of course the carriers became bigger (as did the aircraft in terms of size and weight) but the Forrestals on, through to the Nimitz and now the Fords are capable of carrying over 90 aircraft if it were so desired and of that were the policy. The policy has reduced those numbers to between 60 and 70, but they are capable of the higher number.

bd popeye · Nov 15, 2012

Of course the carriers became bigger (as did the aircraft in terms of size and weight) but the Forrestals on, through to the Nimitz and now the Fords are capable of carrying over 90 aircraft if it were so desired and of that were the policy. The policy has reduced those numbers to between 60 and 70, but they are capable of the higher number. .

100% correct.

In 1981 aboard the USS America this was our air wing;

24 F-14 Air superiority
2 TARPS F-14s
24 A-7 ground/surface attack
12 A6E All weather, heavy ground/surface attack
3 KA6D Tankers
4 E2C AEW
4 EA6B EW
10 S3A ASW
6 SH-3G ASW/SAR

plus two C-2 Greyhounds CODs.

Nimitz or Ford class can easily handle 90+ aircraft. Minor modifications would have to occur. Those extra gyms & store would have to be converted back to berthing. Closed maintaince shops would need to be re-opened. NO BIG DEAL!

Popeye's modern day USN CVW

60 Hornets F/A & Tanker
4 Growlers EW
5 E-2 Hawkeyes AEW
19 SH-60 varaints(This number of helos has been deployed several times)

Pointblank · Nov 15, 2012

Jeff Head said:
To the contrary, with the Forrestal class and onward, the US Navy has had four very large (not smaller, and not fewer) deck edge elevators.

The elevators in the middle of the deck were no longer present, but they had actually gone away when the Midway and older Essex class carriers that were taken through their major overhauls to turn them into modern angle decked carriers. That is when the large deck edge elevators were installed and the decks completely reconfigured at the time fro new catapaults, including closing in the bow and stern of the vessels. It would be interesting to know, from an engineering perspective, if in those two year long overhauls, in essence, they created a strength deck out of the flight decks.

Either way, they most certainly did create complete strength decks with the Forrestals and onward, and the result was not fewer and smaller elevators on the deck edges, and it was not fewer aircraft.

Of course the carriers became bigger (as did the aircraft in terms of size and weight) but the Forrestals on, through to the Nimitz and now the Fords are capable of carrying over 90 aircraft if it were so desired and of that were the policy. The policy has reduced those numbers to between 60 and 70, but they are capable of the higher number.

With Midway and Essex, the flight deck was not the strength deck; it was the hangar deck. As the hangar deck was the strength deck, and the flight deck was treated like the superstructure, there wasn't any overriding concerns about structure that would have caused design issues with deck edge lifts.

The issues regarding the placement of the strength deck on the flight deck or the hangar deck and the impact it has on the carrier's air wing is best showed between two designs representing the two types at a similar tonnage. I will point out the difference between the USN's Yorktown class carriers and the RN's Illustrious class carriers. The Yorktown's had a larger airwing by default even after the RN adopted deck parking of aircraft (Yorktown could carry 90 aircraft on a displacement of ~20,000 tons, while Illustrious could only handle no more than 60 aircraft on a displacement of ~23,000 tons). Likewise, the amount of lifts and their sizes showed; the Illustrious when she received US aircraft, there were significant modifications to the wing folding systems to ensure that they fit in RN carriers, not to mention that Illustrious only had 2 lifts:

Jeff Head · Nov 16, 2012

Pointblank said:
With Midway and Essex, the flight deck was not the strength deck; it was the hangar deck

I know this...I was just speculating on whether additional strength was added to the flight deck as a result of the major conversions several of them underwent to give them an angled deck, deck edge elevators, and to enclose the hanger spaces. Those changes required almost two years in the yards for each carrier so rebuilt.

Those conversions produced the first "modern carriers" in the US inventory and later gave way to the Forrestal class.

With the modifications and complete rebuild of the flight deck, I was just wondring whether structurally more strength had been added by design into the flight deck.

That's all. I know that both Essex and Midway class were designed and built with the hangar deck being the strength deck.

In addition, my other point was, that once the US went over to the flight deck being designed from inception to be the strength deck, the US actually increased the size and number of deck edge elevatrors to four, which remained the same through the
Nimitz class...and those carriers airwings increased as well, though the latter is more related to the larger size of the carrier itself.

asif iqbal · Nov 20, 2012

this months Warship magazine (December issue) has confirmed that the 2 QE Carriers under construction at Roysth will be fully commissioned into the Royal Navy, it comes after speculation that only one would be commissioned and the other in a "high state of readiness" to reduce costs

not only that, US was concerned about UK role and responsibility in NATO and as a result now US will help Royal Navy to use "surge" tatics, which means UK will now train to send both aircraft out at the same time and be able to deploy to a war zone 2 aircraft carriers with full airwing, essentially, 2 carrier battle groups

this is very good news as it will add a considerable force to power projection for UK

this means a single carrier group could have
1 x QE Carrier
4-6 x Type 45 DDG mixed with Type 26 FFG
Mars Replenishment tanker
Astute Class SSN

once again soon we will see Royal Navy sailing the high seas in force

Air Force Brat · Nov 20, 2012

asif iqbal said:
this months Warship magazine (December issue) has confirmed that the 2 QE Carriers under construction at Roysth will be fully commissioned into the Royal Navy, it comes after speculation that only one would be commissioned and the other in a "high state of readiness" to reduce costs

not only that, US was concerned about UK role and responsibility in NATO and as a result now US will help Royal Navy to use "surge" tatics, which means UK will now train to send both aircraft out at the same time and be able to deploy to a war zone 2 aircraft carriers with full airwing, essentially, 2 carrier battle groups

this is very good news as it will add a considerable force to power projection for UK

this means a single carrier group could have
1 x QE Carrier
4-6 x Type 45 DDG mixed with Type 26 FFG
Mars Replenishment tanker
Astute Class SSN

once again soon we will see Royal Navy sailing the high seas in force

Not a moment to soon in my estimation, congratualations to the Brits for stepping up, the F-35B is progressing nicely as well, the first Marine Squadron being stood up at Yuma? pretty cool dudes!

Aircraft Carriers II (Closed to posting)

airsuperiority

Captain

bd popeye

The Last Jedi

delft

Brigadier

bd popeye

The Last Jedi

Jeff Head

General

bd popeye

The Last Jedi

Pointblank

Senior Member

Jeff Head

General

asif iqbal

Lieutenant General

Air Force Brat

Brigadier